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WCDMA Channels10th Aug 2007Deepak
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Logical Channels are not actually channels but rather they canbe defined as different tasks performed by the network and the
UE at different times. They describe the type of information to be transferred.Logical channels are categorized into control channels and
traffic channels.
Control channels carry the control plane informationTraffic Channels carry the user plane information
Transport channels describes how the logical channels will be
transferred, or it can be defined as how and with what
characteristics data is transferred over the interface.
It comes into two groups:Dedicated Channels
Common Channels
WCDMA Channels
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Radio Frame StructureIn WCDMA the information is spread over 5MHz band (Wide
Bandwidth). There are separate radio channels for both uplink
and downlink of 5MHz.
One radio frame consist of 38400 chips and 15 slots. The
duration of the radio frame is 10ms which have ship rate of
3.84 Mcps. Each slots in the radio frame comprises of 2650
chips.
frame #i frame #i+1
timeslot #0 timeslot #1 timeslot #2 timeslot #13 timeslot #14
Radio Frame (10ms)
Time Slot (2560*Tc)
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In uplink and downlink direction, each slot in a radio frame is definedwith a code or a set of codes that carries a set of common and
dedicated channels called Physical Channel.
The information rate of the channel varies from 15 kbps to 1920
kbps for downlink and 30 kbps to 1920 kbps corresponding to
available Spreading Factor. In Downlink spreading factor from 256
to 4 and in downlink from 512 to 4.
Physical channels are the transmission media providing platform
(radio) through which information is going to be transferred
Physical Channels means different kinds of bandwidths allocatedfor different purposes, its actually is the physical existence of the Uu
interface between UE domain and Access domain. Physical channel are defined by specific carrier freq, scrambling
and channelization code
Physical Channel
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Broadcast Control Channel (BCCH):
It broadcast system control information for all mobiles in a cell like Code
values in the cell, neighbors information, allowed power levels in downlink
direction.
Paging Control Channel (PCCH):
It transfer paging information in downlink direction. Network page the mobileto discover the UE location or UE in a cell connected state.
Common Control Channel (CCCH):
Network may have certain tasks which are or may be common to UE in the
cell. Its being used in both direction downlink & uplink. The CCCH is also
used when UE is accessing a new cell after cell reselection.
Dedicated Control Channel (DCCH)
When there is dedicated/active connection means RRC connection between
the network and the mobile, the control information transferred using DCCH.
Its a bi-directional channel.
Logical Channel
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Logical ChannelDedicated Traffic Channel (DTCH):
It is used transfer the user data between the network and the
UE in both uplink and downlink directions.
Common Traffic Channel (CTCH):
It is used to transfer the data from one point to all mobiles ora specified group of mobiles.
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Transport Channels
Transport channels describes how the logical channels to betransferred
Transport channel is defined by how and with what characteristicsdata is transferred over the interface.
It comes into two groups:
Dedicated Channels
Common Channels
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Transport Channels
Dedicated Traffic Channels:Dedicated Channel (DCH):
It is the channel used to send dedicated control and user data between UE and thenetwork in both uplink & downlink directions
Enhanced Dedicated Channel (E-DCH):
It is a enhanced uplink transport channel.
Common Transport Channel :
Random Access Channel (RACH):
It is used to send a control information from UE in the uplink direction. Also may carryshort user packets.
Common Packet Channel (CPCH):
Its an uplink shared channel used for packet data. Several UE can use the samechannel for data transfer.
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Transport ChannelsForward Access Channel (FACH):It is a downlink common channel used to send small amounts of control and
user data.
Downlink Shared Channel (DSCH):
It is common channel used to send dedicated control and user data.
Broadcast Channel (BCH):
It broadcast system information in the downlink direction for all mobilestations in a cell.
Paging Channel (PCH):
Its a downlink common channel used to send paging notification messages.Dedicated Channel (DCH)
It is a channel that is used to send dedicated control and user data between theUE and the network in both directions.
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Physical Channels In Uplink there are both dedicated and common physical
channels.
Dedicated Channels:Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH)
Common Channels:
Physical Random Access Channel
Physical Common Packet Channel
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Physical Channels
Dedicated Physical Control Channel
For each radio link, there is one DPCCH, it carries controlinformation like
Pilot bits (used to support channel estimation at rake receiver)
Transmit Power Control (TPC) commands (Used power control)
Feedback information (FBI) needed with transmit diversity
Transport Format Combination Indicator (TFCI)
Spreading factor is always 256.
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Physical Channels
PilotNpilotbits
TPCNTPCbits
DataNdatabits
Slot #0 Slot #1 Slot #i Slot #14
Tslot
= 2560 chips, 10 bits
1 radio frame: Tf= 10 ms
DPDCH
DPCCHFBI
NFBIbitsTFCI
NTFCIbits
Tslot= 2560 chips, Ndata= 10*2kbits (k=0..6)
Slot #2 Slot #3
Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4
1 subframe = 2 ms
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Physical Channels
Dedicated Physical Data Channel
Each radio link may have no DPDCHs or several DPDCHs.
Spreading factor for the DPDCH can be between 256 and 4.
DPCCH & DPDCH are time multiplexed in downlink butuplink these are I/Q modulation.
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Physical Channels
Physical Random Access Channel (PRACH)
It carries the Random Access Channel (RACH transport Channel).UE uses when physical random access procedure is initiated.
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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Physical Channels
Physical Common Packet Channel (PCPCH)
It carries Common Packet Channel (CPCH Transport Channel). Theaccess transmission consists of Access Preambles (AP), one collision
Detection Preamble (CDP), a DPCCH Power Control Preamble(PCP) and message. Check out the Structure from ECE book.
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Physical Channels
Downlink Dedicated Channel
In downlink there is only one dedicated channel DPCH. Thecontrol data and user data are time multiplexed with one
DPCH. The length of frame is 10 ms divided into 15 slots
The no. of bits in the data part depends on the spreading factorbetween 512 and 4 correspondence of 15kbps to 1,920kbps.
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One radio frame, Tf = 10 ms
TPC
NTPC bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2k bits (k=0..7)
Data2
Ndata2 bits
DPDCH
TFCI
NTFCI bits
Pilot
Npilot bitsData1
Ndata1 bits
DPDCH DPCCH DPCCH
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DPCCH + DPDCH
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Physical ChannelsCommon Pilot ChannelIt has pre-defined bit sequence transmitted with a bit rate of 30 Kbps (Fixed
Scrambling code 256)
CPICH is divided into pilot channels:
Primary Common Pilot Channel (P-CPICH)
Secondary Common Pilot Channel (S-CPICH)Reason for low bit rate as it is transmitted with high power to reduce the
interference. It is phase reference, must be transmitted in whole cell.
Pre-defined bit sequence
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits
1 radio frame: T = 10 ms
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Physical ChannelsPrimary Common Pilot channel (P-CPICH)
It has following characteristics:
The same channelization code is always used
The P-CPICH is scrambled by primary scrambling code
There is only one P-CPICH per cellThe P-CPICH broadcast over the entire cell
Secondary Common Pilot Channel (S-CPICH)
It has following characteristics:
An arbitrary channelization code is used SF256
A S-CPICH may scrambled with primary or secondary
scrambling code
There may be zero, one or several S-CPICH per cell
A S-CPICH transmitted over the entire cell or part of the cell
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Physical ChannelsPrimary Common Control Physical Channel (P-CCPCH)It has fixed bit rate of 30 Kbps (Fixed Scrambling code 256)
There are no TPC, Pilot bits and first 256 chips of the slot are used for theprimary and secondary synchronization Channel. This used to carry theFACH and the PCH.
Data
Ndata1=18 bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits
1 radio frame: Tf = 10 ms
(Tx OFF)
256 chips
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P-CCPCH + SCH
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Physical ChannelsSecondary Common Control Physical Channel (S-CCPCH)It has variable bit rate from 30kbps to 1,920 kbps. There are data bits, pilot
bits and optional TFCI bits. It is transmitted only to smaller are of thecell.
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 20*2k bits (k=0..6)
Pilot
Npilot bits
Data
Ndata1 bits
1 radio frame: Tf = 10 ms
TFCI
NTFCI bits
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The only difference between the P-CCPCH and S-CCPCH the
transport channel mapped on this can only have fixed
predefined transport format combination and in case S-CCPCH
support multiple transport format combination using TFCI
Physical Channels
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Physical ChannelsSynchronization ChannelThis channel used in the cell search procedure. It is divided into the Primary
Synchronization and Secondary Synchronization Channel
Primary Synchronization Channel
It carries primary synchronization codes transmitted in each slot of a radio frame. It issame for cells in the network.
Secondary Synchronization Channel
It consist of the secondary Synchronization codes (SSC). System selects the SSC to betransmitted in a slot, based on the scrambling code group and the slot number.
PrimarySCH
SecondarySCH
256 chips
2560 chips
One 10 ms SCH radio frame
acsi,0
acp
acsi,1
acp
acsi,14
acp
Slot #0 Slot #1 Slot #14
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Physical ChannelsPhysical Downlink Shared Channel (PDSCH)It is used for data transmission by one or-several simultaneous users in the
downlink direction.
CD/CA-ICH
The collision Detection Assignment Indicator Channel is used in the CPCH
Access ProcedureCSICH
The CPCH Status Indicator Channel (CSICH) is associated with a CPCH. Thisis uses the free spaces that occurs in the AICH. It is used to inform theUE about CPCH existence and configuration. The duration of CSICH is
20ms. Each frame consist of 15 slots. The length of slot is 40 bits. Eachslot has a part that is no transmitted and a status indicator part thatincludes 8 status indicator bits.
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Physical ChannelsAcquisition Indicator Channel (AICH)It is used in a random access procedure by the network to indicate that the RACH
preamble was detected.
It has 15 consecutive access slots.
Length of access slot is 5120 chips
Each access slot is further divided into 32 Acquisition indicators and one part hasno transmission.
1024 chi sTransmission Off
AS #14 AS #0 AS #1 AS #i AS #14 AS #0
a1 a2a0 a31a30AI part =4096 chips, 32 real-valued signals
20 ms
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Channel Mapping
The data can be sent through logical layer via
different channels in the transport layer.
And also one transport channel can be sent via
different physical channels.
These selection of channels in the transport and
physical layer depends on the data itself and radio
resource management and its parameters.
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Dedicated Physical Data Channel (DPDCH)Dedicated Physical Control Channel (DPCCH)
Fractional Dedicated Physical Channel (F-DPCH)E-DCH Dedicated Physical Data Channel (E-DPDCH)
E-DCH Dedicated Physical Control Channel (E-DPCCH)E-DCH Absolute Grant Channel (E-AGCH)E-DCH Relative Grant Channel (E-RGCH)
E-DCH Hybrid ARQ Indicator Channel (E-HICH)Physical Random Access Channel (PRACH)
Common Pilot Channel (CPICH)
Primary Common Control Physical Channel (P-CCPCH)
Secondary Common Control Physical Channel (S-CCPCH)
Synchronisation Channel (SCH)
Acquisition Indicator Channel (AICH)Paging Indicator Channel (PICH)MBMS Notification Indicator Channel (MICH)High Speed Physical Downlink Shared Channel (HS-PDSCH)
HS-DSCH-related Shared Control Channel (HS-SCCH)
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Transport Channels
DCH
RACH
BCH
FACH
PCH
Physical Channels
HS-DSCH
E-DCH
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Burst Types Dedicated Physical Channel There are four different types of bursts
All contains two data fields, midamble and GP.
Length of each is different in each bursts.
The no. of data symbol depends on SF or burst type.
Spreading factor(SF)
Burst Type 1 Burst Type 2 Burst Type 3 Burst Type 4
1 1952 2208 1856 2112
2 976 1104 928 N/A
4 488 552 464 N/A
8 244 276 232 N/A
16 122 138 116 132
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Burst Type - I This burst type used for both Uplink and Downlink
It has larger training sequence due to longer midamble field
Data field has 976 chips long, no. of symbol depends on the SF
Midamble is 512 chips long and GP is 96 chips period.
Chip number (CN) Length of field in chips Length of field in symbols Contents of field
0-975 976 Cf table 1 Data symbols976-1487 512 - Midamble
1488-2463 976 Cf table 1 Data symbols
2464-2559 96 - Guard period
Data symbols976 chips
Midamble512 chips
Data symbols976 chips
GP96CP
2560*Tc
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Burst Type - II
This burst type used for both Uplink and Downlink It has shorter training sequence due to longer midamble field
Data field has 1104 chips long, no. of symbol depends on the SF
Midamble is 256 chips long and GP is 96 chips period.
Chip number (CN) Length of field in chips Length of field in symbols Contents of field0-1103 1104 cf table 1 Data symbols
1104-1359 256 - Midamble
1360-2463 1104 cf table 1 Data symbols
2464-2559 96 - Guard period
Data symbols1104 chips
Midamble256 chips
GP96CP
2560*Tc
Data symbols1104 chips
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Burst Type - III
This burst type used for Uplink only It has longer guard period suitable for initial access or accss to new cell after
handover
Data field has 976 and 880 chips long, no. of symbol depends on the SF
Midamble is 512 chips long and GP is 192 chips period.
Data symbols976 chips
Midamble512 chips
GP192CP
2560*Tc
Data symbols
880 chips
Chip number (CN) Length of field in chips Length of field in symbols Contents of field
0-975 976 Cf table 1 Data symbols
976-1487 512 - Midamble
1488-2367 880 Cf table 1 Data symbols
2368-2559 192 - Guard period
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Burst Type - IV This burst type used for downlink MBSFN
It has longer guard period suitable for initial access or accss to new cell afterhandover
It has two data fiels each of 1056 chips long, no. of symbol depends on the SF
Midamble is 320 chips long and GP is 128 chips period.
Data symbols1056 chips
Midamble 320chips
Data symbols1056 chips
GP 128CP
2560*Tc
Chip number (CN) Length of field in chips Length of field in symbols Contents of field0-1055 1056 Cf table 1 Data symbols
1056-1375 320 - Midamble
1376-2431 1056 Cf table 1 Data symbols
2432-2559 128 - Guard period
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TPC Transmission of TPC burst is done in the data parts of traffic burst.
Data in TPC is always transmit at SF 32 irrespective SF of user data
TPC information is to be transmitted immediately after the midamble
Shall be transmitted with same channelization code and timeslot of TFCI
Data symbols Midamble Data symbolsGP
TPC field
512/256 chips
2560*Tc
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TFCI Transmission of TFCI is done in the data parts of the respective physical
channel.
In Downlink the TFCI code word bit and data bit subjected to the samespreading procedure
In Uplink, independent to the SF of data bits TFCI code is applied with SF 32
TFCI is code to be transmitted directly adjacent to the midamble
Data symbols Midamble Data symbols GP
512/320/256 chips
2560*Tc
1st part of TFCI code word 2nd part of TFCI code word
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Questions and discussion