Gsm kpi

L

Optimization

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                                                  Version:               1.0
                                                  Date:                  9/22/2004
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                                                                         GSM KPI Draft.doc
                                                                         GSM Training
             GUIDE                                Author(s):             Cristian Iordache




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CONTENTS:




1. Introduction                                                                                          2
2. GSM PARAMETERS/KPI                                                                                    2
3. GSM Indicators Description                                                                            4
3.1 RX_LEV_DL                                                                                            7
3.2 RX_QUAL                                                                                              8
3.3 SQI                                                                                                  8
3.4 C/I                                                                                                  9
3.5 PATH LOSS                                                                                            11
4 .1 EVENTS                                                                                              12
ANNEX 1: Optimizations Parameters (Alcatel Implementation for 900/1800MHz Bands)                         14
ANNEX 2. GSM OPTIMZATION PARAMETERS                                                                      24
ANNEX 3: Ericsson TEMS Information Parameters List Implementation                                        24
ANNEX 4: MS Power Classes                                                                                24
Bibliography                                                                                             25




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                                            GSM KPI PRESENTATION



    1. Introduction



In GSM technology which is in this moment a fully grown technology with a high complexity of the standard,
the provisional assessment of a network requires tools that could provide a full array of information both in
start-up phase or optimization. Comparative network benchmark tool has to be able to provide an accurate list
of Key Performance Indicators (KPI) that could be use for competitor networks using both GSM and other
technologies. The results could be used then in planning, installation or optimization process.




Radio Network Optimization based on measurement analysis is a part of the global process that allows a healthy network
operation.
The measurement sessions forms the "active part" of the job on the radio part of a running network, while Quality of
Service Monitoring is the "detection & filtering part".
QoS Monitoring activates Fine Tuning when weaknesses or troubles are detected on the network behavior, and more
generally to improve the Quality of Service statistics.
The optimization process has to handle and solve the omissions from each of the previous steps of the network start-up
history.
Then in GSM, according to high complexity of the standard, the provisional assessment of a network is more difficult,
hence the probability to encounter omissions is higher.

The optimizations process is based on the analysis of the information from the system statistic reports, and also on a
cross check with the network description made during the previous stages.
The goal is to optimize the network behaviour and to solve local problems.

The main activities are:

• Radio Coverage problem investigation, dealing with Air interface, on MS and Infrastructure side,
• Telecom parameters optimization, dealing with the network behaviour in Idle and Dedicated mode,
• Traffic load distribution and congestion reduction.

This requires specific external jobs:
• MS monitoring, using Air and Abis interfaces Monitoring (Test phones, Abis interfaces and adequate SW.
• Quality of Service Monitoring (analyze of Network Statistics), which is a basic source/target of Fine Tuning
and thus a strong help to locate troubles.


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The radio problems are identified through different processes:
• by the GSM operator, analyzing end user complaint about faults/difficulties/quality on the calls. The complaint is dealt
by the "Customer Care Centre" who sort the complaints, then correlate the problem with already known origin/area or
detect new problems.
• by a "Mobile Station Monitoring" (Drive-test, walk-test, Scan) during a measurements campaign.
• by a data analysis following an Abis interface monitoring.
• by the "Quality of Service Monitoring" compiling statistics from the OMC-R indicators and A interface monitoring.
Once the solution has been found, it is put in a list of proposed modifications to the network. This list includes the
proposed parameter modifications issued from the System Parameter Check process.
The modifications description and the way they are performed are decided after a common discussion between Network
Planning, Radio Optimization and O&M personnel. Then a work order is sent to the organization/team in charge of the
modification as stated for the solution: aerial adjusting or positioning, radio parameter settings...

The main methodology action items used in optimization process are:

• to identify measurement routes (these routes will still be used after the network start-up, as long as the
coverage remain the same),
• to run systematic measurements on Air Interface, using test tools
• to produce different types of plot maps (coverage, quality, ...),
• to identify radio problems and work out corrections,
• to issue a complete network status document compliant with GSM operator's expectations.

         Obs: There it is also a particular process also called "Cell Verification and Acceptance" that occurs
         only at the end of site installation. The goal is to validate the BTS sites location and configuration, as
         implemented on the basis of RNP specifications. This check is done using real Air interface
         measurements.
         The final goal of this process is to put the local network in accordance with the "Quality and Radio
         Coverage Contract" defined with the GSM operator.

Mobile Station/Test Tool Monitoring

This activity requires the same competencies as for" Cell Verification". The goal is to check the network performance on
the Air interface segment. But since it is run on an operating network, it can be performed either on a regular basis by an
operator's team or punctually by an auditor's team.
MS Monitoring deals with all the drive tests.

The main activities are:
• to conduct air interface measurements on pre-defined routes adapted to the network evolution,
• to produce typical plot maps (showing radio coverage, quality, etc.),
• to locate radio problems. (The test tool results can also be used in order to make corrections of the propagation model
prediction tool software)

A GSM test tool should be able to perform as following:

• to scan/record/process the absolute (analog) GSM bands (Spectrum analysis in 850, 900, 1800, 1900MHz)
• to scan/record every operator using a SIM for each one
• to read the CGI and all the other GSM Layer 1, 2 and 3 parameters
• to measure/record/process the performance parameters both in Idle or Dedicated Mode
• to force a specific ARFCN, cell barring, etc.
• to provide accurate measurements. (Re-calibration feasible)
• to record the measurements geographically based in such a way that the information could be exported and post-
processed by other tools (ex MapInfo, Excel, etc)




2. GSM KPI List




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For an efficient GSM Network assessment using drive tests equipment it is important to be able to select the
most significant downlink parameters and to use the an array of quantified thresholds. It is well known that
each wireless service provider has its own quality standards (coverage thresholds, GoS, etc) conducing to
more or less subjective results.
There it is even a bigger challenge to create a universal tool that is able to make competitive tests for different
technologies with different approaches for subscriber’s QoS assessment.

In to the list shown below are presented the most relevant parameters used in GSM:


Quality Indicators:


RX_LEV – Received Signal Level both in “Idle” and “Dedicated” mode (DL) [dBm]
      Signal Strength on BCCH Carrier, indicating the signal strength on the current BCCH. This element is
      especially useful for obtaining a correct measure of the cell size when frequency hopping is used and
      power control is applied to the TCH’s and for general coverage assessments.


RX_QUAL – Received Signal Quality, a measure of speech quality measured based on BER analysis, both
     in “Idle” and “Dedicated” mode

SQI – Speech Quality Indicator (an additional parameter introduced by Ericsson on their tool TEMS in order
       to obtain a more accurate image of the voice quality than the one offered by RX_QUAL)

TX_PWR – Transmission Power Level (DL – from BTS, UL from MS). In order to reduce interference, the
     power is continuously tuned both in the BTS radios and in MS. It may vary in case of MS with a step
     of 2 dB up or down.

         C/I – Carrier to Interference ratio - indicating the carrier-to-interference ratio for each channel in the
         hopping list (and for each timeslot with multi-slot allocation).

OBS: "Full" and "Sub" Values:
       - Information elements with "Full" in their names are calculated on all blocks.
       - Information elements with "Sub" in their names are calculated only on the blocks known to be sent
       also when downlink DTX is active (in each 104-multiframe, one TCH block with SID information and
       one SACCH block).

TA - Timing Advance, a calculated parameter based on the group delay measurements that appear due to
        distance used in order to keep the UL and DL TS synchronisation.


Statistic Indicators:

         % Call Attempt Rate
         % Call Success Rate
         % Blocked Call Rate
         % Good Initialization Rate
         % Drop Calls Rate
         % No Service Rate
         % Good/Failed HO Rate
         % HO Type (Intra/Inter Cell, Intra/Inter BSC)
         % HO cause Rate
         % Location Area Update Success Rate

Evens:

         Blocked Call
         Call Attempt



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        Call End
        Call Established
        Call Setup
        Cell Reselection
        Dedicated Mode
        Dropped Call
        Handover
        Handover (Intra-cell)
        Handover Failure
        Handover Intra-cell Failure
        Idle Mode
        Limited Service Mode
        Location Area Update
        Location Area Update Failure
        No Service Mode
        Ringing
        Vehicle Speed




Network/Cell Identifiers:

        MCC (Mobile Country Code),
        MNC (Mobile Network Code)
        LAC (Location Area Code)
        CI Cell I.D.
        CGI (Cell Global Identity) = MCC+MNC+LAC+CI
        BSIC = NCC (Network Colour Code) + BCC (BS Colour Code)
        ARFCN = Absolute RF Channel



3. GSM Indicators Description:

3.1 RX_LEV_DL

It is a RF indicator who shows the average signal level at the input of the MS’s receiver. In Idle mode it
indicates the received signal strength from the BCCH physical channel, and in traffic it indicates the signal
strength measured on the current ARFCN channel used for TCH/SDCCH transport.
This element is especially useful for obtaining a correct measure of the cell size when frequency hopping is
used and power control is applied to the TCH’s and for general coverage assessments.


Signal Strength on Hopping List, indicating the signal strength of each channel in the hopping list. This
element gives more information than RxLev, which is an average over all channels in the hopping list.

The following paragraph is an brief description of those features used in GSM design using as an input data,
information’s related to RX_LEV:

RxLev-based Thresholds:


The handover margin represents the necessary overlap between two cells in ensuring the handover with the
good quality of the communication. This margin depends on the environment as follows:
       - In indoor environment the handover is not necessary, so the handover margin is 0 dB.
       - In outdoor environment the handover margin is typically 2 dB.




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        -   In High Speed Train (ex. TGV) environment the handover margin is typically 2 dB. Another
            restriction of this particular case is the overlap length greater than 600 m between two neighbor
            cells.

The design margin is corrects two main errors that can appear during the design and prediction process:
       - Prediction Tool S/W prediction error and
       - Penetration loss evaluation error – in the case of an indoor service
       - A cumulative value for the design margin with a 90% probability is 6 dB.

The design, the prediction and the measure of the service area of a cell will be done with an equilibrated
power budget or with a not equilibrated power budget with the downlink better than the uplink (DL-UL>0). If in
the power budget the downlink is worst than the up-link (DL-UL<0) then the design thresholds will be adjusted
with the max (0, DL-UL [dBm]) value.

*Note that the considerations presented before take into account the method used by the prediction tool which
calculates only the strength of the downlink signal.

The design threshold is the threshold used to design the cells and is defined as the strength of the predicted
signal at the limit of the cell which assures the service inside the cell and the handover with the neighborhood
cells.


Design threshold         =        Mobile handset sensitivity
                         +        Fading / Sensitivity margin
                         +        BTS output power margin
                         +        Penetration losses
                         +        Handover margin
                         +        Design margin at 90%
                         +        max (0, DL-UL)

The prediction threshold is the threshold used to predict the coverage of a cell and is defined as the
strength of the predicted signal at the limit of the cell which assures the service inside the cell.

Prediction threshold     =        Mobile handset sensitivity
                                  +      Fading / Sensitivity margin
                                  +      BTS output power margin
                                  +      Penetration losses
                                  +      Design margin at 90%
                                  +      max (0, DL-UL)

Prediction threshold     =        Design threshold
                                  -      Handover margin


The measure threshold is the threshold used to measure the received signal in outdoor environment.
For outdoor services:

Measure threshold        =        Design threshold
                         -        Design margin at 90%
                         -        Handover margin

For indoor services:

Measure threshold        =        Design threshold
                         -        Design margin at 90%
                         -        Handover margin
                         +        Indoor penetration margin at 90%




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       The following table summarizes the design, prediction and measure thresholds fore several
representative services.

         SERVICE                DESIGN THRESHOLD                 PREDICTION             OUTDOOR MEASURE
                                      AT 90%                     THRESHOLD                 THRESHOLD
                                                                    AT 90%
Indoor Deep                    - 63 dBm                      - 63 dBm                  - 66 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Indoor Light                   - 71 dBm                      - 71 dBm                  - 74 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Indoor in High Speed           - 71 dBm                      - 73 dBm                  -
Trains                         +max(0, DL-UL)                +max(0, DL-UL)
Indoor Window                  - 77 dBm                      - 77 dBm                  - 80 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Outdoor In-car                 - 79 dBm                      - 81 dBm                  - 86 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Outdoor                        - 85 dBm                      - 87 dBm                  - 92 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Outdoor Car-kit                - 88 dBm                      - 90 dBm                  - 95 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)
Outdoor 8W                     - 93 dBm                      - 95 dBm                  - 100 dBm
                               +max(0, DL-UL)                +max(0, DL-UL)            +max(0, DL-UL)

   Notes:
   -       The services marked in bold (Indoor Deep, Indoor Light, Outdoor In-car and Outdoor) are
used by RF designers
   -         For indoor coverage the thresholds to use will be Indoor Deep for cities having dense high
buildings or Indoor Light for small towns.
   -        For coverage on roads the thresholds to use will be Outdoor In-car.

Types of Service Analysis based on RX_LEV measurements and tresholds:

In order to ensure a generic design standard permitting good quality communication inside the cells,
depending on the environment several types of service can be defined.
The description of several types of service is presenting in following table:

     SERVICE                                          DESCRIPTION OF THE SERVICE
Indoor Deep             In 90% of the surface of the ground floor of the building it is possible to have good
                        quality communication using a 2W handset.
Indoor Light            In 90% of the surface of the ground floor of the building (having visibility with the
                        windows) it is possible to have good quality communication using a 2W handset.
Indoor   in  High       In the seats of the train it is possible to have a good quality communication using a 2W
Speed Trains (Ex:       handset.
TGV)
Indoor Window           In 90% of the surface of the ground floor of the building (near the windows) it is
                        possible to have good quality communication using a 2W handset.
Outdoor In-car          In 90% of the outdoor surface it is possible to have good quality communication using a
                        2W handset inside a car.
Outdoor                 In 90% of the outdoor surface it is possible to have good quality communication using a
                        2W handset.
Outdoor Car-kit         In 90% of the outdoor surface it is possible to have good quality communication using a
                        2W handset inside a car equipped with car-kit.
Outdoor 8W              In 90% of the outdoor surface it is possible to have good quality communication using
                        an 8W handset.




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For each environment the penetration loss, the design margin and the handover margin can be estimated
statistically as follows:

      SERVICE                            Penetration losses                       Design margin           Handover
                                                                                     at 90%                margin
Indoor Deep               23 dB - Indoor concrete penetration losses                  6 dB                  0 dB
                          6 dB – Head effect
Indoor Light              15 dB – Indoor intermediary penetration losses               6 dB                 0 dB
                          6 dB – Head effect
Indoor in High Speed      14 dB – Ex: TGV penetration losses                           5 dB                 2 dB
Trains                    6 dB – Head effect
Indoor Window             6 dB – Indoor light penetration losses                       6 dB                 0 dB
                          6 dB – Head effect
Outdoor In-car            6 dB – Car penetration losses                                5 dB                 2 dB
                          6 dB – Head effect
Outdoor                   0 dB – Penetration losses                                    5 dB                 2 dB
                          6 dB – Head effect
Outdoor Car-kit           0 dB – Penetration losses                                    5 dB                 2 dB
                          3 dB – Car-kit equipment losses
                          0 dB – Head effect (not present)
Outdoor 8W                0 dB – Penetration losses                                    5 dB                 2 dB




3.2 RX_QUAL

It is a measure of speech quality measured based on BER analysis. RxQual is obtained by transforming the
bit error rate (BER) into a scale from 0 to 7 (see GSM 05.08). In other words, RxQual is a very basic measure:
it simply reflects the average BER over a certain period of time (0.5 s for TEMS tools).
In a low disturbed area (e.g. a rural cell) a very low received field could be encountered without a big
degradation of the speech quality. On the other end, in an urban area, a good received field doesn’t however
allow a good communication because of a high interference level. That is why a quality assessment is done
on the basis of the bit error rate in the messages (RX_QUAL), on UL and DL.
Range: 0…7 <integer>




Good quality communication is defined as a communication characterized by a value of RXQUAL
parameter better than 4 for a cell without frequency hopping and better than 5 for a cell with frequency
hopping.

Note: When FH is activated, RX_QUAL is impacted: the measured bit error rate becomes worse (usually by
about 1 unit) because of two reasons:
        1 – in the BER computation – at the moment of hopping, the reception radio synthesizer looses
systematically a few synchronization bits, which impacts the low BER values.
        2- because of the averaging effect of the interference levels




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3.3 SQI

SQI - “Speech Quality Index” is an indicator that has been designed by Ericsson for their TEMS investigation
tool to take into consideration all the phenomena omitted by RX_QUAL indicator (Bit error distribution,
Speech Frame erasures, HO effects, Speech codec type). This ensures that it will produce an unbiased
prediction of the speech quality, independently of channel conditions and other circumstances. Somewhat
roughly, the computation of SQI involves:
- the bit error rate (BER)
- the frame erasure rate (FER)
- data on handover events
- statistics on the distributions of each of these parameters.
Furthermore, for each speech codec, SQI is computed by a separate algorithm which is tuned to the
characteristics of that codec.
Like RxQual, SQI is updated at 0.5 s intervals (in TEMS tools).

To give some examples of what the relation may look like, the graph below is included. It shows SQI as a
function of RxQual for the EFR codec and a number of channel conditions. (It must be kept in mind that the
curves represent time-averaged RxQual-to-SQI relations; individual segments of speech may of course
deviate from these.)
Note the considerable differences between the various channel conditions.




Ex: for the same Speech Quality (SQI) of 15 the RxQual may vary from 3 for an urban/No FH area to ~6 in
one area with FH.



3.4 C/I


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The carrier-over-interference ratio is the ratio between the signal strength of the current serving cell and the
signal strength of undesired (interfering) signal components. The C/I measurement function enables the
identification of frequencies that are exposed to particularly high levels of interference, something which
comes in useful in the verification and optimization of frequency plans.
Usually C/I measurement is made in dedicated mode. It is however also possible to measure C/I in idle mode.
This is handy when interacting with a test transmitter which simulates a base station but is not capable of
setting up calls. It should be pointed out that the sampling rate and hence the quality of idle mode C/I values
is critically dependent on the settings governing quality measurement in idle mode

Downlink quality in a radio network can be monitored using Speech Quality Index, SQI. In this way, areas with
inadequate speech quality can be identified. However, if frequency hopping is used in the network, it is
difficult to pinpoint the frequencies that are affected by the degradation. To help resolve such ambiguities, C/I
indicator offers the possibility of measuring average C/I for each of the frequencies used in a call.
To obtain a correct C/I estimate, one must take into account the possible use of power control and/or
discontinuous transmission (DTX). In the past, rough C/I measurements have sometimes been carried out by
comparing the BCCH signal power of the serving cell with that of neighbouring cells using the same traffic
channels (but different BCCHs). Since such a scheme fails to allow for power control and DTX on the TCHs, it
may produce misleading results. There should be considered these network functions to be able to indicate
the actual C/I experienced by the mobile station.

In dedicated mode, average C/I is presented twice a second, which is equal to the ordinary measurement
interval. If frequency hopping is employed, the average C/I for each frequency is presented.
The measurement range extends from -5 dB to +25 dB. A C/I below -5 dB can be regarded as highly unlikely;
in addition, if the number of hopping frequencies is low, C/I values below this limit would normally result in a
dropped call. Beyond the upper limit, the speech quality is not further improved. Hence, the limitation of the
measurement range is not a restriction.
If downlink DTX is used, the number of bursts transmitted from the base station to the mobile station may be
lower than the maximum, depending on the speech activity level on the transmitting side. Then the
measurements should be made only on the bursts actually sent from the base station and disregards burst
not transmitted.

The number of hopping frequencies determines the number of bursts used for the C/I measurement on each
frequency. For example, if four frequencies are used, 25 bursts (on average) per frequency are received in
each 0.5 s interval. With more frequencies, there are fewer bursts for each frequency. This implies that the
accuracy of the measurements is better for small sets of hopping frequencies.
If true C/I is within the range 0 to 15 dB and four frequencies are used for transmission, and there are no DTX
interruptions, the measurement error is typically smaller than 1 dB.

To illustrate the use of C/I, data from a test drive is depicted in the figure below. The test drive lasts 40
seconds. EFR speech coding and cyclic frequency hopping with four frequencies is employed throughout.
The upper part of the graph shows SQI and RxLev, while the lower part shows C/I for each of the four
frequencies:




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As appears from the upper graph, SQI dips sharply towards the end of the test drive (after 35 s), and
indicating poor speech quality. On the other hand, RxLev stays about 50 dB above -110 dBm the whole time.
This means that the dip in quality is not due to low signal power level, that is, the quality problem is to do with
interference rather than coverage. In fact, and interestingly, RxLev increases during the SQI dip, probably
because the power of the interferer increases.
Now, looking at the C/I graph, one sees that two of the four frequencies (the thick lines) have a C/I worse than
10 dB during the SQI dip. This explains the poor speech quality, identifying precisely which channels are
disturbed. Such information can then be utilized in the process of optimizing the frequency plan for the area.

The interference scan consists in mobile locking on the BCCH ARFCN of the disturbed cell and scanning the
ARFCN of the traffic channel that is exposed to interference. Note that these two may be the same. The main
task performed by the identification algorithm is to determine the Base Station Colour Code (BCC) of the
interfering signal, i.e. the second digit of the BSIC (=NCC+BCC).

Obs:
        If BCC is known this fact reduces the number of possible interferers by a factor of 8.
        This is because BCC can take integer values from 0 to 7 (it written and transmitted on a 3-bit length
        sequence) as is a part of BSIC (Base Station Identity Code = NCC + BCC = 3 bit+ 3 bit, where NCC =
        National Color Code or "PLMN color code"). So if we know BSIC/BCC, we can restrict the search for
        interferers.
        BSIC is transmitted in the SCH (and not in BCCH) as a “color code” (like the coloring of maps, unique
        for every cell in one area), so that BTS with same beacon frequency (BCCH ARFCN ch.) use different
        BSIC.
        MS gets from the BTS a list of beacon frequencies to be monitored through BCCH logical channel.
        In measurement report, MS reports BSIC of the monitored cells.
        C/I index is measured for each of the ARFCN RF physical cannel that are involved in hopping list of
        the server cell. The MS is doing the C/I measurements during the other Time Slots (TS) that are not
        allocated to him. These frequencies should be different than those that appear in the neighbor list(!).
        In idle mode the MS reads the BSIC too, in order make sure that it is still monitoring the same cell.

Therefore, knowing the BCC reduces the number of possible interferers by a factor of 8. This is a great step
forward; but even so, the network will normally contain several cells with this BCC, all of which make use of
the disturbed ARFCN as BCCH or TCH. Other means must therefore be used to shorten the list of candidates
further. Fortunately, such means are readily available:
 Many sites proposed as candidates can usually be ruled out simply because they are too far away, or
because they have their antennas pointing away from the disturbed cell.
 During the scan the timing offset between the serving cell and the interferer is determined. This offset can
also be measured by other means, and the scan offset can then be compared with measured offsets to
nearby cells.
In practice, using one or both of these approaches, it is almost invariably possible to point out the exact
source of the interference.

There are many possible causes of poor C/I values. Two common ones are co-channel and adjacent channel
interference. In certain circumstances, however, the main problem is not interference from other callers, but
the fact that the signal is overwhelmed by assorted random disturbances -- i.e. what is usually called "noise".
This means thermal noise generated within the circuits of the mobile station, as well as external background
noise from a plethora of sources, including other man-made signals so faint that they merely add up to a
quasi-random disturbance.

Example of typical C/I degradation due to noise:

{(C/I) worst<10dB} AND {RxLev_Sub<99dBm}
The following event gives a rough indication that the poor C/I is probably due to a noise problem: the poor C/I
coincides with a very low signal strength.

The following table summarizes the C/I* acceptable values:
        CHANNEL                                             MINIMUM C/I*
        BCCH/SDCCH                                          14 dB
        TCH without frequency hopping                       14 dB


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       TCH with frequency hopping                          12 dB (9dB in some networks)



3.5 PATH LOSS


The rough Definition of Path Loss – DL and UL:

PL_DL = BS_TXPWR – RX_LEV_DL + LDL

BS_TX_PWR = BTS Transmission Power
RX_LEV_DL = RF signal level received by MS
LDL = Sum of gains/losses and RX_MS_Sensitivity

PL_UL = MS_TX_PWR – RX_LEV_UL + L_UL

MS_TX_PWR = MS Transmission Power
RX_LEV_UL = RF signal level received by BTS
L_UL = Sum of gains/losses and RX_TRX_Sensitivity


The following tables present the values that must be considered in power budget calculation for downlink and
respectively uplink:

                          =              LOSS / GAIN                        LOSS / GAIN VALUE
Propagation      losses   =     BTS emitter power                     BTS output power
downlink
                          -     BTS emitter power tolerance           1 dB typical value
                          -     Duplexer losses                       Specified by the duplexer supplier
                          -     Feeder losses                         Must be calculated function of the
                                                                      type and the length of the feeder
                          -     LNA losses                            Specified by the LNA supplier
                          -     Power splitter losses                 Specified by the power splitter
                                                                      supplier
EIRP                      +     BTS antenna gain                      Specified by antenna supplier
                          -     Penetration losses                    Depends on the type of service
                          -     Fading / Sensitivity margin           3 dB typical value
                          +     Handset sensitivity                   -102 dBm for 2W handsets
                                                                      -104 dBm for 8 W handsets
                          -     Design margin at 90%                  Depends on the type of service



                          =              LOSS / GAIN                          LOSS / GAIN VALUE
Propagation      losses   =     Mobile handset emitter power          2 W for 2W handsets and
uplink                                                                8 W for 8W handsets.
                          -     Mobile handset emitter power          1 dB typical value
                                tolerance
                          -     Penetration losses                    Depends on the type of service
                          -     Fading / Sensitivity margin           3 dB typical value
                          +     BTS antenna gain                      Specified by antenna supplier
                          +     Diversity gain                        3 dB typical for space diversity rural
                                                                      environment
                                                                      3 dB typical value for polarisation
                                                                      diversity in urban environment




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                            -    Feeder losses                         Must be calculated function of the
                                                                       type and the length of the feeder
                            -    Duplexer losses                       Specified by the duplexer supplier
                            +    LNA gain                              Specified by the LNA supplier
                            +    BTS sensitivity                       Specified by the BTS supplier
                            -    Design margin at 90%                  Depends on the type of service



Power budget equation

The Power budget criterion PBGT is used to estimate the difference of path loss between two
neighboring cells.
PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO
- (BS_TXPWR_MAX - BS_TXPWR)
- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)
- PING_PONG_MARGIN(n,call_ref)
with :
- AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO or A_PBGT_DR
measurements (neighbor cell(n)).
- AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUB
over A_PBGT_HO or A_PBGT_DR measurements (serving cell).
- BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS).
- BS_TXPWR : last BS_POWER value reported by the BTS in the message
MEASUREMENT RESULT (mode B) or last BS_TXPWR value reported
by the BTS in the message PREPROCESSED MEASUREMENT RESULT
(mode A).
- MS_TXPWR_MAX(n) : max power level the MS is allowed to use in its neighbor cell(n).
- MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell.
- PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :
it is the immediately precedent cell on which the call has been,
this cell belongs to the same BSC as the serving cell,
the call has not performed a forced directed retry towards the serving cell,
less than T_HCP seconds have elapsed since the last handover.
In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP.,
If the call was not precedent on cell n, or if the preceding cell was external, or if
the call has just performed a forced directed retry, or if the timer T_HCP has
expired, then PING_PONG_MARGIN(n,call_ref) = 0

With abstraction of the PING_PONG_MARGIN, which is purely a handicap given to the preceding cell
for a certain time, the PBGT can be described in two steps :

BCCH = AV_RXLEV_NCELL(n) - (AV_RXLEV_PBGT_HO + C)
with C = BS_TXPWR_MAX - BS_TXPWR.

BCCH corresponds to the difference of received BCCH signal levels.
A correction factor C is taken into account for the serving cell, because the received signal level (i.e.
AV_RXLEV_PBGT_HO) may not be measured on BCCH,

Then, another correction factor must be taken into account because the maximum BS powers of the
serving and neighboring cells may be different :
######TXPWR = MS_TXPWR_MAX(n) - MS_TXPWR_MAX.
As the first step of calculation is based on the downlink parameters, this correction factor should be
based on the maximum BS powers used in the serving and neighboring cells.
Two reasons (which are not completely de-correlated) for not using the BS powers can be envisaged:
- for a given cell, the GSM does not specify formally the maximum BS power of the neighboring
cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface),
- it is not easy for the evaluating BSC to know the maximum BS powers of the neighboring cells.
The use of the maximum MS powers requires that the difference of MS powers is equal to the


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difference of BS powers. This condition is met in most cases. If it is not the case, the difference can
be corrected by the operator with the HO_MARGIN(0,n) parameter (HO hysteresis).
PBGT >0 : the neighbour cell is more advantageous as the path loss is less than in the current cell.
PBGT <0 : the serving cell is more advantageous as the current cell.
The PBGT equation (without temporary handicap) can be interpreted in another way.
PBGT = ###BCCH - ###TXPWR
The PBGT is a balance or a trade-off between two opposite indicators. As a matter of fact :
### ###BCCH > 0 : the neighboring cell n is more advantageous than the serving cell as the
reception of BCCH is better.
### ###BCCH < 0 : the neighboring cell n is more disadvantageous than the serving cell.
### ###TXPWR > 0 : the neighboring cell n is more disadvantageous than the serving cell as the
maximum permissible power of the MS is higher.
### ###TXPWR < 0 : the neighboring cell n is more advantageous than the serving cell.
The PBGT can be seen as a balance, at MS side, between a probability to have a better reception
and the probability of requests of transmission at higher levels in the neighboring cells.




4 .1 EVENTS – Predefined and user-defined events:

The events detected by a GSM terminal can be identified based on identification of “trigger” values or ranges
of the GSM indicators:

                              Choose information element (See Annex 3).
     Information
     element
     Argument                 If the information element has an argument, specify it here.

     Value: Changed           Choose this to trigger the event whenever the value of the selected
                              information element changes.
                              Choose this to trigger the event when the selected information element
     Value: Threshold         assumes, exceeds or drops below a certain value. Choose a threshold
                              operator ("=", ">", or "<"), and set the threshold value.




The basic list of events to be considered is presented in the table below:



                               It was not possible to establish a call, for example because all traffic
     Blocked Call              channels are busy.
                               A traffic channel has been requested (through the Layer 3 message
                               "Channel Request"). (Note that the request may also be for a signaling
                               channel, in which case no call is actually attempted; the two types of
     Call Attempt              request cannot be distinguished.)
                               The call has been terminated (triggered by the Layer 3 message
     Call End                  "Disconnect").
                               A call has been established (triggered by the Layer 3 message "Connect
     Call Established          Acknowledge").
                               A call has been set up by the mobile (triggered by the Layer 3 message
     Call Setup                "Alerting").
     Cell Reselection          Reselection to a new control channel has taken place.
     Dedicated Mode            The mobile has entered dedicated mode.
     Dropped Call              The established call has been terminated abnormally.


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     Handover                   Successful inter-cell handover.
     Handover (Intracell)       Successful intra-cell handover.
     Handover Failure           An attempted inter-cell handover failed.
     Handover Intracell
     Failure                    An attempted intra-cell handover failed.
     Idle Mode                  The mobile has entered idle mode.
     Limited Service Mode       The mobile has entered limited service mode (emergency calls only).
     Location Area Update       The mobile has changed location areas.
     Location Area Update
     Failure                    The mobile failed in changing its location area.
                                The mobile has entered No Service mode, since it cannot find a control
     No Service Mode            channel.
     Ringing                    The mobile is emitting a ringing signal.
                                The vehicle speed exceeds the limit imposed by the scanner's sample rate
     Vehicle Speed              adaptation algorithm (based on wavelength)




Hand Over Analysis:

Definitions

- internal HO : the handover execution is controlled by the BSC (only intracell and intercell-intra-BSC
HO).
- external HO : the handover execution is controlled by the MSC (necessary for all intercell-inter-BSC
HO, possible for intercell-intra-BSC HO).
- intracell HO : handover between two channels of the same cell.
- intercell HO : handover between two channels of adjacent cells. The old channel belongs to the
serving cell, the new channel to the target cell.
- intra-BSC HO : the serving cell and the target cell belong to the same BSC.
- interzone HO : intracell handover between the inner zone and the outer zone of a concentric cell
configuration.
- intrazone HO : intracell handover within a zone (inner or outer) of a concentric cell configuration.
- directed retry : handover from SDCCH to TCH when the serving cell is congested at the starting
time of the assignment procedure.

HO Types:

 Handover Cause              Situation of Emergency                 Better conditions
 Intracell handover          Emergency Intracell Handover           Better Zone Handover
 Intercell handover          Emergency Intercell Handover           Handover Better Cell Handover




Case of intercell handovers - Emergency intercell handover
These handovers are triggered when the call conditions deteriorate significantly in order to rescue the
call.

The causes are:

- "quality too low"
- "level too low"
- "distance too long from serving cell"
- "consecutive bad SACCH frames"
- "level crossing high threshold"

The “quality” and “level too low” causes are only triggered when the MS or BS power has reached the


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maximum allowed value.
Handover on "too low level" is used to avoid situations where the interference level is low, while the
attenuation is quite high. These conditions may appear for example in big city streets which enable a line of
sight propagation from the BTS antenna. There is in this case a risk of abrupt quality degradation, if the MS
moves away from the line of sight street.
"Distance too long" is provided to prevent macrocells from extending too far out the planned borders,
thus creating a risk for abrupt call degradation and also uplink interferences. This is typical near the
river banks of big cities (canyon effect).
"Bad SACCH frames" and "level dropping under high threshold" are provided to support the rapidly
varying radio conditions of microcellular environment (e.g. street corner effect). In order to have a
sufficient reaction time these causes are independent of the power used by the MS or BTS.
For all these causes, the handover algorithm must privilege the call continuation over the resource
optimization.

Case of intercell handovers - Better cell handover
These handovers are triggered to improve the overall system traffic capacity.
This spans:
interference reduction,
signaling load reduction,
traffic unbalance smoothing.

The basic assumption for these handovers is that they should respect the cell planning decided by the
operator.
In a well configured network, the majority of the handover should be of the better cell type.
For conventional cell environment, they correspond to the cause "power budget".
For concentric cell environment, the cause "power budget" is applied in the inner zone as well as in
the outer zone.
For hierarchical cell environment:
- between cells of the same layer : "power budget"
- from higher to lower layer : "good received level in one overlaid cell",
- from lower to higher layer : no special cause, but the detection that a MS is fast enough, based
on the residence time in an overlaid cell.
For multi-band network, the cause "preferred band" is triggered between two cells which use different
frequency bands.
The main drawback of this handover category is the risk of "ping-pong" effect, which is an oscillating
back and forth handover between two (or three) cells. As the "better cell" handover are meant to find
the "best cell", the variation of the radio conditions will trigger a big amount of better cell handovers,
if the algorithms have a too sensitive reaction. Hence, some mechanisms are forecast, in order to
prevent these oscillations from occurring repeatedly at given places.




Case of intracell handovers - Emergency intracell handover

Emergency handover is triggered for intracell application when the radio link is deemed to suffer a
high level of interference. In this case, the channel assigned to the call is changed for another
channel in the same cell, on which the measured interference level is the smallest possible.
In the case of concentric cell environment, emergency intracell handovers concern handovers from
the inner to the outer zone of the same cell (they are called interzone handovers) as well as
handovers performed within one zone (they are called intrazone handovers).

Case of intracell handovers - Better zone handover
For concentric cells, the "outer zone uplink and downlink level too high" cause forces an intracell
handover from an outer zone TCH to an inner zone TCH. This handover is considered as interzone
handover.




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Functional entities of handover preparation

The handover preparation is in charge of detecting a need for handover and proposing a list of target
Cells.
Therefore it can be divided into two processes :
       -handover detection - process analyses the radio measurements reported by the BTS and triggers
       the candidate cell evaluation process each time a handover cause (emergency or better cell type) is
       fulfilled.

        -handover candidate cell evaluation - works out a list of possible candidate cells for the handover.
        This list is sorted according to the evaluation of each cell as well as the layer they belong to (in a
        hierarchical network) and the frequency band they use (in a multiband network).

Once the handover preparation is completed, the handover decision and execution is performed under the
MSC or BSC control.
Also, the directed retry preparation is performed by the handover preparation function.
Once the directed retry preparation is completed, the directed retry is performed under the BSC
control.

The handover preparation requires indirectly input parameters provided by the function in charge of the radio
link measurements.
Most of the input data required by the handover functions are provided by a function “ Active
channel pre-processing”. It processes raw data given by the radio link measurements (quality, level
and distance).

Obs: The operator has the possibility to inhibit selectively the different handover causes via O&M
commands on a cell basis.




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 Handover causes                                                                                #      Type
 Too low quality on the uplink                                                                  2      Emenrgency
                                                                                                       Cause
 Too low level on the uplink                                                                    3      Emenrgency
                                                                                                       Cause
 Too low quality on the downlink                                                                4      Emenrgency
                                                                                                       Cause
 Too low level on the downlink                                                                  5      Emenrgency
                                                                                                       Cause
 Too long MS-BS distance                                                                        6      Emenrgency
                                                                                                       Cause
 Several consecutive bad SACCH frames received (rescue microcell handover)                      7      Emenrgency
                                                                                                       Cause
 Too low level on the uplink, inner zone (inner to outer zone handover, concentric cell)        10     Emenrgency
                                                                                                       Cause
 Too low level on the downlink, inner zone (inner to outer zone handover, concentric            11     Emenrgency
 cell)                                                                                                 Cause
 Power budget                                                                                   12     Better Condition
 Too high level on the uplink and the downlink, outer zone (out. to in. zone hand.,             13     Better Condition
 concentric cell)
 High level in neighbour lower layer cell for slow mobile                                       14     Better Condition
 Too high interference level on the uplink                                                      15     Emenrgency
                                                                                                       Cause
 Too high interference level on the downlink                                                    16     Emenrgency
                                                                                                       Cause
 Too low level on the uplink in a microcell compared to a high threshold                        17     Emenrgency
                                                                                                       Cause
 Too low level on the downlink in a microcell compared to a high threshold                      18     Emenrgency
                                                                                                       Cause
 Forced Directed Retry                                                                          20     Better Condition
 High level in neighbour cell in the preferred band                                             21     Better Condition




Directed retry preparation

1 System aspects

The directed retry consists in an SDCCH to TCH intercell handover during the call set-up process.
The directed retry is triggered when given radio conditions are met and the serving cell is congested.
The handover to TCH in another cell reduces the call set-up time (queuing phase) and allows the
sharing of resources from one cell with another, thus overcoming traffic load unbalance.


The directed retry may be performed :
- either on handover alarms : If a handover alarm is detected during queuing, and the candidate cell
evaluation process indicates at least an internal or external cell, then the BSS will perform a
directed retry .
- or on alarm of forced directed retry : If during queuing, an internal neighbour cell is reported with a
sufficient level and has free TCH, then the BSS will perform a directed retry .
The expression "Forced directed retry" refers to this case, because the radio conditions in the
serving cell do not represent a need for handover. The cause which leads to forced directed retry is
assimilated to a "better condition cause" in the handover preparation.
This difference on alarms has an impact on the interference level in the network :
- directed retry on handover alarms : After this kind of directed retry, the MS is very likely in the best
cell. The best cell is the one where both required BS and MS transmitted powers are minimized and
consecutively the induced interference in the network.


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- forced directed retry : Considering that :
- In general, the cell the MS is camping on (i.e. as the result of the cell selection process) is the
"best cell",
- the directed retry traffic is located at the edge of the handover area of the target cell


The traffic due to forced directed retry has a high probability to be located inside the emergency
zone of the previously serving cell. Therefore it may cause an increase to the planned level of
interference. This is the drawback for the overall network capacity improvement.

For the sake of simplification :
- two cells are considered (i.e. there is only one target cell). BS1 is the serving cell and BS2 is the
target cell,
- both cells have the same maximum transmit powers for MS and BS,
- both cells have the same minimum level for Cell selection access (RXLEV_ACCESS_MIN) and the same
minimum level for handover access.
- the only cause for handover is Power Budget, with no handover margin.

The directed retry preparation is supported:
- by the same processes as the handover preparation for directed retry on handover alarms,
- by a specific condition in the alarm detection process (new cause pertaining to forced directed retry)
and a specific candidate cell list evaluation process for forced directed retry.

The detection process for directed retry consists in the checking of the handover alarms and of the
forced directed retry alarm.
If an alarm for forced directed retry is raised, then the target cell evaluation is performed by the
candidate cell evaluation process for forced directed retry.
For all other alarms, the target cell evaluation is performed by the candidate cell evaluation process
for handover (ORDER or GRADE).
Note : The intracell handover alarms (inter-zone or due to interference) are ignored by the cell
evaluation process.

Directed retry on handover alarms
The preparation of directed retry on handover alarms is performed by the handover preparation
function. All the processes of this function operate in the same way as for preparation of SDCCH or
TCH handover at the exception of the candidate cell evaluation process.


The candidate cell evaluation process (ORDER or GRADE) looks for target cells so as to do an
SDCCH to TCH handover.
TCH load in neighbor cells may be used for target
cell evaluation and ranking (the TCH load is not known in case of external cells).
Note : in case of handover preparation, the candidate cell evaluation process looks for target cells so
as to do a SDCCH handover. The SDCCH load is not taken into account.

Forced directed retry
The preparation of forced directed retry is composed of two processes:
- forced directed retry detection,
- candidate cell evaluation.
The forced directed retry detection requires specific preprocessed measurements, see section 3.1.
The detection is performed every SACCH measurement reporting period when preprocessed
measurements are available.
The averaged received levels of all neighbor cells are compared to a threshold. If one or several
cells are found with a received level higher than the threshold, an alarm of forced directed retry is
raised : high level in a neighbor cell for forced directed retry. This cause is included in the "better
condition causes" of the handover preparation.
When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, to
the candidate cell evaluation process for forced directed retry if there is no handover alarm raised at
the same time. A handover alarm raised at the same time is prior and is sent to the candidate cell



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evaluation process ORDER or GRADE.
Then, the candidate cell evaluation process looks for cells :
a. where the MS can communicate,
b. where the received level at MS is higher than a given threshold,
c. and which have a minimum number of TCH channels free (in case of internal cell).
The condition b. allows the control of the interference level in the network.
The condition c. is a means to forbid "retry traffic" from a congested cell to a neighbor cell if the
neighbor cell has less than a minimum number of channels free. This condition controls the amount
of "retry traffic" and therefore the additional interference generated by this type of traffic.




ANNEX 1: Optimizations Parameters (Alcatel Implementation for 900/1800MHz Bands)

Rxlev access min (Idle Mode) :

This parameter concerns only the MS.
Rule : The parameter of selection C1 should be null while the measured level by the MS is equal to its
sensitivity.
In Urban, the utilised MS are mostly of type « 2W » and of sensitivity lower or equal to -102dBm.
For 900, in Urban case, Rxlev access min = -102dBm
For 900, in Rural, we assume a use of mobiles of type « 8W » and we admit a Rxlev access min = -108 dBm.

Concerning the 1800 macro cells, since the L_RXLEV_DL_H causes HO at signal strength bellow -99 dBm
and -95 dBm (according if the cell is hopping or not), the Rxlev access min is set to -95 dBm.
Therefore, it minimizes the situations where the MS do call set-up at a low level and leaves immediately in
downlink level alarm.

Handover threshold on low downlink and uplink level:

To make uniform this parameter setting, we admit a sensitivity of -102 dBm for all the MS without distinction
2W/8W. Moreover, the actual performances in reception of the G3 BTS permit us to admit a sensitivity of
-111 dBm for the G3 today versus -104 dBm for the G1 BTS and -108 dBm for the G2 (environment of TU50
and Rxqual 6).

In relation to these thresholds of sensitivity, a rxqual margin [ Rxqual 6 -> Rxqual 4 = 3dB ] and a fading
margin [ TU50 -> TU3 = 0dB with SFH and 3dB w/o SFH] is taken to determine the threshold for DL and UL
level alarms in 900 MHz. :

+ 3 dB in case of use of frequency hopping
+ 6 dB without frequency hopping




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For the uplink, the use of the diversity on the site introduces -3 dB in the benefit of the sensitivity, and a
penalty of 10dB in case of 900 LNA use.
-3dB with diversity
+10 dB with LNA

In last point, a correction factor of 1 dB is used to take into account the fact that the Alcatel algorithms trigger
HO when the ENT( average measure) is strictly inferior to the threshold. For example, if the threshold is
-99dBm, the HO is triggered to -100dBm or lower when we want a HO at -99dBm. Therefore, 1 dB is added to
trigger HO at -99dBm or lower.

+1dB correction factor

For the 1800 cells, the same rule is applied.

Finally:

L Rxlev DL H= -102 + 3+ 1 = -98 dBm with frequency hopping

L Rxlev DL H = -102 + 6 + 1= -95 dBm without frequency hopping

L Rxlev UL H900(G3900) = -111 +3 -3+1= -110 dBm -> -110 dBm with SFH and diversity/ -100 avec LNA.
In fact, in this particular case, no uplink level alarm can be triggered.
L Rxlev UL H900(G3900) = -111 + 3+1 = -107 dBm with frequency hopping and without diversity/ -97 avec
LNA
L Rxlev UL H 900(G3900) = -111 + 6 -3 +1= -107 dBm without frequency hopping and with diversity/ -97 avec
LNA
L Rxlev UL H 900(G3 900) = -111 + 6 +1 = -104 dBm without frequency hopping and without diversity/ -94
avec LNA

L Rxlev UL H900(G2 900) = -108 +3-3+1 = -107 dBm with frequency hopping and diversity/ -97 avec LNA
L Rxlev UL H900(G2 900) = -108 + 3+1 = -104 dBm with frequency hopping and without diversity/ -94 avec
LNA
L Rxlev UL H900(G2 900) = -108 + 6 -3+1 = -104 dBm without frequency hopping and with diversity/ -94 avec
LNA
L Rxlev UL H900(G2 900) = -108 + 6 +1 = -101 Bm without frequency hopping and without diversity/ -91 avec
LNA

L Rxlev UL H900(G1 900) = -104 + 3 -3 + 1= -103 dBm with frequency hopping and diversity/ -93 avec LNA
L Rxlev UL H900(G1 900) = -104 + 3 + 1= -100 dBm with frequency hopping and without diversity/ -90 avec
LNA
L Rxlev UL H900(G1 900) = -104 + 6 -3 +1= -100 dBm without frequency hopping and with diversity/ -90 avec
LNA
L Rxlev UL H900(G1 900) = -104 + 6 + 1= -97 dBm without frequency hopping and without diversity/ -87 avec
LNA
L Rxlev UL H900 (M1M and M1C 900) = -97 + 6 +1 = -90 dBm without frequency hopping and without diversity
L Rxlev UL H900 (M4M) = -107 + 6 + 1= -100 Bm without frequency hopping and without diversity
L Rxlev UL H1800 (G3 1800) = -111 + 3 -3 +1 = -110 dBm with frequency hopping and diversity.
L Rxlev UL H1800 (G3 1800) = -111 + 3 +1= -107 dBm with frequency hopping and without diversity.
L Rxlev UL H1800 (G3 1800) = -111 + 6- 3+1 = -107 dBm without frequency hopping and diversity.
L Rxlev UL H1800 (G3 1800) = -111 + 6 +1= -104 dBm without frequency hopping and without diversity.


PC thresholds on the ULlevel :

Since the thresholds of HO on the UL level have changed, the UL thresholds of PC should change also to be
in agreement with those of HO. The rule applied is based on HO level +8 dB for having the L_RXLEV_UL_P
and +16dB for the U_RXLEV_UL_P.

Quality HO threshold :


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These thresholds should be tuned to trigger the HO when the average Rxqual reaches 4 without frequency
hopping and 5 with frequency hopping (the Rxqual of 5 with frequency hopping activated is equivalent in
audio quality to 4 without frequency hopping).

For the Alcatel BSS, the algorithms use the entire part of the Rxqual average and strict inequalities.
example if we desire to trigger with a Rxqual 4 :
Assumption: Average Rxqual measured = 4.6 -> entire part = 4
                     If the threshold is set to 4, the algorithm do not trigger HO since the value is not strictly
superior to 4. Therefore, the threshold should be set to 3.

We propose to set these thresholds to 3 in all cases (900 or 1800).
In case of cell not hopping, this threshold is adapted.
In case of hopping cell (SFH BBH or synthetised), an offset OFFSET_HOPPING_HO available in B5.1 is
added to the quality alarms thresholds L_RXQUAL_UL_H = L_RXQUAL_DL_H = 3 according to that the TS is
hopping or not ( OFFSET_HOPPING_HO).
We set OFFSET_HOPPING_HO positioned to +1 which results in quality alarms thresholds of 4 for the TS
which are hopping and without impact if the TS are not hopping. With BBH, all the timeslots of the cell use the
« 3+1 » threshold. With synthesised FH, the timeslots on the BCCH TRX use « 3 » and the timeslots on the
other TRX use « 3+1 ».

Finally:
L_RXQUAL_UL_H = L_RXQUAL_DL_H = 3
OFFSET_HOPPING_HO = +1

PC thresholds on the UL quality :

U_RXQUAL_UL_P is changed to 1 on the 900 macros cells to allows reduction of the MS power in case
where the Rxqual measured is 0 and the level is over L_RXLEV_UL_P+2dB.
This modification is introduced in order to have a homogeneous parameter setting between the
manufacturers.

L_RXQUAL_UL_P should be adjusted to the L_RXQUAL_UL_H - 1
This value is set to 2 (3 - 1) .
With SFH, the « OFFSET_HOPPING_PC » is used for the TS which are hopping. It is set to +1, and then PC
uses 3 with SFH.

Average windows in level, PBGT and DR :

The concern is to uniform the parameter setting between all classes of 900 macro cells.
A_LEV_HO and A_PBGT_HO are chosen to be identical and set to 6 for all the classes of 900 and 1800
macros.

A_PBGT_DR is set to 4 to allows a quick FDR in case of activation of this feature.

Extension of the maximum number of neighbours :

The NBR_ADJ is changed to 64 . The GSM norm authorise a maximum number of 32 channels on the both
band (900 + 1800 Mhz) broadcasted by the BSS and measured by the MS.
In case that in the same band (900Mhz or 1800Mhz), more than 32 neighbours are necessary , having a
neighbour list of 64 offers the possibility to have more than 32 neighbours with the condition of a maximum of
32 channels (2 neighbours can have the same channel but identified by a different BSIC).

Normally, the Alcatel OMC or/and BSC should refuse more than 32 channels broadcasted on the network
( control of coherence made) . For example, the case of 25 channels in 900Mhz and 15 channels in 1800
Mhz is forbidden by the BSS.

Full balanced power of the µcells :




             This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version    Page

                                                                                                 1.0       24


It is chosen , today, to use full balanced power of µ cells in order to increase the coverage and increase the
traffic.
Knowing that the M1M and M1C have a maximum output power of 27 dBm, this value will not change for this
case.
However, for the M2M and M4M, we propose to use an higher power.

Neihbouring Cell valuation: Rxlevmin(n)

We propose to set Rxlevmin(n) equal to L_Rxlev_DL_H, the low threshold for the downlink level HO. On this
HO cause, it seems better to go to cell having at least the same level. To go to a cell with a lower level could
quickly produces a new alarm HO.
In fact, as the comparison is strict, the level of the target cell will have more than 1 dB than L_Rxlev_DL_H of
the originating cell.




Introduction of the Ho_margin of qual and lev between couples of cells :

The B5 release introduces a filtering process if the flag EN_PBGT_FILTERING is enable before the process
of evaluation of the candidates neighbours ORDER and GRADE (used for all the causes excepted for cause
20) :

. PBGT(n)> HO_MARGIN_XX(0,n) + Cause_Margin_P_X
       - with HO_MARGIN_XX(0,n) = HO_MARGIN_QUAL(0,n) if cause=2,4 or 7
       - with HO_MARGIN_XX(0,n) = HO_MARGIN_LEV(0,n) if cause=3,5,6,17 or 18
       - with HO_MARGIN_XX(0,n) = HO_MARGIN(0,n) if cause 12

 In order to come nearer to the parameter setting of the others suppliers, the B5 parameter setting changes by
introducing the HO_MARGIN_QUAL(0,n) and HO_MARGIN_LEV(0,n) by couple of cells instead of using the
HO_MARGIN(0,n) + cause_Margin_P_X (cell parameter which is used for all the neighbour as in the B4
behaviour).
By this way, we have a higher flexibility of optimisation and control of the chosen neighbours.

Since we propose to use the HO_MARGIN_QUAL(0,n) and HO_MARGIN_LEV(0,n) for the causes 2,4,3,5
and 6, it is no more necessary to have Cause_Margin_P_X and are voluntary changed to 0.

In B4, the process of GRADE was including the criteria :
PBGT(n) > HO_MARGIN + Cause_Margin_P_X
In B5, the process of GRADE doesn’t contain this criteria and is replaced by the filtering conditions presented
above when the EN_PBGT_FILTERING is enable.
In B4 as in B5 , the process of ORDER applied on the µcells was not containing any filtering conditions.
In B5, we propose to have on all the cells the EN_PBGT_FILTERING enabled (concern of an homogeneous
parameter setting) and to use very negative values of HO_MARGIN_QUAL and HO_MARGIN_LEV if we
want to avoid filtering.

Therefore, new tables of the crossed parameters are introduced between the layers and adapted for an
expected behaviour [ HO_MARGIN(0,n); HO_MARGIN_LEV(0,n); HO_MARGIN_QUAL(0,n);
LINK_Factor(0,n); PRIORITY(0,n) ].

We have to take care of the difference between the L_Rxlev_DL_H of the originating cell and the Rxlevmin(n)
of the target cell. The idea is to have HO_margin_lev(0,n) coherent with this difference.
Therefore, we propose to set the HO_MARGIN_LEV(0,n) like follows

HO_MARGIN_LEV(0,n) = Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1)

By putting the values set in the tables, the following behaviour is expected :




             This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version     Page

                                                                                                 1.0        25


- On the M900 cells :
         - For comfort HO, capture HO occurs on the 900 µ cells or on the M1800 cells and PBGT happens
between M900 cells.
         - In case of urgency HO, the MS is redirected preferably on the best M900 cell over Rxlevmin(n) and
satisfying the criterion of Ho_margin_lev(0,n) = Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) or
Ho_margin_qual(0,n) = -2dB. Otherwise, in a second priority the µ900 over Rxlevmin(n) and satisfying the
criterion of Ho_margin_lev(0,n)= Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) and Ho_margin_qual(0,n)=-127
and in last choice the M 1800 over Rxlevmin(n) and under the criterion of Ho_margin_lev=-127 and
Ho_margin_qual=-127

- On the µ900 cells :
         - For comfort HO, capture HO occurs on the M1800 cells and PBGT happens between µ900 cells.
         - In case of urgency HO, the MS is redirected preferably on the best M900 cell over Rxlevmin(n) and
satisfying the criterion of Ho_margin_lev(0,n) =-127dB or Ho_margin_qual(0,n) = -127dB. Otherwise, in a
second priority the µ900 over Rxlevmin(n) and satisfying the criterion of Ho_margin_lev(0,n)= Max (-2,
Rxlevmin(n) - L_Rxlev_DL(0)+1) and Ho_margin_qual(0,n)=-2 and in last choice the M 1800 over
Rxlevmin(n) and under the criterion of Ho_margin_lev=-127 and Ho_margin_qual=-127

Suppression of templates :

The suburb 900 macro template is no more justified by a real need of a specific parameter setting. We
proposes to suppress it and to replace it either by an urban template, either by the rural one according to its
environment.

The Umbrella macros 900 templates only differs from the normal macros 900 only by the fact that the cause
14 is inhibited or not.
In the case there is no micros cells under a macro cell with cause 14 activated, since there is no cells of layer
type « lower » as neighbour, the behaviour of the network is the same that with the cause 14 inhibited.
Therefore, we propose to replace the Simple Dense Urban parameter setting by the templates Umbrella
Dense Urban.


The Dense Urban templates differs from the Urban templates, by the fact that the load factor are used in the
Dense Urban templates when there are not used in the Urban templates.
We proposes to merge these templates in one with the load factors used by default.

Finally, on the macro cells, there is no more than 2 classes (Urban and Rural) with thresholds of levels alarms
and levels PC different according to the BTS used, the diversity and LNA use.

Introduction of the synchronised HO in the grid :

WITH_SYNCHRONISED_HO: enables synchronised HO, set to 1

Change of name of some parameters :

In B5, CELL_LAYER_TYPE replaces CELL_COVERAGE _TYPE and can take 3 states, « lower , « upper »
or « single ».

Then, the 900 micros cells takes the values of « lower » and replace 2 for « recovered » and the 900 macros
cells are set as « upper » and replace 1 for « umbrella ».

L_RXLEV_CPT_HO(n) replaces L_RXLEV_OCHO(n) and is used as capture threshold for the cause 14 (µ
cell neighbour) and is also utilised for the cause 21 (1800 neighbour).

Introduction of new parameters (excepted dual band parameters) :

EN_IM_ASS_REJ: enables the use of the immediate assignement reject, set to 1
EN_SEND_OLD_CHAN_MODE: enables the transmission of the used speech version to the target BSS, set
to 1



             This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version   Page

                                                                                                1.0      26


DTX_INDICATOR_SACCH: defines the uses of the dtx in TCH/HR or/and TCH/FR.
FREQUENCY RANGE: indicates which range is used in the cell: P-GSM, DCS1800, E-GSM, DCS1900. Can
only be readen since the value is set by the equipment affected to the cell (P-GSM, GSM 1800 BTS, ...). Do
not appear in the grid
OFFSET_HOPPING_PC and OFFSET_HOPPING_HO: an offset can be used. It’s added to the low rxqual
threshold for the trx using SFH.

Change of some timers :

T8 (=3103): those timers are used in the process who allows the mobile to come back on the old channel
after a handover fail. Their new value is 15 s (old value = 12 s)

T(conn-est): it a SCCP timer. When the message « connection request » is sent, a message like « Connexion
Confirm » or « Connection refused » is expected. If it doesn’t occur, when this timer is out, the connexion
process is cancelled. Its new value is 5s (old value = 12 s)

T(rel): it a SCCP timer. It normaly used by the MSC in the release of a SCCP connection. The message
« Released » is sent to the BSC and the MSC waits the message « Release complete ». If this acknowledge
isn’t received, « Released » is sent again. But in anormal case, the BSC can use this timer to release itself
this connection. Its new value is 5 s (old value = 15 s)

New timers :

These 4 timers set any delays between the « Assignement reject » and a new sending of « Channel request »
WI_CR: cause « call reestablishment »
WI_EC: cause « emergency call »
WI_OC: cause « originating call »
WI_OP: cause « other procedures »

These parameters are set by default to 5s before optimisation.


Introduction of the dual band feature :


      Impact of the dual band activation on the existing classes in 900Mhz :

      We recommend, by default, the dual band feature activation, on all the 900 cells and all the Alcatel
      BSC of France for the following reasons :
       . This feature should be activated , every where, even on BSc without 1800 neighbours to allows later
      HO on the 1800 layer during the call when the MS has initiated a call on a BSc far away from the dual
      band zone.
       . In case of special needs of capacity of traffic to cover a temporary event or a permanent hot spot, no
      parameter setting adjustments are necessary to open a dual band zone. A simple integration of 1800
      cells is sufficient.

      Of course, in no way, the activation of the dual band feature has impact in the behaviour of the 900 MS.
      Moreover, the dual band MS has the same behaviour than a 900 MS in case there is no 1800 cells.

       To reach this goal, the following parameters are necessary on all the Alcatel BSCs for an unlocking
      of the dual band feature :

      . EN_INTERBAND_NEIGH : BSC lock of the broadcast of all the opposite band neighbours (set to 1 to
        enable)
      . PREFERRED_BAND : BSC parameter that specifies which band is preferred for inter-band
      handovers (set to 2 for GSM 1800).
      . LOAD_EV_PERIOD : DLS parameter (hardly coded) that specifies the number of time necessary for
      the calculation of the load_average of the cell (set to 60s).




            This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version     Page

                                                                                          1.0        27


. Activation of the Early Classmark sending on the Alcatel BSC :
           - ECSC (DLS basis) : set to 1 for enabling the early classmark sending of the dual band MS
           - EN_SEND_CM3 : set to 1 in order to allows the sending of the CM3 to the NSS .
           - STRIP_O5_CM2 : set to 0 for having no change of the octet 5 of CM2 IE being passed to
the MSC.

The modifications on all the Alcatel cells for an unlocking of the dual band feature are the following :

  . EN_PREFERRED_BAND_HO : This new parameter is a cell lock of the preferred band HO 900 ->
1800 cause 21 (set to 1 on all the 900 cells to enable dual band HO). Set to 0 on the 1800 cells since it
is unnecessary.
          . MULTI_BAND_LOAD_LEVEL : Threshold of load in the 900 serving cell which enables a
dual band HO (set to 0%).
          . L_RXLEV_CPT_HO(n) : Used for the cause 14 and 21. On the 1800 cells, it corresponds to
the signal strength threshold which allows a dual band HO (-85 dBm). On the µ900, it is the capture
threshold from M900 to µ900.
          . MULTI_BAND_REPORTING : (Specs GSM 04.08; broadcasted on the Sys_Info5ter layer 3
message) set to 1 on the 900 cells to allows that the dual band MS reports to the BSS, measurements
on the best neighbour in 1800. In case, there is no 1800 cell as neighbour, the MS still report the 6 best
neighbours in 900 Mhz.

The management of the dual band HO by Alcatel is done by the introduction of the cause 21 on the
900 cells (HO toward the preferred band by capture). The cause is triggered under the following
conditions :
          . AV_LOAD(0)>MUTIBAND_LOAD_LEVEL (average % of busy TCH)
          . AV_RXLEV_NCELL(n)>L_RXLEV_CPT_HO(n) + max(0, MSTXPWR_MAX(n) -P)

AV_RXLEV_NCELL(n) is calculated with a averaging window of A_PBGT_HO size. The A_PBGT_HO
is using the available samples and filling the resting with 0 (-110dBm).
The interband HO could be possible also by the use of the cause 14. However, the timer of triggering
are also applied to the M1800, delaying the capture process. Possibility recommended for the µ1800.

In B5, the evaluation process of the candidates neighbours has changed for the management of a
multi-layer dual band network and is conducted as followed :

    • 1) List and first ranking of the neighbours :
         • for "better cell" HO :
               • pref_layer = none ; all the neighbours that satisfy the HO cause (cause12, cause 14,
                  cause20 and cause 21)
              • pref_layer = upper; while the cell is cell_layer_type= lower, the HO cause is 12 and
                  the MS_SPEED=fast
         • for "rescue" HO , all the neighbours with the preferences :
              • pref_layer = upper if cell_layer_type=lower and en_recue_um=enable
              • pref_layer=lower if cell_layer_type=lower and en_rescue_um=disable
              • none if cell_layer_type=lower and en_rescue_um=indefinite
               • upper+single if cell_layer_type=upper
    • 2) Ranking of the neighbours by priority order (highest to lowest):
         • preferred layer (value of pref_layer)
         • priority(0,n)
         • same frequency band than the serving cell
         • process of evaluation ORDER(n) or GRADE(n)(excepted for cause 20)
              • cell_ev=0 (ORDER)
                     • if en_load_order=enable, order(n)=PBGT(n)+LINKfactor(0,n)+FREEfactor(n)-
                         FREEfactor(0)-HO_MARGIN_XX(0,n)
                     • if en_load_order=disable or external HO, order(n)=PBGT(n)+LINKfactor(0,n)-
                         HO_MARGIN_XX(0,n)


      This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version   Page

                                                                                                1.0      28


                           • Av_rxlev_ncell(n)>Rxlevmin(n)+max(0;ms_txpwr_max(n)-P)

                     • cell_ev=1 (GRADE)
                          • if en_load_order=enable, grade(n)=PBGT(n)+LINKfactor(0,n)+LOADfactor(n)-
                               LOADfactor(0)+FREEfactor(n)-FREEfactor(0)
                           •   if en_load_order=disable, grade(n)=PBGT(n)+LINKfactor(0,n)
                           •   Av_rxlev_ncell(n)>Rxlevmin(n)+max(0;ms_txpwr_max(n)-P)
                           •   GRADE(n)>DISTmargin+Cause_Margin_G_X


          • 3) A filtering process can take place (EN_PBGT_FILTERING=enable) before the process of
             GRADE or ORDER (excepted for cause 20):
                 • PBGT(n)> HO_MARGIN_XX(0,n) + Cause_Margin_P_X
                 • with HO_MARGIN_XX(0,n) = HO_MARGIN_QUAL(0,n) if cause= 2, 4 or 7
                 • with HO_MARGIN_XX(0,n) = HO_MARGIN_LEV(0,n) if cause=3,5,6,17or 18
                 • with HO_margin_XX(0,n) = HO_MARGIN(0,n) if cause 12
                 cause_margin_P_14=-127dB; cause_margin_P_21=-127dB (to avoid filtering in PBGT
                     and simulate a capture process)


       For having dual band HO from µ900 or M900 to the 1800 neighbours, new crossed neighbour
      relations are introduced to M1800 from collocated, surrounding M900 and µ900 which are
      overlapped by the M1800 cells.
      The parameters specifics to the neighbour relation are :

      . HO_MARGIN(0,n)= HO_MARGIN_QUAL(0,n)=HO_MARGIN_LEV(0,n)= -127 dB
      . LINKFACTOR(0,n) = 0dB
      . PRIORITY(0,n) = 0

      when the 1800 cell parameters used in the neighbour relation are :
      RXLEV_MIN(n)=L_RXLEV_DL_H=-98dBm (SFH) or -95dBm (w/o hopping); L_RXLEV_CPT_HO(n)=
      -85dBm; LOADfactor1-5(n)=0dB; FREEfactor1-5(n)=0dB; L_RXLEV_NCELL_DR(n)=-47dBm;
      FREELEVEL_DR(n)=127


      According to the process of ranking and filtering developed above and the parameters used in the
      neighbour relation to the M1800 cells, the expected behaviour for dual band MS on µ900 and M900 is
      the following :

     •  Expected behaviour on the µ 900:
                 - On call set-up, SDCCH900 ->TCH 900 (no FDR activated)
                 - In case of urgency HO, the MS is redirected preferably on the best M900 cell over
                 Rxlevmin(n) and satisfying the criterion of Ho_margin(lev et qual = -127). Otherwise, in
        second priority the µ900 over Rxlevmin(n) and the criterion of Ho_margin(lev , qual               =-
2dB) since M1800 and µ900 have the same priority and in last choice the M1800 over                 Rxlevmin(n)
and the criterion of Ho_margin(lev and qual = -127).
                 - In PBGT, a capture on the 1800 M cell occurs (cause 21) on the best 1800M cell above -
                 85dBm

     • Expected behaviour on the M 900:
                - On call set-up, SDCCH900 ->TCH 900 (no FDR activated)
                - In case of urgency HO, the MS is redirected preferably on the best M900 cell ( consideration
                of load taking into account by the LOADFACTOR effect in the process of Grade) over
                Rxlevmin(n) and satisfying the criterion of Ho_margin(lev ; qual=-2dB). Otherwise, in
       second priority the µ900 over Rxlevmin(n) and satisfying the criterion of Ho_margin(lev            ;
qual=-127) since M1800 and µ900 have the same priority and in last choice the M1800               over
Rxlevmin(n) and under the criterion of Ho_margin(lev=-127 and qual=-127).


            This document is Nexius Wireless Inc. property and cannot be reproduced without permission
Reference                  Version   Page

                                                                                          1.0      29


          - In PBGT, a capture on the 1800 M cell occurs (cause 21) on the best 1800M cell above -
          85dBm. Otherwise, a capture cause 14 HO occurs on a µ900.


Introduction of a new class of cell (macro 1800 cells) :

The parameter setting of the M1800 cells are common to those of M900 cells of dense urban class
excepted for the following specific parameters :



. CELL_LAYER_TYPE : The 1800 cell is declared as « lower » with EN_RESCUE_UM=ENABLE.
Thus, in case of rescue HO, pref_layer=upper and the best ranked cells are the M900 (same behaviour
than the µ900). agressiveness to encourage HO on preferred band (1800).
. CELL_EV= ORDER and EN_LOAD_ORDER=DISABLE As for the µcells, we chose order in the
evaluation process and no consideration of load ( FREE_FACTOR )in the choice of the neighbours for
outgoing HOs from the 1800 cells. No consideration of load between the 1800 cells in the Grade
process from M900 cells (LOAD_FACTOR 1-5=0dB).
. MULTI_BAND_REPORTING (Specs GSM 04.08; broadcasted on the Sys_Info5ter layer 3 message)
set to 3 on the 1800 cells to allows that the dual band MS reports to the BSS, measurements on the 3
best neighbour in 900 and 3 neighbours in 1800.). This choice is made in order to favour the HO on the
1800 neighbours without to compromise a rescue HO on the 900 layer.
  . BS_TXPWR_MAX, BS_TXPWR_MAX_INNER of the 1800 cell is proposed to be identical to that
the collocated 900 cell for the case where there is 900 indoor cell that we can’t declare as neighbour of
the Umbrella 1800 cell (due to the limitation of 32 neighbours in the 900 neighbour list that could be
reached) . Therefore, the pass from the M1800 to Indoor 900 could be done in 2 steps through the
M900 cells.
  . MS_TXPWR_MAX, MS_TXPWR_MAX_INNER, MS_TXPWR_MAX_CCH of the 1800 cells is set to
30dBm that is the maximum power that can be used on the 1800 band.
  . U_TIME_ADV is the alarm threshold on timing advance on 1800 and is set to 2.2 km. For an
average timing advance over 4 (5=2.7km), an alarm in distance is triggered. This is the only way, with
Alcatel to control the service range of the M1800 cells

 . The C2 parameters is applied only on the 1800 cells in order to favour the reselection on the 1800
cells even and while the signal strength is bellow the 900 cells.
          - CELL_RESELECT_PARAM_IND : lock per cell that enable the broadcast of C2 cell
 reselection parameters on the BCCH of the cell (set to 1).
          - CELL_RESELECT_OFFSET : set to 16 dB. M1800 cells are favoured of 16 dB but the
 effective favour weight is bellow and around 9dB since the Rxlevaccesmin
 of the M1800 is upper the M900.
          - PENALTY_TIME : set to 0 = 20s (identical to that in 900)
          - TEMPORARY_OFFSET : set to 0dB (identical to that in 900). No penalty is applied on
 the M1800 cells
          - RXLEV_ACCESS_MIN : set to -95 dBm . The MS can camp on the M1800
 cell only if the C1>0 (Rxlev>-95dBm).

 . Since the dual band MS are « forced » to camp on the M1800 cells, it is recommended to activate,
by default, the Forced Directed Retry on the M1800 cells in case of saturation of the M1800 cells :
          - EN_FORCED_DR (per cell basis) : set to 1 and allows the Forced Directed Retry on the
neighbours
          - EN_DR (per cell basis) : set to 1. For unlock the DR and FDR from the M1800 cells on the
neighbours

 In case of congestion of the M1800 cells, the process of the neighbour choice is as followed :

List of the neighbours :
     • AV_RXLEV_NCELL_DR(n)> L_RXLEV_NCELL_DR(n)
Filtering and Ranking of the neighbours :
     • AV_RXLEV_NCELL_DR(n)>RXLEVmin(n)+max(0,MSTXPWR_MAX(n)-P)

      This document is Nexius Wireless Inc. property and cannot be reproduced without permission
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Gsm kpi

  • 1. Reference: - Version: 1.0 Date: 9/22/2004 Last page: 25 Final status: [-] GSM KPI File name: Domain: GSM KPI Draft.doc GSM Training GUIDE Author(s): Cristian Iordache Distribution List: Public x Internal Restricted Confidential AUTHORIZED STATUS TYPE • GENERAL PROCEDURE • DRAFT x CREATION x • ORGANISATIONAL PROCEDURE • REVIEWED MODIFICATION • TECHNICAL PROCEDURE • APPROVED CANCELLING • STANDARDS, MANUALS, REPORTS x Quality Review: Quality Supervisor / Quality Correspondent SIGNATURE STAMP Name/Function Quality Supervisor Quality Correspondent Reviewed By: FUNCTION NAME DATE SIGNATURE Approved By: FUNCTION NAME DATE SIGNATURE DISTRIBUTION LIST (When document is in final status) COMPANY ATTENTION TO NUMBER OF COPIES MODIFICATIONS HISTORY Creation Creation for the document Update Update Update This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 2. Reference Version Page 1.0 2 CONTENTS: 1. Introduction 2 2. GSM PARAMETERS/KPI 2 3. GSM Indicators Description 4 3.1 RX_LEV_DL 7 3.2 RX_QUAL 8 3.3 SQI 8 3.4 C/I 9 3.5 PATH LOSS 11 4 .1 EVENTS 12 ANNEX 1: Optimizations Parameters (Alcatel Implementation for 900/1800MHz Bands) 14 ANNEX 2. GSM OPTIMZATION PARAMETERS 24 ANNEX 3: Ericsson TEMS Information Parameters List Implementation 24 ANNEX 4: MS Power Classes 24 Bibliography 25 This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 3. Reference Version Page 1.0 3 GSM KPI PRESENTATION 1. Introduction In GSM technology which is in this moment a fully grown technology with a high complexity of the standard, the provisional assessment of a network requires tools that could provide a full array of information both in start-up phase or optimization. Comparative network benchmark tool has to be able to provide an accurate list of Key Performance Indicators (KPI) that could be use for competitor networks using both GSM and other technologies. The results could be used then in planning, installation or optimization process. Radio Network Optimization based on measurement analysis is a part of the global process that allows a healthy network operation. The measurement sessions forms the "active part" of the job on the radio part of a running network, while Quality of Service Monitoring is the "detection & filtering part". QoS Monitoring activates Fine Tuning when weaknesses or troubles are detected on the network behavior, and more generally to improve the Quality of Service statistics. The optimization process has to handle and solve the omissions from each of the previous steps of the network start-up history. Then in GSM, according to high complexity of the standard, the provisional assessment of a network is more difficult, hence the probability to encounter omissions is higher. The optimizations process is based on the analysis of the information from the system statistic reports, and also on a cross check with the network description made during the previous stages. The goal is to optimize the network behaviour and to solve local problems. The main activities are: • Radio Coverage problem investigation, dealing with Air interface, on MS and Infrastructure side, • Telecom parameters optimization, dealing with the network behaviour in Idle and Dedicated mode, • Traffic load distribution and congestion reduction. This requires specific external jobs: • MS monitoring, using Air and Abis interfaces Monitoring (Test phones, Abis interfaces and adequate SW. • Quality of Service Monitoring (analyze of Network Statistics), which is a basic source/target of Fine Tuning and thus a strong help to locate troubles. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 4. Reference Version Page 1.0 4 The radio problems are identified through different processes: • by the GSM operator, analyzing end user complaint about faults/difficulties/quality on the calls. The complaint is dealt by the "Customer Care Centre" who sort the complaints, then correlate the problem with already known origin/area or detect new problems. • by a "Mobile Station Monitoring" (Drive-test, walk-test, Scan) during a measurements campaign. • by a data analysis following an Abis interface monitoring. • by the "Quality of Service Monitoring" compiling statistics from the OMC-R indicators and A interface monitoring. Once the solution has been found, it is put in a list of proposed modifications to the network. This list includes the proposed parameter modifications issued from the System Parameter Check process. The modifications description and the way they are performed are decided after a common discussion between Network Planning, Radio Optimization and O&M personnel. Then a work order is sent to the organization/team in charge of the modification as stated for the solution: aerial adjusting or positioning, radio parameter settings... The main methodology action items used in optimization process are: • to identify measurement routes (these routes will still be used after the network start-up, as long as the coverage remain the same), • to run systematic measurements on Air Interface, using test tools • to produce different types of plot maps (coverage, quality, ...), • to identify radio problems and work out corrections, • to issue a complete network status document compliant with GSM operator's expectations. Obs: There it is also a particular process also called "Cell Verification and Acceptance" that occurs only at the end of site installation. The goal is to validate the BTS sites location and configuration, as implemented on the basis of RNP specifications. This check is done using real Air interface measurements. The final goal of this process is to put the local network in accordance with the "Quality and Radio Coverage Contract" defined with the GSM operator. Mobile Station/Test Tool Monitoring This activity requires the same competencies as for" Cell Verification". The goal is to check the network performance on the Air interface segment. But since it is run on an operating network, it can be performed either on a regular basis by an operator's team or punctually by an auditor's team. MS Monitoring deals with all the drive tests. The main activities are: • to conduct air interface measurements on pre-defined routes adapted to the network evolution, • to produce typical plot maps (showing radio coverage, quality, etc.), • to locate radio problems. (The test tool results can also be used in order to make corrections of the propagation model prediction tool software) A GSM test tool should be able to perform as following: • to scan/record/process the absolute (analog) GSM bands (Spectrum analysis in 850, 900, 1800, 1900MHz) • to scan/record every operator using a SIM for each one • to read the CGI and all the other GSM Layer 1, 2 and 3 parameters • to measure/record/process the performance parameters both in Idle or Dedicated Mode • to force a specific ARFCN, cell barring, etc. • to provide accurate measurements. (Re-calibration feasible) • to record the measurements geographically based in such a way that the information could be exported and post- processed by other tools (ex MapInfo, Excel, etc) 2. GSM KPI List This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 5. Reference Version Page 1.0 5 For an efficient GSM Network assessment using drive tests equipment it is important to be able to select the most significant downlink parameters and to use the an array of quantified thresholds. It is well known that each wireless service provider has its own quality standards (coverage thresholds, GoS, etc) conducing to more or less subjective results. There it is even a bigger challenge to create a universal tool that is able to make competitive tests for different technologies with different approaches for subscriber’s QoS assessment. In to the list shown below are presented the most relevant parameters used in GSM: Quality Indicators: RX_LEV – Received Signal Level both in “Idle” and “Dedicated” mode (DL) [dBm] Signal Strength on BCCH Carrier, indicating the signal strength on the current BCCH. This element is especially useful for obtaining a correct measure of the cell size when frequency hopping is used and power control is applied to the TCH’s and for general coverage assessments. RX_QUAL – Received Signal Quality, a measure of speech quality measured based on BER analysis, both in “Idle” and “Dedicated” mode SQI – Speech Quality Indicator (an additional parameter introduced by Ericsson on their tool TEMS in order to obtain a more accurate image of the voice quality than the one offered by RX_QUAL) TX_PWR – Transmission Power Level (DL – from BTS, UL from MS). In order to reduce interference, the power is continuously tuned both in the BTS radios and in MS. It may vary in case of MS with a step of 2 dB up or down. C/I – Carrier to Interference ratio - indicating the carrier-to-interference ratio for each channel in the hopping list (and for each timeslot with multi-slot allocation). OBS: "Full" and "Sub" Values: - Information elements with "Full" in their names are calculated on all blocks. - Information elements with "Sub" in their names are calculated only on the blocks known to be sent also when downlink DTX is active (in each 104-multiframe, one TCH block with SID information and one SACCH block). TA - Timing Advance, a calculated parameter based on the group delay measurements that appear due to distance used in order to keep the UL and DL TS synchronisation. Statistic Indicators: % Call Attempt Rate % Call Success Rate % Blocked Call Rate % Good Initialization Rate % Drop Calls Rate % No Service Rate % Good/Failed HO Rate % HO Type (Intra/Inter Cell, Intra/Inter BSC) % HO cause Rate % Location Area Update Success Rate Evens: Blocked Call Call Attempt This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 6. Reference Version Page 1.0 6 Call End Call Established Call Setup Cell Reselection Dedicated Mode Dropped Call Handover Handover (Intra-cell) Handover Failure Handover Intra-cell Failure Idle Mode Limited Service Mode Location Area Update Location Area Update Failure No Service Mode Ringing Vehicle Speed Network/Cell Identifiers: MCC (Mobile Country Code), MNC (Mobile Network Code) LAC (Location Area Code) CI Cell I.D. CGI (Cell Global Identity) = MCC+MNC+LAC+CI BSIC = NCC (Network Colour Code) + BCC (BS Colour Code) ARFCN = Absolute RF Channel 3. GSM Indicators Description: 3.1 RX_LEV_DL It is a RF indicator who shows the average signal level at the input of the MS’s receiver. In Idle mode it indicates the received signal strength from the BCCH physical channel, and in traffic it indicates the signal strength measured on the current ARFCN channel used for TCH/SDCCH transport. This element is especially useful for obtaining a correct measure of the cell size when frequency hopping is used and power control is applied to the TCH’s and for general coverage assessments. Signal Strength on Hopping List, indicating the signal strength of each channel in the hopping list. This element gives more information than RxLev, which is an average over all channels in the hopping list. The following paragraph is an brief description of those features used in GSM design using as an input data, information’s related to RX_LEV: RxLev-based Thresholds: The handover margin represents the necessary overlap between two cells in ensuring the handover with the good quality of the communication. This margin depends on the environment as follows: - In indoor environment the handover is not necessary, so the handover margin is 0 dB. - In outdoor environment the handover margin is typically 2 dB. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 7. Reference Version Page 1.0 7 - In High Speed Train (ex. TGV) environment the handover margin is typically 2 dB. Another restriction of this particular case is the overlap length greater than 600 m between two neighbor cells. The design margin is corrects two main errors that can appear during the design and prediction process: - Prediction Tool S/W prediction error and - Penetration loss evaluation error – in the case of an indoor service - A cumulative value for the design margin with a 90% probability is 6 dB. The design, the prediction and the measure of the service area of a cell will be done with an equilibrated power budget or with a not equilibrated power budget with the downlink better than the uplink (DL-UL>0). If in the power budget the downlink is worst than the up-link (DL-UL<0) then the design thresholds will be adjusted with the max (0, DL-UL [dBm]) value. *Note that the considerations presented before take into account the method used by the prediction tool which calculates only the strength of the downlink signal. The design threshold is the threshold used to design the cells and is defined as the strength of the predicted signal at the limit of the cell which assures the service inside the cell and the handover with the neighborhood cells. Design threshold = Mobile handset sensitivity + Fading / Sensitivity margin + BTS output power margin + Penetration losses + Handover margin + Design margin at 90% + max (0, DL-UL) The prediction threshold is the threshold used to predict the coverage of a cell and is defined as the strength of the predicted signal at the limit of the cell which assures the service inside the cell. Prediction threshold = Mobile handset sensitivity + Fading / Sensitivity margin + BTS output power margin + Penetration losses + Design margin at 90% + max (0, DL-UL) Prediction threshold = Design threshold - Handover margin The measure threshold is the threshold used to measure the received signal in outdoor environment. For outdoor services: Measure threshold = Design threshold - Design margin at 90% - Handover margin For indoor services: Measure threshold = Design threshold - Design margin at 90% - Handover margin + Indoor penetration margin at 90% This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 8. Reference Version Page 1.0 8 The following table summarizes the design, prediction and measure thresholds fore several representative services. SERVICE DESIGN THRESHOLD PREDICTION OUTDOOR MEASURE AT 90% THRESHOLD THRESHOLD AT 90% Indoor Deep - 63 dBm - 63 dBm - 66 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Indoor Light - 71 dBm - 71 dBm - 74 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Indoor in High Speed - 71 dBm - 73 dBm - Trains +max(0, DL-UL) +max(0, DL-UL) Indoor Window - 77 dBm - 77 dBm - 80 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Outdoor In-car - 79 dBm - 81 dBm - 86 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Outdoor - 85 dBm - 87 dBm - 92 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Outdoor Car-kit - 88 dBm - 90 dBm - 95 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Outdoor 8W - 93 dBm - 95 dBm - 100 dBm +max(0, DL-UL) +max(0, DL-UL) +max(0, DL-UL) Notes: - The services marked in bold (Indoor Deep, Indoor Light, Outdoor In-car and Outdoor) are used by RF designers - For indoor coverage the thresholds to use will be Indoor Deep for cities having dense high buildings or Indoor Light for small towns. - For coverage on roads the thresholds to use will be Outdoor In-car. Types of Service Analysis based on RX_LEV measurements and tresholds: In order to ensure a generic design standard permitting good quality communication inside the cells, depending on the environment several types of service can be defined. The description of several types of service is presenting in following table: SERVICE DESCRIPTION OF THE SERVICE Indoor Deep In 90% of the surface of the ground floor of the building it is possible to have good quality communication using a 2W handset. Indoor Light In 90% of the surface of the ground floor of the building (having visibility with the windows) it is possible to have good quality communication using a 2W handset. Indoor in High In the seats of the train it is possible to have a good quality communication using a 2W Speed Trains (Ex: handset. TGV) Indoor Window In 90% of the surface of the ground floor of the building (near the windows) it is possible to have good quality communication using a 2W handset. Outdoor In-car In 90% of the outdoor surface it is possible to have good quality communication using a 2W handset inside a car. Outdoor In 90% of the outdoor surface it is possible to have good quality communication using a 2W handset. Outdoor Car-kit In 90% of the outdoor surface it is possible to have good quality communication using a 2W handset inside a car equipped with car-kit. Outdoor 8W In 90% of the outdoor surface it is possible to have good quality communication using an 8W handset. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 9. Reference Version Page 1.0 9 For each environment the penetration loss, the design margin and the handover margin can be estimated statistically as follows: SERVICE Penetration losses Design margin Handover at 90% margin Indoor Deep 23 dB - Indoor concrete penetration losses 6 dB 0 dB 6 dB – Head effect Indoor Light 15 dB – Indoor intermediary penetration losses 6 dB 0 dB 6 dB – Head effect Indoor in High Speed 14 dB – Ex: TGV penetration losses 5 dB 2 dB Trains 6 dB – Head effect Indoor Window 6 dB – Indoor light penetration losses 6 dB 0 dB 6 dB – Head effect Outdoor In-car 6 dB – Car penetration losses 5 dB 2 dB 6 dB – Head effect Outdoor 0 dB – Penetration losses 5 dB 2 dB 6 dB – Head effect Outdoor Car-kit 0 dB – Penetration losses 5 dB 2 dB 3 dB – Car-kit equipment losses 0 dB – Head effect (not present) Outdoor 8W 0 dB – Penetration losses 5 dB 2 dB 3.2 RX_QUAL It is a measure of speech quality measured based on BER analysis. RxQual is obtained by transforming the bit error rate (BER) into a scale from 0 to 7 (see GSM 05.08). In other words, RxQual is a very basic measure: it simply reflects the average BER over a certain period of time (0.5 s for TEMS tools). In a low disturbed area (e.g. a rural cell) a very low received field could be encountered without a big degradation of the speech quality. On the other end, in an urban area, a good received field doesn’t however allow a good communication because of a high interference level. That is why a quality assessment is done on the basis of the bit error rate in the messages (RX_QUAL), on UL and DL. Range: 0…7 <integer> Good quality communication is defined as a communication characterized by a value of RXQUAL parameter better than 4 for a cell without frequency hopping and better than 5 for a cell with frequency hopping. Note: When FH is activated, RX_QUAL is impacted: the measured bit error rate becomes worse (usually by about 1 unit) because of two reasons: 1 – in the BER computation – at the moment of hopping, the reception radio synthesizer looses systematically a few synchronization bits, which impacts the low BER values. 2- because of the averaging effect of the interference levels This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 10. Reference Version Page 1.0 10 3.3 SQI SQI - “Speech Quality Index” is an indicator that has been designed by Ericsson for their TEMS investigation tool to take into consideration all the phenomena omitted by RX_QUAL indicator (Bit error distribution, Speech Frame erasures, HO effects, Speech codec type). This ensures that it will produce an unbiased prediction of the speech quality, independently of channel conditions and other circumstances. Somewhat roughly, the computation of SQI involves: - the bit error rate (BER) - the frame erasure rate (FER) - data on handover events - statistics on the distributions of each of these parameters. Furthermore, for each speech codec, SQI is computed by a separate algorithm which is tuned to the characteristics of that codec. Like RxQual, SQI is updated at 0.5 s intervals (in TEMS tools). To give some examples of what the relation may look like, the graph below is included. It shows SQI as a function of RxQual for the EFR codec and a number of channel conditions. (It must be kept in mind that the curves represent time-averaged RxQual-to-SQI relations; individual segments of speech may of course deviate from these.) Note the considerable differences between the various channel conditions. Ex: for the same Speech Quality (SQI) of 15 the RxQual may vary from 3 for an urban/No FH area to ~6 in one area with FH. 3.4 C/I This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 11. Reference Version Page 1.0 11 The carrier-over-interference ratio is the ratio between the signal strength of the current serving cell and the signal strength of undesired (interfering) signal components. The C/I measurement function enables the identification of frequencies that are exposed to particularly high levels of interference, something which comes in useful in the verification and optimization of frequency plans. Usually C/I measurement is made in dedicated mode. It is however also possible to measure C/I in idle mode. This is handy when interacting with a test transmitter which simulates a base station but is not capable of setting up calls. It should be pointed out that the sampling rate and hence the quality of idle mode C/I values is critically dependent on the settings governing quality measurement in idle mode Downlink quality in a radio network can be monitored using Speech Quality Index, SQI. In this way, areas with inadequate speech quality can be identified. However, if frequency hopping is used in the network, it is difficult to pinpoint the frequencies that are affected by the degradation. To help resolve such ambiguities, C/I indicator offers the possibility of measuring average C/I for each of the frequencies used in a call. To obtain a correct C/I estimate, one must take into account the possible use of power control and/or discontinuous transmission (DTX). In the past, rough C/I measurements have sometimes been carried out by comparing the BCCH signal power of the serving cell with that of neighbouring cells using the same traffic channels (but different BCCHs). Since such a scheme fails to allow for power control and DTX on the TCHs, it may produce misleading results. There should be considered these network functions to be able to indicate the actual C/I experienced by the mobile station. In dedicated mode, average C/I is presented twice a second, which is equal to the ordinary measurement interval. If frequency hopping is employed, the average C/I for each frequency is presented. The measurement range extends from -5 dB to +25 dB. A C/I below -5 dB can be regarded as highly unlikely; in addition, if the number of hopping frequencies is low, C/I values below this limit would normally result in a dropped call. Beyond the upper limit, the speech quality is not further improved. Hence, the limitation of the measurement range is not a restriction. If downlink DTX is used, the number of bursts transmitted from the base station to the mobile station may be lower than the maximum, depending on the speech activity level on the transmitting side. Then the measurements should be made only on the bursts actually sent from the base station and disregards burst not transmitted. The number of hopping frequencies determines the number of bursts used for the C/I measurement on each frequency. For example, if four frequencies are used, 25 bursts (on average) per frequency are received in each 0.5 s interval. With more frequencies, there are fewer bursts for each frequency. This implies that the accuracy of the measurements is better for small sets of hopping frequencies. If true C/I is within the range 0 to 15 dB and four frequencies are used for transmission, and there are no DTX interruptions, the measurement error is typically smaller than 1 dB. To illustrate the use of C/I, data from a test drive is depicted in the figure below. The test drive lasts 40 seconds. EFR speech coding and cyclic frequency hopping with four frequencies is employed throughout. The upper part of the graph shows SQI and RxLev, while the lower part shows C/I for each of the four frequencies: This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 12. Reference Version Page 1.0 12 As appears from the upper graph, SQI dips sharply towards the end of the test drive (after 35 s), and indicating poor speech quality. On the other hand, RxLev stays about 50 dB above -110 dBm the whole time. This means that the dip in quality is not due to low signal power level, that is, the quality problem is to do with interference rather than coverage. In fact, and interestingly, RxLev increases during the SQI dip, probably because the power of the interferer increases. Now, looking at the C/I graph, one sees that two of the four frequencies (the thick lines) have a C/I worse than 10 dB during the SQI dip. This explains the poor speech quality, identifying precisely which channels are disturbed. Such information can then be utilized in the process of optimizing the frequency plan for the area. The interference scan consists in mobile locking on the BCCH ARFCN of the disturbed cell and scanning the ARFCN of the traffic channel that is exposed to interference. Note that these two may be the same. The main task performed by the identification algorithm is to determine the Base Station Colour Code (BCC) of the interfering signal, i.e. the second digit of the BSIC (=NCC+BCC). Obs: If BCC is known this fact reduces the number of possible interferers by a factor of 8. This is because BCC can take integer values from 0 to 7 (it written and transmitted on a 3-bit length sequence) as is a part of BSIC (Base Station Identity Code = NCC + BCC = 3 bit+ 3 bit, where NCC = National Color Code or "PLMN color code"). So if we know BSIC/BCC, we can restrict the search for interferers. BSIC is transmitted in the SCH (and not in BCCH) as a “color code” (like the coloring of maps, unique for every cell in one area), so that BTS with same beacon frequency (BCCH ARFCN ch.) use different BSIC. MS gets from the BTS a list of beacon frequencies to be monitored through BCCH logical channel. In measurement report, MS reports BSIC of the monitored cells. C/I index is measured for each of the ARFCN RF physical cannel that are involved in hopping list of the server cell. The MS is doing the C/I measurements during the other Time Slots (TS) that are not allocated to him. These frequencies should be different than those that appear in the neighbor list(!). In idle mode the MS reads the BSIC too, in order make sure that it is still monitoring the same cell. Therefore, knowing the BCC reduces the number of possible interferers by a factor of 8. This is a great step forward; but even so, the network will normally contain several cells with this BCC, all of which make use of the disturbed ARFCN as BCCH or TCH. Other means must therefore be used to shorten the list of candidates further. Fortunately, such means are readily available: Many sites proposed as candidates can usually be ruled out simply because they are too far away, or because they have their antennas pointing away from the disturbed cell. During the scan the timing offset between the serving cell and the interferer is determined. This offset can also be measured by other means, and the scan offset can then be compared with measured offsets to nearby cells. In practice, using one or both of these approaches, it is almost invariably possible to point out the exact source of the interference. There are many possible causes of poor C/I values. Two common ones are co-channel and adjacent channel interference. In certain circumstances, however, the main problem is not interference from other callers, but the fact that the signal is overwhelmed by assorted random disturbances -- i.e. what is usually called "noise". This means thermal noise generated within the circuits of the mobile station, as well as external background noise from a plethora of sources, including other man-made signals so faint that they merely add up to a quasi-random disturbance. Example of typical C/I degradation due to noise: {(C/I) worst<10dB} AND {RxLev_Sub<99dBm} The following event gives a rough indication that the poor C/I is probably due to a noise problem: the poor C/I coincides with a very low signal strength. The following table summarizes the C/I* acceptable values: CHANNEL MINIMUM C/I* BCCH/SDCCH 14 dB TCH without frequency hopping 14 dB This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 13. Reference Version Page 1.0 13 TCH with frequency hopping 12 dB (9dB in some networks) 3.5 PATH LOSS The rough Definition of Path Loss – DL and UL: PL_DL = BS_TXPWR – RX_LEV_DL + LDL BS_TX_PWR = BTS Transmission Power RX_LEV_DL = RF signal level received by MS LDL = Sum of gains/losses and RX_MS_Sensitivity PL_UL = MS_TX_PWR – RX_LEV_UL + L_UL MS_TX_PWR = MS Transmission Power RX_LEV_UL = RF signal level received by BTS L_UL = Sum of gains/losses and RX_TRX_Sensitivity The following tables present the values that must be considered in power budget calculation for downlink and respectively uplink: = LOSS / GAIN LOSS / GAIN VALUE Propagation losses = BTS emitter power BTS output power downlink - BTS emitter power tolerance 1 dB typical value - Duplexer losses Specified by the duplexer supplier - Feeder losses Must be calculated function of the type and the length of the feeder - LNA losses Specified by the LNA supplier - Power splitter losses Specified by the power splitter supplier EIRP + BTS antenna gain Specified by antenna supplier - Penetration losses Depends on the type of service - Fading / Sensitivity margin 3 dB typical value + Handset sensitivity -102 dBm for 2W handsets -104 dBm for 8 W handsets - Design margin at 90% Depends on the type of service = LOSS / GAIN LOSS / GAIN VALUE Propagation losses = Mobile handset emitter power 2 W for 2W handsets and uplink 8 W for 8W handsets. - Mobile handset emitter power 1 dB typical value tolerance - Penetration losses Depends on the type of service - Fading / Sensitivity margin 3 dB typical value + BTS antenna gain Specified by antenna supplier + Diversity gain 3 dB typical for space diversity rural environment 3 dB typical value for polarisation diversity in urban environment This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 14. Reference Version Page 1.0 14 - Feeder losses Must be calculated function of the type and the length of the feeder - Duplexer losses Specified by the duplexer supplier + LNA gain Specified by the LNA supplier + BTS sensitivity Specified by the BTS supplier - Design margin at 90% Depends on the type of service Power budget equation The Power budget criterion PBGT is used to estimate the difference of path loss between two neighboring cells. PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO - (BS_TXPWR_MAX - BS_TXPWR) - (MS_TXPWR_MAX(n) - MS_TXPWR_MAX) - PING_PONG_MARGIN(n,call_ref) with : - AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO or A_PBGT_DR measurements (neighbor cell(n)). - AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUB over A_PBGT_HO or A_PBGT_DR measurements (serving cell). - BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS). - BS_TXPWR : last BS_POWER value reported by the BTS in the message MEASUREMENT RESULT (mode B) or last BS_TXPWR value reported by the BTS in the message PREPROCESSED MEASUREMENT RESULT (mode A). - MS_TXPWR_MAX(n) : max power level the MS is allowed to use in its neighbor cell(n). - MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell. - PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if : it is the immediately precedent cell on which the call has been, this cell belongs to the same BSC as the serving cell, the call has not performed a forced directed retry towards the serving cell, less than T_HCP seconds have elapsed since the last handover. In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP., If the call was not precedent on cell n, or if the preceding cell was external, or if the call has just performed a forced directed retry, or if the timer T_HCP has expired, then PING_PONG_MARGIN(n,call_ref) = 0 With abstraction of the PING_PONG_MARGIN, which is purely a handicap given to the preceding cell for a certain time, the PBGT can be described in two steps : BCCH = AV_RXLEV_NCELL(n) - (AV_RXLEV_PBGT_HO + C) with C = BS_TXPWR_MAX - BS_TXPWR. BCCH corresponds to the difference of received BCCH signal levels. A correction factor C is taken into account for the serving cell, because the received signal level (i.e. AV_RXLEV_PBGT_HO) may not be measured on BCCH, Then, another correction factor must be taken into account because the maximum BS powers of the serving and neighboring cells may be different : ######TXPWR = MS_TXPWR_MAX(n) - MS_TXPWR_MAX. As the first step of calculation is based on the downlink parameters, this correction factor should be based on the maximum BS powers used in the serving and neighboring cells. Two reasons (which are not completely de-correlated) for not using the BS powers can be envisaged: - for a given cell, the GSM does not specify formally the maximum BS power of the neighboring cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface), - it is not easy for the evaluating BSC to know the maximum BS powers of the neighboring cells. The use of the maximum MS powers requires that the difference of MS powers is equal to the This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 15. Reference Version Page 1.0 15 difference of BS powers. This condition is met in most cases. If it is not the case, the difference can be corrected by the operator with the HO_MARGIN(0,n) parameter (HO hysteresis). PBGT >0 : the neighbour cell is more advantageous as the path loss is less than in the current cell. PBGT <0 : the serving cell is more advantageous as the current cell. The PBGT equation (without temporary handicap) can be interpreted in another way. PBGT = ###BCCH - ###TXPWR The PBGT is a balance or a trade-off between two opposite indicators. As a matter of fact : ### ###BCCH > 0 : the neighboring cell n is more advantageous than the serving cell as the reception of BCCH is better. ### ###BCCH < 0 : the neighboring cell n is more disadvantageous than the serving cell. ### ###TXPWR > 0 : the neighboring cell n is more disadvantageous than the serving cell as the maximum permissible power of the MS is higher. ### ###TXPWR < 0 : the neighboring cell n is more advantageous than the serving cell. The PBGT can be seen as a balance, at MS side, between a probability to have a better reception and the probability of requests of transmission at higher levels in the neighboring cells. 4 .1 EVENTS – Predefined and user-defined events: The events detected by a GSM terminal can be identified based on identification of “trigger” values or ranges of the GSM indicators: Choose information element (See Annex 3). Information element Argument If the information element has an argument, specify it here. Value: Changed Choose this to trigger the event whenever the value of the selected information element changes. Choose this to trigger the event when the selected information element Value: Threshold assumes, exceeds or drops below a certain value. Choose a threshold operator ("=", ">", or "<"), and set the threshold value. The basic list of events to be considered is presented in the table below: It was not possible to establish a call, for example because all traffic Blocked Call channels are busy. A traffic channel has been requested (through the Layer 3 message "Channel Request"). (Note that the request may also be for a signaling channel, in which case no call is actually attempted; the two types of Call Attempt request cannot be distinguished.) The call has been terminated (triggered by the Layer 3 message Call End "Disconnect"). A call has been established (triggered by the Layer 3 message "Connect Call Established Acknowledge"). A call has been set up by the mobile (triggered by the Layer 3 message Call Setup "Alerting"). Cell Reselection Reselection to a new control channel has taken place. Dedicated Mode The mobile has entered dedicated mode. Dropped Call The established call has been terminated abnormally. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 16. Reference Version Page 1.0 16 Handover Successful inter-cell handover. Handover (Intracell) Successful intra-cell handover. Handover Failure An attempted inter-cell handover failed. Handover Intracell Failure An attempted intra-cell handover failed. Idle Mode The mobile has entered idle mode. Limited Service Mode The mobile has entered limited service mode (emergency calls only). Location Area Update The mobile has changed location areas. Location Area Update Failure The mobile failed in changing its location area. The mobile has entered No Service mode, since it cannot find a control No Service Mode channel. Ringing The mobile is emitting a ringing signal. The vehicle speed exceeds the limit imposed by the scanner's sample rate Vehicle Speed adaptation algorithm (based on wavelength) Hand Over Analysis: Definitions - internal HO : the handover execution is controlled by the BSC (only intracell and intercell-intra-BSC HO). - external HO : the handover execution is controlled by the MSC (necessary for all intercell-inter-BSC HO, possible for intercell-intra-BSC HO). - intracell HO : handover between two channels of the same cell. - intercell HO : handover between two channels of adjacent cells. The old channel belongs to the serving cell, the new channel to the target cell. - intra-BSC HO : the serving cell and the target cell belong to the same BSC. - interzone HO : intracell handover between the inner zone and the outer zone of a concentric cell configuration. - intrazone HO : intracell handover within a zone (inner or outer) of a concentric cell configuration. - directed retry : handover from SDCCH to TCH when the serving cell is congested at the starting time of the assignment procedure. HO Types: Handover Cause Situation of Emergency Better conditions Intracell handover Emergency Intracell Handover Better Zone Handover Intercell handover Emergency Intercell Handover Handover Better Cell Handover Case of intercell handovers - Emergency intercell handover These handovers are triggered when the call conditions deteriorate significantly in order to rescue the call. The causes are: - "quality too low" - "level too low" - "distance too long from serving cell" - "consecutive bad SACCH frames" - "level crossing high threshold" The “quality” and “level too low” causes are only triggered when the MS or BS power has reached the This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 17. Reference Version Page 1.0 17 maximum allowed value. Handover on "too low level" is used to avoid situations where the interference level is low, while the attenuation is quite high. These conditions may appear for example in big city streets which enable a line of sight propagation from the BTS antenna. There is in this case a risk of abrupt quality degradation, if the MS moves away from the line of sight street. "Distance too long" is provided to prevent macrocells from extending too far out the planned borders, thus creating a risk for abrupt call degradation and also uplink interferences. This is typical near the river banks of big cities (canyon effect). "Bad SACCH frames" and "level dropping under high threshold" are provided to support the rapidly varying radio conditions of microcellular environment (e.g. street corner effect). In order to have a sufficient reaction time these causes are independent of the power used by the MS or BTS. For all these causes, the handover algorithm must privilege the call continuation over the resource optimization. Case of intercell handovers - Better cell handover These handovers are triggered to improve the overall system traffic capacity. This spans: interference reduction, signaling load reduction, traffic unbalance smoothing. The basic assumption for these handovers is that they should respect the cell planning decided by the operator. In a well configured network, the majority of the handover should be of the better cell type. For conventional cell environment, they correspond to the cause "power budget". For concentric cell environment, the cause "power budget" is applied in the inner zone as well as in the outer zone. For hierarchical cell environment: - between cells of the same layer : "power budget" - from higher to lower layer : "good received level in one overlaid cell", - from lower to higher layer : no special cause, but the detection that a MS is fast enough, based on the residence time in an overlaid cell. For multi-band network, the cause "preferred band" is triggered between two cells which use different frequency bands. The main drawback of this handover category is the risk of "ping-pong" effect, which is an oscillating back and forth handover between two (or three) cells. As the "better cell" handover are meant to find the "best cell", the variation of the radio conditions will trigger a big amount of better cell handovers, if the algorithms have a too sensitive reaction. Hence, some mechanisms are forecast, in order to prevent these oscillations from occurring repeatedly at given places. Case of intracell handovers - Emergency intracell handover Emergency handover is triggered for intracell application when the radio link is deemed to suffer a high level of interference. In this case, the channel assigned to the call is changed for another channel in the same cell, on which the measured interference level is the smallest possible. In the case of concentric cell environment, emergency intracell handovers concern handovers from the inner to the outer zone of the same cell (they are called interzone handovers) as well as handovers performed within one zone (they are called intrazone handovers). Case of intracell handovers - Better zone handover For concentric cells, the "outer zone uplink and downlink level too high" cause forces an intracell handover from an outer zone TCH to an inner zone TCH. This handover is considered as interzone handover. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 18. Reference Version Page 1.0 18 Functional entities of handover preparation The handover preparation is in charge of detecting a need for handover and proposing a list of target Cells. Therefore it can be divided into two processes : -handover detection - process analyses the radio measurements reported by the BTS and triggers the candidate cell evaluation process each time a handover cause (emergency or better cell type) is fulfilled. -handover candidate cell evaluation - works out a list of possible candidate cells for the handover. This list is sorted according to the evaluation of each cell as well as the layer they belong to (in a hierarchical network) and the frequency band they use (in a multiband network). Once the handover preparation is completed, the handover decision and execution is performed under the MSC or BSC control. Also, the directed retry preparation is performed by the handover preparation function. Once the directed retry preparation is completed, the directed retry is performed under the BSC control. The handover preparation requires indirectly input parameters provided by the function in charge of the radio link measurements. Most of the input data required by the handover functions are provided by a function “ Active channel pre-processing”. It processes raw data given by the radio link measurements (quality, level and distance). Obs: The operator has the possibility to inhibit selectively the different handover causes via O&M commands on a cell basis. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 19. Reference Version Page 1.0 19 Handover causes # Type Too low quality on the uplink 2 Emenrgency Cause Too low level on the uplink 3 Emenrgency Cause Too low quality on the downlink 4 Emenrgency Cause Too low level on the downlink 5 Emenrgency Cause Too long MS-BS distance 6 Emenrgency Cause Several consecutive bad SACCH frames received (rescue microcell handover) 7 Emenrgency Cause Too low level on the uplink, inner zone (inner to outer zone handover, concentric cell) 10 Emenrgency Cause Too low level on the downlink, inner zone (inner to outer zone handover, concentric 11 Emenrgency cell) Cause Power budget 12 Better Condition Too high level on the uplink and the downlink, outer zone (out. to in. zone hand., 13 Better Condition concentric cell) High level in neighbour lower layer cell for slow mobile 14 Better Condition Too high interference level on the uplink 15 Emenrgency Cause Too high interference level on the downlink 16 Emenrgency Cause Too low level on the uplink in a microcell compared to a high threshold 17 Emenrgency Cause Too low level on the downlink in a microcell compared to a high threshold 18 Emenrgency Cause Forced Directed Retry 20 Better Condition High level in neighbour cell in the preferred band 21 Better Condition Directed retry preparation 1 System aspects The directed retry consists in an SDCCH to TCH intercell handover during the call set-up process. The directed retry is triggered when given radio conditions are met and the serving cell is congested. The handover to TCH in another cell reduces the call set-up time (queuing phase) and allows the sharing of resources from one cell with another, thus overcoming traffic load unbalance. The directed retry may be performed : - either on handover alarms : If a handover alarm is detected during queuing, and the candidate cell evaluation process indicates at least an internal or external cell, then the BSS will perform a directed retry . - or on alarm of forced directed retry : If during queuing, an internal neighbour cell is reported with a sufficient level and has free TCH, then the BSS will perform a directed retry . The expression "Forced directed retry" refers to this case, because the radio conditions in the serving cell do not represent a need for handover. The cause which leads to forced directed retry is assimilated to a "better condition cause" in the handover preparation. This difference on alarms has an impact on the interference level in the network : - directed retry on handover alarms : After this kind of directed retry, the MS is very likely in the best cell. The best cell is the one where both required BS and MS transmitted powers are minimized and consecutively the induced interference in the network. This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 20. Reference Version Page 1.0 20 - forced directed retry : Considering that : - In general, the cell the MS is camping on (i.e. as the result of the cell selection process) is the "best cell", - the directed retry traffic is located at the edge of the handover area of the target cell The traffic due to forced directed retry has a high probability to be located inside the emergency zone of the previously serving cell. Therefore it may cause an increase to the planned level of interference. This is the drawback for the overall network capacity improvement. For the sake of simplification : - two cells are considered (i.e. there is only one target cell). BS1 is the serving cell and BS2 is the target cell, - both cells have the same maximum transmit powers for MS and BS, - both cells have the same minimum level for Cell selection access (RXLEV_ACCESS_MIN) and the same minimum level for handover access. - the only cause for handover is Power Budget, with no handover margin. The directed retry preparation is supported: - by the same processes as the handover preparation for directed retry on handover alarms, - by a specific condition in the alarm detection process (new cause pertaining to forced directed retry) and a specific candidate cell list evaluation process for forced directed retry. The detection process for directed retry consists in the checking of the handover alarms and of the forced directed retry alarm. If an alarm for forced directed retry is raised, then the target cell evaluation is performed by the candidate cell evaluation process for forced directed retry. For all other alarms, the target cell evaluation is performed by the candidate cell evaluation process for handover (ORDER or GRADE). Note : The intracell handover alarms (inter-zone or due to interference) are ignored by the cell evaluation process. Directed retry on handover alarms The preparation of directed retry on handover alarms is performed by the handover preparation function. All the processes of this function operate in the same way as for preparation of SDCCH or TCH handover at the exception of the candidate cell evaluation process. The candidate cell evaluation process (ORDER or GRADE) looks for target cells so as to do an SDCCH to TCH handover. TCH load in neighbor cells may be used for target cell evaluation and ranking (the TCH load is not known in case of external cells). Note : in case of handover preparation, the candidate cell evaluation process looks for target cells so as to do a SDCCH handover. The SDCCH load is not taken into account. Forced directed retry The preparation of forced directed retry is composed of two processes: - forced directed retry detection, - candidate cell evaluation. The forced directed retry detection requires specific preprocessed measurements, see section 3.1. The detection is performed every SACCH measurement reporting period when preprocessed measurements are available. The averaged received levels of all neighbor cells are compared to a threshold. If one or several cells are found with a received level higher than the threshold, an alarm of forced directed retry is raised : high level in a neighbor cell for forced directed retry. This cause is included in the "better condition causes" of the handover preparation. When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, to the candidate cell evaluation process for forced directed retry if there is no handover alarm raised at the same time. A handover alarm raised at the same time is prior and is sent to the candidate cell This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 21. Reference Version Page 1.0 21 evaluation process ORDER or GRADE. Then, the candidate cell evaluation process looks for cells : a. where the MS can communicate, b. where the received level at MS is higher than a given threshold, c. and which have a minimum number of TCH channels free (in case of internal cell). The condition b. allows the control of the interference level in the network. The condition c. is a means to forbid "retry traffic" from a congested cell to a neighbor cell if the neighbor cell has less than a minimum number of channels free. This condition controls the amount of "retry traffic" and therefore the additional interference generated by this type of traffic. ANNEX 1: Optimizations Parameters (Alcatel Implementation for 900/1800MHz Bands) Rxlev access min (Idle Mode) : This parameter concerns only the MS. Rule : The parameter of selection C1 should be null while the measured level by the MS is equal to its sensitivity. In Urban, the utilised MS are mostly of type « 2W » and of sensitivity lower or equal to -102dBm. For 900, in Urban case, Rxlev access min = -102dBm For 900, in Rural, we assume a use of mobiles of type « 8W » and we admit a Rxlev access min = -108 dBm. Concerning the 1800 macro cells, since the L_RXLEV_DL_H causes HO at signal strength bellow -99 dBm and -95 dBm (according if the cell is hopping or not), the Rxlev access min is set to -95 dBm. Therefore, it minimizes the situations where the MS do call set-up at a low level and leaves immediately in downlink level alarm. Handover threshold on low downlink and uplink level: To make uniform this parameter setting, we admit a sensitivity of -102 dBm for all the MS without distinction 2W/8W. Moreover, the actual performances in reception of the G3 BTS permit us to admit a sensitivity of -111 dBm for the G3 today versus -104 dBm for the G1 BTS and -108 dBm for the G2 (environment of TU50 and Rxqual 6). In relation to these thresholds of sensitivity, a rxqual margin [ Rxqual 6 -> Rxqual 4 = 3dB ] and a fading margin [ TU50 -> TU3 = 0dB with SFH and 3dB w/o SFH] is taken to determine the threshold for DL and UL level alarms in 900 MHz. : + 3 dB in case of use of frequency hopping + 6 dB without frequency hopping This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 22. Reference Version Page 1.0 22 For the uplink, the use of the diversity on the site introduces -3 dB in the benefit of the sensitivity, and a penalty of 10dB in case of 900 LNA use. -3dB with diversity +10 dB with LNA In last point, a correction factor of 1 dB is used to take into account the fact that the Alcatel algorithms trigger HO when the ENT( average measure) is strictly inferior to the threshold. For example, if the threshold is -99dBm, the HO is triggered to -100dBm or lower when we want a HO at -99dBm. Therefore, 1 dB is added to trigger HO at -99dBm or lower. +1dB correction factor For the 1800 cells, the same rule is applied. Finally: L Rxlev DL H= -102 + 3+ 1 = -98 dBm with frequency hopping L Rxlev DL H = -102 + 6 + 1= -95 dBm without frequency hopping L Rxlev UL H900(G3900) = -111 +3 -3+1= -110 dBm -> -110 dBm with SFH and diversity/ -100 avec LNA. In fact, in this particular case, no uplink level alarm can be triggered. L Rxlev UL H900(G3900) = -111 + 3+1 = -107 dBm with frequency hopping and without diversity/ -97 avec LNA L Rxlev UL H 900(G3900) = -111 + 6 -3 +1= -107 dBm without frequency hopping and with diversity/ -97 avec LNA L Rxlev UL H 900(G3 900) = -111 + 6 +1 = -104 dBm without frequency hopping and without diversity/ -94 avec LNA L Rxlev UL H900(G2 900) = -108 +3-3+1 = -107 dBm with frequency hopping and diversity/ -97 avec LNA L Rxlev UL H900(G2 900) = -108 + 3+1 = -104 dBm with frequency hopping and without diversity/ -94 avec LNA L Rxlev UL H900(G2 900) = -108 + 6 -3+1 = -104 dBm without frequency hopping and with diversity/ -94 avec LNA L Rxlev UL H900(G2 900) = -108 + 6 +1 = -101 Bm without frequency hopping and without diversity/ -91 avec LNA L Rxlev UL H900(G1 900) = -104 + 3 -3 + 1= -103 dBm with frequency hopping and diversity/ -93 avec LNA L Rxlev UL H900(G1 900) = -104 + 3 + 1= -100 dBm with frequency hopping and without diversity/ -90 avec LNA L Rxlev UL H900(G1 900) = -104 + 6 -3 +1= -100 dBm without frequency hopping and with diversity/ -90 avec LNA L Rxlev UL H900(G1 900) = -104 + 6 + 1= -97 dBm without frequency hopping and without diversity/ -87 avec LNA L Rxlev UL H900 (M1M and M1C 900) = -97 + 6 +1 = -90 dBm without frequency hopping and without diversity L Rxlev UL H900 (M4M) = -107 + 6 + 1= -100 Bm without frequency hopping and without diversity L Rxlev UL H1800 (G3 1800) = -111 + 3 -3 +1 = -110 dBm with frequency hopping and diversity. L Rxlev UL H1800 (G3 1800) = -111 + 3 +1= -107 dBm with frequency hopping and without diversity. L Rxlev UL H1800 (G3 1800) = -111 + 6- 3+1 = -107 dBm without frequency hopping and diversity. L Rxlev UL H1800 (G3 1800) = -111 + 6 +1= -104 dBm without frequency hopping and without diversity. PC thresholds on the ULlevel : Since the thresholds of HO on the UL level have changed, the UL thresholds of PC should change also to be in agreement with those of HO. The rule applied is based on HO level +8 dB for having the L_RXLEV_UL_P and +16dB for the U_RXLEV_UL_P. Quality HO threshold : This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 23. Reference Version Page 1.0 23 These thresholds should be tuned to trigger the HO when the average Rxqual reaches 4 without frequency hopping and 5 with frequency hopping (the Rxqual of 5 with frequency hopping activated is equivalent in audio quality to 4 without frequency hopping). For the Alcatel BSS, the algorithms use the entire part of the Rxqual average and strict inequalities. example if we desire to trigger with a Rxqual 4 : Assumption: Average Rxqual measured = 4.6 -> entire part = 4 If the threshold is set to 4, the algorithm do not trigger HO since the value is not strictly superior to 4. Therefore, the threshold should be set to 3. We propose to set these thresholds to 3 in all cases (900 or 1800). In case of cell not hopping, this threshold is adapted. In case of hopping cell (SFH BBH or synthetised), an offset OFFSET_HOPPING_HO available in B5.1 is added to the quality alarms thresholds L_RXQUAL_UL_H = L_RXQUAL_DL_H = 3 according to that the TS is hopping or not ( OFFSET_HOPPING_HO). We set OFFSET_HOPPING_HO positioned to +1 which results in quality alarms thresholds of 4 for the TS which are hopping and without impact if the TS are not hopping. With BBH, all the timeslots of the cell use the « 3+1 » threshold. With synthesised FH, the timeslots on the BCCH TRX use « 3 » and the timeslots on the other TRX use « 3+1 ». Finally: L_RXQUAL_UL_H = L_RXQUAL_DL_H = 3 OFFSET_HOPPING_HO = +1 PC thresholds on the UL quality : U_RXQUAL_UL_P is changed to 1 on the 900 macros cells to allows reduction of the MS power in case where the Rxqual measured is 0 and the level is over L_RXLEV_UL_P+2dB. This modification is introduced in order to have a homogeneous parameter setting between the manufacturers. L_RXQUAL_UL_P should be adjusted to the L_RXQUAL_UL_H - 1 This value is set to 2 (3 - 1) . With SFH, the « OFFSET_HOPPING_PC » is used for the TS which are hopping. It is set to +1, and then PC uses 3 with SFH. Average windows in level, PBGT and DR : The concern is to uniform the parameter setting between all classes of 900 macro cells. A_LEV_HO and A_PBGT_HO are chosen to be identical and set to 6 for all the classes of 900 and 1800 macros. A_PBGT_DR is set to 4 to allows a quick FDR in case of activation of this feature. Extension of the maximum number of neighbours : The NBR_ADJ is changed to 64 . The GSM norm authorise a maximum number of 32 channels on the both band (900 + 1800 Mhz) broadcasted by the BSS and measured by the MS. In case that in the same band (900Mhz or 1800Mhz), more than 32 neighbours are necessary , having a neighbour list of 64 offers the possibility to have more than 32 neighbours with the condition of a maximum of 32 channels (2 neighbours can have the same channel but identified by a different BSIC). Normally, the Alcatel OMC or/and BSC should refuse more than 32 channels broadcasted on the network ( control of coherence made) . For example, the case of 25 channels in 900Mhz and 15 channels in 1800 Mhz is forbidden by the BSS. Full balanced power of the µcells : This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 24. Reference Version Page 1.0 24 It is chosen , today, to use full balanced power of µ cells in order to increase the coverage and increase the traffic. Knowing that the M1M and M1C have a maximum output power of 27 dBm, this value will not change for this case. However, for the M2M and M4M, we propose to use an higher power. Neihbouring Cell valuation: Rxlevmin(n) We propose to set Rxlevmin(n) equal to L_Rxlev_DL_H, the low threshold for the downlink level HO. On this HO cause, it seems better to go to cell having at least the same level. To go to a cell with a lower level could quickly produces a new alarm HO. In fact, as the comparison is strict, the level of the target cell will have more than 1 dB than L_Rxlev_DL_H of the originating cell. Introduction of the Ho_margin of qual and lev between couples of cells : The B5 release introduces a filtering process if the flag EN_PBGT_FILTERING is enable before the process of evaluation of the candidates neighbours ORDER and GRADE (used for all the causes excepted for cause 20) : . PBGT(n)> HO_MARGIN_XX(0,n) + Cause_Margin_P_X - with HO_MARGIN_XX(0,n) = HO_MARGIN_QUAL(0,n) if cause=2,4 or 7 - with HO_MARGIN_XX(0,n) = HO_MARGIN_LEV(0,n) if cause=3,5,6,17 or 18 - with HO_MARGIN_XX(0,n) = HO_MARGIN(0,n) if cause 12 In order to come nearer to the parameter setting of the others suppliers, the B5 parameter setting changes by introducing the HO_MARGIN_QUAL(0,n) and HO_MARGIN_LEV(0,n) by couple of cells instead of using the HO_MARGIN(0,n) + cause_Margin_P_X (cell parameter which is used for all the neighbour as in the B4 behaviour). By this way, we have a higher flexibility of optimisation and control of the chosen neighbours. Since we propose to use the HO_MARGIN_QUAL(0,n) and HO_MARGIN_LEV(0,n) for the causes 2,4,3,5 and 6, it is no more necessary to have Cause_Margin_P_X and are voluntary changed to 0. In B4, the process of GRADE was including the criteria : PBGT(n) > HO_MARGIN + Cause_Margin_P_X In B5, the process of GRADE doesn’t contain this criteria and is replaced by the filtering conditions presented above when the EN_PBGT_FILTERING is enable. In B4 as in B5 , the process of ORDER applied on the µcells was not containing any filtering conditions. In B5, we propose to have on all the cells the EN_PBGT_FILTERING enabled (concern of an homogeneous parameter setting) and to use very negative values of HO_MARGIN_QUAL and HO_MARGIN_LEV if we want to avoid filtering. Therefore, new tables of the crossed parameters are introduced between the layers and adapted for an expected behaviour [ HO_MARGIN(0,n); HO_MARGIN_LEV(0,n); HO_MARGIN_QUAL(0,n); LINK_Factor(0,n); PRIORITY(0,n) ]. We have to take care of the difference between the L_Rxlev_DL_H of the originating cell and the Rxlevmin(n) of the target cell. The idea is to have HO_margin_lev(0,n) coherent with this difference. Therefore, we propose to set the HO_MARGIN_LEV(0,n) like follows HO_MARGIN_LEV(0,n) = Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) By putting the values set in the tables, the following behaviour is expected : This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 25. Reference Version Page 1.0 25 - On the M900 cells : - For comfort HO, capture HO occurs on the 900 µ cells or on the M1800 cells and PBGT happens between M900 cells. - In case of urgency HO, the MS is redirected preferably on the best M900 cell over Rxlevmin(n) and satisfying the criterion of Ho_margin_lev(0,n) = Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) or Ho_margin_qual(0,n) = -2dB. Otherwise, in a second priority the µ900 over Rxlevmin(n) and satisfying the criterion of Ho_margin_lev(0,n)= Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) and Ho_margin_qual(0,n)=-127 and in last choice the M 1800 over Rxlevmin(n) and under the criterion of Ho_margin_lev=-127 and Ho_margin_qual=-127 - On the µ900 cells : - For comfort HO, capture HO occurs on the M1800 cells and PBGT happens between µ900 cells. - In case of urgency HO, the MS is redirected preferably on the best M900 cell over Rxlevmin(n) and satisfying the criterion of Ho_margin_lev(0,n) =-127dB or Ho_margin_qual(0,n) = -127dB. Otherwise, in a second priority the µ900 over Rxlevmin(n) and satisfying the criterion of Ho_margin_lev(0,n)= Max (-2, Rxlevmin(n) - L_Rxlev_DL(0)+1) and Ho_margin_qual(0,n)=-2 and in last choice the M 1800 over Rxlevmin(n) and under the criterion of Ho_margin_lev=-127 and Ho_margin_qual=-127 Suppression of templates : The suburb 900 macro template is no more justified by a real need of a specific parameter setting. We proposes to suppress it and to replace it either by an urban template, either by the rural one according to its environment. The Umbrella macros 900 templates only differs from the normal macros 900 only by the fact that the cause 14 is inhibited or not. In the case there is no micros cells under a macro cell with cause 14 activated, since there is no cells of layer type « lower » as neighbour, the behaviour of the network is the same that with the cause 14 inhibited. Therefore, we propose to replace the Simple Dense Urban parameter setting by the templates Umbrella Dense Urban. The Dense Urban templates differs from the Urban templates, by the fact that the load factor are used in the Dense Urban templates when there are not used in the Urban templates. We proposes to merge these templates in one with the load factors used by default. Finally, on the macro cells, there is no more than 2 classes (Urban and Rural) with thresholds of levels alarms and levels PC different according to the BTS used, the diversity and LNA use. Introduction of the synchronised HO in the grid : WITH_SYNCHRONISED_HO: enables synchronised HO, set to 1 Change of name of some parameters : In B5, CELL_LAYER_TYPE replaces CELL_COVERAGE _TYPE and can take 3 states, « lower , « upper » or « single ». Then, the 900 micros cells takes the values of « lower » and replace 2 for « recovered » and the 900 macros cells are set as « upper » and replace 1 for « umbrella ». L_RXLEV_CPT_HO(n) replaces L_RXLEV_OCHO(n) and is used as capture threshold for the cause 14 (µ cell neighbour) and is also utilised for the cause 21 (1800 neighbour). Introduction of new parameters (excepted dual band parameters) : EN_IM_ASS_REJ: enables the use of the immediate assignement reject, set to 1 EN_SEND_OLD_CHAN_MODE: enables the transmission of the used speech version to the target BSS, set to 1 This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 26. Reference Version Page 1.0 26 DTX_INDICATOR_SACCH: defines the uses of the dtx in TCH/HR or/and TCH/FR. FREQUENCY RANGE: indicates which range is used in the cell: P-GSM, DCS1800, E-GSM, DCS1900. Can only be readen since the value is set by the equipment affected to the cell (P-GSM, GSM 1800 BTS, ...). Do not appear in the grid OFFSET_HOPPING_PC and OFFSET_HOPPING_HO: an offset can be used. It’s added to the low rxqual threshold for the trx using SFH. Change of some timers : T8 (=3103): those timers are used in the process who allows the mobile to come back on the old channel after a handover fail. Their new value is 15 s (old value = 12 s) T(conn-est): it a SCCP timer. When the message « connection request » is sent, a message like « Connexion Confirm » or « Connection refused » is expected. If it doesn’t occur, when this timer is out, the connexion process is cancelled. Its new value is 5s (old value = 12 s) T(rel): it a SCCP timer. It normaly used by the MSC in the release of a SCCP connection. The message « Released » is sent to the BSC and the MSC waits the message « Release complete ». If this acknowledge isn’t received, « Released » is sent again. But in anormal case, the BSC can use this timer to release itself this connection. Its new value is 5 s (old value = 15 s) New timers : These 4 timers set any delays between the « Assignement reject » and a new sending of « Channel request » WI_CR: cause « call reestablishment » WI_EC: cause « emergency call » WI_OC: cause « originating call » WI_OP: cause « other procedures » These parameters are set by default to 5s before optimisation. Introduction of the dual band feature : Impact of the dual band activation on the existing classes in 900Mhz : We recommend, by default, the dual band feature activation, on all the 900 cells and all the Alcatel BSC of France for the following reasons : . This feature should be activated , every where, even on BSc without 1800 neighbours to allows later HO on the 1800 layer during the call when the MS has initiated a call on a BSc far away from the dual band zone. . In case of special needs of capacity of traffic to cover a temporary event or a permanent hot spot, no parameter setting adjustments are necessary to open a dual band zone. A simple integration of 1800 cells is sufficient. Of course, in no way, the activation of the dual band feature has impact in the behaviour of the 900 MS. Moreover, the dual band MS has the same behaviour than a 900 MS in case there is no 1800 cells.  To reach this goal, the following parameters are necessary on all the Alcatel BSCs for an unlocking of the dual band feature : . EN_INTERBAND_NEIGH : BSC lock of the broadcast of all the opposite band neighbours (set to 1 to enable) . PREFERRED_BAND : BSC parameter that specifies which band is preferred for inter-band handovers (set to 2 for GSM 1800). . LOAD_EV_PERIOD : DLS parameter (hardly coded) that specifies the number of time necessary for the calculation of the load_average of the cell (set to 60s). This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 27. Reference Version Page 1.0 27 . Activation of the Early Classmark sending on the Alcatel BSC : - ECSC (DLS basis) : set to 1 for enabling the early classmark sending of the dual band MS - EN_SEND_CM3 : set to 1 in order to allows the sending of the CM3 to the NSS . - STRIP_O5_CM2 : set to 0 for having no change of the octet 5 of CM2 IE being passed to the MSC. The modifications on all the Alcatel cells for an unlocking of the dual band feature are the following : . EN_PREFERRED_BAND_HO : This new parameter is a cell lock of the preferred band HO 900 -> 1800 cause 21 (set to 1 on all the 900 cells to enable dual band HO). Set to 0 on the 1800 cells since it is unnecessary. . MULTI_BAND_LOAD_LEVEL : Threshold of load in the 900 serving cell which enables a dual band HO (set to 0%). . L_RXLEV_CPT_HO(n) : Used for the cause 14 and 21. On the 1800 cells, it corresponds to the signal strength threshold which allows a dual band HO (-85 dBm). On the µ900, it is the capture threshold from M900 to µ900. . MULTI_BAND_REPORTING : (Specs GSM 04.08; broadcasted on the Sys_Info5ter layer 3 message) set to 1 on the 900 cells to allows that the dual band MS reports to the BSS, measurements on the best neighbour in 1800. In case, there is no 1800 cell as neighbour, the MS still report the 6 best neighbours in 900 Mhz. The management of the dual band HO by Alcatel is done by the introduction of the cause 21 on the 900 cells (HO toward the preferred band by capture). The cause is triggered under the following conditions : . AV_LOAD(0)>MUTIBAND_LOAD_LEVEL (average % of busy TCH) . AV_RXLEV_NCELL(n)>L_RXLEV_CPT_HO(n) + max(0, MSTXPWR_MAX(n) -P) AV_RXLEV_NCELL(n) is calculated with a averaging window of A_PBGT_HO size. The A_PBGT_HO is using the available samples and filling the resting with 0 (-110dBm). The interband HO could be possible also by the use of the cause 14. However, the timer of triggering are also applied to the M1800, delaying the capture process. Possibility recommended for the µ1800. In B5, the evaluation process of the candidates neighbours has changed for the management of a multi-layer dual band network and is conducted as followed : • 1) List and first ranking of the neighbours : • for "better cell" HO : • pref_layer = none ; all the neighbours that satisfy the HO cause (cause12, cause 14, cause20 and cause 21) • pref_layer = upper; while the cell is cell_layer_type= lower, the HO cause is 12 and the MS_SPEED=fast • for "rescue" HO , all the neighbours with the preferences : • pref_layer = upper if cell_layer_type=lower and en_recue_um=enable • pref_layer=lower if cell_layer_type=lower and en_rescue_um=disable • none if cell_layer_type=lower and en_rescue_um=indefinite • upper+single if cell_layer_type=upper • 2) Ranking of the neighbours by priority order (highest to lowest): • preferred layer (value of pref_layer) • priority(0,n) • same frequency band than the serving cell • process of evaluation ORDER(n) or GRADE(n)(excepted for cause 20) • cell_ev=0 (ORDER) • if en_load_order=enable, order(n)=PBGT(n)+LINKfactor(0,n)+FREEfactor(n)- FREEfactor(0)-HO_MARGIN_XX(0,n) • if en_load_order=disable or external HO, order(n)=PBGT(n)+LINKfactor(0,n)- HO_MARGIN_XX(0,n) This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 28. Reference Version Page 1.0 28 • Av_rxlev_ncell(n)>Rxlevmin(n)+max(0;ms_txpwr_max(n)-P) • cell_ev=1 (GRADE) • if en_load_order=enable, grade(n)=PBGT(n)+LINKfactor(0,n)+LOADfactor(n)- LOADfactor(0)+FREEfactor(n)-FREEfactor(0) • if en_load_order=disable, grade(n)=PBGT(n)+LINKfactor(0,n) • Av_rxlev_ncell(n)>Rxlevmin(n)+max(0;ms_txpwr_max(n)-P) • GRADE(n)>DISTmargin+Cause_Margin_G_X • 3) A filtering process can take place (EN_PBGT_FILTERING=enable) before the process of GRADE or ORDER (excepted for cause 20): • PBGT(n)> HO_MARGIN_XX(0,n) + Cause_Margin_P_X • with HO_MARGIN_XX(0,n) = HO_MARGIN_QUAL(0,n) if cause= 2, 4 or 7 • with HO_MARGIN_XX(0,n) = HO_MARGIN_LEV(0,n) if cause=3,5,6,17or 18 • with HO_margin_XX(0,n) = HO_MARGIN(0,n) if cause 12 cause_margin_P_14=-127dB; cause_margin_P_21=-127dB (to avoid filtering in PBGT and simulate a capture process) For having dual band HO from µ900 or M900 to the 1800 neighbours, new crossed neighbour relations are introduced to M1800 from collocated, surrounding M900 and µ900 which are overlapped by the M1800 cells. The parameters specifics to the neighbour relation are : . HO_MARGIN(0,n)= HO_MARGIN_QUAL(0,n)=HO_MARGIN_LEV(0,n)= -127 dB . LINKFACTOR(0,n) = 0dB . PRIORITY(0,n) = 0 when the 1800 cell parameters used in the neighbour relation are : RXLEV_MIN(n)=L_RXLEV_DL_H=-98dBm (SFH) or -95dBm (w/o hopping); L_RXLEV_CPT_HO(n)= -85dBm; LOADfactor1-5(n)=0dB; FREEfactor1-5(n)=0dB; L_RXLEV_NCELL_DR(n)=-47dBm; FREELEVEL_DR(n)=127 According to the process of ranking and filtering developed above and the parameters used in the neighbour relation to the M1800 cells, the expected behaviour for dual band MS on µ900 and M900 is the following : • Expected behaviour on the µ 900: - On call set-up, SDCCH900 ->TCH 900 (no FDR activated) - In case of urgency HO, the MS is redirected preferably on the best M900 cell over Rxlevmin(n) and satisfying the criterion of Ho_margin(lev et qual = -127). Otherwise, in second priority the µ900 over Rxlevmin(n) and the criterion of Ho_margin(lev , qual =- 2dB) since M1800 and µ900 have the same priority and in last choice the M1800 over Rxlevmin(n) and the criterion of Ho_margin(lev and qual = -127). - In PBGT, a capture on the 1800 M cell occurs (cause 21) on the best 1800M cell above - 85dBm • Expected behaviour on the M 900: - On call set-up, SDCCH900 ->TCH 900 (no FDR activated) - In case of urgency HO, the MS is redirected preferably on the best M900 cell ( consideration of load taking into account by the LOADFACTOR effect in the process of Grade) over Rxlevmin(n) and satisfying the criterion of Ho_margin(lev ; qual=-2dB). Otherwise, in second priority the µ900 over Rxlevmin(n) and satisfying the criterion of Ho_margin(lev ; qual=-127) since M1800 and µ900 have the same priority and in last choice the M1800 over Rxlevmin(n) and under the criterion of Ho_margin(lev=-127 and qual=-127). This document is Nexius Wireless Inc. property and cannot be reproduced without permission
  • 29. Reference Version Page 1.0 29 - In PBGT, a capture on the 1800 M cell occurs (cause 21) on the best 1800M cell above - 85dBm. Otherwise, a capture cause 14 HO occurs on a µ900. Introduction of a new class of cell (macro 1800 cells) : The parameter setting of the M1800 cells are common to those of M900 cells of dense urban class excepted for the following specific parameters : . CELL_LAYER_TYPE : The 1800 cell is declared as « lower » with EN_RESCUE_UM=ENABLE. Thus, in case of rescue HO, pref_layer=upper and the best ranked cells are the M900 (same behaviour than the µ900). agressiveness to encourage HO on preferred band (1800). . CELL_EV= ORDER and EN_LOAD_ORDER=DISABLE As for the µcells, we chose order in the evaluation process and no consideration of load ( FREE_FACTOR )in the choice of the neighbours for outgoing HOs from the 1800 cells. No consideration of load between the 1800 cells in the Grade process from M900 cells (LOAD_FACTOR 1-5=0dB). . MULTI_BAND_REPORTING (Specs GSM 04.08; broadcasted on the Sys_Info5ter layer 3 message) set to 3 on the 1800 cells to allows that the dual band MS reports to the BSS, measurements on the 3 best neighbour in 900 and 3 neighbours in 1800.). This choice is made in order to favour the HO on the 1800 neighbours without to compromise a rescue HO on the 900 layer. . BS_TXPWR_MAX, BS_TXPWR_MAX_INNER of the 1800 cell is proposed to be identical to that the collocated 900 cell for the case where there is 900 indoor cell that we can’t declare as neighbour of the Umbrella 1800 cell (due to the limitation of 32 neighbours in the 900 neighbour list that could be reached) . Therefore, the pass from the M1800 to Indoor 900 could be done in 2 steps through the M900 cells. . MS_TXPWR_MAX, MS_TXPWR_MAX_INNER, MS_TXPWR_MAX_CCH of the 1800 cells is set to 30dBm that is the maximum power that can be used on the 1800 band. . U_TIME_ADV is the alarm threshold on timing advance on 1800 and is set to 2.2 km. For an average timing advance over 4 (5=2.7km), an alarm in distance is triggered. This is the only way, with Alcatel to control the service range of the M1800 cells . The C2 parameters is applied only on the 1800 cells in order to favour the reselection on the 1800 cells even and while the signal strength is bellow the 900 cells. - CELL_RESELECT_PARAM_IND : lock per cell that enable the broadcast of C2 cell reselection parameters on the BCCH of the cell (set to 1). - CELL_RESELECT_OFFSET : set to 16 dB. M1800 cells are favoured of 16 dB but the effective favour weight is bellow and around 9dB since the Rxlevaccesmin of the M1800 is upper the M900. - PENALTY_TIME : set to 0 = 20s (identical to that in 900) - TEMPORARY_OFFSET : set to 0dB (identical to that in 900). No penalty is applied on the M1800 cells - RXLEV_ACCESS_MIN : set to -95 dBm . The MS can camp on the M1800 cell only if the C1>0 (Rxlev>-95dBm). . Since the dual band MS are « forced » to camp on the M1800 cells, it is recommended to activate, by default, the Forced Directed Retry on the M1800 cells in case of saturation of the M1800 cells : - EN_FORCED_DR (per cell basis) : set to 1 and allows the Forced Directed Retry on the neighbours - EN_DR (per cell basis) : set to 1. For unlock the DR and FDR from the M1800 cells on the neighbours In case of congestion of the M1800 cells, the process of the neighbour choice is as followed : List of the neighbours : • AV_RXLEV_NCELL_DR(n)> L_RXLEV_NCELL_DR(n) Filtering and Ranking of the neighbours : • AV_RXLEV_NCELL_DR(n)>RXLEVmin(n)+max(0,MSTXPWR_MAX(n)-P) This document is Nexius Wireless Inc. property and cannot be reproduced without permission