Describe what is transported (i.e., the information to be
Describe how the logical channels are to be transmitted.
Represent the “transmission media” providing the
platform through which the information is actually
Protocol stack of the Uu interface
C-plane signalling U-plane information
Control Channel (CCH) Broadcast Control Channel (BCCH)
Paging Control Channel (PCCH)
Dedicated Control Channel (DCCH)
Common Control Channel (CCCH)
Traffic Channel (TCH) Dedicated Traffic Channel (DTCH)
Common Traffic Channel (CTCH)
Random Access Channel (RACH)
Broadcast Channel (BCH)
Paging Channel (PCH)
Forward Access Channel (FACH)
Common Packet Channel (CPCH)
Common Transport Channels
Downlink Shared Channel (DSCH)
Dedicated Channel (DCH)
Dedicated Physical Channel (DPCH)
Physical Random Access Channel (PRACH)
Physical Common Packet Channel (PCPCH)
Uplink Physical Channels
Secondary Common Control Physical Channel (S-CCPCH)
Common Pilot Channel (CPICH)
Primary Common Control Physical Channel (P-CCPCH)
Synchronization Channel (SCH)
Physical Downlink Shared Channel (PDSCH)
Downlink Physical Channels
Acquisition Indication Channel (AICH)
Page Indication Channel (PICH)
Dedicated Physical Channel (DPCH)
The physical channel is in a 3-layer structure by
One superframe lasts 720ms, and consists of 72 radio frames.
One radio frame has a period of 10ms, and comprises 15
timeslots with the same length. Corresponding to 38400 chips,
it is a basic unit of the physical layer.
A timeslot is a unit composed of a bit domain, corresponding to
2560 chips. The bit number and structure of a timeslot depends
on the specific type of the physical channel.
The frame structure of the physical channels is shown:
Tslot #1 Tslot #2 Tslot #I Tslot #15
Ttimeslot= 2560 chip
Frame #0 Frame #1 Frame #I Frame #71
Uplink physical channel
2 UL Dedicated physical channel (DPDCH and
2 UL Common physical channel (PRACH and
UL Common physical
UL Dedicated physical
Control channel DPCCH
Physical Random Access Channel
PRACH consists preamble part and message part
Random access transmit 1or more 4096 chips length
preambles and 10ms or 20ms length message part.
4096 chips 10 ms (one radio frame)
4096 chips 20 ms (two radio frames)
PRACH transmitted structure
Physical Random Access Channel
10ms message part is split into 15 timeslots, each timeslot consists
Each timeslot includes data part and control part. They are
transmitted in parallel .
Data part :SF=32~256 , control part: SF=256.
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2k
Message part radio frame T
RACH = 10 ms
Downlink physical channel
DL physical channel include Dedicated physical channel、1 Shared
physical channel and five Common control channels.
DL common physical
There is 2 types of CPICH:P-CPICH and S-CPICH
P-CPICH of different cell uses the same Cch,256,0 OVSF code to
spread ,the bit rate of P-CPICH is also fixed.
The P-CPICH is scrambled by the primary scrambling code.
There is one and only P-CPICH per cell.
The P-CPICH is broadcast over the entire cell. it is used to search cell
scrambling code during cell selection procedure. And it is also used
for measurement and estimation during handover, cell selection and cell
A arbitrary channelization code of SF=256 is used for the S-CPICH.
A S-CPICH is scrambled by either the primary or a secondary scrambling
There may be 0,1 or several S-CPICH per cell.
A S-CPICH may be transmitted over the entire cell or part of the cell. It is
may be a phase reference for a dl DPCH, but it is decided by high layer
The Synchronization Channel (SCH) is a downlink signal
used for cell search.
The SCH consists of two sub channels, the Primary and
The 10 ms radio frames of the Primary and Secondary
SCH are divided into 15 slots, each of length 2560 chips.
Structure of synchronization channel
The Primary SCH consists of a modulated code of length
256 chips. The modulated code need not spreading and
The primary synchronization code (PSC) is transmitted once
The PSC is the same for every cell in the system.
The Secondary SCH consists of repeatedly transmitting a
length 15 sequence of modulated codes of length 256 chips.
the Secondary Synchronization Codes (SSC), transmitted in
parallel with the Primary SCH.
Each SSC is chosen from a set of 16 different codes of
This sequence on the Secondary SCH indicates which of the
code groups the cell's downlink scrambling code belongs to.
UE has to get the system information before it
registers with the network and access to services.
The system information is beared in the BCH
channel, and its data is mapped into the Primary
So the cell search procedure is mainly to decode
the data of P-CCPCH.
Cell search procedure (1)
The cell search is typically carried out in three
Step1: Slot synchronization
During the first step of the cell search procedure the UE
uses the SCH channel's primary synchronization code
to acquire slot synchronization to a cell.
This is typically done with a single matched filter (or any
similar device) matched to the primary synchronization
code which is common to all cells. The slot timing of the
cell can be obtained by detecting peaks in the matched
Cell search procedure (2)
Step2: Frame synchronization and code-group
During the second step of the cell search procedure, the
UE uses the SCH channel's secondary synchronization
code to find frame synchronization and identify the code
group of the cell found in the first step.
This is done by correlating the received signal with all
possible secondary synchronization code sequences,
and identifying the maximum correlation value. Since
the cyclic shifts of the sequences are unique the code
group as well as the frame synchronization is
Cell search procedure (3)
Step3: Scrambling-code identification
During the third and last step of the cell search
procedure, the UE determines the exact primary
scrambling code used by the cell.
The primary scrambling code is typically identified
through symbol-by-symbol correlation over the CPICH
with all codes within the code group identified in the
After the primary scrambling code has been
identified, the Primary CCPCH can be detected so
that the cell specific BCH information can be read.
Summary of the process
Chip, Slot, Symbol
Synchronization 256 chips
The same in all cells
(one of 64)
15-code sequence of secondary
synchronization codes. There are 16
secondary synchronization codes. There
are 64 S-SCH sequences corresponding to
the 64 scrambling code groups 256 chips,
different for different cells and slot intervals
Scrambling code (one
To find the primary scrambling code from
common pilot CH
Fixed 30 kbps channel spreading factor 256
UE decodes BCH to find out the available RACH sub-channels and
their scrambling codes and signatures
It selects randomly one of the available sub-channels and signatures
The downlink power is measured and the initial RACH power level is
set with a proper margin due to open loop inaccuracy
UE transmits 1 ms long preamble with the selected signature
Node B replies by repeating the preamble using Acquisition Indication
UE decodes AICH message to see whether the NodeB has detected
If AICH is not detected, the preamble is resend with 1 dB higher transmit
If AICH is detected, a 10 or 20 ms long message part is transmitted with
the same power as the last preamble
pls write down the 3 types of channel and describe
their mapping relations.
One radio frame has a period of ( )ms, and
comprises( ) timeslots with the same length.
Corresponding to ( ) chips, it is a basic unit of
the physical layer.
pls describe the main function of each physical
pls describe the cell search procedure.
pls describe RACH procedure.