GSM BSS dimensioning Alcatel

GSM BSS Dimensioning
1062A
Student Guide
Guide release: 15.02
Guide status: Standard
Date: July, 2005
Part Number: 1062A
NORTEL CONFIDENTIAL – FOR TRAINING PURPOSES ONLY

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Information subject to change without notice.
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Visit us at: nortel.com/training

Description
This course explains the Nortel Networks method to dimension the Base Station Subsystem
(BSS) of a GSM network. This course applies to the V15.0.1 version of the BSS.
Intended audience
Anyone responsible for designing BSS networks with Nortel Networks equipment (BTS, BSC,
TCU) .
Prerequisites
Before taking this course, a general knowledge of GSM/GPRS/EDGE standards and products is
required. An excellent way to obtain it is to attend the 5 days 1061A course (GSM GPRS System
Overview - Technical), the 3 days GP1 (GPRS Technical Description), the 2 days 1597AB (GSM
GPRS System Release V15.0) and the 1 day 1599A (GSM/GPRS/EDGE System Release V15.1
Delta).
Objectives
After completing this course, you will be able, from a given mobile traffic model, to dimension a
BSS and:
• calculate the number of signaling and traffic radio resources per sector, the number of TRX per
sector, the number of Abis and Ater PCM links,
• compute the size and configuration of the BSS equipment: BTS, BSC, TCU and PCUSN.
Course introduction
Overview

References
The following documents provide additional information:
Document title
NTP 000-
0000-000

Contents
1. Introduction
2. Basics on Mobile Network Dimensioning
3. BTS Dimensioning
4. BSC/TCU 12000 Dimensioning
5. BSC3000/TCU3000 Dimensioning
6. PCU Dimensioning
7. BSS Dimensioning Review
8. Exercise Solutions
9. Appendix: Erlang B Tables

Publication History
Compliant with V15.1 BSS
Release
July
2005
15.02
Creation
Compliant with V15.0.1 BSS
Release
May
2005
15.01
CommentsDateVersion

1
nortel.com/training
Section 1
Introduction

2
2
About Knowledge Services
> Knowledge Services offers three programs to help
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Nortel Homepage
www.nortel.com

4
4
Training & Certification Page
www.nortel.com
• Select Training
• Select the appropriate product family …
• …Choose a product…
• …And get the content
Select the appropriate geographic region and language - allows you to customize
your view
Point of Contacts:
• CAMs (Customer Account Managers) – The customer can direct
questions/issues to their internal training prime, who can be in contact with the
Nortel CAM.
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• Instructor – provide business cards/email address/phone number

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Training Page
Page that appears when “Training” is selected
Depending on your selection, you see the training offer in your region (NA, EMEA,
ASIAPAC, CALA) or the global offer.

6
6
Curriculum Paths Page
Page that appears when “Curriculum Path” is selected.
You can select the appropriate training according to your job function.

7
7
Technical Documentation
www.nortel.com
Select Support & Training
Select Technical Documentation

8
8
GSM BSS Nortel Technical Publications
BSS Product
Documentation
411-9001-000
BSS Overview
411-9001-001
OMC-R
Architecture and
Reference Manual
411-9001-006
TCU
Reference Manual
411-9001-016
BSC
Reference Manual
411-9001-022
S4000/S4000C
Indoor BTS
Reference Manual
411-9001-043
S2000 H/L BTS
Reference Manual
411-9001-035
S8000/S8002/
S8003/S8006 BTS
Reference Manual
411-9001-063
e-cell BTS
Reference Manual
411-9001-092
PCUSN
Reference Manual
411-9001-091
BSC/TCU 3000
Reference Manual
411-9001-126
S12000
Reference Manual
411-9001-142
BTS 18000
Reference Manual
411-9001-160
Concepts
EDGE Deployment Guide
411-9001-801
Planning and
Engineering
What’s New in the
V15 BSS NTP Suite
411-9001-088
Upgrading
CT2000
User Manual
411-9001-137
PCU CIQ
User Manual
411-9001-140
CT2000 User
Procedures Manual
411-9001-148
Configuring
OMC-R User
Manual Vol 3 of 3:
Security, Administration,
SMS-CB and
Help menus
411-9001-130
Administration
and Security
BSS Operating
Principles
411-9001-007
BSS Operating
Procedures
411-9001-034
OMC-R User
Manual Vol 1 of 3:
Objects and
Faults Menus
411-9001-128
BSS Parameter
Dictionary
411-9001-124
RACE Reference
and User Manual
411-9001-127
Operations Fault and Performance Management
S12000
Maintenance Manual
411-9001-144
BSS Maintenance
Principles
411-9001-039
BTS 18000
Maintenance Manual
411-9001-162
Fault Number Description
Volume 1 of 6:
BSC and TCU
411-9001-101
Volume 2 of 6:
S2000/2000E
and S4000 BTS
411-9001-102
Volume 3 of 6:
S8000/8002,
S8003 and S8006
411-9001-103
Volume 4 of 6:
S2000H/L and
e-cell BTS
411-9001-104
Volume 5 of 6:
Advanced Maintenance
Procedures
411-9001-105
Volume 6 of 6: PCUSN
411-9001-106
S12000 BTS
411-9001-143
BTS 18000
411-9001-161
BTS/TCU 3000
411-9001-131
Call Trace/Call Path
Trace Analyzer
User Manual
411-9001-060
OMC-R User
Manual Vol 2 of 3:
Configuration,
Performance and
Maintenance menus
411-9001-129
Observation
Counter Dictionary
411-9001-125
TML (BSC/TCU)
User Manual
411-9001-050
TML (BTS)
User Manual
411-9001-051
TML
(BSC 3000/TCU 3000)
User Manual
411-9001-139
OMC-R Preventive and
Corrective Maintenance
411-9001-032
BSC
Maintenance Manual
411-9001-041
TCU
Maintenance Manual
411-9001-042
BSC 3000
Maintenance Manual
411-9001-132
e-cell BTS
Maintenance Manual
411-9001-090
S2000 H/L
Maintenance Manual
411-9001-049
S4000 BTS
Maintenance Manual
411-9001-047
S8000/S8003 BTS
Maintenance Manual
411-9001-048
S8002 BTS
Maintenance Manual
411-9001-084
S8006 BTS
Maintenance Manual
411-9001-085
GSM BSS Nortel Technical Publication
This suite is sorted by job functions category.

9
9
Contents
> GSM/GPRS/UMTS Training Curriculum
> BSS Nortel Technical Publications
> Objectives
> Course Architecture

10
10
Objectives
> Upon completion of this course, ability is acquired to
determine or compute:
• Traffic radio resources number per cell
• Signaling resources number per cell
• TRX number per cell
• BTS types and number
• BSC types and number
• TCU number
• PCU number
• Number of Abis, Ater, Agprs and A interfaces PCM links
• BSS size and configuration
During this course the method of dimensioning computation of BSS part of a GSM
network is explained and given.
The results obtained depend mainly on Traffic Model parameter values for
transmission. Some of these values deal with field parameters as cellular planning,
subscriber activity and mobility.
Each operator must define his own traffic model.
Other assumptions are also given, relating to traffic operation. They are operator
dependent:
• No Queuing (loss of excess call attempts)
• Radio interface blocking rate: traffic = 2%; signaling = 0.1%
• A interface blocking rate: 0.1%
Notes
This course is applicable for V15.0.1 release of Nortel Networks BSS.

11
11
Course Architecture
> Section 1 – Introduction
> Section 2 – Basics on Mobile Network Dimensioning
> Section 3 – BTS Dimensioning
> Section 4 – BSC/TCU 12000 Dimensioning
> Section 5 – BSC3000/TCU3000 Dimensioning
> Section 6 – PCU Dimensioning
> Section 7 – BSS Dimensioning Review
> Section 8 – Exercise Solutions
> Section 9 – Appendix: Erlang B Tables

1
nortel.com/training
Section 2
Basics on Mobile Network Dimensioning

2
2
Lesson Objectives
Upon completion of this section, the student will be able to:
> Define Erlang unit
> Use Erlang Law B Tables
> Describe a Traffic Model (parameters and typical values)
> Define the Dimensioning Procedure
This is obtained through a full understanding of:
> Components of the GSM System Traffic
> Definition of offered traffic, blocking rate, Erlang laws

3
3
Contents
> Generalities about GSM/GPRS Network
> Erlang Law
> Traffic Model
> Dimensioning Procedure

4
4
GSM/GPRS/EDGE Network
BTS
BSC
TRAU
Abis Ater
PCU
Agprs
Frame
Relay
Backbone
Gb
MSC
VLR
PSTN
SGSN
GGSN
Gn Gn
External
Packet Networks
Intranet, Internet
Gi
HLR/
AuC
D
C
Gr
MS
Private
IP
Backbone
Um
A
Gb
BSS
The GSM network is the foundation of the wireless network. It provides circuit-
switched voice service from mobile users to other mobile and land line users.
The General Packet Radio Service (GPRS) is a wireless packet data service that
is an extension of the GSM network. It provides an efficient method to transfer
data by optimizing the use of network resources.
New from V15.0
EDGE is an extension of the GSM/GPRS Access network. In that sense, it largely
inherits the administration, maintenance and supervision of the currently deployed
BSS.
The GPRS Coding Schemes are enhanced with 7 EDGE Modulation and Coding
Schemes (MCS2, MCS3 and MCS5 to MCS9). This set of Modulation and radio
coding schemes increases the peak radio throughput of a carrier by a factor 3
compared to GPRS.
In order to benefit from those new Coding Schemes, a specific hardware is
needed on the BTS side (namely E--DRX & E--PA) and an extension of the
backhaul is requested to take benefit of the full range of MCS.
EDGE is part of the rel--99 of the 3GPP specifications, and thus, BSS complies
with that version of the specification on the radio interface. It is noted that a rel--97
SGSN also supports EDGE.

5
5
Generalities
1 – Traffic channel types: speech case
TCU BSCMSC
Radio
InterfaceA Interface Ater Interface Abis Interface
NSS BSS MS
BTS
(1) depends on the AMR Full Rate mode:
4.75; 5.15; 5.9; 6.7; 7.4; 7.95; 10.2 or 12.2 kbps
(2) depends on the AMR Half Rate mode:
4.75; 5.15; 5.9; 6.7; 7.4 or 7.95 kbps
A Interface Ater Interface Abis Interface Radio Interface
Gross rate Raw rate Gross rate Raw rate
TCH/FS
TCH/EFS
TCH/AFS
TCH/HS
TCH/AHS
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
64 kbps
16 kbps
16 kbps
16 kbps
8/16 kbps
16 kbps
13 kbps
12.2 kbps
(1)
5.6 kbps
(2)
Gross rate Raw rate
16 kbps
16 kbps
16 kbps
8/16 kbps
8 kbps
13 kbps
12.2 kbps
(1)
5.6 kbps
(2)
Gross rate Raw rate
22.8 kbps
22.8 kbps
22.8 kbps
11.4 kbps
11.4 kbps
13 kbps
12.2 kbps
(1)
5.6 kbps
(2)
Speech
The raw data rate is specified by the channel type:
• TCH/FS: 13 kbps conveyed into a 16 kbps channel on Ater and Abis interfaces
• TCH/EFS: 12.2 kbps conveyed into a 16 kbps channel on Ater and Abis
interfaces
• TCH/HS: 5.6 kbps conveyed either into a 8 kbps or into a 16 kbps channel on
Ater and Abis interfaces. Not available at the present time.
• TCH/AFS: there are 8 AMR Full Rate modes (4.75; 5.15; 5.90; 6.70; 7.40;
7.95; 10.20 and 12.20 kbps) conveyed into a 16 kbps channel on Ater and Abis
interfaces
• TCH/AHS: there are 6 AMR Half Rate modes (4.75; 5.15; 5.90; 6.70; 7.40;
7.95) conveyed either into a 8 kbps or into a 16 kbps channel on Ater and Abis
interfaces
The speech transmission is always bi-directional.
Remarks:
• On Abis and Ater interfaces, the difference between the gross rate and the raw
rate is used for signaling between TRAU and BTS. On radio interface, this
difference corresponds to the channel coding.
• TCH/HS is not supported by Nortel. On Abis and Ater interfaces, from the
GSM recommendation (TS 08.61) point of view, there are two possible
implementations: TRAU frame on 16 kbps or on 8 kbps channel.
• For TCH/AHS, there are the same two possibilities. Nevertheless, Nortel chose
to use the 8 kbps TRAU frame but on a 16 kbps channel on Ater and on a 8
kbps channel on Abis.

6
6
Generalities
2 – Traffic channel types: data case over NSS
TCU BSCMSC
Radio
InterfaceA Interface Ater Interface Abis Interface
NSS BSS MS
BTS
Ater/Abis Interface Radio Interface
TCH/F14.4
TCH/F9.6
TCH/F4.8
TCH/F2.4
TCH/H4.8
TCH/H2.4
Gross rate User Service rate
16 kbps
16 kbps
16 kbps
16 kbps
8 kbps
8 kbps
14.4 kbps
9.6 kbps
4.8 kbps
2.4 kbps
4.8 kbps
2.4 kbps
Gross rate Raw rate
22.8 kbps
22.8 kbps
22.8 kbps
22.8 kbps
11.4 kbps
11.4 kbps
14.5 kbps
12 kbps
6 kbps
3.6 kbps
6 kbps
3.6 kbps
Data over NSS = Circuit Switched Data
The different bi-directional data transmission types are: TCH/F14.4, TCH/F9.6,
TCH/F4.8, TCH/F2.4, TCH/H4.8 and TCH/H2.4.
Data transmission at rates of 1200 bps or less or equal than 600 bps are also
possible. There are using either a TCH/F2.4 or a TCH/H2.4.
High Speed Circuit Switch Data (HSCSD) feature allows to one user up to 4 such
data traffic channel type. HSCSD is really interesting with four TCH/F14.4 leading
to a raw rate of 57.6 kbps. Nevertheless, it is very resource consuming as four
radio and four terrestrial resources are allocated to the same user.
Enhanced Circuit Switch Data (ECSD) feature defines three new channel types:
E-TCH/F43.2, E-TCH/F32.0 and E-TCH/F28.8 using 8PSK modulation. It allows to
reach the same data rates (on radio interface) as for HSCSD but with less
terrestrial resources.

7
7
Generalities
3 – Traffic channel types: Data case over GPRS core network
MS
PCUSN BSC
Radio
InterfaceAgprs Interface Abis Interface
BSS
BTS
Gb Interface
SGSN
GPRS Network
9.05/13.4 kbps - GMSK
15.6/21.4 kbps - GMSK
8.8/11.2 kbps - GMSK
14.8/17.6 kbps - GMSK
22.4 kbps - 8PSK
29.6 kbps - 8PSK
44.8 kbps - 8PSK
54.4/59.2 kbps - 8PSK
PDTCH/CS1-CS2
PDTCH/CS3-CS4
PDTCH/MCS1-MCS2
PDTCH/MCS3-MCS4
PDTCH/MCS5
PDTCH/MCS6
PDTCH/MCS7
PDTCH/MCS8-MCS9
Gross rate Raw rate
16 kbps
2x16 kbps
16 kbps
2x16 kbps
2x16 kbps
3x16 kbps
4x16 kbps
5x16 kbps
9.05/13.4 kbps
15.6/21.4 kbps
8.8/11.2 kbps
14.8/17.6 kbps
22.4 kbps
29.6 kbps
44.8 kbps
54.4/59.2 kbps
Gross rate Raw rate - Mod
22.8 kbps
22.8 kbps
22.8 kbps
22.8 kbps
69.6 kbps
69.6 kbps
69.6 kbps
69.6 kbps
Abis InterfaceAgprs/ Radio Interface
Data over GPRS core network = Packet Switched Data
The data transmission over the GPRS core network always uses one and only one
full rate traffic channel on the radio interface whatever the coding scheme applied
(CS1 to CS4 for GPRS or MCS1 to MCS9 for EDGE). On the other hand, for high
data rates (over 13.4 kbps for GPRS (CS2) and over 11.2 kbps for EDGE
(MCS2)), more than one terrestrial resource (16 kbps channel) is required.
For example, using MCS6, RLC user data payload is 74 bytes to be transmitted in
20 ms. For this, 26 bytes are transmitted in one "main" 16 kbps channel and 24
bytes are transmitted in each of the two "joker" channels. Therefore, the raw data
rates are not the same in each of the 16 kbps channels ("main" and "joker"). In
above table, only the global raw data rates (sum of the rate of the "main" and
"joker" channels) are indicated.
Nevertheless, from the user point of view, the data transfer mode is a packet
mode. That is to say, up to 8 radio TS can be assigned to one user. And
simultaneously, one radio TS can be shared between several users. Moreover, the
number of radio TS allocated to one user in downlink can be different than the
number of radio TS allocated to the same user in uplink.
Remarks:
• From Release V15.0, EDGE supports the maximum data rate of 59.2 kbps
utilizing up thru MCS8-9.

8
8
Generalities
EDGE : Enhanced GPRS
GMSK
modulation
8PSK
modulation
59.2
8.8
22.4
17.6
MCS1
MCS2
MCS3
MCS4
MCS5
MCS6
MCS7
MCS8
MCS9
EDGE
CS1
CS2
CS3
CS420.8
8.8
GMSK
modulation
GPRS
GMSK
modulation
8PSK
modulation
59.2
8.8
22.4
17.6
MCS1
MCS2
MCS3
MCS4
MCS5
MCS6
MCS7
MCS8
MCS9
EDGE
GMSK
modulation
8PSK
modulation
59.2
8.8
22.4
17.6
MCS1
MCS2
MCS3
MCS4
MCS5
MCS6
MCS7
MCS8
MCS9
EDGE
CS1
CS2
CS3
CS420.8
8.8
GMSK
modulation
GPRS
CS1
CS2
CS3
CS420.8
8.8
GMSK
modulation
GPRS
EDGE offers better performances than GPRS
> Optimized throughput versus propagation channel
performance
> Enhanced Features:
• Link Adaptation (GPRS/EDGE)
• Measurement coding scheme adaptation
• Incremental Redundancy (EDGE)
• dynamic redundancy added with block repetition
• RLC/MAC layer improvement. No window stalling limitation
EDGE uses an additional modulation scheme (8-PSK) that enables to transmit
more information per radio symbol (3 bits, instead of 1 with GMSK). Drawback is
that it is more dependant on radio conditions.
By adapting the coding schemes to the radio channel conditions dynamically, it is
possible to optimise communication performances and throughput. This is done by
Link Adaptation: through radio measurements, the network (PCUSN) chooses the
best MCS and adapts it. Estimated best MCS is used in each position of the cell.
Moreover Incremental Redundancy provides the possibility to retransmit a data
block using a different puncturing method (additional redundancy) and to recombine
it with retransmitted packets. By this way, probability to receive a correct block is
increased.
The RLC/MAC layer has been significantly improved in EDGE development. For
handsets supporting multiple TS, performance limitations in GPRS due to the limited
size of the acknowledge window is not reproduced in EDGE, i.e. in GPRS RLC
window size is 64, i.e. the transmitter cannot transmit block N+64 if block N has not
been correctly acknowledged by the receiver. In EDGE, windows size has been
extended to 1024 blocks, avoiding loss of incorrect blocks because of too bad radio
conditions.

9
9
Generalities
Speech on the BTS-TCU interface: Abis vs. Ater mapping
TCU BSC
BTS
Ater Interface Abis Interface
0 1 2 3 4 5 6 7
TS i
TS 1/0
TS 24/31
0 1 2 3 4 5 6 7
TS j
AMR HR TCH (TCH/AHS)
FR TCH (TCH/FS or TCH/EFS)
AMR FR TCH (TCH/AFS6.7, TCH/AFS5.9 or TCH/AFS4.75)
8 kbps channel carrying supplementary information in downlink, padding in uplink.
0 1 2 3 4 5 6 7
TS m
TS 1/0
TS 24/31
0 1 2 3 4 5 6 7
TS n
TS p
0 1 2 3 4 5 6 7
8 kbps channel carrying supplementary information (in uplink and in downlink).AMR FR TCH (TCH/AFS10.2)
Reminder: The Nortel BSS does only provide Half Rate Traffic Channel with AMR
introduction:
On the Abis interface, half rate channels induce 8 kbps TS, instead of 16 kbps for
full rate channels. As the same radio TS can be used as a FR or HR channel, the
associated 16 kbps Abis TS is used as one 16 kbps TS in case of FR channel and
two 8 kbps TS in case of HR channel, using the following rules:
• FR: 16 kbps
• HR with T = 0: 8 kbps (the most significant bit of the 16 kbps TS)
• HR with T = 1: 8 kbps (the least significant bit of the 16 kbps TS)
where T indicates the sub-channel number of the Air interface.
In case of FR channel, the 16 kbps Abis TS is naturally connected to the associated
16 kbps Ater TS.
In case of HR channel, the 8 kbps Abis channel is connected to the most significant
bit of the 16 kbps Ater TS. The least significant bit of the 16 kbps Ater TS is not
used and padded using silent pattern by the BSC, in the uplink path.
For the downlink path on the Ater interface, the TCU used always both 8 kbps
whatever the AMR channel type FR or HR. But in case of HR, the BSC ignores the
least significant bit and sends to the BTS the most significant bit.
The 8 kbps channel (on Ater) corresponding to the least significant bit, is used to
manage proprietary frame, in order to ensure a « 16 kbps quality » for the FR
channel for AMR FR codec modes of 6.7 kbps, 5.9 kbps and 4.75 kbps.

10
10
Generalities
Network Engineering
System Dimensioning
Sites layout
Capacity
Cost minimization
Required quality
Number & Type
of Equipment
and Links
Inputs
Constraints
Outputs
The result of network engineering is a definition of the equipment and links of the
networks.
These results must be optimized to minimize installation/operation/maintenance
costs while maintaining the required quality.
To reach these objectives, the available variable parameters intervene in system
dimensioning, taking into account that cellular planning is fixed. Indeed, sites/cells
layout are defined by site population (rural/urban), site topography, etc..

11
11
Generalities
Traffic model overview
TRAFFIC
MODEL
Quality
of
Service
Subscribers
Behavior
Cellular
Planning
System Dimensioning is based on a Traffic Model. A traffic model is a set of
parameters which represent the behavior of the subscribers at the busy hour.
Every operator must define his Traffic Model, which is the result of three influences:
• Cellular planning: the sites/cells layout has been fixed; for instance, a higher
number of cells increases handover, then CPU capacity needs.
• Quality of service: it depends on blocking rate values of traffic and signaling
channels, on network operation, on supplementary services provided, on
subscription costs.
• Subscribers: higher the distribution of GSM subscribers within the population,
higher the number of communications between GSM and PSTN networks. The
rural/urban distribution of GSM subscribers, their activity rate, their mobility are
other influent parameters.

12
12
Generalities
Clutters
Radio waves behave differently depending on the environment, and the radio range
can vary from few hundred meters to several kilometers.
It is then important to classify the different types of environment included in the area
to be provided with GSM service.
As an example the map presented above shows a city and its surroundings,
classified into fourteen types of environment or clutters.
A link budget is established for each clutter, defining a specific cell size.
Example of Dense Urban clutter
Areas within urban perimeter. This includes dense urban
areas with dense development where built-up features
do not appear distinct from each other. It also includes built-
up features of the downtown district with heights below 40
m.
Example of Mean Urban clutter
Areas with urban perimeter. The mean urban clutter
should have mean street density with no pattern, the major
streets are visible, the built-up features appear distinct from
each other. Some small vegetation could be included.
Average height is below 40 m.

13
13
Generalities
Theoretical cells
All areas to be provided with GSM service are characterized and classified.
For areas where traffic is the limiting factor, the site number is just resulting from the
division of number of subscribers in the area by the maximum subscribers managed
by one site.
For each clutter where coverage is the limiting factor, one link budget is established
giving a theoretical size of the corresponding cell with which the area is “paved”.
This step gives a first estimation of the number and type of sites needed to reach
the marketing goals.
Before deployment, Cell Planning has to be performed carefully to determine the
exact site positions and practical coverage, taking into account the existing and
friendly sites.
This is performed with the help of a planning tool which inputs are terrain database
with clutters, sites characteristics and EIRP and signal strength coming from the link
budgets.
The final step is to deliver a list and characteristics of sites after frequency planning
is performed.
This process is iterative until theoretical site positions match to practical ones.

14
14
Generalities
Components of the GSM/GPRS System traffic
Subscriber Activity
(intentional activity)
Mobility Events
(transparent for the subscriber)
Traffic Model
System
SMS
(Point
to
Point)
Call
Attempts
rate
Attach/
Detach
Inter
PLMN
Roaming
Location/
Routing Area
updating
Handover
SMS
Cell broadcast
Periodic
registration
Data
Sessions
The GSM dynamic parameters which define the Traffic Model are specified:
• Subscriber activity: call attempt rate is the most influent parameter.
• Mobility events:
—Handover: their number is linked to the cell sizes
—Location updating/registration: the information concerning the location area
increases with mobility and the definition of the location area
—Inter PLMN roaming: it is of negligible influence on Traffic Model
• System:
—Cell broadcast: this function allows the operator to send various types of
information (traffic, weather forecast, advertising for instance) on MS in
idle mode
—Periodic registration: this action is optional but most operators use it. It is a
periodic update supervised by the system (SDCCH)

15
15
Erlang Law
Definition
Network dimensioning according to the “busy hour” traffic
Unit for occupancy averages of links = Erlang
Traffic Intensity in Erlang =
Resource(s) occupancy duration
Reference period duration
The Erlang unit is not a GSM specific unit. It is used to express a traffic intensity or a traffic
activity.
In GSM, when we focus on a specific radio resource, we compute the traffic intensity of this
resource (value < 1). When we focus on the total network traffic, we compute the network
activity (value may be > 1).
Traffic in Erlangs =
1 Erlang = Total resource occupancy duration of one hour observed on the reference
busy hour.
Example 1: A traffic of 0.5 Erl may correspond to 1 resource occupied during 50% of the
busy hour or 2 resources during 25% or ….
Example 2: A traffic of 3.5 Erl may correspond to 3.5 resources during 100% of the busy
hour or 14 resources during 25% or ….
ERLANGS ON THE AIR INTERFACE
SDCCHTCH
TRAFFIC
(Speech, Data)
SIGNALING
(Beginning of communication)
(End of communication)
(Handover)
SIGNALING
(various procedures)
1
2
T
T
durationperiodreference
durationoccupancy)resource(s
=

16
16
Erlang Law
Offered and carried traffics
Equipment with
blocking rate x%
Offered Traffic Carried Traffic
Increasing blocking - Increase of subscribers number (more offered traffic)
- Decrease of grade of service, while maintaining it
sufficient
Decreasing blocking - Decrease of subscribers number (less offered traffic)
- Increase of grade of service
Assuming x = blocking rate:
Carried Traffic = (1 - x/100) * Offered Traffic
Carried Traffic < Offered Traffic (if x ≠ 0)
In this course we will use the following assumptions:
• Blocking rate for traffic on Radio interface: 2%
• Blocking rate for signaling on radio interface (SDCCH) = 0.1%
• Blocking rate for PSTN interface = 0.5%
• Blocking rate for A interface = 0.1%
• Blocking rate for Abis interface = 0%
• Blocking rate for Ater interface = 0.1%
Those values of blocking rate are typical values. They may change according to
the environment and the QoS we want to offer to the final subscriber.
As blocking rates are always small, we admit that:
Carried Traffic ≅ Offered Traffic

17
17
Erlang Law
Erlang Law with losses (Erlang B)
Maximum
resource
Resources
request
Blocking factor
time1 hour
Yi = occupancy rate of resource i
Offered traffic on
each resource
A
Y1 = 0.6 E
Y2 = 0.75 E
Y3 = 0.45 E
Y4 = 0.35 E
Y5 = 0.4 E
Y6 = 0.5 E
A = 3.05 E
Offered traffic
6
5
4
3
2
1
0
1
2
3
4
5
6
3 9 57
Lost calls
Carried traffic
A’ = 2.9 E
We need 6 resources to match the requests
Average busy
resource
It is assumed (teaching example):
• Offered traffic needs, at some times, up to six resources.
• At a time, only 4 resources max. are available.
Then:
• For each period equal to 3 minutes, the number of resources needed is
computed: i.e. for first period, resources 1, 2 and 6 are requested, given 3
resources.
• Offered traffic on resource 1 includes 12 periods of 3 minutes, giving a traffic
value equal to:
(12 x 3)/60 = 0.6 Erlang.
• Total offered traffic is equal to 3.05 Erlangs, needing an average number of
busy resources of 3.05.
• Three call attempts are rejected.
Note 1
Traffic in Erlangs = Summation of events duration (for each event, on a reference
period):
for instance, reference period = one hour.
Note 2
This teaching example only introduces the traffic notion evaluated in Erlangs.
It does not correspond to the Erlang Law which deals with:
• Very high number of events
• Number of events following a Poisson Law
• Distribution of event duration following a negative exponential law

18
18
Erlang Law
Erlang number computation
A is the Erlang number
λ is the mean rate of events per unit of time
T is the average duration of an event
A = λT
Example on the previous page:
T1 = duration of the observation period (usually it is the busy hour = 60’)
T2 = total channel occupancy duration
X = number of channel requests during T1
3.05ErlTA5.0833
36
183
T0.6
60
36
36X'183T2'60T1
=
X
T2
x
T1
X
T1
T2
A
hourbusytheatrequestpertimeoccupancychannelaverage
X
T2
T
hourbusytheduringtimeofunitperrequestschannelofnumber
T1
X
======
===
==
==
==
λλ
λ
λ
T

19
19
Erlang Law
Erlang B Law tables
6 1.146 1.325 1.622 1.909
n
B
0.001 0.002 0.005 0.010 0.020 0.030 0.050 0.070 0.100 0.200
1
2
3
4
5
7
8
9
10
0.001
0.046
0.194
0.439
0.762
1.579
2.051
2.557
3.092
0.002
0.065
0.249
0.535
0.900
1.798
2.311
2.855
3.427
0.005
0.105
0.349
0.701
1.132
2.157
2.730
3.333
3.961
0.010
0.153
0.455
0.869
1.361
2.501
3.128
3.783
4.461
0.020
0.223
0.602
1.092
1.657
2.276
2.935
3.627
4.345
5.084
0.031
0.282
0.715
1.259
1.875
2.543
3.250
3.987
4.748
5.529
0.053
0.381
0.899
1.525
2.218
2.960
3.738
4.543
5.370
6.216
0.075
0.470
1.057
1.748
2.504
3.305
4.139
4.999
5.879
6.776
0.111
0.595
1.271
2.045
2.881
3.758
4.666
5.597
6.546
7.511
0.250
1.000
1.930
2.945
4.010
5.109
6.230
7.369
8.522
9.685
Formula for lost calls (no queuing):
• N = Resources number for offered traffic
• A = Erlang number
The Erlang B formula is quite complicated. A good approximate result can be
obtained by using the following formula:
Resources N = A + k √(A)
with
• Blocking Rate Br = 10-k
• Traffic (Erlang) = A
The results of the Erlang B formula are summarized in the Erlang B tables provided
in the last section.
rateBlocking
!N
A...
!1
A1
!N
A
]A[E N
N
N =
+++
=

20
20
Erlang Law
Erlang Law with queuing (Erlang C)
Resources
request
Y1 = 0.6 Erlang
Y2 = 0.75 Erlang
Y3 = 0.45 Erlang
Y4 = 0.35 Erlang
Y5 = 0.4 Erlang
Y6 = 0.5 Erlang
A = 3.05 Erlang
time (minutes)
1 hour
Yi = occupancy rate of resource i
Offered traffic on:
Resource
A
0
1
2
3
4
5
6
6
5
1
2
3
4
3 69 18 42 57
Time Out
calls rejected
Queued calls
Carried traffic
A’ = 3.05
A’ = Offered traffic
Offered traffic
Maximum number of
available resource
Average number of
busy resources
It is assumed (teaching example):
• Offered traffic needs, at some times, up to six resources.
• At a time, only 4 resources max. are available.
Then:
• For each period equal to 3 minutes, the number of resources needed is
computed: i.e. for first period, resources 1, 2 and 6 are requested, given 3
resources.
• Offered traffic on resource 1 concerns 12 periods of 3 minutes, giving a traffic
value equal to:
(12 x 3)/60 = 0.6 Erlang.
• Total offered traffic is equal to 3.05 Erlangs, needing an average number of
busy resources of 3.05.
• The three call attempts which would be rejected without Queuing, are
registered and processed with some delay.
Nevertheless after a defined waiting delay, they are definitely rejected.

21
21
Erlang Law
Traffic management: Queuing of TCH requests
FIFO Management on cell basis
1
2
Priority 0
1
2
64
Priority 1
1
2
64
Priority 7
WT1 WT7
TCH allocation request
> r01 to r00
TCH attributedTCH attributedFIFO (*)
FIFO (*) FIFO (*) TCH attributed
0 (max)
1 to 7
Available TCH in the pool
TCH request priority
3
WT0
T11
time out
request
rejected
Example
Emergency Call
Call Reestablishment
....
Paging
Handover
....
= 5= 5
64
Management performed by the BSC, only for TCH (no queuing for SDCCH).
Priority 0 to 7: In order to improve the Traffic Management, priority has been defined
on call basis:
• Internal priorities (0 to 7), per cell; max. priority = 0; one queue per priority
• Level 0 priority can be defined for example for: emergency call, call re-
establishment....
Priority threshold (allocPriorityThreshold O&M parameter; example of value: 2):
• r0 resources are reserved for requests of level 0 priority in the pool of available
TCH
• r0 resources must be available to allow processing of a level 1 to 7 priority
request
• If all these r0 resources are busy, a new level 0 priority request may be queued
in level zero priority Queue.
Waiting Threshold WT0 to WT7 (allocWaitThreshold O&M parameter; example of
value: 10):
• This threshold defines, for each priority level 0 to 7, in each cell, a number of
queued requests; its use is given just below.
• For example:
—Priority 0: WT0=5 and 3 requests are queued
—Priority 1: WT1=5 and 2 requests are queued
A third request in P1 queue can not be accepted because the total number of
requests queued in the queue P0 and P1 (3+2) is equal to WT1.

22
This can be explained generally with the following expression:
So, a request of priority Pi can be queued only if, at this moment, the above
condition is satisfied.
Protection Timer (T11 time out; AllocPriorityTimers O&M parameter; standard
value: 5 seconds):
• TCH request still stored at end of time out is erased from the queue.
Note: when the Pi Queue is full, the related level i priority request is rejected (i
range: 0 to 7).
FIFO (*): (number of Queued requests in Pj Queues) ≤ WTiΣ
j
j i
=
=
0

23
23
Erlang Law
Exercise
> How many resources are necessary for an offered traffic of 65
Erl with a blocking rate value of 2%?
> What is the maximum offered traffic that 95 resources can
manage without exceeding a blocking rate value of 0.1%?
> How many resources are necessary for an offered traffic of 290
Erl with a blocking rate value of 0.1%?
manage without exceeding a blocking rate value of 10%?
manage without exceeding a blocking rate value of 2%?

24
24
Traffic Model
BSS Reference call and mobility profile: detailed
computations for CS voice
Mobile Originating calls
MO = 66%
Mobile Terminating calls
MT = 34%
16.72 s 90.1 s
Call
Establishment
Ringing
MO and MT calls description
Successful
No response called party
Busy
MO
85%70%
Legend MT
10%
20%
5%
10%
{

25
25
Traffic Model
BSS Reference call and mobility profile: detailed
computations
MO busy called-party:
- Setup
MO Duration *
(s)
MO calls
ratio τ 1
MO successful:
- Setup
- Ringing
- Conversation
70%
66%
120
10%
10
15
25
MO calls
ratio τ 2
MO no response:
- Setup
- Ringing
10
20
30
20%
10
MT successful
- Ringing
- Conversation
85%5
120 34%
MT no response
- To paging
- or busy
- Ringing
10%
5%25
TOTAL
MT
Duration
(s)
MT calls
ratio τ 1
MT calls
ratio τ 2
* : This is the duration of traffic channels occupancy on the radio interface, either for traffic (ex:
conversation) or for signaling (ex: setup, ringing)
46.2
6.6%
13.2%
28.9%
3.4%
1.7%
τ1 x τ2
τ1 x τ2
46.2%
(19.8%)
28.9%
(5.1%)
-Successful calls: 75.1%
-Unsuccessful calls: 24.9%
Successful calls
(unsuccessful)
Successful calls
(unsuccessful)
55.44
(120 x 0.462)
11.55
(25 x 0.462)
1.98
(30 x 0.066)
1.32
(10 x 0.132)
1.445
34.66
0.425
(25 x 0.017)
106.82
including
conversation:
90.1
TCH occupancy
(s)
TCH
occupancy
(s)

26
26
Traffic Model
Standard traffic model. Observed figures
Number of observed subscribers = 4000
Total call attempts at the busy hour = 4000
Mean TCH occupancy duration per call
attempt (traffic) = 90.1 s
Mean TCH occupancy duration per call
attempt (signaling) = 16.72 s
Mean SDCCH occupancy duration per
call attempt = 4 s
Mean SDCCH occupancy duration for
Loc./Rout. Area update, Attach/Detach,
SMS, Supplementary Services = 4 s
Call attempts per subscriber during
the busy hour = 1
100
20
60 100
20
Average number of
requests for SDCCH,
except those for call
attempts, during the BH,
for the whole subscribers
= 26920
Mean TCH occupancy per call attempt (total) = 106.82 s
Exercise: ATCH ?
Exercise: ASDCCH ?
Exercise:
Find ATCH and ASDCCH for 1 subscriber at the busy hour.
ATCH = λTCH * TTCH
λTCH ?
TTCH ?
ASDCCH = ?
What is the ratio between SDCCH and TCH traffic?
In the rest of this course we will apply this ratio. (We consider that proportion
between signaling and traffic is constant).

27
27
Traffic Model
High mobility and short call duration traffic model
0.61.6Handover per subscriber at BH
1.724.54
Loc./Rout. update, periodic
update, attach/detach, SMS, per
subscriber in BH
37 s90 sAverage call duration
45 s120 sAverage call holding time
5050
Number of cells managed by the
BSC
4000040000Active subscribers in the LAC
2.251BHCA per customer
0.025 Erl0.025 ErlTraffic per customer
Short call durationHigh mobility

28
28
Traffic Model
PS communication types
File Size
per transaction
in Kbytes
Information Service & E-commerce
UL
E-mail (without attachment)
E-mail (with attachments)
Web Access (no file downloading)
Web Access (file downloading)
0.7
Simple Messaging
0.3
2.7
4
12
204
612
180
8
680
10
0.3UL
UL
UL
UL
UL
DL
DL
DL
DL
DL
DL
Communication UL / DL

29
29
Traffic Model
Subscriber Categories
Active Data Terminals
in X’s network (k units) BH
Business 1038
Consumer 20132
Field Service 1028
Telemetry 323
Total
221

30
30
Traffic Model
Subscriber profile example
Business File Size
per
transaction
Number of
transactions
at BH
in Kbytes
Information Services & E-commerce
UL 0.300
DL 2.700
E-mail (without attachments)
UL 4.000
DL 12.000
E-mail (with attachments)
UL 204.000
DL 612.000
Web Access (no file downloading)
UL 8.000
DL 180.000
Web Access (file downloading)
UL 10.000
DL 680.000
1.95
0.98
0.24
0.19
0.05
55.485
Kbytes in one
hour (BH) in
UL
232.105
Kbytes in one
hour (BH) in
DL
GPRS and EDGE call profiles include for each type of subscriber (Business,
Consumer, Field Service and Telemetry) the types of service used and the
description of the amount of traffic each service generates.

31
31
Traffic Model
Busy hour throughput example
BH peak bit/s (max UL,DL) sigma
Business 10 1857 3,00
Consumer 20 986 2,00
Field Service 10 326 4,00
Telemetry 3 2 20,00
Network 20 503 bit/s (max UL/DL)
Subscribers’
repartition
38/221
132/221
28/221
23/221
Average throughput per subscriber
according to GPRS Busy Hours
0,0
400,0
800,0
1200,0
1600,0
2000,0
0
2
4
6
8
10
12
14
16
18
20
22
hours
Averagebit/spersubs
Total (max UL, DL)
Business
Consumer
Telemetry
Field Service
The last parameter to discuss is the subscriber Busy Hour.
If we assume that the GPRS traffic profile is gaussian like, we have a sigma and a
peak time (Busy Hour) for each category. Using the number of active GPRS
subscribers per category (deduced from marketing inputs) as coefficients, it is
possible to compute an average throughput per subscriber at each time of the day
(curve “Total(max UL, DL)”). Its peak value is the average throughput per
subscriber at Network Busy Hour.
Thus, according to GPRS Busy Hour, the average traffic per subscriber can be very
different (almost double). If the busy hour is different for each subscriber, then the
average throughput per subscriber is reduced.
The Busy Hour is largely determined by Operator Tarifications and subscribers
behavior. It has to be considered carefully.

32
32
Dimensioning Procedure
Network dimensioning according
to the busy hour traffic
End dimensioning
Radio Interface
Start dimensioning
Cell
BTS
Abis
BSC
Ater
TCU (TRAU)
A interface
MSC/VLR
HLR
PCU
Agprs
SGSN
GGSN
SY2
EDGE dependant
Cell organization (omni or multi-sector sites, cell dimension) depends on expected
traffic, but also on dedicated radio propagation and interference problems.
These problems are in charge of radio-engineers. And cell organization is admitted
as entry data for the other part of GSM dimensioning which is described hereafter:
• Radio interface: number of TCH/BCCH/SDCCH channels.
• Abis/Ater/A interface: number of PCM links.
• BTS: number of TRX, BTS and interface boards (possibility of “drop and insert”
techniques).
• BSC: number of interface boards, BSC type.
• TCU (TRAU): number of shelves.
Main EDGE dimensioning constraints are:
• Number of PDTCH configured per cell
• Number of Joker TS configured per cell
From theses assumptions are computed additional resources (number of PCMs,
HW upgrades, products adaptation) required to implement EDGE.

1
nortel.com/training
Section 3
BTS Dimensioning

2
2
Lesson Objectives
> For cell, compute:
• The TCH and PDTCH numbers
• The SDCCH number
• The CCCH number
• The TRX number
> For site, dimension:
• The BTS type
• The BTS configuration
• Total PCM TS on Abis link, including LAPD TS and Joker DS0
(EDGE)
You will also be able to quickly obtain these results using look-up tables
summarizing all above computations
Upon completion of this section, the student will be
able to
This section describes and justifies the several computation steps for BTS
dimensioning.
Starting site data are:
• Offered traffic
• Site layout: number of sectors per site, number of TRX per cell
• Blocking rate currently taken for BTS on TCH: 2%
• Blocking rate currently taken for BTS on SDCCH: 0.1%

3
3
Contents
> Overall Information
> Dimensioning Detailed Method
> Packet Logical Channels
> BTS Connections
> Terrestrial Link Optimization

4
4
Overall Information
Cell subscriber repartition (Example)
100
100
100
20
60 100
100
60 60
20
20
20
20
20
20
60
40 20
20
Town
Rural
Suburb
Highway
The cellular planning determines the cell distribution per BTS; the traffic per cell is
obtained from the average number of mobile stations assumed in each cell, with a
fixed average value of traffic per subscriber.
For the example of the diagram:
• Traffic is given per cell or per site, in Erlangs; for instance, assuming an
average traffic value of 25 mE per subscriber, 2400 subscribers correspond to
a traffic value of 60 Erlangs.
• Three types of traffic area are shown:
— a high traffic area with low surface cells: center of a town
— two medium traffic areas: a suburban area and a straight motorway area
— a low traffic area with large surface cells: countryside

5
5
Overall Information
BTS Dimensioning methods
1. First method: detailed understanding
- TCH
- PDTCH
- SDCCH (BCCH)
- TRX
Offered traffic on site
Site layout
TABLES
Abis PCM link
PCM circuit Nbr
SDCCH/8 Nbr
BCCH Nbr
TCH Nbr
TRX Nbr
Abis Joker DS0 (EDGE)
Abis LAPD TSLAPD Nbr
2. Second method: look-up tables (for voice standard traffic model)
CS - Voice/data traffic (Erlangs)
Signaling (Erlangs)
Blocking rate
Site layout
BTS limits
Abis PCM links
Abis LAPD TS
LAPD
Concentration
(2G only)
PS - data traffic (bits/s)
Abis Joker DS0 (EDGE)
First method: detailed understanding
Starting from the site data, and using the Erlang B, a didactic and detailed method
is given; it is a step by step analytic method.
This method is general, despite the choice of waiting or blocking rate values in the
computation completed hereafter.
Second method
Computations of first method are summarized in tables.
These tables are of quick and general use for standard BTS dimensioning.
Final checks are done
On TRX number relating to radio TS number.
On BTS load constraints.

6
6
Overall Information
> BTS Model provisioning
• Radio interface dimensioning:
TCH, PDTCH, SDCCH, CCCH, TRX, BTS Type
• Abis interface dimensioning:
Traffic and signaling (LAPD) TS and Joker DS0 (EDGE)
• BCF units dimensioning:
PCM interface boards (PCMI)
Signaling concentration boards (DSC)
• CBCF units dimensioning:
PCM interface boards (CPCMI)
Radio interface dimensioning:
Three groups of channels:
• traffic channels TCH, PDTCH
• dedicated channels SDCCH
• common channels CCCH
Abis interface dimensioning:
• Radio interface will be defined, as TRX number
• Number of traffic TS = 2 x (TRX number)
•
• Number of Joker DS0 depending on the expected MCS distribution within the
cell (EDGE), ranging from 0 to 8
• Depending on the product range BTS 18000, S12000 or S8000
( )
( )integerupper
BTS18000for9or8
numberTRX
LAPDofNumber =

7
7
Overall Information
GSM/GPRS Logical channels on radio interface TSs
FACCH
Frequency correction
Synchronization
Broadcast control
Access request
Subscriber paging
Answer to Access request
Broadcast info
Dedicated Signaling
Sys Info 5, 5bis, 5ter 6 + SMS
Traffic (speech – CS data)
Associated Signaling
BTS
0 1 2 3 4 5 6 7TS
MS
FCCH
SCH
BCCH
PCH
AGCH
CBCH
SDCCH
SACCH
TCH
FACCH
SDCCH
SACCH
FCCH
SCH
BCCH
RACH
PCH
AGCH
RACH
CBCH
TCH
Traffic (speech – CS data)
Radio Measurement + SMS
Broadcast info
Dedicated Signaling
M.S. Pre-synchronization
Access request
Subscriber paging
Answer to Access request
MF51
MF26
PDTCH
PACCH
Traffic (PS data)PDTCH
PACCH
Traffic (PS data)
MF52
Three groups of logical channels:
• 1. Traffic channels (TCH; PDTCH), and associated channels (FACCH,
SACCH; PACCH, PTCCH):
• Number computed from Erlang B law, starting from offered traffic,
according to the traffic model.
• 2. Dedicated signaling channels (SDCCH, SACCH, CBCH):
• Number computed from Erlang B law, using figures given by the traffic
model.
• The CBCH is optionally used; when activated, it uses permanently one
SDCCH resource.
• 3. Common channels (CCCH), BCCH and synchronization channels
(FCCH, SCH)
• Theoretical studies on message exchanges on radio interface have
shown that one common channel is often sufficient, for low to medium offered
traffic on CELL.
• “BCCH combined”: common channel pattern for small capacity cells
(O1): Signaling channels SDCCH/SACCH are included in same frame as
common channels:
Traffic CHannel
Packet Data Traffic CHannel
TCH
PDTCH
Fast Associated Control CHannel
Packet Associated Control Channel
Packet Timing advance Control
CHannel
FACCH
PACCH
PTCCH
Stand-alone Dedicated Control CHannelSDCCHFrequency Control CHannelFCCH
Signaling CHannelSCHCommon Control CHannelCCCH
Slow Associated Control CHannelSACCHCommon Broadcast CHannelCBCH
Random Access CHannelRACHBroadcast Control CHannelBCCH
Paging CHannelPCHAccess Grant CHannelAGCH

8
8
Overall Information
FR vs. HR TCH
BTS
Abis interface (E1/T1)
0 1 2 3 4 5 6 7
TS n
TS 1/0
TS 24/31
16 kbps
TCH/F
2x8 kbps
TCH/H
Um interface
Capacity
improvements
thanks to AMR
introduction
0 1 2 3 4 5 6 7TS
f0
TS p
4 5 70 1 2 3 6TS
f1
But, there can be holes at a time being.
A Full Rate call may not be established.
Full Rate blocking rate increases.
AMR Half Rate allows to double the number of calls that could be carried on a Abis
PCM. Therefore, AMR HR offers the possibility to have a capacity increase in terms
of Erlang with the quality of a FR speech.
Indeed, one Full Rate Traffic CHannel (TCH/F) requires one 16 kbps TS on Abis
and one complete Radio TS. Whereas, the same resources (the 16 kbps TS on Abis
and the Radio TS) can be shared by two Half Rate Traffic CHannels (TCH/H).
The Nortel BSS does only provide Half Rate Traffic Channel with AMR introduction:
• Adaptative multi-rate Half rate Traffic CHannel (TCH/AHS)
• Adaptative multi-rate Full rate Traffic CHannel (TCH/AFS)

9
9
Overall Information
BTS Product range: cell layout
8 TRXs
8 TRXs
8 TRXs 8 TRXs
8 TRXs
Omni Bi sectorial Tri sectorial
8 TRXs
For BSC12000: 24 TRXs max per site
16 TRXs
16 TRXs
16 TRXs 16 TRXs
16 TRXs
Omni Bi sectorial Tri sectorial
16 TRXs
For BSC3000: 48 TRXs max per site (V15.1) with BTS18000
The Diagrams show the max. number of TRX which can be installed per cell, on one
site managed by a BTS.
Note that in the case of a BSC3000, a max of 48 TRXs per site is defined only with
the introduction of the BTS 18000 and in a S161616 config.
Reminder: for high traffic densities, the solution is to create multi-sectorial sites,
instead of increasing the number of omni-sectorial sites of reduced coverage, which
would result in:
• Higher installation cost
• Difficulties to find sites
Currently, the most used configurations are:
• Omni-sectorial layout for low traffic sites
• Tri-sectorial layout for medium and high density urban sites
• Bi-sectorial layout for roads

10
10
Overall Information
Full Range Family
e-cell
Outdoor
Microcellular coverage
34.5 liters
S8006 Street
DeployableS8002 GSM-RS8000 Indoor S8000 Outdoor
S2000H
Integrated self
contained cell-site
Common package
Indoor/Outdoor
No fans,
natural convection
S12000 Indoor
S12000 Outdoor
Highest capacity
Lowest foot print
Up to 12 TRXs
per cabinet
S8000 Outdoor and Indoor
• 8 TRXs per cabinet and up to 3 (with BSC 2G) or 6 (with BSC e3) cabinets
• DRX architecture: 1 (e)TRX = 1 (e)DRX + 1 ((H)e)PA
• Compact BCF (or CBCF)= CMCF and CPCMI boards
S8002
• 2 TRXs outdoor BTS (O2) designed for railway applications (R-GSM band)
• Environmental performances equal or better than current S8000
• Re-using common S8000 equipment: CBCF, DRX, PA, RX splitter, rectifiers
• User compartment (6 U)
S8006
• 6 TRXs outdoor BTS designed for installation along streets and roads without
requirement for building permits (O6, S222, S33 and S42)
• Environmental performances equal or better than current S8000
• Diversity radio path as standard
• Re-using common S8000 equipment: CBCF, DRX, PA, RX splitter, rectifiers
S2000H&L
• 2 TRXs outdoor/indoor BTS in 1 cabinet, expandable to 4 TRXs with an additional
cabinet
• Small BCF (or SBCF) = 1 SMCF + 1 SPCMI boards
• Internal antenna for S2000L (optional)
e-cell
• 2 TRXs BTS in 1 cabinet, expandable to 4 TRXs with an additional cabinet
• 1 antenna (integrated or external)
S12000 Outdoor and Indoor
• 12 TRXs per cabinet and up to 3 (with BSC 2G) or 4 (with BSC e3) cabinets
• DRX architecture: 1 (e)TRX = 1 (e)DRX + 1 ((H)e)PA
• CBCF with CMCF and CPCMI boards (for up to 3 cabinets) or XCBCF with CMCF
Phase 3 and 4 CPCMI boards (for 4 cabinets)

11
11
Overall Information
Full Range Family
BTS 18000 OutdoorBTS 18000 Indoor
BTS 18020 Outdoor:
• Fully Integrated self contained cell-site:
• 18 TRXs (DRX + PA) in a single cabinet (16 TRXs limitation with BSC3000 in V15.1).
• Rectifiers, battery back-up, cooling and heating and 220 Vac main (or 2 x 110 Vac live)
• Optimized size versus capacity ratio : Cabinet size 150 x 135 x 70 cm
• PA TX Power: 30 W (1800/1900) / 40 W (850/900) / 60 W (900 HPRM)
• Extended operating temperature range: -40 °C to +50 °C
• Max consumption : Total for cabinet : 6642 VA ( with heater on : 9442 VA and with heater on and
batteries in charge : 11234 VA )
• Cabinet weight: when fully equipped = 500 kg.
BTS 18010 Indoor:
• Compact packaging:
• 18 TRX (DRX + PA) in each cabinet. (Divided in 6 RM’s)
• New BCF integrated in the main cabinet and up to 3 radio cabinets.
• Modular and flexible configuration: from S666, or O18 or S99 in 1 cabinet and up to S161616 in 3 cabinets
(with a BSC3000) or S888 in 2 cabinets (with a BSC 12000)
• Dimensions: Height : 175 cm Width : 60 cm Depth : 60 cm
• PA TX Power: 30 W 30 W (1800/1900) / 40 W (850/900) / 60 W (900 HPRM)
• Max Consumption : 5123 W
• Extended operating temperature range: -5 °C to +45 °C
• Cabinet weight: when fully equipped =300 kg
Nortel Networks has also developed the BTS 18000 Combo (indoor/outdoor) which is a
UMTS/GSM BTS, and the BTS 18020 MCPA which is an outdoor 1900 GSM BTS with a MCPA
cabinet for the coupling system.

12
nortel.com/training
Lesson or Module Title
Lesson or Module # or Module # –
Lesson #
nortel.com/training
Dimensioning Detailed Method
This chapter gives all the computation steps needed to evaluate:
• The number of traffic channels TCH in a cell.
• The number of signaling channels SDCCH in a cell.
• The number of TRX per cell.
• The total number of time slots on Abis link (including signaling and EDGE DS0
TS).
• The number of boards inside the BCF.

13
13
Traffic channels reminder
AiTi
26 frames = 120 ms
T0 A0T0 T0 T0 T0 T0 T0 T0 T0 T0 T0 T0T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 T1 A1 time
Half Rate - Downlink & Uplink
T
: TCH
(FR)
A : SACCH : IDLETi : TCH (HR)
sub-channel
no. i
Ai : SACCH
sub-channel
no. i
26 frames = 120 ms
Full Rate - Downlink & Uplink
time
T AT T T T T T T T T T TT T T T T T T T T T T T
Full rate speech transmission
When a Mobile Station is in communication mode, speech is coded every 20 ms in
blocks. These blocks are coded in 8 half-bursts, whose information quantity is
equivalent to 4 entire bursts. Then, one burst has to be delivered every 4.615 ms.
So, in 26 frames lasting 120 ms, 24 bursts are used for speech transmission. One
burst is used for an SACCH. The last one in the sequence is an idle burst. During
this burst, the mobile is not idle, but it uses this time to monitor the neighboring cell
frequencies.
Half rate speech transmission
When the half rate speech transmission is in use, the 26 frames of a given time
slot can be separated between two users, since only 12 coded speech bursts are
used per user.
So, in 26 frames lasting 120 ms, the odd burst numbers are restricted to one user,
and the other numbers are for the other user. SACCH bursts are in the 13th
and
26th
positions. In this case, the monitoring is more frequent.
4.75 kbpsAMR 4k75
5.9 kbpsAMR 5k9
6.7 kbpsAMR 6k7
10.2 kbpsAMR 10k2
5.6 kbpsHR
12.2 kbpsEFR
13 kbpsFR
Source coding rate

14
14
Number of traffic channels in a cell
Erlang ‘B’
Loss
Formula
Erlang ‘B’
Loss
Formula
/2
X
Number of
subscribers
Subscriber
activity
blocking
rate
Number of TCH/F resources
+ Number of
TCH TS
Percentage
of HR calls
Number of TCH/H
resources
X
Percentage
of FR calls
X
blocking
rate
.planned
cell traffic
planned
cell traffic
Subscriber activity: traffic per subscriber at busy hour = 25 mE (example).
Number of subscribers = 1700 (example). Then planned traffic in the cell including
the 1700 subscribers = 42.5 Erlangs (example).
With only Full Rate calls:
Number of necessary resources with a blocking rate of 2%, obtained from Erlang
B table: n = 53.
Conclusion: TCH channels = 53 for 42.5 Erlangs cell and blocking rate = 2%.
With 20% Half Rate calls:
Planned traffic in the cell for Full Rate calls: 0.8x42.5 = 34 Erlangs.
Number of necessary Full Rate resources with a blocking rate of 2%, obtained
from Erlang B table: n1 = 44.
Planned traffic in the cell for Half Rate calls: 0.2x42.5 = 8.5 Erlangs.
Number of necessary Half Rate resources with a blocking rate of 2%, obtained
from Erlang B table: n2 = 15.
Conclusion: TCH/F Channels = 44 + 15/2 = 52 for 42.5 Erlangs cell and blocking
rate = 2%.
Another approach consists in dimensioning the number of TCH TS only considering
Full Rate TCH and then calculating the capacity increase in terms of Erlang with p%
of Half Rate allocations.
53 Full Rate resources correspond to 2x53 = 106 Half Rate resources; With a
blocking rate of 2%, the Erlang B table gives a traffic of 93.8 Erlangs that is to say a
gain of 120%.

15
15
Dedicated signaling channels reminder
A : SACCH D : SDCCH : IDLE
51 frames = 235 ms
A5 A6 A7 A0
A4
D7D6D5D4D3D2D1D0
D7D6D5D4D3D2D1D0A1 A2 A3
time
Uplink
51 frames = 235 ms
A1 A2 A3A0D7D6D5D4D3D2D1D0
A5 A6 A7A4D7D6D5D4D3D2D1D0
time
Downlink
The dedicated channels are combined into two multi-frames of 51 frames. In the
uplink and the downlink directions, the configuration is almost the same one, only
shifted by 15 frames.
The dedicated channels combination broadcasts a group of 8 SDCCH frames (2
groups of 4 consecutive SDCCH frames), each of them is associated to 4
consecutive SACCH frames. Each different group is used by a different dedicated
communication. The multi-frame configuration is shown on the above figure.
So 8 users can use the same physical channel simultaneously, and the different
communications associated to their SACCH signaling are spread on a cycle of 102
frames (2 51-multi-frames). In such a multiplexing cycle, 6 frames are unused (idle
TS).

16
16
BCCH Combined reminder
R R
R R D2
D2
D1
D1
D0
D0A1
A3
A0
A2R
R
R
R
D3
D3
51 frames = 235 ms
time
Uplink
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
A : SACCH D : SDCCH : IDLEB : BCCHS : SCHF : FCCH
: AGCH
/PCH
C R : RACH
A3A2
A1D3D2
D3D2
D1
D1
D0
D0 FSFSFSC CC FSBFS
FSFSFSC CC FSBFS
51 frames = 235 ms
A0
time
Downlink
In the case of a low capacity cell, it is possible to combine on the same physical
channel some dedicated channels with some common control channels.
Their configuration is done on 2x51 frames and is indicated in the SI type 3.
This combination contains all the channels of dedicated and common combinations:
FCCH, SCH, BCCH, PCH, AGCH, SDCCH, SACCH and RACH.
Downlink way
From a common control combination, FCCH, SCH and BCCH keep their
configuration (FCCH+SCH: 0, 10, 20, 30 and 40; BCCH: 2 to 5) for both multi-
frames.
PCH and AGCH are still dynamically configured but only on the bursts: 6-9 (except
when extended BCCH are used), 12-15 and 16-19, for both multi-frames.
On the bursts left, 4 blocks of 4 SDCCH TSs, each of them associated with a
SACCH block of 4 TSs, and one idle TS at the end of each multi-frame. Each
different group is used by a different sub-channel.
Uplink way
On 102 frames, 27 RACH frames are kept and the other ones are replaced by 4
blocks of 4 SDCCH TSs, each of them associated with a block of 4 SACCH TSs.

17
17
Number of SDCCH in a cell
planned cell
traffic (ATCH)
ASDCCH
Number
of SDCCH
resources
blocking rate
•
• 8
Number
of SDCCH
Time slots
Erlang‘B’
Loss
Formula
X
100
x
call attempts/second
location update rate…
mean SDCCH occupancy time
Traffic model at X%
Since 1 SDCCH TS carries up to 8 SDCCH channels, we divide by 8 the number of
resources obtained from Erlang B table.
If ATCH = 42.5 Erl, ASDCCH = 28% * 42.5 = 11.9 Erl
So the number of SDCCH resources = 24 for a blocking rate of 0.1%.
=> number of SDCCH TS = 24/8 = 3 SDCCH TS
Remark: if the number of TCH TS necessary is ≤ 7, then, the BCCH combined
configuration can be used if the number of SDCCH resources is ≤ 4.
Caution: for a given (TCH, SDCCH) configuration, an increase of the Half Rate
traffic requires a new dimensioning of the SDCCH resources.
Example:
• Dimensioning for Full Rate only:
ATCH = 42.5 Erl gives NTCH = 53 for a BrTCH = 2%
Therefore, ASDCCH = 11.9 Erl requiring NSDCCH = 24 (3 SDCCH TS) for a
BrSDCCH = 0.1%
• Dimensioning for full Half Rate:
N’TCH = 2x53 = 106 gives A’TCH = 93.8 Erl for a Br’TCH = 2%
Therefore, A’SDCCH = 0.28x93.8 = 26.3 Erl requiring N’SDCCH = 44 (6 SDCCH
TS) for a Br’SDCCH = 0.1%

18
18
Packet Logical Channels
Multi-frame structure
0 1
Radio Blocks
Cycle of 52 TDMA frames divided in:
♦ 12 radio blocks B0-B11 (of 4 consecutive
frames)
♦ 4 idle frames (X)
Idle frames
TDMA Frame 0 1 2 3 4 5 6 7 8 9 10111213141516171819 20212223 24252627282930313233 34353637383940 4142434445464748495051
Block B 0 B 1 B 2 0 B 3 B 4 B 5 1 B 6 B 7 B 8 2 B 9 B 10 B 11 3
2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
GPRS Time Slot (PDCH)
TDMA Frame
= 4.615 ms
The packet channels carry either RLC data blocks or RLC/MAC control blocks
(except PRACH and PTCCH UL, which use an access burst instead of normal
bursts). Each of these radio blocks are mapped after channel coding and
interleaving onto 4 radio TS (called radio blocks because they carry logical radio
blocks).
The mapping in time of the packet logical channels carried by the same PDCH is
defined by a multi-frame structure. The multi-frame structure for PDCH consists in a
cycle of 52 successive TDMA frames, divided into 12 blocks (of 4 TS each) and 4
idle frames according to the above drawing.
The multiplexing of the packet channels on a PDCH is not fixed like in the GSM
system. It is managed by some parameters and the following block order: B0, B6,
B3, B9, B1, B7, B4, B10, B2, B8, B5, B11. For example, if there are 4 PBCCH
blocks in the cell, those will be carried by the blocks B0, B6, B3 and B9 (on the
same TS indicated in System Information 13 on BCCH).
The idle frames are used by the MS for signal measurements and BSIC decoding
on the SCH of neighboring cells (idle 1 and 3) or for TA update (sending an access
burst on PTCCH UL in idle 0 or 2 and receiving an RLC/MAC control block on
PTCCH DL in idle 0 and 2 of 2 successive multi-frames = 4 TS in total).

19
19
Packet Logical Channels
PDTCH Allocation
TS0 TS1 TS2 TS3 TS4 TS6TS5 TS7
TDMA2
TDMA3
TDMA4
Combined GSM/GPRS TS
Configuration TCH/PDTCH
GPRS TS (PDTCH: packet switched)
TDMA1
GSM TS (TCH:circuit switched)
The TS configuration is declared for each TS at the OMC-R.
Some TS are reserved for the GSM system only (circuit switched TS): TCH,
some others are reserved for the GPRS only (packet switched TS: PDTCH),
some others TS can be used either as TCH or PDTCH on demand.
The possible configurations for the packet switched channels (PDTCH) are:
• PDTCH
• PCCCH/PDTCH
• PBCCH/PCCCH
• PBCCH/PCCCH/PDTCH
These configuration will result in different packet channels multiplexing on the same
PDTCH (for more details, see the multi-frame at 52 TS).

20
20
How many TRX per cell?
Take the
upper
integer
multiple
of 8
Number of CCCH
Between 1 (TS 0) and 4
radio time slots
(TS 0/2/4/6)
÷
8
+
Number of SDCCH
radio time slots
Number of TCH radio
time slots
Total
radio time
slots
Number of
TRX
Number of PDTCH radio
time slots
CCCH rule
Number of CCCH radio time slots = 1 per cell.
In some cases (microcell, dual band), we may need more than 1 CCCH: up to 4 in
total (TS0, 2, 4, 6) as specified in the GSM recommendations. The addition of
CCCH TS will depend on the traffic model, the LAC repartition and the environment.
2 CCCH TS may be necessary in a single layer cell if, with 1 CCCH TS, the number
of TRX per cell is > 6 and the offered traffic per LAC is > 1200 Erls.
In a multi layer cell, a second CCCH TS may be necessary if, with 1 CCCH TS, the
number of TRX per cell > 5.
In our example:
Number of TCH radio time slots = 53 (example: cell with 1700 subscribers).
Number of SDCCH/8 radio time slots = 3.
Total number of radio time slots: 53 + 3 + 2(CCCH) = 58.
Number of TRX (8 radio TS per TRX): 58/8 = 8 TRXs.
Exercise: In this configuration, what will be the distribution between SDCCH and
TCH for full Full Rate? For full Half Rate?
Remark: if the cell is extended, the number of TRX is obtained by dividing the total
number of radio TS by 4.

21
21
How many traffic Abis time slots?
TRX
Dimensioning
/ 8
*2
Total Number of
radio timeslots
number
of TRX
number of Abis
traffic
timeslots (64 kbps)
/ 4
2 PCM TS at 64 kbps
8 radio TS carrying 16 HR TCH
64 kbps 64 kbps
Air interface
8 radio TS carrying 8 FR TCH
Abis interface
8 radio TS carrying FR & HR TCH
A PCM TS supports up to 8 half rate traffic channels with a switching matrix at 8
kbps (half rate speech). Concentration from 4 time slots on radio interface towards 1
time slot on Abis interface is performed by BTS.
1 TRX handles 8 radio TS:
number of traffic time slots on Abis/Ater = (number of TRX) x 2
For the chosen example (8 TRXs):
• Number of traffic TS on Abis and Ater interfaces (8 x 2) = 16 TS
Note: 16 time slots on Abis PCM link correspond to 64 Full Rate TCH traffic
channels up to 128 Half Rate TCH traffic channels on radio interface.
4 full rate traffic channels are supported by:
4 TS
(on 4 radio channels)
1 TS (4x16 kbit/s)
(on one PCM link)
1 TS (4x16 kbit/s)
(on one PCM link)
4 TS (4x64 kbit/s)
Radio interface Abis interface Ater interface A interface
8 half rate traffic channels are supported by:
4 TS
(on 4 radio channels)
1 TS (8x8 kbit/s)
(on one PCM link)
2 TS (8x16 kbit/s)
(on one PCM link)
8 TS (8x64 kbit/s)
Radio interface Abis interface Ater interface A interface

22
22
LAPD Frame Reminder
FCS : Frame Check Sequence SAPI : Service Access Point Identifier (0, 1, 3, 62)
F : Flag TEI : Terminal Equipment Identifier
0 to 260 octets
FCS Control AddressF
N (R) N (S) TEI SAPI
Information F
LAPD
Start of
frame
End of
frame
On Abis interface for each BSC and related BTS terminal port (TEI), three types of
links may be activated depending on the SAPI parameter value:
The Radio Signaling Link:
• Radio resource management procedures SAPI = 0
• Short messages, point to point SAPI = 3
The Operation and Maintenance Link: O&M procedures SAPI = 62.
LAPD messages on Abis:
• OML: software download, channel configuration, notification (event report)
• RSL: paging, HO command, channel requirement
On Agprs, between BSC and PCU, same OML SAPI number = 62 is used for radio
configuration. RSL SAPI number = 0 is used for allocation of GPRS TS. An extra
link exists: GSL(GPRS Radio Signaling Link) using SAPI number = 1 for
communication between BTS and PCU for TBF (Temporary Block Flow) related
messages.

23
23
Abis Interface Protocols
RSL = Radio Signaling
Link
OML = Operation and
Maintenance
Link
GSL = GPRS Radio
Signaling Link
RSM = Radio Subsystem
Management
O&M = Operation and
Maintenance
RSM O&M
RSMO&M O&M
Level 1 layer
RSL OML
TRX
BCF
Level 3
layer
LAPD
Level 2
layer
BTS side BSC side
GSL
RSL OMLGSL
This interface located between BTS and BSC has these features:
• Partly normalized
• No inter-operability (currently) proprietary
It is organized in three levels:
• Level 1 PCM transmission (E1 or T1):
— Speech:
– Conveyed in timeslots at 4 (full rate) to 8 (half rate) x 16 kbps (remote
transcoders)
— Data:
– Conveyed in timeslots at 4 x 16 kbps
– The initial user rate (CS), which can be 300, 1200, 1200/75, 2400, 4800
9600 or 14400 bps is adjusted to 16 kbps.
– For Packet Switch data, 9.05, 13.4 kbps (GPRS CS1 and CS2), 8.8 and 11.2
kbps (EDGE MCS1 and MCS2) channels are each using a 16 kbps timeslot.
For all other PS data rates, more than one 16 kbps timeslot are used.
• Level 2 LAPD protocol: Standard HDLC procedure:
— RSL = Radio Signaling Link
— GSL = GPRS Radio Signaling Link
— OML = Operation and Maintenance Link
• Level 3 application protocols:
— RSM = Radio Subsystem Management
— O&M = Operation and Maintenance procedure

24
24
Concentrated LAPD with CBCF
CMCF
CPCMI
Switching
Matrix
8 DRXs
Signaling
TS
BSC
Abis
FP1 FP2 FP3 FP4 FP5 FP6 FP7 FP8
LAPD
concentration
Up to 8 DRXs
(+ CBCF)
1 internal TS
(concentrated LAPD)
CMCF board
Core unit of the CBCF manages the switching matrix, the synchronization,
concentration and routing tasks.
Remark: With the introduction of half rate, the number of LAPD messages per
TRX, increases. Nevertheless, considering the actual proportion of AMR mobiles
in a network, one LAPD for 8 TRX might be sufficient.
In V12.4, DRX, eDRX and DRX-ND3 are all treated and displayed as DRX. In
V14.3, eDRX becomes identifiable, while DRX and DRX-ND3 remain un-identifiable.
In V15.0, each equipment type is identified, processed and treated independently.
This implementation reduces the total cost of ownership for Nortel equipment and is
then a benefit for Maintenance and Provisioning process. From V15, CMCF phase 1
and phase 2 are not fully compatible anymore from a feature point a view.
The CMCF phase 1 / phase 2 differentiation permits the operator to deploy V15
system release on BTS in the best way as some V15 features are not fully
supported by CMCF phase 1 or cannot be activated on phase 1 / phase 2 duplex
BTS.

25
25
Abis PCM dimensioning without EDGE
LAPD
dimensioning
Engineering Rule
Total 64 kbps TS
on Abis land lines
Nbr of LAPD
from TRX
+ BCF
Nbr of ABIS
Traffic TS
Nbr of
concentrated LAPD
E1 PCM
•
•
31
Number of E1
PCM = upper
integer value
T1 PCM
•
•
24
+
Number of T1
PCM = upper
integer value
Reminder: TS on Abis carry traffic time slots and signaling LAPD time slots solely.
TRX number:
• TRX number has been previously obtained starting from radio TS number
• Example continued: 64 radio TS, then 8 TRXs
Number of Abis traffic TS = (number of TRX) x 2:
• Example continued (8 x 2) = 16 TS on Abis
LAPD dimensioning (see previous page):
• One concentrated LAPD on Abis processes signaling for 8 TRXs
• Example continued:
8 TRXs ⇒1 LAPD TS on Abis
Total number of Abis TS:
(TS for traffic = 16) + (TS for LAPD = 1) = 17 TS
E1 PCM link (32 TS. TS0 never available: used for link synchronization): 31 TS
available.
T1 PCM link: 24 TS available.
Example continued: 1 E1 PCM link necessary for 17 TS
1 T1 PCM link necessary for 17 TS

26
26
S12000/
S8000
To be dimensioned
CBCF
Private
PCM bus
CMCF
BSC
Switching
CMCF
DRX
CPCMI
CPCMI
CPCMI
PCM
Interface
Control,
Signal.Concentr.
Synchronization
Management
S8000 if the CBCF is used: CPCMI and CMCF (1+1).
S12000 with CBCF: CPCMI and CMCF (1+1).

27
27
CBCF Units dimensioning
CBCF
dimensioning rules
Number of
Abis PCM
Number of
CPCMI boards
Number of CPCMI = Upper Integer[number of Abis PCM / 2]
External
PCM
C
P
C
M
I
CBCF
S8000/
S12000
Internal
PCM
Available Resources:
Rules:
• One CPCMI board has been designed to handle two PCM links of Abis
interface.
1 PCM link 1 CPCMI board
S8000 S12000
CMCF 2 2
CPCMI 3 3

28
28
BCF Unit for BTS 18000
IFM
ICM
SPM
The BCF for the BTS 18000 is composed of the following cards:
• IFM + ICM + SPM
The backplane where they are connected is called IBP.
• IFM : The Interface Module provides the following access for the ICM
• ICM : The Interface Control Module is designed to manage the whole BTS site in
simplex configuration. It is the equivalent of the CMCF and CPCMI modules of the
S8000 or S12000.
• SPM : The Spare Module (SPM) is reserved for future use. It may be designed to
manage the whole site network packetization for example (or RLC/MAC in the
BTS).

29
29
BCF Unit for BTS 18000
IFM board
ICM board
IFM board:
The IFM is only used in the BTS18000 base cabinet. It is not present in the
extension cabinets. The IFM is composed of a single passive board with
connections on the IBP and on the front panel. The IFM provides connectivity and
secondary protection on the PCM links.
Maximum number per cabinet: 2.
Ext Abis connector: E1/T1 links to Abis interface
Shared Abis connector: E1/T1 links to ICM board
ICM board:
The ICM is only used in the BTS18000 base cabinet. It is not present in the
extension cabinets. It is designed tomanage the whole BTS18000 site in simplex or
redundant mode.
Redundancy can optionally be introduced using two ICMs in the digital rack. In such
a mode, called duplex, there is one active ICM and one passive ICM

30
nortel.com/training
Lesson #
nortel.com/training
EDGE Dimensioning Detailed Method
7 New Coding Schemes (MCS2, MCS3 and MCS5 to MCS9) are implemented
with EDGE. They permit to increase significantly the peak radio throughput (up to
59.2 kbps with MCS9).
For data circuit channels using MCS3 and greater, more than one 16 kbps TS is
required. Therefore, in order to fully benefit from these new Coding Schemes, an
extension of the Abis resources is requested. Moreover, a specific hardware on
BTS side must be implemented for the BTS to be fully EDGE compatible.
To configure EDGE on a network, several steps must be followed. The purpose
of these steps are to define the number of additional TS (called DS0) that must be
configured on the Abis interface to fully benefit from the new coding schemes. Then,
Abis (and Agprs) interface dimensioning must be modified accordingly to take into
account additional DS0. Finally, BTS hardware must be checked to ensure a full
EDGE compatibility. An eye must be kept as well on the BSC3000 and PCU
dimensioning.
First step to perform is a radio interface analysis to obtain an MCS distribution at
each position of the cell. Then, using this MCS distribution, additional DS0 TS can
be computed. Radio Site Mask and Abis PCM dimensioning must be modified
accordingly to the additional DS0 number, and BTS architecture must be checked.
Let’s have a look at all these steps in the following slides.

31
31
Introduction: Methodology for EDGE Dimensioning
Radio interface
analysis
Throughput
Joker dimensioning
on Abis
Number of joker to
be configured
BTS hardware
provisioning
HW Upgrades
Abis Interface
dimensioning
PCM#,Radio site Mask
Agprs Interface
dimensioning
PCM#
Upgrades
BSC/PCU
engineering
Upgrades,
Dimensioning
In section 6
In sections 5 and 6
First Step: Radio interface
Based on radio condition and network design (cell radius, C/I,…) the expected radio
TS throughput, the MCS distribution and the average BLER values can be
computed.
Second Step: DS0 joker on Abis
The second step consists in determining the required number of joker DS0 to be
configured on Abis to support the higher throughput per TS. This number of DS0 is
obtained from the MCS distribution provided by the radio analysis.
Third Step: Abis backhaul dimensioning
This additional number of DS0 joker must be taken into account in the radio site
mask definition and in the Abis PCM number computation.
Fourth step: BTS hardware compatibility:
BTS/DRX imposes constraint on the ability to enable EDGE on one cell/site.
Additional limitation can be set on the maximum number of joker DS0 that can be
configured per TDMA.
Fifth step: Agprs dimensioning.
Agprs interface should be re-dimensioned to add capacity for the joker TS.
Sixth step: BSC/PCU dimensioning.
BSC3000 and PCU will likely require an upgrade due to the increased number of
DS0 & PCM (Abis and Agprs).
Note that there is no EDGE impact on engineering rules on Gb and Core Packet.

32
32
First Step: Radio Interface Analysis
cell range
Offered throughput
0
Excellent QoS Poor QoS
Max
Throughput varies with : BLER
BLER varies with : C/I and Eb/No
For each (C/I, Eb/No), offered
throuhput can be predicted at each
position on the cell
1
10
100
-10 0 10 20 30
C/(I+N) (dB)
BLER(%)
MCS1
MCS2
MCS3
MCS4
MCS5
MCS6
MCS7
MCS8
MCS9
BLER = f (C/(I+N))
TU 50, 1900 MHz, without Frequency Hopping, without IR
860 688 516 344 172 0 172 344 516 688 860
860
688
516
344
172
0
172
344
516
688
860
55
55
55
55
50
50
50
50
45
45
45
45
45
40
40
40
40
40
40
35
35
35
35
35
35
30
30
30
30
30
30
30
30
25
25
25
25
20
20
2020
Cumulative Averaged Throughput
AT
The purpose of this step is to obtain the expected radio TS throughput through
the MCS distribution (equivalent to throughput distribution) within the cell, depending
on its range:
• C/I (frequency plan dependant) & Eb/No (environment dependant) distributions
are first computed on the cell. The result provides C/(N+I) distribution over the cell.
• BLER distribution f[C/(I+N)] on cell is then deduced for each MCS using R&D
simulations. Indeed, BLER distribution depends on radio conditions and
estimations between them have been obtained through software signal processing
simulator at air-interference layer where transmitter, receiver, interference and
multipath channels were modelled.
• Throughput distribution on cell is deduced from BLER distribution for each
MCS. Following formula is used to calculate effective throughput per TS (at
RLC/MAC level) according to the BLER:
EffectiveThroughput = MaxThroughput_MCS x (1-BLER)
Maximum Throughput per TS according to the MCS. *MCS1 and MCS4 are not implemented
in V15.1
Finally, having throughput value per TS at each position of the cell, mean
throughput per TS is obtained by integrating data throughput over the covered
area.
MCS1* MCS2 MCS3 MCS4* MCS5 MCS6 MCS7 MCS8 MCS9
8.8kbps 11.2kbps 14.8kbps 17.6kbps 22.4kbps 29.6kbps 44.8kbps 54.4kbps 59.2kbps

33
33
Example of an Urban MCS Usage Distribution
Distance
(km)
Throughput /
TS
(kbps)
MCS usage
(%)
Mean Throughput / TS
calculation
0.00 59.200 MCS-9 0.037
0.03 59.200 0.296
0.06 59.200 0.592
0.09 59.200 0.888
0.12 54.340 MCS-8 1.087
0.15 53.707 1.343
0.17 52.393 1.572
0.20 50.273 1.760
0.23 47.347 1.894
0.26 43.771 1.970
0.29 39.637 1.982
0.32 35.290 1.941
0.35 31.804 MCS-7 1.908
0.38 28.686 1.865
0.41 25.575 1.790
0.44 22.488 1.687
0.47 19.989 MCS-6 1.599
0.50 18.369 1.561
0.52 16.741 1.507
0.55 15.155 1.440
0.58 13.660 0.674
Mean Throughput/TS (kbps): 29.391
% Users % Users Cumulative Mean BLER when used BLER at cell edge
MCS-1 0.0 100.0 0.0 14.4
MCS-2 0.0 100.0 0.0 19.7
MCS-3 0.0 100.0 0.0 29.7
MCS-4 0.0 100.0 0.0 45.2
MCS-5 0.0 100.0 0.0 41.3
MCS-6 39.9 100.0 42.6 53.9
MCS-7 27.0 60.1 40.1 75.7
MCS-8 30.0 33.1 17.0 84.6
MCS-9 3.1 3.1 0.0 100.0
Mean BLER 32.9
MCS9 to MCS6 8-PSK modulation are only used
Hypothesis:
Assuming a cell radius of 580 m,
C/I = 12 dB, in Downlink 1800/1900
MHz and in TU3 Km/h no IR
1. BLER distribution for each MCS
using R&D simulations
2. Throughput distribution on cell for each MCS
deduced from BLER distribution ; MCS distribution over the cell
3. Average theoretical throughput = 29.4 kbps / TS in DL
In this example, it can be seen from the BLER distribution table that only MCS 6 to 9
are used. These results are computed through signal processing simulators
depending on C/I, cell radius, and TU3 environment.
MCS 9 will be used only by MS having very good radio conditions, i.e. MS close to
the BTS. With a uniform user repartition within the cell, 3.1% of the users will benefit
from MCS 9 (users being located from 0 to 0.09 km). Users located at cell edge will
use MCS 6 and the minimum available throughput at this cell edge will be of 13.66
kbps.
Throughput distribution on cell is deduced from BLER distribution for each MCS.
Mean throughput per TS at each position of the cell is equal to the
MaxThroughput_MCS x (1-BLER).
Finally, mean throughput per TS is obtained by integrating data throughput over the
covered area and is equal to 29.4 kbps.
Note that MCS thresholds are optimised by the Link Adaptation function (graph
presented on the following slide).

34
34
Example of an Urban EDGE Data Throughput
Distribution per TS
Maximum data Throughput vs cell position
0
10
20
30
40
50
60
70
0.000.200.400.60
Cell Position
MaximumData
Throughput
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
LA
Link Adaptation sets thresholds between 2 different MCS
Depending on the MCS distribution over the cell, the Link Adaptation function sets
MCS to be used at each position on the cell.
Actual real throughput varies with the number of aggregated TS (additional
configured DS0) per MS. This computation is to be seen in coming slides.

35
35
Example of a Rural MCS Usage Distribution
MCS7, MCS6 and MCS5 8-PSK
modulation are mainly used
GMSK modulation is used at
cell edge in DL (high BLER
so low MCS)
Distance
(km)
Throughput /
TS
(kbps)
MCS usage
(%)
0.00 40.3 MCS-7
0.24 40.3
0.48 40.3
0.73 40.3
0.97 40.3
1.21 39.3
1.45 37.8
1.69 36.2
1.93 33.7
2.18 30.7
2.42 28.1 MCS-6
2.66 27.2
2.90 25.6
3.14 23.9
3.38 21.2
3.63 18.7 MCS-5
3.87 17.3
4.11 15.4
4.35 13.5
4.59 9.3 MCS-2
4.84 8.8
Rural 1900 MHz % Users
MCS-1 0.0
MCS-2 14.4
MCS-3 0.0
MCS-4 0.0
MCS-5 33.0
MCS-6 30.0
MCS-7 22.6
MCS-8 0.0
MCS-9 0.0
Minimum Data Throughput/TS (kbps): 8.8
In this example of a rural site, MCS-2 must be used at cell edge. This is due to the
size of the cell, 4.84 km. The data throughput per TS is 8.8 kbps at this cell edge,
and mean data throughput per TS is 22.3 kbps.
Note that both 8-PSK and GMSK modulations are used, the latter being used only
at cell edge.

36
36
Second Step: Dimensioning of DS0 Joker on Abis
> Main TS: 16k TS used for voice, data circuit and GPRS dedicated to one radio TS
> Joker TS: each TDMA is associated to a set of 64k TS (DS0) on Abis
• each 64k TS is divided into 16k TS, dedicated to EDGE
• dynamically shared on a TDMA basis
radio frameAbis
main
joker
joker
Main & Joker TS Definition
Each joker frame indicates
its associated main TS
Every radio TS (voice or GPRS) is mapped statically on one 16 k bearer (1/4 of
DS0) on the Abis interface. Since V15.0, new EDGE coding schemes are managed
up to MCS9 (59.2 kbps). So the current Abis (and Agprs) interface, based on 16
kbps TS, has to be enhanced in order to manage this new throughput. Nortel has
implemented a dynamic solution based on "main+joker TS", which allow the
operator to define:
• A classical set of 16 kbps Abis TS (called Main TS) used in order to manage
circuit switch calls and part of the packet data bandwidth
• A number of Abis TS used for EDGE only by all radio TS of one TRX, called
Joker TS. The 64k granularity for joker TS is due to the 64k switching matrix of
the BTS
Each radio frame is managed on Abis by:
• One main TS
• n joker TS, dynamically shared
• Each frame on a joker TS indicates its associated main TS at each occurrence

37
37
8.8
11.2
14.8
17.6
22.4
29.6
44.8
54.4
59.2
0.0 16.0 32.0 48.0 64.0 80.0
Required Bandwidth (kbps)
MCS1
MCS3
MCS5
MCS7
MCS9
EDGE Data To Backhaul Requirements
Payload
Control field
Additional CRC
START & STOP pattern
RLC/MAC Hdr + FBI/E
Unused
Required Bandwidth (kbps)
MAIN Joker1 Joker4Joker3Joker2
The total number of required Joker TS (1/4 of DS0) can be computed
from the MCS distribution provided by the radio analysis
4 Joker TS at 16 kbps
= 1 Joker DS0 at 64 kbps
Joker TS are dynamically shared on a TDMA basis. Every 20 ms, the allocator will
adjust the bandwidth on Abis to the MS requirements. A number of joker DS0
(between 0 to 8) must be provisioned for every EDGE TDMA. This number of DS0
joker can be computed from the MCS distribution provided by the radio analysis.
The following formulas provide the statistical number of joker required as a function
of the EDGE number of TS and the number of joker required per TS
• 16k Joker TS dimensioning: Nb_of_Joker_per_EDGE_TS*Nb_of_EDGE_TS
• 64k Joker DS0: round_up(Nb_of_16k_Joker/4)
Following table provides the number of additional 16k DS0 for one radio TS
depending on the MCS selected:

38
38
Example
> Example for a TDMA with 4 PDTCH and following assumptions about
radio environment: DL, cell radius = 580m, 1800/1900 MHz with IR,
TU3
> 16k joker TS dimensioning:
Nb_of_Joker_per_EDGE_TS*Nb_of_EDGE_TS
> 64K joker DS0: round_up(Nb_of_16k_Joker/4)
MCS % Users Joker 1/4 DS0
Requirement
MCS1 0.0 0
MCS2 0.0 0
MCS3 0.0 1
MCS4 0.0 1
MCS5 0.0 1
MCS6 4.9 2
MCS7 49.5 3
MCS8 27.5 4
MCS9 18.1 4
Mean 16k Joker per
EDGE TS 3.407
% of users per MCS is provided by radio analysis (first step)
• Number of 16k Joker TS = 3.407 x 4 = 13.6 Joker TS
• Number of 64k Joker DS0 = 13.6 / 4 = 3.4
Round_up (3.4) = 4 Joker DS0
A TDMA with 4 PDTCH would therefore require 4 DS0 Joker
configured on the Abis interface in order to fully benefit from
the available radio throughput
These 2 formulas provide the statistical number of 64k joker DS0 required on Abis
as a function of the EDGE number of TS (PDTCH) and the number of 16k joker per
EDGE TS.
In the above example, if a 4+1 MS close to the site requires MCS-9 on all PDTCH,
the allocator will allocate 4 TS with MCS-9.
If only 3 DS0 are configured instead of 4, the 4+1 MS will only use 3 TS with MCS-9
and 1 TS with MCS-2 (corresponding to a normal GPRS TS). The average TS
throughput is therefore decreased.

39
39
Third Step: Abis Interface Dimensioning
> Radio Site Mask for BTS configured with EDGE must be updated
to take into account additional Joker DS0:
Abis TS = 2 x TRX + DS0 Jokers + LAPD TS
> PDTCH and Jokers TS for EDGE must be declared for all the
different concerned TDMA and for all the cells of a site
Additional PCM may be required
The introduction of joker TS induces some impacts on the PCM dimensioning:
• without joker TS, one TDMA uses on Abis 2 DS0. The maximum number of
TDMA per PCM is therefore:
o E1 PCM (30 DS0): 15 TDMA
o T1 PCM (23 DS0): 11 TDMA
• with 4 joker TS, one TDMA uses on Abis 2+4 = 6 DS0, which are all configured
on one PCM, so the maximum number of TDMA per PCM is:
o E1 PCM (30 DS0): 5 TDMA, which use 5*6=30 DS0, so no DS0 remains
available
o T1 PCM (23 DS0): 3 TDMA, which use 3*6=18 DS0, so 5 DS0 can be
allocated to small TDMA (for example 2 TDMA without joker)
• As the maximum number of PCM per site is 6, joker TS induce some limitation
in terms of number of TDMA per site. Moreover, it would not be possible to
declare a full EDGE capacity for all the TDMA of the site

40
40
Third Step: Abis Interface Dimensioning - Example
> Hypothesis: 1 tri-sectorial BTS, single band, 3 TRX per sector, 4 PDTCH and
2 EDGE TDMA per sector, 1 E1 Abis PCM, up to MCS9, 3DS0 Jocker/TDMA.
• Before EDGE activation
3 TRX, 3 cells 3 x 3 = 9 TRX for the whole BTS
1 TRX = 2 TS on Abis 9 x 2 = 18 TS on Abis for traffic
9 TRX > 8 TRX therefore 1 Primary (RDV TS) and 2 secondary LAPD
18 TS for traffic + 2 TS for signaling
• After EDGE activation
4 PDTCH TS per cell and 3 joker DS0 per EDGE TDMA
3 TRX, 3 cells 3 x 3 = 9 TRX for the whole BTS
1 TRX = 2 TS on Abis 9 x 2 = 18 TS on Abis for traffic
3 joker DS0 per EDGE TDMA & 2 EDGE TDMA/sect 2 x 3 x 3 = 18 Joker DS0 on Abis
9 TRX > 8 TRX therefore 1 Primary (RDV TS) and 2 secondary LAPD
18 TS for traffic + 2 TS for signaling + 18 TS (DS0)

41
41
Third Step: Abis PCM dimensioning
LAPD
dimensioning
Engineering Rule
Total 64 kbps TS
on Abis land lines
Nbr of LAPD
from TRX
+ BCF
Nbr of Joker
TS for EDGE
Nbr of LAPD TS
E1 PCM
•
•
31
Number of E1
PCM = upper
integer value
T1 PCM
•
•
24
+
Nbr of ABIS
Traffic TS
Number of T1
PCM = upper
integer value
With EDGE activated on a network, additional DS0 TS required on Abis must be
taken into account on the PCM computation.
Note that EDGE is only available with BSC3000. As BSC3000 can support a high
number of LAPD channels, there is no more need to concentrate them (to be seen
on coming section).

42
42
Fourth Step: BTS Hardware Provisioning
8E-cell
10BTS 18000
8CBCF CMCF phase II
6CBCF CMCF phase I
6BCF new GTW PROM
2BCF old GTW PROM
2S2000 H/L
2CSW DCU4
Max number of DS0 per TRXType of site
GPRS + EDGEeCell
GPRS + EDGEeDRX + (H)ePA
GPRSeDRX + legacy PA
GPRSDRX-ND3
GPRSDRX
GPRSDCU4
NoneDCU2
Optimum data capabilityTRX
BTS Hardware constraints table TRX capability table
Both chains of the site must have the same level of hardware
Both eDRX & (H)ePA are required to support EDGE
Each type of site (BCF, CBCF, CSWM…) is able to connect a given number of DS0
to one TRX.
As an example, the BSC can configure one TDMA with 6 DS0 only if the site is:
• a BCF equipped with new GTW PROM (old GTW PROM does not support any
Edge TDMA configuration)
• a CBCF equipped with CMCF phase I
• a CBCF equipped with CMCF phase II
• a CBCF equipped with 2 CMCF phase I and II
• an e-cell.
In other cases, the TDMA is not configured.
The BTS 18000 is able to configure 1 TDMA with 10 DS0 (2 DS0 main + 8 DS0
jocker).
One mandatory rule is to have in the BTS the same level of site hardware
(BCF, CSWM…) for both chains.
If this rule is not verified, the board having the most constraining limitation will
provide the EDGE capability of the site (CMCF Ph 1 + CMCF Ph 2 : 6 DS0 instead
of 8)
In V15, the BTS H/W configuration can be audited by the operator through new
EDGE Data Display commands available at OMC-R.

43
43
BSC Location in relation to BTS Sites
The BSC is the center of gravity of BTS sites
BTS
BTS
BTS
BTS
BTS
BTS
BTS
The BSC has a strong concentration
effect when Abis links are underused
TCU
BSC
MSC
The BTS must be connected to the MSC.
One way to make the connection is to connect each BTS to the MSC with a
separate point to point link. This is generally not acceptable due to prohibitive costs.
Another way to make the BTS to MSC connection is to use a BSC as a remote
concentrator to facilitate the sharing of a high capacity line among several terminals.
Furthermore Abis links represent a substantial part of the operational costs of a
PLMN knowing that a lot of BTS are used in a network and that each BTS site
requires a relatively small number of circuits and PCM redundancy can be used for
a better quality of service.
The BSC3000 can switch up to 4056 DS0 on Abis/Agprs/Ater interfaces. This
switching capacity (provided by the SRT8K module in the BSC3000 Interface Node)
becomes a significant limiting factor with EDGE penetration.

44
44
BTS Connections
Example of BTS Connections
Air
interface
Abis
interface
Star
connection
Chain
connection
Loop
connection
(single multi-drop)
MS
(full multi-drop)
Hub & Spoke
connection
The chained or looped BTS configurations (Drop and Insert) optimize the use of E1
and T1 PCM time slot (TS) resources.
The 64 kbps time slots for speech and signaling do not fill the 2.048 Mbps E1 PCM
or 1.544 Mbps T1 PCM links.
Links may be under-used in a star configuration.
BTSs are chained to fill the links.
Chained or looped configurations allow the use of remaining time slots for other
BTSs, thus reducing the number of E1 or T1 PCM links.

45
45
Terrestrial Link Optimization by Drop
and Insert
The system sees:
The system sees:
The chain configuration The loop configuration
BSC BTS BTS BTS
BTS
BTS
BTSBSC
BSC
BSC
BTS BTS BTS
BTS
BTS
BTS
When BTSs are chained together, they must not exceed ten. But NORTEL
guarantees a good functioning of the chain with up to 6 BTSs. The failure of any
component involved in transmission may affect security.
For a chained connection, the availability of one BTS depends not only on those
above it but also on the links between those above BTSs.
So the chain is closed and the farthest BTS of the BSC is directly connected to the
BSC. That is the loop configuration.
In the looped configuration, PCM redundancy is N+1.
The parameter bscSitePcmList (btsSiteManager logical object) provides the list of
connections [bscPortNumber ~ btsPortNumber], between a BTS and its managing
BSC. This can explain why the BSC does not see the intermediate BTS in a chain
or in a loop.

46
nortel.com/training
Lesson #
nortel.com/training
Dimensioning Look-up Tables for
Standard Traffic Model at
28% Erlang signaling
These tables are a summary of the detailed method results of the previous chapter,
using a traffic model with 28% dedicated signaling and with
• A blocking rate on traffic (TCH) equals to 2%
• A blocking rate on signaling (SDCCH) equals to 0.1%

47
47
Dimensioning Look-up Tables
Offered traffic (Erlangs) & Abis interface:
omnisectorial sites
22342631196.65106.40O 16
22322631116.5898.65O 15
21302631036.4990.88O 14
2128253966.4784.10O 13
2126252896.4477.34O 12
1124252816.3369.65O 11
1122242746.2962.94O 10
1120242666.1555.33O 9
1117142585.9747.76O 8
1115132515.8841.19O 7
1113131445.7834.68O 6
1111131365.4727.34O 5
119121295.2621.04O 4
117121214.6814.04O 3
115111144.108.20O 2
113101*72.942.94O 1
T1 PCME1 PCM
Total PCM
Time slots
Number of
LAPD TS
SDCCH/8CCCHTCH/FE/TRXErlangsConfig.
PCM E1 (31 TS) / PCM T1 (24 TS) Blocking factor for traffic = 2.0% 8 TRXs/LAPD
* Combined BCCH
These tables are a summary of the detailed method results of the previous chapter,
using a traffic model with 28% dedicated signaling.

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