WCDMA Specifications

1

WCDMA Specifications

Takehiro Ikeda
06/03/02

2

Target of IMT-2000
High spectrum efficiency, high capacity
Reasons:
- Lack of the spectrum (2G, especially in Japan)
- Huge demand for wireless communications

High speed and high quality multimedia services
Reasons:
- Increasing demands for various applications,
such as video chat, music download, etc…

Global and Seamless connectivity
Reasons:
- GSM covers large area all over the world, but not everywhere
(IS-54/IS-95 in the U.S., PDC in Japan)

3

IMT-2000 Terrestrial Radio Interface
CDMA Families

So-called

IMT-2000 CDMA Direct Spread

UTRA FDD, WCDMA, UMTS

IMT-2000 CDMA Multi-Carrier

cdma2000

IMT-2000 CDMA TDD

UTRA TDD, TD-SCDMA

(by 3GPP)

(by 3GPP2)

(by 3GPP+CWTS)

TDMA Families
IMT-2000 Single Carrier

UWC-136

IMT-2000 FDMA/TDMA

DECT

(by TIA)
(by ETSI)

Recommendation ITU-R M.1457

4

Network Architecture
Radio Access Network (RAN)
RNC

SCF

MSC/VLR

SGSN

HLR

GMSC

PLMN, PSTN

GGSN

Internet

Core Network (CN)
Node B
(BTS)

The number of BTSs per RNC:
- 48 (maximum)
- 6-10 (in practical)

WCDMA
Air interface
UE

cf. based on GPRS infrastructure
ATM-based network (Release 99)
IP network (Release 4/5)

UE: User Equipment
BTS: Base Transceiver Station
RNC: Radio Network Controller
SGSN: Serving GPRS Support Node
GGSN: Gateway GPRS Support Node
GPRS: General Packet Radio Service
MSC: Mobile-Services Switching Center

VLR: Visitor Location Register
GMSC: Gateway MSC
SCF: Service Control Function
HLR: Home Location Register
PLMS: Public Land Mobile Network
PSTN: Public Switched Telephone Network

5

Prime technologies of WCDMA
Purpose

Technology

High capacity

1-Cell Reuse

High quality
Multimedia

Transmission Power Control
Rake Combining
Soft Handover (aka. Site Diversity)
Multi-rate Transmission

6

1-Cell Reuse
Purpose:
- to increase the system capacity
- to free from the frequency planning
Solution:
- Layered spreading code
Scrambling code (long code) Gold-sequence (10 ms, 38400 chips)
Uplink: UE identification
Downlink: Cell/Sector identification
Channelization code (short code) OVSF (4 - 512 chips)
Uplink: channel identification for each UE
Downlink: channel identification for each sector
OVSF: Orthogonal Variable Spreading Factor

7

1-Cell Reuse (cont.)
Downlink
spreader

UE

BTS/sector ID
code

Channel ID
code

Transmitted
data

BTS

Uplink
Transmitted
data

UE

spreader

Channel ID
code

User ID
code

BTS
short code
long code

8

Transmission Power Control
Purpose:
- to solve the near-far problem (uplink)
- to reduce the unnecessary transmission power (uplink)
→ increase of system capacity
- to overcome MPI and ICI (downlink)
Solution:
- SIR-based power control
Open-loop power control
Closed-loop power control
Inner loop power control
Outer loop power control

MPI: multi-path interference
ICI: inter cell interference

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Transmission Power Control (cont.)

4.Data
transmission
3.Decision of
transmission
power
UE

BTS

1.Common Pilot
Channel
2.Measurement of
propagation loss

Open-loop power control

1.Data
5.Data
transmission

UE

2.Measurement of
received SIR
3.TCP
BTS command
generation
4.TCP command
(up or down)

5.Set of
transmission power

Closed-loop power control (uplink)

10

Transmission Power Control (cont.)
Inner loop power control
- to compare the received SIR and the target
SIR
- to generate TCP command bits
Outer loop power control
- to compare the received BLER and the target
BLER
- to determine the target SIR
*BLER: block error rate
time

time

Same SIR,
But different BLER (maybe)

11

Transmission Power Control (cont.)
Received
signal

Outer loop
Coherent
Rake combining

MF

SIR
measurement

Channel
decoding

+

Block error
detection

- Target SIR

Inner loop
TPC command bits
(+/- step-size [1 dB])

TPC command
generator

BLER
measurement
+

-

Target
BLER

Generation of
Target SIR

MF: Matched Filter
BLER: Block Error Rate

Closed-loop power control (uplink)

12

Rake Combining
Purpose:
- to improve the received quality
- (to increase the system capacity)
Solution:
- Coherent combination of effective multi paths

13

Rake Combining (Cont.)
Effective paths
Received signal

threshold

Path resolution:
1/3.84Mcps = 0.26 μsec

time

- separation to each path

- phase compensation*
- coherent combination

* Maximum ratio combining can
be achieved by doing phase
compensation.

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Rake Combining (cont.)
The number of fingers = 4
For path L

Received
signal

For path 1
Correlator

Spreading code
generator

Delay

*

Pilot symbol-assisted
Channel estimation

Spreading code: scrambling code x channelization code

Rake combiner
cf. the number of effective
paths is 1-3 in typical
outdoor environments.

15

Rake Combining (cont.)
Pilot symbol-assisted fading compensation
Transmitted symbol

Received symbol

Q-ch

Q-ch

Pre-determined

Pilot symbol

Fading variation:ξ
ξ
(amplitude, phase)

I-ch

Q-ch

Data symbol

I-ch

xξ
ξ*

I-ch

Data symbol after
fading compensation

Q-ch
received
symbol

I-ch

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Soft Handover/Site Diversity
Purpose:
- to improve the received quality at the cell edge
(downlink)
- to improve the received quality and reduce the
transmission power at the cell edge (uplink)
Solution:
- Simultaneous connection with multiple cells/sectors
Soft handover:
- simultaneous connection with multiple cells
Softer handover:
- simultaneous connection with multiple sectors in a BTS

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Soft Handover/Site Diversity (cont.)
Soft handover
Core Network

Core Network
Selective combining

copy

RNC

BTS 1

RNC

BTS 2

decoding
BTS 1

(RAKE) combining

UE

Downlink

UE

Uplink

BTS 2

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Soft Handover/Site Diversity (cont.)
Softer handover

cf. the number of sectors: 3 or 6

Core Network

Core Network

RNC

BTS
Sector 1

Sector 2

RNC
Maximum ratio
combining
Sector 1

BTS

Sector 2

(RAKE) combining

UE

Downlink

decoding

UE

Uplink

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Multi-rate Transmission
Purpose:
- to support multimedia (variable bit rate) services
without increasing the peak transmission power
Solution:
- OSVF (Orthogonal Variable Spreading Factor)
Multi-code

Variable spreading factor
(single code)
12.2kbps
(SF=128)

64kbps
(SF=32)

144kbps
(SF=16)

2Mbps
(3 Multi-code)

384kbps
(SF=4)

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Multi-rate Transmission (cont.)
OVSF code tree

C4,0 = (1,1,1,1)

C2,0 = (1,1)
C4,1 = (1,1,-1,-1)
C1,0 = (1)
C4,2 = (1,-1,1,-1)
C2,1 = (1,-1)
C4,3 = (1,-1,-1,1)

SF=1

SF=2

SF=4

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WCDMA Specifications
Multiple Access Scheme

Direct Sequence CDMA
FDD
5 MHz
3.84 Mcps
200 kHz
Up to 2 Mbps (SF=4, 3 multi-code)
10 ms (15 slots/frame, 666.666μs)

Duplex Scheme
Bandwidth
Chip Rate
Carrier Interval
Bit Rate
Frame Length
Code
Channelization
Scrambling

Gold-sequence (10 ms, 38400 chips)
OVSF (4 – 512 chips)

Inter-BTS Asynchronous/
Synchronous Operation

Asynchronous
Synchronous (optional)

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WCDMA Specifications (UE)
Transmit Frequency
Receive Frequency

1920 MHz – 1980 MHz
2110 MHz – 2170 MHz

Maximum Output Power

Class 1: +33 dBm (0.63 W)
Class 2: +27 dBm (0.16 W)
Class 3: +24 dBm (0.08 W)
Class 4: +21 dBm (0.04 W)

Forward Error Correction
Modulation Data
Spreading

Japan

Convolutional coding (voice)
Turbo coding (data)
QPSK (downlink), BPSK (uplink)
QPSK (downlink), HPSK (uplink)
HPSK (Hybrid Phase Shift Keying):
repetition of QPSK and 2/πBPSK chip-by-chip

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Transceiver Configuration
Transmitter
Transmitted
data

Pilot bits
Channel
encoding

Interleaving

Data mapping
(QPSK)

MUX
TPC bits

Spreading

Square-root
Nyquist filter

D/A

RF Tx.

Receiver
From
antenna

To antenna

SIR
measurement

RF Rx.

A/D

Coherent
Rake combiner

Square-root
Nyquist filter

Deinterleaving

Matched
filter

Channel
decoding

TPC
command
generator
Recovered
data

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Channel
Transport Channel
BCH (Broadcast Channel)
FACH (Forward Access Channel)
PCH (Paging Channel)
RACH (Random Access Channel)
DCH (Dedicated Channel)
DSCH (Down Link Shared Channel)
CPCH (Common Packet Channel)

Mapping to
P-CCPCH
S-CCPCH
S-CCPCH
PRACH
DPCH
PDSCH
PCCPCH

Physical Channel
DPCH (Dedicated Physical Channel)
CPICH (Common Pilot Channel)
P-CCPCH (Primary-Common Control Physical Channel)
S-CCPCH (Secondary-Common Control Physical Channel)
PRACH (Physical Random Access Channel)
PCPCH (Physical Common Packet Channel)
SCH (Physical Random Access Channel)
PDSCH (Physical Downlink Shared Channel)
AICH (Acquisition Indication Channel)
PICH (Page Indication Channel)

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Transport Channel
BCH (Broadcast Channel)
Downlink channel for broadcasts.
FACH (Forward Access Channel)
Downlink common channel for low-rate data
transmission.
PCH (Paging Channel)
Downlink channel for paging.
RACH (Random Access Channel)
Uplink common channel for low-rate data
transmission.

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Transport Channel (cont.)
DCH (Dedicated Channel)
Uplink and Downlink dedicated channel for
data transmission.
DSCH (Down Link Shared Channel)
Downlink shared channel for high-rate data
transmission.
CPCH (Common Packet Channel)
Uplink common channel for high-rate data
transmission.

27

Physical Channel
DPCH (Dedicated Physical Channel)
DPDCH (Dedicated Physical Data Channel)
Dedicated channel for data transmission.
SF = 4 to 256 for downlink,
4 to 512 for uplink.
DPCCH (Dedicated Physical Control Channel)
Dedicated channel for control information
between the system and the UE.

28

Physical Channel (cont.)
Uplink DPCH format
1 time slot (666 μsec, 2560 chips)
DPDCH
(I-Ch.)
DPCCH
(Q-Ch.)

Data (10 – 640 bits)
Pilot
(3–6 bits)

TFCI
FBI
(0-4 bits) (0-2 bits)

Slot #0 Slot #1

Slot #k

TPC
(1-2 bits)

TFCI: Transport Format
Combination Indicator
-> This is used for the indication
of the number and kinds of
transport channels.
FBI: Feedback Information
-> This is used for the closedloop transmission diversity
and site-diversity.

Slot#14

1 frame (10 msec)
DPCH: Dedicated Physical Channel
DPDCH: Dedicated Physical Data Channel
DPCCH: Dedicated Physical Control Channel

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Physical Channel (cont.)
Downlink DPCH format
1 time slot (666 μsec, 2560 chips)
Data1
TPC
TFCI
(0-248 bits) (2-16 bits) (0-16 bits)
DPDCH

Slot #0 Slot #1

Data2

(4-1000 bits)

DPCCH

DPDCH

Slot #k
1 frame (10 msec)

Pilot
(2-32 bits)
DPCCH

Slot#14

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Physical Channel (cont.)
CPICH (Common Pilot Channel)
Downlink Pilot channel for reference timing.
The bit rate is 30 kbps with SF = 256.
1 time slot (666 μsec)

Pre-defined symbol sequence
2560 chips, 20 bits (10 symbols)

Slot #0 Slot #1

Slot #k
1 frame (10 msec)

Slot#14

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Physical Channel (cont.)
P-CCPCH (Primary-Common Control Physical Channel)
Downlink common channel for broadcasts.
The bit rate is 30 kbps with SF = 256.
1 time slot (666 μsec)
Tx OFF
(256 chips)

Data (18 bits)

2560 chips, 20 bits (10 symbols)

Slot #0 Slot #1

Slot #k
1 frame (10 msec)

Slot#14

32

Physical Channel (cont.)
S-CCPCH (Secondary-Common Control Physical Channel)
Downlink common channel for paging and
low-rate data transmission.
1 time slot (666 μsec)
TFCI
(0-8 bits)

Data2
(12-1256 bits)

Pilot
(0-16 bits)

SF = 4-256.

2560 chips, 20 bits (10 symbols)

Slot #0 Slot #1

Slot #k
1 frame (10 msec)

Slot#14

33

Physical Channel (cont.)
PRACH (Physical Random Access Channel)
Uplink random access channel based on
slotted-ALOHA for low-rate data transmission.
1 time slot (666 μsec)
Data
(I-Ch.)
Control
(Q-Ch.)

Data (10 – 80 bits)
Pilot (8 bits)

TFCI (2 bits)

SF = 256.

PCPCH (Physical Common Packet Channel)
Uplink random access channel for high-rate
data transmission. (similar to PRACH)

34

Physical Channel (cont.)
SCH (Synchronization Channel)
Downlink channel for the cell search.
1 time slot (666 μsec)
SCH
(256 chips)

Slot #0 Slot #1

Tx OFF
(2304 chips)

Slot #k
1 frame (10 msec)

Slot#14

35

Physical Channel (cont.)
PDSCH (Physical Downlink Shared Channel)
Downlink channel for high-rate data transmission.
1 time slot (666 μsec)

Data (20 - 1280)

SF = 4-256.

2560 chips, 20 bits (10 symbols)

Slot #0 Slot #1

Slot #k
1 frame (10 msec)

Slot#14

36

Physical Channel (cont.)
AICH (Acquisition Indication Channel)
Downlink channel for the response of PRACH
and PCPCH.
AI part: 4096 chips, 32 symbols

a0 a1 a2

AS #0

AS #1

a31

AS #k
20 msec

Tx OFF
(1024 chips)

AS #14
AS: Access Slot

37

Physical Channel (cont.)
PICH (Page Indication Channel)
Downlink channel for the paging.
288 bits for paging indication

b0 b1 b2

b287

Tx OFF
(12 bits)

1 frame (10 msec)

Number of paging indicators per frame (Np): 18, 36, 72, 144
Note: An UE belongs to a paging indicator group.
An UE receives only its paging indication.
If the received paging indication shows a call arrival,
all UEs which belong to the paging indicator group must receive
its corresponding S-CCPCH to check the arriving call is for them.

38

Signaling for Uplink DCH

4. Radio
link
Connection
10.
6.2.Connection
Establish
setup
request
response
complete
confirm

RNC

5.Connection
Establish
3.7.Radio
link
request
setuprequest
setup
Connection
9. 1.
Connection
request
complete
8. Connection
setup

UE

BTS
setup time: 150 – 200 ms !!!

39

Enhancement technologies for WCDMA
cancel this MAI

Interference Canceller
- increase the uplink capacity
- cancel the MAI (multiple
access interference) at BTS

f
f

Desired user

Adaptive Antenna Array
- increase uplink and downlink
capacity
- control the beam pattern
of BTS antenna

f

Undesired user

create a beam
pattern to the
desired user

Desired user

Undesired user

40

System Beyond IMT-2000
3.5 G
High Speed Downlink Packet Access (HSDPA)
- Adaptive Modulation and Coding (AMC)
Modulation scheme: 8PSK, 16QAM, 64QAM
Coding rate: 1/4 – 3/4
- Hybrid ARQ
Combination of ARQ and FEC
- Fast Cell Selection (transmission diversity)

4 G (for DoCoMo)
VSF-OFCDM
-

(Variable Spreading FactorOrthogonal Frequency and Code Division Multiplexing)

Two dimensional spreading in time- and frequency- domain
Bandwidth: 100 MHz
Maximum Bit Rate: 20 Mbps (uplink), 100 Mbps (downlink)
Service in 2007 (?)

41

More Information
http://www.3gpp.org/
http://www.arib.or.jp/IMT-2000/

42

Appendix: DoCoMo’s Terminals
Visual-phone
Conventional type
type

PCMCIA type
(packet only)

P2401
Mobile Router type
P2101V

N2002

D2101V
F2611

43

Appendix: Network Nodes

BTS

RNC
By NEC

44

Appendix: WCDMA vs. cdma2000

Multiple Access Scheme
Bandwidth
Chip Rate
Code
Channelization
Scrambling
Inter-BTS Asynchronous
Synchronous Operation
Core Network

WCDMA

cdma2000

DS-CDMA

Uplink: DS-CDMA
Downlink: MC-CDMA

5 MHz

1x: 1.25 MHz
3x: 3.75 MHz

3.84 Mcps

N x 1.2288 Mcps

Gold-sequence
OVSF
Asynchronous

Walsh
M-sequence
Synchronous

GPRS

ANSI-41

Synchronous (optional)