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8/11/2019 WR_BT03_E1_1 Channel Structure and Function 44.pdf
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WR_BT03_E1_1
Channel Structure and Function
ZTE University
WCDMA BSS Course
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
RNS RNS
CN
RNCRNC
Iu Iu
Iur
Iub IubIub Iub
Archi tecture of UMTS
Classification of c hannels
UE
NodeB NodeB NodeB NodeB
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Channel Type
Physical channel
Transport channel
Logical channel
Node B RNC
Physical channel
Transport channel
Logical channel
UE
Classification of c hannels
Concept of channel
PHY layer
MAC layer
RLC layer
Transport channel
Physical channel
Logical channel
L1
L2
Classification of c hannels
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Channel Type
Logical channels:
Describe what is transported (i.e., the 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.
Classification of c hannels
Protocol s tack of the Uu interface
L 3
c o n t r o l
c o n t r o l
c o n t r o l
c o n t r o l
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-pla ne s igna l l ing U -pla ne inform a t ion
P H Y
L 2 / M A C
L 1
R LC
D C N 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 io n a v o i d a n c e
U u S b o u n d a r y
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 C N tG C
R a d i o
B e a r e r s
R R C
Classification of c hannels
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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)
Classification of c hannels
Transpor t 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)
Classification of c hannels
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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)
Classification of c hannels
Logic
Channel
Transport
Channel
CCCHDCCH
DTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCHDCCH
DTCHCCCH CTCH
PCH BCH FACH DSCH DCH
Mapping relationship
Classification of c hannels
Transport
Channel
CCCHDCCH
DTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCHDCCH
DTCHCCCH 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)
Classification of c hannels
Classification of channels
Structure and Function of channels
Physical layer procedure
Content
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WCDMA frame structure
Structure and Function of channels
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
Uplink physical channel
2 UL Dedicated physical channel (DPDCH and DPCCH)
2 UL Common physical channel (PRACH 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 channelPRACH
Physical common
Packet channel
PCPCH
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Structure and Function of channels
Uplink Dedicated physical channel
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 split i nto 15 timeslots, each timeslot consists of
2560chips.
Each timeslot includes data part and control part. They are transmi tted in
parallel .
Data part :SF=32~256 , con tro l part : SF=256.
Pilot
Npilot 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
Downlink phys ical channel
DL physical channel include Dedicated physical channel、1 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
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
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
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
PICH
PICH carries PI(Page Indication),SF=256,radio frame=10ms,
consists 300bits,288 bits for paging indication,12 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
Cell Search
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 CCPCH.
So the cell search procedure is mainly to decode the data of
P-CCPCH.
Physical layer procedure
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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 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 filter output.
Physical layer procedure
Sketch of Slot Synchronization
Physical layer procedure
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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 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
determined.
Physical layer procedure
…
Downlink Scrambling Code Grouping
8176:PSC
8177:SSC
…
8191:SSC
8176
8177
8191
No. 511 Scrambling Code Group
8160:主扰码
8161:辅扰码
…
8175:辅扰码
8160
8161
8175
No. 510 Scrambling Code Group
8064:主扰码
8065:辅扰码
…
8079:辅扰码
8064
8065
8079
No. 504 Scrambling Code Group
…
8176:PSC
8177:辅扰码
…
8191:辅扰码
112
113
127
No. 7 Scrambling Code Group
16:PSC
17:SSC
…
31:SSC
16
17
31
No. 1 Scrambling Code Group
0:PSC
1:SSC
…
15:SSC
0
1
15
No. 0 Scrambling Code Group
No.63 Primary Scrambling Code Group
… …
No.0 Primary Scrambling Code Group
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Mapping of the Secondary Synchronization Code
Physical layer procedure
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 thecode group identified in the second step.
Af ter the primary scrambling code has been identif ied, the
Primary CCPCH can be detected so that the cell specific
BCH information can be read.
Physical layer procedure
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Cell search procedure
Physical layer procedure
Summary of the process
To find the primary scrambling code from common
pilot CH
Scrambling code (one of 8)Common
Pilot CH
Fixed 30 kbps channel spreading factor 256Synchronization,
BCCH info
PCCPCH
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
Frame Synchronization,
Code Group
(one of 64)
Secondary
SCH
Synchronization 256 chips
The same in all cells
Chip, Slot, Symbol
Synchronization
Primary SCH
NoteSynchronization
acquiredChannel
Physical layer procedure
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RACH procedure
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
Channel (AICH)
UE decodes AICH message to see whether the NodeB has detected the
preamble
If AICH is not detected, the preamble is resend with 1 dB higher transmit power
If AICH is detected, a 10 or 20 ms long message part is transmitted with the
same power as the last preamble
Physical layer procedure
RACH procedure
Physical layer procedure
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Exercise
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 channel.
pls describe the cell search procedure.
pls describe RACH procedure.