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7/28/2019 ZTE Channel Structure and Function
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Objectives
At the end of this course, you will be able to master:
¾ Classification of channels
¾ Structure and Function of channels
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Concept of channel
PHY layer
MAC layer
RLC layer
Transport channel
Physical channel
Logical channel
L1
L2
Classification of channels
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Protocol stack 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 - p l a n e s i g n a l l i n g U - p l a n e in f o r m a t i o n
P H Y
L 2 / M A C
L 1
R L C
D C N tG C
L 2 / R L C
M A C
R L C
R L CR L C
R L C
R L CR L C
R L C
D u p l i c a ti o n a v o i d a n c e
U u S b o u n d a ry
B M C L 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 channels
Cl ifi ti f h l
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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 channels
Cl ifi ti f h l
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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)
Classification of channels
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Classification of channels
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LogicChannel
Transport
Channel
CCCH
DCCH
DTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCH
DCCH
DTCHCCCH CTCH
PCH BCH FACH DSCH DCH
Mapping relationship
Classification of channels
Transport
Channel
CCCH
DCCH
DTCH
RACH CPCH DCH
Uplink Downlink
PCCH BCCH
DCCH
DTCHCCCH CTCH
PCH BCH FACH DSCH DCH
Classification of channels
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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 channels
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Classification of channels
Structure and Function of channels
Physical layer procedure
Content
Structure and Function of channels
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WCDMA frame structure
Structure and Function of channels
Structure and Function of channels
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Physical Channels(1)
The physical channel is in a 3-layer structure by the time:
f Superframe
y One superframe lasts 720ms, and consists of 72 radio frames.
f radio frame
yOne radio frame has a period of 10ms, and comprises 15timeslots with the same length. Corresponding to 38400 chips,
it is a basic unit of the physical layer.
f Timeslot
y 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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Structure and Function of channels
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Uplink physical channel
2 UL Dedicated physical channel (DPDCH and DPCCH)
2 UL Common physical channel (PRACH and PCPCH)
UL Common physical
channel
UL Dedicated physical
channel
Dedicated physicalControl channel DPCCH
Dedicated physicaldata channel
DPDCH
Physical randomAccess channel
PRACH
Physical commonPacket channel
PCPCH
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Structure and Function of channels
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PRACH
Physical Random Access Channel
f PRACH consists preamble part and message part
f 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
f 10ms message part is split into 15 timeslots, each t imeslot consists of
2560chips.
f Each timeslot includes data part and control part. They are transmitted in
parallel .
f 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
PRACH
Structure and Function of channels
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Downlink physical channel
DL physical channel include Dedicated physical channel、1 Shared
physical channel and five Common control channels.
DPCH
SCH
CPICH
PICH
AICH
CCPCH
PDSCH
DL common physical
channel
Structure and Function of channels
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Downlink dedicated physical channel
Structure and Function of channels
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CPICH
Structure and Function of channels
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CPICH
There is 2 types of CPICH:P-CPICH and S-PICH
P-CPICH:
f P-CPICH of different cell uses the same Cch,256,0 OVSF code to spread ,the bit rate
of P-CPICH is also fixed.
f The P-CPICH is scrambled by the primary scrambling code.
f There is one and only P-CPICH per cell.
f 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:
f A arbitrary channelization code of SF=256 is used for the S-CPICH.
f A S-CPICH is scrambled by either the primary or a secondary scrambling code.
f There may be 0,1 or several S-CPICH per cell.
f A S-CPICH may be transmitted over the entire cell or part of the cell. It is may be aphase reference for a dl DPCH, but it is decided by high layer signalling.
Structure and Function of channels
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P-CCPCH
Structure and Function of channels
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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
f The Primary SCH consists of a modulated code of length 256
chips. The modulated code need not spreading and scrambling.
f The primary synchronization code (PSC) is transmitted once every
slot
f The PSC is the same for every cell in the system.
S-SCH
f The Secondary SCH consists of repeatedly transmitting a length
15 sequence of modulated codes of length 256 chips.
f the Secondary Synchronization Codes (SSC), transmitted inparallel with the Primary SCH.
f Each SSC is chosen froma set of 16 different codes of length 256.
f 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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S-CCPCH
Structure and Function of channels
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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
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Classification of channelsStructure and Function of channels
Physical layer procedure
Content
Physical layer procedure
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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
f 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.
f 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
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Sketch of Slot Synchronization
Physical layer procedure
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Cell search procedure (2)
Step2: Frame synchronization and code-group identification
f 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.
f 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 sequencesare unique the code group as well as the frame synchronization is
determined.
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…
Downlink Scrambling Code Grouping
No. 511 Scrambling Code Group
8176
8177
8191
8176:PSC
8177:SSC
…
8191:SSC
No. 510 Scrambling Code Group
8160
8161
8175
8160:主扰码
8161:辅扰码
…
8175:辅扰码
No. 504 Scrambling Code Group
8064
8065
8079
8064:主扰码
8065:辅扰码
…
8079:辅扰码
…
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 Scrambl ing Code Group
… …
No.0 Primary Scrambling Code Group
Physical layer procedure
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Mapping of the Secondary Synchronization Code
Physical layer procedure
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Cell search procedure (3)
Step3: Scrambling-code identification
f During the third and last step of the cell search procedure, the UE
determines the exact primary scrambling code used by the cell.
f 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 so that the cell specificBCH information can be read.
Physical layer procedure
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Cell search 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
RACH d
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
f If AICH is not detected, the preamble is resend with 1 dB higher transmit power
f If AICH is detected, a 10 or 20 ms long message part is transmitted with the
same power as the last preamble
RACH d
Physical layer procedure
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RACH procedure
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