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Channel Structure and Function
ZTE University
TD&W&PCS BSS Course Team
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Objectives
At the end of this course, you will be able to master:
Classification of channels
Structure and Function of channels
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Classification of channels
Structure and Function of channels
Physical layer procedure
Content
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Channel Type
Physical channel
Transport channel
Logical channel
Node BRNC
Physical channel
Transport channel
Logical channel
UE
Classif ication of channels
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Concept of channel
PHY layer
MAC layer
RLC layer
Transport channel
Physical channel
Logical channel
L1
L2
Classif ication of channels
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Channel Type
Logical channels:
Describe what is transported (i.e., the types of
information to be transmitted)
Transport channels:
Describe how the logical channels are to be transmitted
Physical channels:
Represent the transmission media providing the platform
through which the information is actually transferred
Classif ication of channels
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Protocol stack of the Uu interface
L 3
control
control
control
control
L o g i c a l
C h a n n e l s
T r a n s p o r t
C h a n n e l s
C - p l a n e s i g n a l li n g U - p l a n e i n f o r m a t i o n
P H Y
L 2 / M A C
L 1
R L C
D CN tG C
L 2 / R L C
M A C
R L CR L C
R L CR L C
R L CR L C
R L C
D u p l i c a t i o n a v o i d a n c e
U u S b o u n d a ry
B M CL 2 / B M C
c o n t r o l
P D C PP D C P L 2 / P D C P
D CN tG C
R a d i o
B e a r e r s
R R C
Classif ication of channels
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Logical Channels
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)
Classif ication of channels
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Transport Channel
Random Access Channel (RACH)
Broadcast Channel (BCH)
Paging Channel (PCH)
Forward Access Channel (FACH)
Common Packet Channel (CPCH)
Common Transport Channels
Dedicated Transport Channels
Downlink Shared Channel (DSCH)
Dedicated Channel (DCH)
Classif ication of channels
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Physical Channel
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)
Classif ication of channels
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Logic
Channel
Transport
Channel
CCCH DCCHDTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCH DCCHDTCH
CCCH CTCH
PCH BCH FACH DSCH DCH
Mapping relationship
Classif ication of channels
Transport
Channel
CCCH DCCHDTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCH DCCHDTCH
CCCH CTCH
PCH BCH FACH DSCH DCH
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Mapping relationship
Transport Channels
DCH
RACH
CPCH
BCH
FACH
PCH
DSCH
Physical Channels
Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH)
Physical Random Access Channel (PRACH)
Physical Common Packet Channel (PCPCH)
Common Pilot Channel (CPICH)Primary Common Control Physical Channel (P-CCPCH)
Secondary Common Control Physical Channel (S-CCPCH)
Synchronization Channel (SCH)
Physical Downlink Shared Channel (PDSCH)
Acquisition Indication Channel (AICH)
Page Indication Channel (PICH)
Classif ication of channels
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Classification of channels
Structure and Function of channels
Physical layer procedure
Content
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WCDMA frame structure
Structure and Function of channels
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Physical Channels(1)
The physical channel is in a 3-layer structure by the time:
Superframe
One superframe lasts 720ms, and consists of 72 radio frames.
radio frame
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.
Timeslot
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.
Structure and Function of channels
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Physical Channels(2)
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
Tframe=10 ms
Tsuperframe=720 ms
Structure and Function of channels
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Uplink physical channel
2 UL Dedicated physical channelDPDCH and DPCCH
2 UL Common physical channelPRACH and PCPCH
Structure and Function of channels
UL Common physical
channel
UL Dedicated physical
channel
Dedicated physical
Control channel DPCCH
Dedicated physical
data channelDPDCH
Physical random
Access channel
PRACH
Physical common
Packet channel
PCPCH
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Structure and Function of channels
Uplink Dedicated physical channel
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PRACH
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.
Message partPreamble
4096 chips 10 ms (one radio frame)
Preamble Preamble
Message partPreamble
4096 chips 20 ms (two radio frames)
Preamble Preamble
PRACH transmitted structure
Structure and Function of channels
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Physical Random Access Channel
10ms message part is spl it into 15 timeslots, each timeslot consists of
2560chips.
Each timeslot includes data part and control part. They are transmitted in
parallel .
Data part :SF=32~256 , control part: SF=256.
PilotNpilot bits
DataNdata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2k bits (k=0..3)
Message part radio frame TRACH = 10 ms
Data
ControlTFCI
NTFCI bits
Structure and Function of channels
PRACH
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Downlink physical channel
DL physical channel include Dedicated physical channel1 Shared
physical channel and five Common control channels.
Structure and Function of channels
DPCH
SCH
CPICH
PICH
AICH
CCPCH
PDSCH
DL common physical
channel
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Structure and Function of channels
Downlink dedicated physical channel
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Structure and Function of channels
CPICH
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CPICH
There is 2 types of CPICH:P-CPICH and S-PICH
P-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 primary
scrambling code during cell selection procedure. And it is also used for
measurement and estimation during handover, cell selection and cell re-selection.
S-CPICH:
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 code.
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 signalling.
Structure and Function of channels
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Structure and Function of channels
P-CCPCH
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SCH (1)
The Synchronization Channel (SCH) is a downlink signal used for cellsearch.
The SCH consists of two sub channels, the Primary and SecondarySCH.
The 10 ms radio frames of the Primary and Secondary SCH aredivided into 15 slots, each of length 2560 chips.
Structure of synchronization channel
Structure and Function of channels
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SCH (2)
P-SCH
The Primary SCH consists of a modulated code of length 256 chips. The
modulated code need not spreading and scrambling.
The primary synchronization code (PSC) is transmitted once every slot
The PSC is the same for every cell in the system.
S-SCH 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 length 256.
This sequence on the Secondary SCH indicates which of the code groups
the cell's downlink scrambling code belongs to.
Structure and Function of channels
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Structure and Function of channels
S-CCPCH
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PICH
PICH carries PIPage IndicationSF=256radio frame=10ms
consists 300bits288 bits for paging indication12 bits Tx Off
PICH relates to S-CCPCH which mapping to PCH
b1b0
288 bits for paging indication12 bits (transmission
off)
One radio frame (10 ms)
b287 b288 b299
PICH frame structure
Structure and Function of channels
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Classification of channels
Structure and Function of channels
Physical layer procedure
Content
Ph i l l d
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Cell search procedure (1)
The cell search is typically carried out in three steps:
Step1: Slot synchronization
During the first step of the cell search procedure the UE uses the
SCH'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 filter output.
Physical layer procedure
Ph i l l d
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Cell search procedure (2)
Step2: Frame synchronization and code-group identification
During the second step of the cell search procedure, the UE uses the
SCH'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
determined.
Physical layer procedure
Physical layer procedure
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Cell search procedure (3)
Step3: Scrambling-code identif ication
During the third and last step of the cell search procedure, the UE
determines the exact primary scrambling code used by the found
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 second step.
After the primary scrambling code has been identified, the
Primary CCPCH can be detected and the system- and cell
specific BCH information can be read.
Physical layer procedure
Physical layer procedure
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Cell search procedure
Physical layer procedure
Physical layer procedure
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Summary of the process
ChannelSynchronization
acquiredNote
Primary SCH Chip, Slot, Symbol
Synchronization
Synchronization 256 chips
The same in all cells
Secondary
SCH
Frame Synchronization,Code Group
(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
Common
Pilot CH
Scrambling code (one of 8) To find the primary scrambling code from common
pilot CH
PCCPCH Synchronization,
BCCH info
Fixed 30 kbps channel spreading factor 256
Physical layer procedure
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Exercise
pls write down the 3 type of channel. and describe their
category.
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 channel.
pls describe the cell search procedure.
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