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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
www.huawei.com
Internal
WCDMA Radio Interface Physical Layer
ISSUE 1.0
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The physical layer offers data transport services
to higher layers.
The access to these services is through the use
of transport channels via the MAC sub-layer.
The physical layer is expected to perform the
following functions in order to provide the data
transport service, for example Modulation and
spreading/demodulation and despreading, Inner -
loop power control etc.
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References
TS 25.104 UTRA (BS) FDD Radio Transmission and Re
ception
TS 25.201 Physical layer-general description
TS 25.211 Physical channels and mapping of
transport channels onto physical channels (FDD)
TS 25.212 Multiplexing and channel coding (FDD)
TS 25.213 Spreading and modulation (FDD)
TS 25.214 Physical layer procedures (FDD)
TS 25.308 UTRA High Speed Downlink Packet Access
(HSDPA); Overall description; Stage 2
TR 25.877 High Speed Downlink Packet Acces (HSDPA) -
Iub/Iur Protocol Aspects
TR 25.858 Physical layer aspects of UTRA High Speed D
ownlink Packet Access
HUAWEI TECHNOLOGIES CO., LTD. Page 4All rights reserved
Upon completion of this course, you will be
able to:
Outline radio interface protocol
Architecture
Describe key technology of UMTS
physical layer
Describe UMTS physical layer procedures
HUAWEI TECHNOLOGIES CO., LTD. Page 5All rights reserved
Chapter 1 Physical Layer OverviewChapter 1 Physical Layer Overview
Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology
Chapter 3 Physical Layer ProceduresChapter 3 Physical Layer Procedures
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UTRAN Protocol Structure
RNS
RNC
RNS
RNC
Core Network
NodeB NodeB NodeB NodeB
Iu Iu
Iur
Iub IubIub Iub
HUAWEI TECHNOLOGIES CO., LTD. Page 7All rights reserved
Radio Interface Protocol Structure
L3
con
tro
l
con
tro
l
con
tro
l
con
tro
l
Logical Channels
Transport Channels
C-plane signaling U-plane information
PHY
L2/MAC
L1
RLC
DCNtGC
L2/RLC
MAC
RLCRLC
RLCRLC
RLCRLCRLC
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCPPDCP L2/PDCP
DCNtGC
Radio Bearers
RRC
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Spreading Technology Spreading consists of 2 steps :
Channelization operation, which transforms data symbols into chips. Thus increasing the bandwidth of the signal, The number of chips per data symbol is called the Spreading Factor ( SF ) .The operation is done by multiplying with OVSF code.
Scrambling operation is applied to the spreading signal .
Data bit
OVSF code
Scrambling code
Chips after spreading
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Channelization Code
OVSF code is used as channelization code
The channelization codes are uniquely described as Cch,SF,k, where SF is the
spreading factor of the code and k is the code number, 0 k SF-1.
SF = 1 SF = 2 SF = 4
Cch,1,0 = (1)
Cch,2,0 = (1,1)
Cch,2,1 = (1,-1)
Cch,4,0 =(1,1,1,1)
Cch,4,1 = (1,1,-1,-1)
Cch,4,2 = (1,-1,1,-1)
Cch,4,3 = (1,-1,-1,1)
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Scrambling Code
Scrambling code: GOLD sequence.
Scrambling code period: 10ms ,or 38400 chips.
The code used for scrambling of the uplink DPCCH/DPDCH may be of
either long or short type, There are 224 long and 224 short uplink
scrambling codes. Uplink scrambling codes are assigned by higher
layers.
For downlink physical channels, a total of 218-1 = 262,143 scrambling
codes can be generated. scrambling codes k = 0, 1, …, 8191 are used.
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Scrambling codes for downlink physical channels
Set 0
Set 1
…
Set 511
Primary scrambling code 0
……
Secondary scrambling code 1
Secondary scrambling code 15
Primary scrambling code
511×16
……
Secondary scrambling code 511×1
6+ 15
8192 scrambling codes
512 sets
Primary Scrambling Code
……
A primary scrambling code and 15 secondary scrambling codes are
included in a set.
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Primary Scrambling Code Group
Primary scrambling codes for downlink physical channels
Group 0
…
Primary scrambling code 0
……
Primary scrambling code
8*63
……
Primary scrambling code 63*8+
7
512 primary scrambling codes
……
Group 1
Group 63
Primary scrambling code 1
Primary scrambling code 7
64 primary scrambling code groups
Each group consists of 8 primary scrambling codes
HUAWEI TECHNOLOGIES CO., LTD. Page 13All rights reserved
Chapter 1 Physical Layer OverviewChapter 1 Physical Layer Overview
Chapter 2 Physical Layer Key TechnologyChapter 2 Physical Layer Key Technology
Chapter 3 Physical Layer ProceduresChapter 3 Physical Layer Procedures
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Chapter 2 Physical Layer Key TechnologyChapter 2 Physical Layer Key Technology
Section 1 Physical ChannelSection 1 Physical Channel Structure and FunctionsStructure and Functions
Section 2 Channel MappingSection 2 Channel Mapping
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WCDMA radio interface has three kinds of channels
In terms of protocol layer, the WCDMA radio interface has three channels: Physical channel, transport channel and logical channel.
Logical channel: Carrying user services directly. According to the types of the carried services, it is divided into two types: Control channel and service channel.
Transport channel: It is the interface of radio interface layer 2 and physical layer, and is the service provided for MAC layer by the physical layer. According to whether the information transported is dedicated information for a user or common information for all users, it is divided into dedicated channel and common channel.
Physical channel: It is the ultimate embodiment of all kinds of information when they are transmitted on radio interfaces. Each kind of channel which uses dedicated carrier frequency, code (spreading code and scramble) and carrier phase (I or Q) can be regarded as a dedicated channel.
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Control channel
Traffic channel
Dedicated traffic channel (DTCH)
Common traffic channel (CTCH)
Broadcast control channel (BCCH)
Paging control channel (PCCH)
Dedicate control channel (DCCH)
Common control channel (CCCH)
Logical Channel
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Dedicated Channel (DCH)
-DCH is an uplink or downlink channel
Broadcast channel (BCH)
Forward access channel (FACH)
Paging channel (PCH)
Random access channel (RACH)
High-speed downlink shared channel
(HS-DSCH)
Common transport channel
Dedicated transport channel
Transport Channel
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Physical Channel
A physical channel is defined by a specific carrier frequency, code
(scrambling code, spreading code) and relative phase.
In UMTS system, the different code (scrambling code or spreading
code) can distinguish the channels.
Most channels consist of radio frames and time slots, and each radio
frame consists of 15 time slots.
Two types of physical channel:UL and DL
Physical Channel
Frequency, Code, Phase
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Downlink Physical Channel
Downlink Dedicated Physical Channel
(Downlink DPCH)
Downlink Common Physical Channel
Common Control Physical Channel (CCPCH)
Synchronization Channel (SCH)
Paging Indicator Channel (PICH)
Acquisition Indicator Channel (AICH)
Common Pilot Channel (CPICH)
High-Speed Packet Downlink Shared Channel (HS-PDSCH)
High-Speed Shared Control Channel (HS-SCCH)
Downlink Physical Channel
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Uplink Physical Channel
Uplink Dedicated Physical Channel
Uplink Dedicated Physical Data Channel (Uplink DPDCH)
Uplink Dedicated Physical Control Channel (Uplink DPCCH)
High-Speed Dedicated Physical Channel (HS-DPCCH)
Uplink Common Physical Channel
Physical Random Access Channel
(PRACH)
Uplink Physical Channel
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Function of physical channel
Node B UE
P-CCPCH-Primary Common Control Physical ChannelSCH- Synchronisation Channel
P-CCPCH-Primary Common Control Physical ChannelSCH- Synchronisation Channel
P-CPICH-Primary Common Pilot Channel S-CPICH-Secondary Common Pilot ChannelP-CPICH-Primary Common Pilot Channel S-CPICH-Secondary Common Pilot Channel
Cell broadcast channels
DPDCH-Dedicated Physical Data ChannelDPDCH-Dedicated Physical Data Channel
DPCCH-Dedicated Physical Control ChannelDPCCH-Dedicated Physical Control Channel
Dedicated channels
Paging channels
PICH-Paging Indicator ChannelPICH-Paging Indicator Channel
S-CCPCH-Secondary Common Control Physical ChannelS-CCPCH-Secondary Common Control Physical Channel
PRACH-Physical Random Access ChannelPRACH-Physical Random Access Channel
AICH-Acquisition Indicator ChannelAICH-Acquisition Indicator Channel
Random access channels
HS-DPCCH-High Speed Dedicated Physical Control ChannelHS-DPCCH-High Speed Dedicated Physical Control Channel
HS-SCCH-High Speed Share Control Channel HS-SCCH-High Speed Share Control Channel
HS-PDSCH-High Speed Physical Downlink Share ChannelHS-PDSCH-High Speed Physical Downlink Share Channel
High speed downlink share channels
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Primary Synchronization Channel (P-SCH) Used for cell search Two sub channels: P-SCH and S-SCH. SCH is transmitted at the first 256 chips
of every time slot. PSC is transmitted repeatedly in each
time slot.
SSC specifies the scrambling code groups of the cell.
SSC is chosen from a set of 16 different codes of length 256, and there are altogether 64 SSC sequences correspond to 64 primary scrambling code groups.
Primary SCH
Secondary SCH
Slot #0 Slot #1 Slot #14
acsi,0
pac pac pac
acsi,1 acs
i,14
256 chips
2560 chips
One 10 ms SCH radio frame
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slot number Scrambling Code Group #0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
…
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
Secondary Synchronization Channel (S-SCH)
……..
2560 chips
acp
Slot # ?
P-SCH acp
Slot #?
16 6S-SCH
acp
Slot #?
11 Group 2Slot 7, 8, 9
256 chips
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Common Pilot Channel(CPICH) Common Pilot Channel (CPICH)
Carries pre-defined sequence.
Fixed rate 30Kbps , SF=256
Primary CPICH
Uses the fixed channel code -- Cch,256,0
Scrambled by the primary scrambling code
Only one CPICH per cell
Broadcast over the entire cell
The P-CPICH is a phase reference for SCH, Primary CCPCH, AICH, PICH. By default, it is also a phase reference for downlink DPCH.
Pre-defined symbol sequence
Slot #0 Slot #1 Slot # i Slot #14
Tslot = 2560 chips , 20 bits
1 radio frame: Tr = 10 ms
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Primary Common Control Physical Channel (PCCPCH) Fixed rate, fixed OVSF code ( 30kbps , Cch,256,1 ) Carry BCH transport channel The PCCPCH is not transmitted during the first 256 chips of each time slot. Only data part STTD transmit diversity may be used
PCCPCH Data
18 bits
Slot #0
1 radio frame: T f = 10 ms
Slot #1 Slot #i
256 chips
Slot #14
T slot = 2560 chips,20 bits
SCH
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Paging Indicator Channel (PICH) PICH is a fixed-rate (SF=256) physical channel used to carry the Paging Indicators (PI). Frame structure of PICH: one frame of length 10ms consists of 300 bits of which 288 bits
are used to carry paging indicators and the remaining 12 bits are not defined. N paging indicators {PI0, …, PIN-1} in each PICH frame, N=18, 36, 72, or 144. If a paging indicator in a certain frame is set to 1, it indicates that UEs associated with
this paging indicator should read the corresponding frame of the associated S-CCPCH.
One radio frame (10 ms)
b1 b0
288 bits for paging indication
12 bits (undefined)
b287 b288 b299
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Secondary Common Control Physical Channel (SCCPCH) Carry FACH and PCH. Two kinds of SCCPCH: with or without TFCI. UTRAN decides if a TFCI should be transmitted, UE must support TFCI. Possible rates are the same as that of downlink DPCH
SF =256 - 4. FACH and PCH can be mapped to the
same or separate SCCPCHs. If
mapped to the same S-CCPCH, they
can be mapped to the same fame.
DataN bits
Slot #0 Slot #1 Slot #i Slot #14
1 radio frame: T f = 10 ms
T slot = 2560 chips,
Data
PilotN bitsPilotN bits
TFCITFCI
20*2 k bits (k=0..6)
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Physical Random Access Channel (PRACH) The random-access transmission data consists of two parts:
One or several preambles : each preamble is of length 4096chips and consists of 256 repetitions of a signature whose length is 16 chips , 16 available signatures totally
10 or 20ms message part
Which signature is available and the length of message part are determined by higher layer
Message partPreamble
4096 chips10 ms (one radio frame)
Preamble Preamble
Message partPreamble
4096 chips 20 ms (two radio frames)
Preamble Preamble
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PRACH Access Timeslot Structure
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
5120 chips
radio frame: 10 ms radio frame: 10 ms
Access slot #0 Random Access Transmission
Access slot #1
Access slot #7
Access slot #14
Random Access Transmission
Random Access Transmission
Random Access TransmissionAccess slot #8
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PRACH Message Structure
PilotN bits
Slot # 0 Slot # 1 Slot # i Slot # 14
Message part radio frame TRACH = 10 ms
Tslot = 2560 chips, 10*2
Pilot
TFCI
N bitsTFCI
DataN data bitsData
Control
k bits (k=0..3)
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Acquisition Indicator Channel (AICH) Frame structure of AICH : two frames, 20 ms , consists of a repeated
sequence of 15 consecutive AS, each of length 40 symbols(5120 chips).
Each time slot consists of two parts , an Acquisition-Indicator(AI) and a
part of duration 1024chips with no transmission.
Acquisition-Indicator AI have 16 kinds of Signature.
CPICH is the phase reference of AICH.
AS #14 AS #0 AS #1 AS #i AS #14 AS #0
a1 a2a0 a31 a32a30 a33 a38 a39
AI part Unused part
20 ms
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Uplink Dedicated Physical Channel (DPDCH&DPCCH)
DPDCH and DPCCH are I/Q code multiplexed within each radio frame
DPDCH carries data generated at Layer 2 and higher layer
DPCCH carries control information generated at Layer 1
Each frame is 10ms and consists of 15 time slots, each time slot
consists of 2560 chips
The spreading factor of DPDCH is from 4 to 256
The spreading factor of DPDCH and DPCCH can be different in the
same Layer 1 connection
Each DPCCH time slot consists of Pilot, TFCI , FBI , TPC
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Frame Structure of Uplink DPDCH/DPCCH
Pilot Npilot bits
TPC NTPC bits
DataNdata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2 k bits (k=0..6)
1 radio frame: T = 10 msf
DPDCH
DPCCHFBI
NFBI bitsTFCI
NTFCI bits
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Downlink Dedicated Physical Channel (DPDCH+DPCCH)
DCH consists of dedicated data and control information.
Control information includes : Pilot 、 TPC 、 TFCI(optional).
The spreading factor of DCH can be from 512 to 4,and can be changed during connection
DPDCH and DPCCH is time multiplexed.
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Frame Structure of Downlink DPCH
One radio frame, Tf = 10 ms
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2 k bits (k=0..7)
Data2Ndata2 bits
DPDCH
TFCI NTFCI bits
Pilot Npilot bits
Data1Ndata1 bits
DPDCH DPCCH DPCCH
TPC NTPC bits
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High-Speed Physical Downlink Shared Channel (HS-PDSCH)
Bear service data and layer2 overhead bits mapped from the transport
channel
SF=16, can be configured several channels to increase data service
Slot #0 Slot#1 Slot #2
T slot = 2560 chips, M*10*2k bits (k=4)
DataN Data 1 bits
1 subframe: Tf = 2 ms
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High-Speed Shared Control Channel (HS-SCCH)
Carries physical layer signalling to a single UE ,such as modulation scheme (1 bit) ,channelization code set (7 bit), transport Block size (6bit),HARQ process number (3bit), redundancy version (3bit), new data indicator (1bit), Ue identity (16bit)
HS-SCCH is a fixed rate (60 kbps, SF=128) downlink physical channel used to carry downlink signalling related to HS-DSCH transmission
Slot #0 Slot#1 Slot #2
T slot= 2560 chips, 40 bits
DataN Data 1 bits
1 subframe: T f = 2 ms
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High-Speed Dedicated Physical Control Channel (HS-DPCCH )
HS-DPCCH carries information to acknowledge downlink transport
blocks and feedback information to the system for scheduling and link
adaptation of transport block
CQI and ACK/NACK
Physical Channel ,Uplink, SF=256,power control
Subframe #0 Subframe # i Subframe #4
HARQ-ACK CQI
One radio frame T f = 10 ms
One HS-DPCCH subframe (2 ms)
2 T slot = 5120 chips T slot = 2560 chips
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Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology
Section 1 Physical Channel Structure and FunctionsSection 1 Physical Channel Structure and Functions
Section 2 Channel MappingSection 2 Channel Mapping
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Mapping Between ChannelsLogical channels Transport channels Physical channels
BCCH BCH P-CCPCH
FACH S-CCPCH
PCCH PCH S-CCPCH
CCCH RACH PRACH
FACH S-CCPCH
CTCH FACH S-CCPCH
DCCH, DTCH DCH DPDCH
HS-DSCH HS-PDSCH
RACH, FACH PRACH, S-CCPCH
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Chapter 1 Physical Layer OverviewChapter 1 Physical Layer Overview
Chapter 2 Physical Layer Key TechnologyChapter 2 Physical Layer Key Technology
Chapter 3 Physical Layer ProceduresChapter 3 Physical Layer Procedures
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Synchronization Procedure—Cell Search
Frame synchronization and code-group identification
Scrambling-code identification
UE uses SSC to find frame synchronization and identify the code group of the cell found in the first step
UE determines the primary scrambling code through correlation over the CPICH with all codes within the identified group, and then detects the P-CCPCH and reads BCH information。
Slot synchronizationUE uses PSC to acquire slot synchronization to a cell
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Synchronization Procedure— Channel Timing Relationship
AICH access slo ts
Secondary SCH
Primary SCH
S-CCPCH,k
10 ms
PICH
#0 #1 #2 #3 #14 #13 #12 #11 #10 #9 #8 #7 #6 #5 #4
P -CCPCH, (SFN modulo 2) = 0 P -CCPCH, (SFN modulo 2) = 1
Any CPICH
k:th S -CCPCH
PICH for k:th S -CCPCH
n:th DPCH DPCH,n
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Random Access Procedure START
Choose a RACH sub channel fromavailable ones
Get available signatures
Set Preamble Retrans Max
Set Preamble _Initial _ Power
Send a preamble
Check the corresponding AI
Increase message part power by p-m based on preamble power
Set physical status to be RACH message transmitted Set physical status to be Nack
on AICH received
Choose a access slot again
Counter> 0 & Preamble power-maximum allowed power<6 dB
Choose a signature and increase preamble transmit power
Set physical status to be Nack on AICH received
Get negative AI
No AI
Report the physical status to MAC
END
Get positive AI
The counter of preamble retransmit Subtract-1, Commanded preamble power
increased by Power Ramp Step
N
Y
Send the corresponding message part
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Random Access Procedure—RACH
Physical random access procedure
1. Derive the available uplink access slots, in the next full access slot set, for the set of available RACH sub-channels within the given ASC. Randomly select one access slot among the ones previously determined. If there is no access slot available in the selected set, randomly select one uplink access slot corresponding to the set of available RACH sub-channels within the given ASC from the next access slot set. The random function shall be such that each of the allowed selections is chosen with equal probability ;
2. Randomly select a signature from the set of available signatures within the given ASC. ;
3. Set the Preamble Retransmission Counter to Preamble_ Retrans_ Max
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Random Access Procedure—RACH
4. Set the parameter Commanded Preamble Power to Preamble_Initial_Power
5. Transmit a preamble using the selected uplink access slot, signature, and preamble transmission power.
6. If no positive or negative acquisition indicator (AI +1 nor –1) corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot:
− A: Select the next available access slot in the set of available RACH sub-channels within the given ASC;
− B: select a signature;
− C: Increase the Commanded Preamble Power;
− D: Decrease the Preamble Retransmission Counter by one. If the Preamble Retransmission Counter > 0 then repeat from step 6. Otherwise exit the physical random access procedure.
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Random Access Procedure—RACH
7. If a negative acquisition indicator corresponding to the selected
signature is detected in the downlink access slot corresponding to
the selected uplink access slot, exit the physical random access
procedure Signature
8. If a positive acquisition indicator corresponding to the selected
signature is detected , Transmit the random access message three
or four uplink access slots after the uplink access slot of the last
transmitted preamble
9. exit the physical random access procedure
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Transmit diversity Mode
Application of Tx diversity modes on downlink Application of Tx diversity modes on downlink physical channelphysical channel
Physical channel type Open loop mode Closed loop mode
TSTD STTD Mode 1 Mode 2
P-CCPCH – applied – –
SCH applied – – –
S-CCPCH – applied – –
DPCH – applied applied applied
PICH – applied – –
HS-PDSCH – applied applied –
HS-SCCH – applied – –
AICH – applied – –
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Transmit Diversity-STTD
Space time block coding based transmit antenna diversity(STTD ) 4 consecutive bits b0, b1, b2, b3 using STTD coding
b0 b1 b2 b3
b0 b1 b2 b3
-b2 b3 b0 -b1
Antenna 1
Antenna 2Channel bits
STTD encoded channel bitsfor antenna 1 and antenna 2.
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Transmit Diversity-TSTD
Time switching transmit diversity (TSTD) is used Time switching transmit diversity (TSTD) is used only on SCH channel.only on SCH channel.
Antenna 1
Antenna 2
ac si,0
acp
acsi,1
acp
acsi,14
acp
Slot #0 Slot #1 Slot #14
acsi,2
acp
Slot #2
(Tx OFF)
(Tx OFF)(Tx OFF)
(Tx OFF)
(Tx OFF)
(Tx OFF)(Tx OFF)(Tx OFF)
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Transmit Diversity - Closed Loop Mode Closed loop mode transmit diversity
Used in DPCH and PDSCH ; Channel coding, interleaving and spreading are done as in non-
diversity mode. The spread complex valued signal is fed to both TX
antenna branches, and weighted with antenna specific weight
factors w1 and w2.
The weight factors are determined by the UE, and signalled to the
UTRAN access point (=cell transceiver) using the D-bits of the FBI
field of uplink DPCCH.
The calculation of weight factor is the key point of closed loop Tx di
versity.there are two modes with different calculation methods of w
eight factor :
− 1 、 mode 1 uses phase adjustment ; the dedicated pilot sym
bols of two antennas are different(orthogonal)
− 2 、 mode 2 uses phase/amplitude adjustment ; the dedicate
d pilot symbols of two antennas are the same.
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Summary
This course mainly introduces the basic concept,
key technology and procedures of WCDMA phy
sical layer.
This is very helpful for comprehension of Uu int
erface features and further study .
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