Wcdma channels

WCDMA Channels
10th Aug 2007
Deepak

Logical Channels are not actually channels but rather they can
be 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 information
•Traffic 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

Radio Frame Structure
In 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)

In uplink and downlink direction, each slot in a radio frame is
defined with 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
allocated for 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

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 mobile
to 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

Logical Channel
Dedicated 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 or
a specified group of mobiles.

Transport Channels
 Transport channels describes how the logical channels to be
transferred
 Transport channel is defined by how and with what characteristics
data is transferred over the interface.
 It comes into two groups:
 Dedicated Channels
 Common Channels

Transport Channels
 Dedicated Traffic Channels:
Dedicated Channel (DCH):
It is the channel used to send dedicated control and user data between UE and the
network 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 carry
short user packets.
Common Packet Channel (CPCH):
Its an uplink shared channel used for packet data. Several UE can use the same
channel for data transfer.

Transport Channels
Forward 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 mobile
stations in a cell.
Paging Channel (PCH):
It’s 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 the
UE and the network in both directions.

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

Physical Channels
Dedicated Physical Control Channel
For each radio link, there is one DPCCH, it carries control
information 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.

Physical Channels
Pilot
Npilot bits
TPC
NTPC bits
Data
Ndata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10 bits
1 radio frame: T f = 10 ms
DPDCH
DPCCH
FBI
NFBI bits
TFCI
NTFCI bits
Tslot = 2560 chips, N data = 10*2k
bits (k=0..6)
Slot #2 Slot #3
Subframe #0 Subframe #1 Subframe #2 Subframe #3 Subframe #4
1 subframe = 2 ms

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 but
uplink these are I/Q modulation.

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 chips
10 ms (one radio frame)
Preamble Preamble
Message partPreamble
4096 chips 20 ms (two radio frames)
Preamble Preamble

Physical ChannelsRACH Preamble Part
Each preamble is of length 4096 chips and consist of 256 repetitions of a
signature of length 16 chips.
RACH Message Part
The 10 ms message part spilt into 15 slots each length of 2560 ships. Each slot
consist of data part onto which RACH transport part is mapped and
control part that carries layer 1 control information. The 20ms message
consists of two consecutive 10ms message part radio frames.
Pilot
Npilot bits
Data
Ndata bits
Tslot = 2560 chips, 10*2k
bits (k=0..3)
Message part radio frame TRACH = 10 ms
Data
Control
TFCI
NTFCI bits

Physical Channels
 Physical Common Packet Channel (PCPCH)
It carries Common Packet Channel (CPCH Transport Channel). The
access 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.

Physical Channels
Downlink Dedicated Channel
 In downlink there is only one dedicated channel DPCH. The
control 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
factor between 512 and 4 correspondence of 15kbps to
1,920kbps.

One radio frame, Tf = 10 ms
TPC
NTPC bits
bits (k=0..7)
Data2
Ndata2 bits
DPDCH
TFCI
NTFCI bits
Pilot
Npilot bits
Data1
Ndata1 bits
DPDCH DPCCH DPCCH

Physical Channels
Common Pilot Channel
It 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
Tslot = 2560 chips , 20 bits
1 radio frame: Tf = 10 ms

Physical Channels
Primary 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 cell
•The 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

Physical Channels
Primary 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 the
primary and secondary synchronization Channel. This used to carry the
FACH and the PCH.
Data
Ndata1=18 bits
Tslot = 2560 chips , 20 bits
(Tx OFF)
256 chips

Physical Channels
Secondary 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 the
cell.
bits (k=0..6)
Pilot
Npilot bits
Data
Ndata1 bits
TFCI
NTFCI bits

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

Physical Channels
Synchronization Channel
This 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 is
same for cells in the network.
 Secondary Synchronization Channel
It consist of the secondary Synchronization codes (SSC). System selects the SSC to be
transmitted in a slot, based on the scrambling code group and the slot number.
Primary
SCH
Secondary
SCH
256 chips
2560 chips
One 10 ms SCH radio frame
acs
i,0
acp
acs
i,1
acp
acs
i,14
acp
Slot #0 Slot #1 Slot #14

Physical Channels
Physical 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 Procedure
CSICH
The CPCH Status Indicator Channel (CSICH) is associated with a CPCH. This
is uses the free spaces that occurs in the AICH. It is used to inform the
UE about CPCH existence and configuration. The duration of CSICH is
20ms. Each frame consist of 15 slots. The length of slot is 40 bits. Each
slot has a part that is no transmitted and a status indicator part that
includes 8 status indicator bits.

Physical Channels
Acquisition 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 has
no transmission.
1024 chips
Transmission Off
AS #14 AS #0 AS #1 AS #i AS #14 AS #0
a1 a2a0 a31a30
AI part = 4096 chips, 32 real-valued signals
20 ms

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.

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)
Dedicated Physical Control Channel (uplink) for HS-
Transport Channels
DCH
RACH
BCH
FACH
PCH
Physical Channels
HS-DSCH
E-DCH

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

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 symbols
976-1487 512 - Midamble
2464-2559 96 - Guard period
Data symbols
976 chips
Midamble
512 chips
Data symbols
976 chips
GP
96
CP
2560*Tc

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
0-1103 1104 cf table 1 Data symbols
1104-1359 256 - Midamble
1360-2463 1104 cf table 1 Data symbols
2464-2559 96 - Guard period
Data symbols
1104 chips
Midamble
256 chips
GP
96
CP
2560*Tc
Data symbols
1104 chips

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
Data symbols
976 chips
Midamble
512 chips
GP
192
CP
2560*Tc
Data symbols
880 chips
976-1487 512 - Midamble
2368-2559 192 - Guard period

Burst Type - IV
 This burst type used for downlink MBSFN
 It has longer guard period suitable for initial access or accss to new cell after
handover
 It has two data fiels each of 1056 chips long, no. of symbol depends on the SF
Data symbols
1056 chips
Midamble 320
chips
Data symbols
1056 chips
GP 128
CP
2560*Tc
1056-1375 320 - Midamble
2432-2559 128 - Guard period

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 symbols
GP
TPC field
512/256 chips
2560*Tc

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 same
spreading 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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