gsm-fesfrsgrdgdgciples of the wcdma system_v1.0

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Internal

Principles of the WCDMA System

GSM-to-UMTS Training Series_V1.0

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

Date Version Description Author

2008-10-25 1.0 Draft Completed. Zang Liang

2008-12-31 1.1 Updated the access technology in the latest products in page 8.

Added the comparison of frequency computation between the GSM and the WCDMA in page 13.

Added the comparison of encoding process in page 27.

Added explanations about closed loop power control in page 66.

Added explanations about handover in page 79.

Dong Qihuan

2009-01-14 1.11 Added information about EGSM/RGEM frequency bands in page 10.

Added handover modes and interference modes to the major differences between the GSM and the UMTS in page 11.

Added the method of computing frequencies at the EGSM/RGEM frequency bands in page 13.

Added association control channels in page 47.

Kuang Jun


Objectives

Know the similarities and differences between the GSM and the WCDMA technologies.

Master the basic principles of the CDMA technology.

Master the structure and radio interfaces of the WCDMA system.

Master the principle of WCDMA radio resource management.

Know technical features of the WCDMA FDD.

After studying this course, you will be able to:


Contents

Chapter 1 Introduction: GSM and WCDMA

Chapter 2 Overview of CDMA Principles

Chapter 3 WCDMA Radio Interface Physical Channel

Chapter 4 Overview of Radio Resource Management

Chapter 5 Technical Features of WCDMA FDD


Evolution from GSM to WCDMA

GSMMainly designed for the speech service Theoretical rate/actual rate: 64 kbit/s/9.6 kbit/s

GPRS

Supports higher data rates through the introduction of packet channels Theoretical rate/actual rate: 171.2 kbit/s/20 kbit/s-40 kbit/s

EDGE

With the introduction of new modulation mode, the theoretical rate is three times higher than that of the GPRS Theoretical rate/actual rate: about 473.6 kbit/s/100 kbit/s

WCDMA

Has the capability of high-speed data access and provide various servicesTheoretical rate/actual rate: R99 and R4: 2 Mbit/s/384 kbit/sR5 (HSDPA): 14.4 Mbit/s/1 Mbit/s higher


FrequencyTime

Power

FDMA

FrequencyTime

Power

TDMA

Multiple Access Technology - Distinguish Different Users

Power

Time

CDMA

Frequency


Comparison of Multiple Access Technology Between the GSM and the WCDMA

WCDMA: FDMA + CDMA

Bandwidth of a single carrier: 5 MHz

Strong anti-interference capability. C/I: > -8

dB

The capacity is not fixed (soft capacity),

closely related to user distribution, service

type, and interference.

Users interfere with each other. They must

be well controlled.

Bandwidth of a single carrier: 200 kHz

Weak anti-interference capability. C/I: >

9 dB

With eight timeslots for a single carrier,

the system capacity is relatively

fixed. It can be estimated according to

the timeslot quantity.

Since different users occupy different

timeslots, they rarely interfere with each

other.

GSM: FDMA + TDMA


Comparison of Radio Access Technology Between the GSM and the WCDMA

GSM WCDMA

Source coding

FR: RPE － LTP coding, 13 kbit/s EFR: enhancing the voice quality, 13 kbit/s HR: increasing the system capacity, 6.5 kbit/s AMR coding

AMR: eight types of speech ratesCompatible with the coding of current main-stream mobile communication systems, helpful for designing multimode terminals Provided with the traffic-adaptive capability: able to automatically adjust the speech rate so that the system can balance between the coverage, capacity, and speech quality

Channel coding Convolutional code (1/2) Speech service: convolutional code (1/2 and 1/3) High-speed data service: Turbo code

ChannelizationPacked in the pulse mode, data is sent out in different timeslots.

Through spread spectrum and scrambling, data is combined and outputted.

Modulation technology

GMSK, 8PSK (EDGE) QPSK, 16QAM (HSDPA)

Power control technology

Slow power control (2 Hz)Fast power control (1500 Hz): used to restrain fading

Transmit diversity

Transmit diversity (BTS3012) Transmit diversity

Receiving technology (anti-

fading)

Space diversity and polarization diversityThe effect similar to that of the frequency diversity can be realized through frequency hopping.

Space diversity and polarization diversityFrequency diversity: rake receiver


Comparison Between GSM and WCDMA Network Interfaces

RNS

RNC

RNS

RNC

WCDMA Core Network

Node B Node B Node B Node B

Iu － CS Iu

Iur

Iub IubIub Iub

Iu － PS

BSS

BSC

GSM NSS

BTS BTS

A

AbisAbis

Gb

Sector = Cell. One cell can include multiple carriers.

One sector can include multiple cells. Cell = Carrier


Comparison Between GSM and WCDMA Protocols

GSM WCDMA

A/Iu-CS

L3: BSSAP L3: RANAP

L2: MTP L2: ATM

L1: E1 L1: E1 or STM － 1

Abis/Iub

L3: BTSM L3: NBAP

L2: LAPD L2: ATM

L1: E1 L1: E1 or STM － 1

Radio interface

L3: RR RRC

L2 (data link layer): LAPDm L2 (data link layer): RLC/MAC

L1 (radio frequency band) (MHz):

890-915/935-960

1710-1785/1805-1880

L1 (radio frequency band) (MHz):

Major frequency band: 1920-1980 / 2110-2170

Supplementary frequency band: 1710-

1785/1805-1880

(In China, only 30 MHz in the high frequency

band serves as a supplementary frequency

band.)


Major Differences Between WCDMA and GSM Air InterfacesMajor Differences Between WCDMA and GSM Air Interfaces

GSM WCDMA

Carrier spacing 200 kHz 5 MHz

Frequency reuse coefficient

1-18 1

Method for differentiating cells

Frequency + BSIC Frequency + Scrambling code

Power control frequency

2 Hz or lower 1500 Hz

QoS controlNetwork planning (frequency planning)

Algorithm of radio resource management

Frequency diversity Frequency hoppingThe 3.84-MHz bandwidth enables the network to use the rake receiver for multipath diversity

Packet dataTimeslot-based scheduling in the GPRS

Packet scheduling based on loads

Downlink transmit diversity

Not supported by the standards but applicable

Supported for increasing the capacity of downlinks


1850 1900 1950 2000 2050 2100 2150 2200 2250

ITU

Europe

USA MSSPCS

A D B BC D CE F A FE MSSReserveBroadcast auxiliary

2165 MHz1990 MHz

1850 1900 1950 2000 2050 2100 2150

2200 2250

1880 MHz 1980 MHz

UMTSGSM 1800 DECT MSS

1885 MHz 2025 MHz

2010 MHz

IMT 2000

MSSUMTS

Japan MSSIMT 2000MSSIMT 2000PHS

1895

1918

BC

1885

A A.

2170 MHz

IMT 20002110 MHz 2170 MHz

MSS MSS

CDMATDDWLL

FDDWLL

1980

2025 MHz

GSM1800

CDMAFDDWLL

1960

1920

1945

China

cellular(1) cellular(2) cellular(2)

1805 MHz

1865

1865

1870

1885

1890

1895

1910

1930

1945

1965

1970

1975

Allocation of 3G Spectrum


Comparison of Frequency Computation Between the WCDMA and the GSM

Main working bands: 1920 － 1980 MHz/2110 － 2170 MHzFormula for computing WCDMA frequencies:Frequency number = Frequency x 5Central frequency number of uplink: 9612 － 9888Central frequency number of downlink: 10562 － 10838

Supplementary working bands: 1755 － 1785 MHz/1850 － 1880 MHz The currently existing GSM frequency bands of China Mobile and China Union can be used for the WCDMA later.

Computing WCDMA frequencies

GSM900: BS reception: f1 (n) = 890 + n x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 45 MHz

GSM1800: BS reception: f1 (n) = 1710 + (n - 511) x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 95 MHz

Computing GSM frequencies


Contents







Overview of CDMA Principles

Radio Propagation EnvironmentRadio Propagation Environment

Multiple Access Technology and Multiple Access Technology and Duplex TechnologyDuplex Technology

CDMA Principles and Rake ReceiverCDMA Principles and Rake Receiver


Multipath Environment

Time

Rx signals

Tx signals

Intensity


FadingTx data

-40

-35

-30

-25

-20

-15

-10

-5

0

dB

Rx data


Fading

Distance (m)

Rx power (dBm)

10 20 30

-20

-40

-60

Slow fading

Fast fading


Frequency-Selective Fading

Narrowband system (GSM)

Large fadingLarge fading

Tx signalsTx signals Rx fading signalsRx fading signalsFrequencyFrequencyFrequencyFrequency

IntensityIntensity IntensityIntensity

Large fadingLarge fading

Tx signalsTx signals Rx fading signalsRx fading signalsFrequencyFrequencyFrequencyFrequency

IntensityIntensity IntensityIntensity

Broadband system (CDMA)


Classification of Typical Radio Mobile Channels

Static channels (static)

Pedestrian channels in typical urban areas (TU3)

Vehicle-mounted channels in typical urban areas (TU30)

Vehicle-mounted channels in rural areas (RA50)

Vehicle-mounted channels on expressways (HT120)


Duplex Technology – Distinguish User’s UL and DL Signal Frequency division duplex (FDD): Distinguish uplink and downlink according to

frequencies. Adopted by the WCDMA and CDMA2000

Advantage: It can be easily implemented.

Disadvantage: The spectrum utilization is low when the uplink and downlink services

(mainly the data services) are asymmetrical. Time division duplex (TDD): Distinguish uplink and downlink according to timeslots.

Adopted by the TD-SCDMA

Advantage: The uplink and downlink can be allocated with different numbers of timeslots

when the uplink and downlink services are asymmetrical. Therefore, the spectrum

utilization is high.

Disadvantage:

− It cannot be easily implemented and needs precise synchronization. In the CDMA

system, GPS synchronization is needed.

− When it is used with the CDMA technology, it is difficult to control interference

between the uplink and the downlink.


Code Division Multiple Access (CDMA)

Multiple users share a same frequency at the same time. This greatly improves spectrum utilization. Users are identified through pseudo numbers.

The CDMA system supports soft capacity.

For all the users, the system performance deteriorates when the number of users increases. Contrarily, the system performance improves when the number of users decreases.

That is, the CDMA system can obtain larger capacity by deteriorating parts of the system performance.

Disadvantages of the CDMA system:

It occupies a wide bandwidth.

It is a self-interference system. This causes mutual interference between users.

It is difficult to implement such technologies as power control and load control.


Common Terms Bit, symbol and chip

Bit (bit/s): the data that is obtained upon source coding and contains

information.

Symbol (sps): the data obtained upon channel coding and interleaving.

Chip (cps): the data obtained upon final spreading.

− The spreading rate of WCDMA is: 3.84 Mcps

Processing gain

It refers to the ratio of the final spreading rate to the bit rate (cps/bit/s).

In the WCDMA system, the processing gain depends on the specific

service.


Spreading Factor and Service Rate

Symbol rate = (service rate + check code) × channel code ×repetition or punching rate

For WCDMA, if the service rate is 384 Kbit/s and the channel code is 1/3 Turbo, the symbol rate is 960 Kbit/s.

For CDMA2000-1x, if the service rate is 9.6 Kbit/s and the channel code is 1/3 convolutional code, the symbol rate is 19.2 Kbit/s.

Chip rate = symbol rate spreading factor

For WCDMA, if the chip rate is 3.84 MHz and the spreading factor is 4, the symbol rate is 960 Kbit/s.

For CDMA2000-1x, if the chip rate is 1.2288 MHz and the spreading factor is 64, the symbol rate is 19.2 Kbit/s.


Basic Block Diagram of CDMA System

Source coding

InterleavingChannel coding

and interleaving

ScramblingSpreading ModulationRF

emission

Source decoding

deinterleavingDe-

interleavingChannel decoding

DescramblingDe-spreading Demodulation RF reception

Radio channel


Source Coding in WCDMA

Source coding Interleaving

Channel coding and interleaving


emission

The WCDMA system adopts the adaptive multi-rate (AMR) speech coding. A total of eight coding modes are available. The coding rate ranges from 12.2

Kbit/s to 4.75 Kbit/s.

Multiple voice rates are compatible with the coding modes used by current mainstream mobile communication systems. This facilitates the design of multi-mode terminals.

The system automatically adjusts the voice rate according to the distance between the user and the NodeB, thus reducing the number of handovers and call drop.

The system automatically decreases the voice rate of some users according to

the cell load, thus saving power and containing more users.


Source coding

InterleavingChannel

coding and interleaving


emission

Channel Coding in WCDMA

Channel coding can enhance symbol correlation to recover signals in the

case of interference.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Code type

Voice service: convolutional code (1/2 and 1/3).

Data service: Turbo code (1/3).


Interleaving Interleaving is used to disarrange symbol correlation and reduce the impact

caused by fast fading and interference of the channel.

1 2 3 4 5 6 7 8 ... ... 452 453 454 ……1 2 3 4 5 6 7 8 ... ... 452 453 454 ……

8

16

24

32

.

.

456

8

16

24

32

.

.

456

2

10

18

26

.

.

450

2

10

18

26

.

.

450

6

14

22

30

.

.

454

6

14

22

30

.

.

454

1

9

17

25

.

.

449

1

9

17

25

.

.

449

4

12

20

28

.

.

452

4

12

20

28

.

.

452

7

15

23

31

.

.

455

7

15

23

31

.

.

455

3

11

19

27

.

.

451

3

11

19

27

.

.

451

5

13

21

29

.

.

453

5

13

21

29

.

.

453

.... ....

A4 A5 A6 A7 B0 B1 B2 B3 B4 B5 B6 B7 C0 C1 C2 C3

{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}

Ist interleaving

2nd interleaving


Spreading Principle

Source coding

InterleavingChannel coding and interleaving


emission

Users who need to send information: UE1, UE2 and UE3

UE1 uses c1 for spreading: UE1 x c1



c1, c2 and c3 are orthogonal to each other

Information sent: UE1 x c1 + UE2 x c2 + UE3 x c3


De-spreading Principle

UE1 uses c1 for de-spreading.

(UE1 x c1 + UE2 x c2 + UE3 x c3) x c1

= UE1 x (c1 x c1) + UE2 x (c2 x c1) + UE3 x (c3 x c1)

= UE1 x 1 + UE2 x 0 + UE3 x 0

= UE1

In the same way, UE2 uses c2 for de-spreading and UE3

uses c3 for de-spreading to get their own signals.


Spreading and De-spreading (DS-CDMA)Spreading and De-spreading (DS-CDMA)

Spreading

De-spreading

Chip

Symbol

Data

Spreading code

Spreading signal = Data x Code word

Spreading code

Data = Spreading signal x

Code word

1

-1

1

-1

1

-1

1

-1

1

-1


____________

UE1: ＋ 1 － 1

1 _____________

UE2: － 1 ＋ 1

c1: ＋ 1 － 1 ＋ 1 － 1 ＋ 1 － 1 ＋ 1

－ 1

c2: ＋ 1 ＋ 1 ＋ 1 ＋ 1 ＋ 1 ＋ 1 ＋ 1

＋ 1

UE1×c1: ＋ 1 － 1 ＋ 1 － 1 － 1 ＋ 1 － 1

＋ 1

UE2×c2: － 1 － 1 － 1 － 1 ＋ 1 ＋ 1 ＋ 1

＋ 1

UE1×c1 ＋ UE2×c2: 0 － 2 0 － 2 0 ＋ 2 0 ＋ 2

Spreading Principle


UE1×c1 ＋ UE2×c2 ： 0 -2 0 -2 0 +2 0 +2

De-spreading Principle

Question: How to generate those orthogonal codes like c1 and c2?

UE1 de-spreading with c1: +1 -1 +1 -1 +1 -1 +1 -1

De-spreading result: 0 +2 0 +2 0 -2 0 -2

Integral: +4 -4

Decision: +4/4 = +1 -4/4 = -1

UE2 de-spreading with c2: +1 +1 +1 +1 +1 +1 +1 +1

De-spreading result: 0 -2 0 -2 0 +2 0 +2

Integral: -4 +4

Decision : -4/4 = -1 +4/4 = +1


UE1 × c1 + UE2 × c2: 0 － 2 0 － 2 0 ＋ 2 0 ＋ 2

UE1 × c1 + UE2 × c2 error code: 2 － 2 0 － 2 1 ＋ 2 0 ＋ 2

If error codes occur in the propagation process

UE1 uses c2 for de-spreading: c2 ＋ 1 － 1 ＋ 1 － 1 ＋ 1 － 1 ＋ 1 －1

De-spreading result: 2 － 2 0 － 2 0 ＋ 2 0 ＋ 2

Integral detection: － 2 ＋ 4

Normalization: － 2/4= － 0.5 ＋ 4/4=1

UE1 uses c1 for de-spreading: c1 ＋ 1 － 1 ＋ 1 － 1 ＋ 1 － 1 ＋ 1 －1

De-spreading result: 2 ＋ 2 0 ＋ 2 0 － 2 0 － 2

Integral detection: ＋ 6 － 4

Normalization: +6/4=1.5 - 4/4= -1


OVSF and Walsh

OVSF codes (Walsh) are completely orthogonal and their mutual correlation is zero.

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)


Use of OVSF Code

Over downlink channels, OVSF codes are used to differentiate users.

Over uplink channels, OVSF codes are used to differentiate the services

of a user.

Typical ServiceData Rate

(bit/s)Downlink SF

Uplink

SF

AMR 12.2 + 3.4 128 64

Modem 28.8 kbit/s 28.8 + 3.4 64 32

12.2 kbit/s AMR and 64 kbit/s

packet data12.2 + 64 + 3.4 32 16


packet data12.2 + 144 + 3.4 16 8


packet data12.2+384+3.4 8 4


Scrambling in the WCDMA System

Source coding

InterleavingChannel coding and interleaving


emission

Downlink: Different cells (sector carrier frequencies) have different

downlink scrambling codes.

Each cell is configured with a unique downlink scrambling code. The UE

identifies a cell based on the scrambling code.

OVSF codes are used to differentiate different users in a cell.

Uplink: Scrambles are used to differentiate different users.

In a cell, each user is configured with a unique uplink scrambling code.

OVSF codes are used to differentiate the services of a user.


WCDMA Scrambling Code: Gold Sequence

Over downlink channels, OVSF codes are used to differentiate

users.

There are 224 uplink long scrambling codes and 224 uplink short

scrambling codes.

Over downlink channels, scrambling codes are used to differentiate

cells (sectors/carriers).

There are (218 - 1 = ) 262143 scrambling codes on the downlink.

Currently, however, only the primary scrambling codes in the

scrambling codes from No.0 to No.8191 are used.

A scrambling code is repeated every 10 ms. It is 38400 chips long.


Do

wn

link

scramb

ling

cod

e

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 511×16 ＋ 1

Secondary scrambling code 511×16 ＋ 15

8192 scrambling codes

512 sets

Each set contains 1 primary scrambling

code and 15 secondary

scrambling codes.

Currently, the system mainly uses primary scrambling codes.

Primary and Secondary Scrambling Codes


Do

wn

link

scramb

ling

cod

e

Group 0

Group 1

…

Group 63



…



…



512 scrambling codes

64 groups

Each group contains eight scrambling codes, one of which is the primary scrambling code.

Scrambling code planning in the network planning is to plan and allocate the 512 primary scrambling codes.

Primary Scrambling Codes and Scrambling Code Groups


Allowed maximum interference level

Eb/No required

Spreading/De-spreading Principle — Explanations for Frequency Domain

Power spectrum

Power sharable for all users

a2Tbit = Ebit

Gain

Other user interference signals

Echip

Eb/No = Ec/Io × Gain


The CDMA broadband spreading technology effectively avoids frequency-selective fading of radio channels.

Spreading code

Spreading code

Signal combination

Spectrum Change in CDMA

Narrowband signal

f

P(f)

Broadband signal

P(f)

f

Noise

P (f)

f

Noise + broadband signal

P (f)

f

Separation of signals and noise

P (f)

f


Rake Receiver

Front-end receiver

Receiving path 1

Receiving path 2

Receiving path 3

Delay estimatorCompute delay and

phase deflection

Signal synthesizer Consolidate

signals

tt

s(t) s(t)


Contents







Mapping of Channel Function Between the GSM and the WCDMA

GSM WCDMA

Cell search

FCCH: frequency correction channel (P － )CPICH: (Primary) common pilot channel

SCH: synchronization channelSCH: synchronization channel, but has different functions from that in the GSM system

BCCH: broadcast control channelP-CCPCH: primary common control physical channel

Paging PCH: paging channel

PICH: page indicator channel, helpful for power saving on a terminalS-CCPCH: secondary common control physical channel

Access

Uplink: RACH: random access channelSDCCH: stand-alone dedicated control channel

Uplink: PRACH: physical random access channel

Downlink: AGCH: access grant channel SDCCH: stand-

alone dedicated control channel

Downlink: AICH: acquisition indication channel S-CCPCH: secondary common control physical channel

Speech service

TCH: traffic channelDPDCH: dedicated physical data control channelDPDCH: dedicated physical data control channel

Data service

PDCH: packet data channel

HS-PDSCH: high-speed physical downlink shared channelHS-SCCH: high-speed shared control channelHS-DPCCH: high-speed dedicated control channel


Classification of WCDMA Channels

In terms of protocol layer, the WCDMA radio interface has three channels:

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 : Provided service 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 final form of all kinds of information when they are transmitted on radio interfaces.


TCH

CCH

Logical Channels

Broadcast Control Channel （ BCCH）Paging control channel (PCCH)

Dedicate control channel (DCCH)

Common control channel (CCCH)

Dedicated traffic channel (DTCH)

Common traffic channel (CTCH)


Dedicated Channel (DCH)

-DCH can be uplink or downlink

channel

Broadcast channel (BCH)

Forward access channel (FACH)

Paging channel (PCH)

Random access channel (RACH)

Common transport channel

Dedicated transport channel

Transport Channels


The timeslot concept in the WCDMA system differs greatly from that

in the GSM system.

Physical Channels

Physical channels are divided into uplink and down physical channels.

A physical channel can be determined by a carrier, codes (channel code and scrambling code), and a phase. Most channels consist of radio frames and timeslots. Each radio frame has 10 ms and consists of 15 timeslots.

Data

Timeslot 0 Timeslot 1 Timeslot 14

T timeslot = 2560 chips

T = 10 ms, 38400 chips

Data

Timeslot i


Uplink Common Physical Channel

Physical Random Access Channel

(PRACH)

Uplink Dedicated Physical Channel

Uplink Dedicated Physical Data Channel

(Uplink DPDCH)

Uplink Dedicated Physical Control

Channel (uplink DPCCH)Uplink Physical

Channel

Uplink Physical Channel


Downlink Common Physical Channel

Common Control Physical Channel

(CCPCH)

Synchronization Channel (SCH)

Paging Indicator Channel (PICH)

Acquisition Indicator Channel (AICH)

Common Pilot Channel (CPICH)

Downlink Dedicated Physical Channel

(downlink DPCH)

Downlink Physical Channel

Downlink Physical Channel


Configuration Example of Downlink Physical Channel

SF 4 8 16 32 64 128 256 512 ┏ ━ ●C(256, 0): PCPI CH 2 ┏ 0 ┫ ┃ ┗ ━ ●C(256, 1): PCCPCH 3 ┏ 0 ┫ ┃ ┃ ┏ ━ ●C(256, 2): AI CH 6 ┃ ┗ 1 ┫ ┃ ┗ ━ ●C(256, 3): PI CH 10 ┏ 0 ┫ ┃ ┗ ━ ●C(64, 1): SCCPCH 8 ┏ 0 ┫ ┃ ┃ ┏ ━ ●C(64, 2): SCCPCH 9 ┃ ┗ 1 ┫ ┃ ┗ ━ ○3 ┏ 0 ┫ ┃ ┗ ━ ○1 ┏ 0 ┫ ┃ ┗ ━ ○1 ┃ ┗ ━ ○1

┏ ━ ○2 ┃ ┗ ━ ○3

Pilot channel (PICH)

Used to bear broadcast channels (BCHs)

Used to bear forward access channels

(FACHs) and paging channels (PCHs)

Allocated to dedicated physical channels

(DPCHs) in real time

Synchronization channel (SCH)

SCH 0,1


Functions of Physical Channels

NodeB (BS)

User equipment (UE)

P-CCPCH: primary common control physical channel SCH: synchronization channel

P-CPICH: primary common pilot channel S-CPICH: secondary common pilot channel

Cell broadcast channel (CBCH)

DPDCH: dedicated physical data channel

DPCCH: dedicated physical control channel

Dedicated access channel

Paging channel (PCH)

PICH: paging indicator channel

S-CCPCH: secondary common control physical channel

PRACH: physical random access channel

AICH: acquisition indication channel

Random access channel (RACH)

HS-DPCCH: high-speed dedicated control channel

HS-SCCH: high-speed shared control channel

HS-PDSCH: high-speed physical downlink shared channel

High-speed downlink shared channel


Functions of Common Physical Channels

SCH: used for cell search

Divided into P-SCH and S-SCH

CPICH: used to identify scrambling codes

Divided into P-CPICH and S-CPICH

− P-CPICH: Their channel codes are fixed to be Cch,256,0. They

use primary scrambling codes.

− P-CPICH is the power benchmark of other physical downlink

channels. S-CPICH: used for smart antennas

P-CCPCH: used to carry system messages

channel codes are fixed to be Cch,256,1.

Each cell must be configured with all these channels, but only

one for each type.


Functions of Common Physical Channels

S-CCPCH: used to carry downlink signaling messages

PICH: used to carry paging indicators. A PICH must be configured with an S-

CCPCH as a pair.

PRACH: used to carry uplink signaling messages

The interval for timeslot access is 5120 chips, indicating that the maximum

coverage radius of a WCDMA BS is 200 km.

AICH: used to carry acquisition indications of PRACH prefix. An AICH must be

configured with a PRACH as a pair.

Each cell must be configured with all these channels, at least one for each

type.


Functions of Dedicated Physical Channels

DPDCH: used to carry users' service data. The maximum data rate of a single

code channel is 384 kbit/s.

DPCCH: used to carry control information, and provide control data such as

demodulation and power control for DPDCHs

On the uplink, DPDCHs and DPCCHs transmit signals over different code

channels. On the downlink, DPDCHs and DPCCHs transmit signals in the mode

of time multiplexing.

When the required data rate is higher than the maximum data rate of a single

code channel, the system can use multiple code channels for transmission.

Maximum uplink data rate: 384 kbit/s x 6 code channels

Maximum downlink data rate: 384 kbit/s x 7 code channels


Mapping Between Logical Channels and Transport Channels

Logical Channels Transport Channels

CCCH (uplink) RACH

DCCH/DTCH (uplink) RACH

DCH

BCCH (downlink) BCH

PCCH (downlink) PCH

CCCH/CTCH (downlink) FACH

DCCH/DTCH (downlink) DCH

FACH

DTCH (downlink) HS-DSCH


Mapping Between Transport Channels and Physical ChannelsMapping Between Transport Channels and Physical Channels Transport Channels Physical Channels

DCH Dedicated Physical Data Channel (DPDCH)

Dedicated Physical Control Channel (DPCCH)

RACH Physical Random Access Channel (PRACH)

BCH Primary Common Control Physical Channel (P-CCPCH)

FACH Secondary Common Control Physical Channel (S-CCPCH)

PCH

Synchronization Channel (SCH)

Acquisition Indicator Channel (AICH)

Paging Indicator Channel (PICH)

HS-DSCH High Speed Physical Downlink Shared Channel (HS-PDSCH)

HS-DSCH-related Shared Control Channel (HS-SCCH)

Dedicated Physical Control Channel (uplink) for Hs-DSCH

HS-DPCCH


Contents







Overview of Radio Resource Management

RRM － Radio Resource Management

Since the WCDMA system is a self-interference system, the use of

power is incompatible in WCDMA system.

On one hand, increasing the Tx power for a user can improve the

quality of service (QoS) of this user.

On the other hand, as WCDMA is self interference system, power

enhancement will interfere other user and make the reception

quality worse. .

Power is a final radio resource. The only way to make radio resources

utility is to strictly control the use of power.

The RRM is to manage the power by combining QoS objectives.


Purposes of RRM

The RRM is intended to:

Ensure the QoS requested by the CN

Enhance the system coverage

Improve the system capacity


Tasks of RRM

Channel configuration: To ensure the QoS requested by the CN, the RRM maps the

QoS into some features of the access stratum and thus uses the resources at the

access stratum to serve the local connection.

Power control: When the QoS requested by the CN is ensured, the RRM minimizes the

Tx power of a UE to reduce the interference of this UE to the entire system, and to

improve the system capacity and coverage.

Mobility management: The RRM maintains the QoS when a UE moves.

Load control: After a certain number of UEs access to the system, the RRM must

ensure that the load of the entire system retains at a stable level to ensure the QoS of

each connection in the system.

QoS assurance and power saving run through the entire RRM.


Power Control—Near-Far Effect

The CDMA has not been put into commercial use in a large scale since it

was put forward. That is because it cannot overcome the near-far effect.

All other signals are overwhelmed by the signals of a UE closest to the BS. Communications fail.

One UE can congest an entire cell


Purpose and Classification of Power Control

Owing to the near-far effect, the WCDMA system must introduce power

control. In addition, power control can also bring many other benefits:

Adjust the transmit power to maintain the uplink and downlink communication

quality.

Overcome slow and fast fading.

Reduce network interference and improve the system quality and capacity.

Power control is classified into:

Open loop power control

Closed loop power control

- Uplink and downlink inner loop power control

- Uplink and downlink outer loop power control


Principles of Open Loop Power Control

Basic principle Suppose the coupling loss between the transmit power and the received

power is the same as the interference level between them. Use the previously-

measured received power to determine the initial transmit power.

If the BS fails to receive the initial transmit power, there is a retransmission

mechanism for improving the power.

Basic function

To overcome slow fading and path loss

Major disadvantage

Asymmetry between the wave power of the uplink and downlink channels is not

considered, so accuracy cannot be guaranteed.

Major application Uplink: applied to PRACHs and DPCCHs

Downlink: applied to DPCCHs


Principles of Open Loop Power Control

Principles of setting initial transmit powerPrinciples of setting initial transmit power

DL

UL UL

DL UL

_ _ ............................(1)

_ _ ....................(2)

Suppose the uplink and downlink path losses are the same: ....................(3

CPICH RSCP CPICH Pow PL

X EcNo X Pow PL Interference

PL PL

UL

)

_ _ _ _X Pow CPICH Pow CPICH RSCP Interference X EcNo


Open Loop Power Control over the PRACH

NodeB UERACH

BCH: Transmit power of CPICH UL interference level

The open loop power control is intended to roughly estimate the initial transmit power. It estimates the path loss and interference level according to measurement results, and thus calculates the initial transmit power.

The UE measures the received power of the CPICH and calculates the initial uplink transmit power.


Open Loop Power Control over the PRACHOne access slot

p-a

p-m

p-p

Pre-amble

Pre-amble Message part

Acq.Ind.

AICH accessslots RX at UE

PRACH accessslots TX at UE

Access process of the PRACH: A UE transmits a PRACH preamble signal over the PRACH. After a BS successfully captures the preamble signal, the BS responds with an AI over the downlink AICH. If the UE receives the AI signal, the UE transmits a PRACH message. If the UE fails to receive the AI signal at the time point τp-

a, the UE will increase the power and transmit next preamble signal after a certain time τp-p. The UE will continue such an action over and over until it receives the AI signals.


Open Loop Power Control over the PRACH

Preamble_Initial_Power = PCPICH DL TX power - CPICH_RSCP + UL interference

+ Constant Value

Note: The PCPICH DL TX power, UL Interference, and Constant Value are delivered in system

messages. The CPICH_RSCP is measured by the UE.

In the early stage of network construction, the coverage is limited, so the Constant Value can be

set to a larger value (-16 dB or -15dB).

In this way, the network can receive the preamble signals sent by the UE in time. In addition, the

parameter Power Ramp Step can also be set to a larger value to increase the network probability

of capturing preamble signals.

Method for setting the transmit power of the first preamble signal over the uplink PRACH:

Default settings:

Constant Value: -20 dB

PowerRampStep: 2 dB

PreambleRetransMax: 20


Open Loop Power Control over the Uplink DPCCH

DPCCH_Initial_power = DPCCH_Power_offset - CPICH_RSCP

Note: The CPICH_RSCP is measured by a UE.

The DPCCH_Power_offset is the offset of the initial transmit power of the DPCCH. The RNC

allocates it to a UE at the beginning of an RRC connection setup. The formula for computing it

is as follows:

DPCCH_Power_offset = Primary CPICH DL TX power + UL Interference

+ Default Constant Value

In the formula,

the Primary CPICH DL TX power is the downlink transmit power of the P-CPICH.

The UL interference is the uplink interference.

The Default Constant Value is the default constant value of the initial transmit power of the

DPCCH.

Method for setting the initial power of the uplink DPCCH:

Understanding


Open Loop Power Control over the Downlink DPCCH

P = (Ec/Io) Req - CPICH_Ec/Io + PCPICH

Note: The (Ec/Io) Req is the required Ec/Io for a UE to correctly receive the dedicated

channel. The CPICH_Ec/Io is the Ec/Io of the CPICH measured by the UE,

and it is reported to the UTRAN through the RACH. The PCPICH is the

transmit power of the CPICH.

Method for setting the initial power of the downlink DPCCH:

Understanding


Uplink Inner Loop Power Control

NodeB UE

Send TPC bits

Measure SIRs of received signals and compare them

Inner loop

Set SIRtar

1500 Hz

The inner loop power control is intended to ensure equal bit energy for each UE signal received at the NodeB.

Each UE has its own control loop.


Uplink Inner Loop Power Control

NodeB UE

Send TPC bits

Measure SIRs of received signals and compare them

Inner loop

Set SIRtar

Obtain the service data with a stable BLER

Measure the BLER over the transport channel

Outer loop

RNC

Measure BLERs of received data and

compare them

Set SIRtar

10-100Hz


Downlink Inner Loop Power Control

NodeB

Set SIRtar

Send TPC

Measure SIRs and compare them

Measure BLERs and compare them

Outer

loop

Inner loop

Physical layer of the UE

Layer 3 of the UE

Downlink inner loop and outer loop power control

1500 Hz 10-100 Hz


Physical

Channel

Open Loop

Power

Control

Inner

Closed

Loop

Outer

Closed

Loop

No

Power

Control

PRACH √

DPCCH √ √ √

DPDCH √ √

PCPICH √

PCCPCH √

SCCPCH √

AICH √

PICH √

Power Control Application in the WCDMA System


MML Commands Related to Power Control

MML commands related to open loop power control:

ADD PRACHBASIC

SET FRC

MML commands related to inner loop power control:

SET FRC

ADD CELLSETUP

MML commands related to outer loop power control:

ADD TYPRABOLPC

SET OLPC

MML commands related to power balance:

SET DPB


Classification of WCDMA Handover

Soft handover:

Soft handover

Softer handover

Hard handover:

Intra-frequency hard handover

Inter-frequency hard handover

Inter-system handover


Soft Handover

Time

Data received/sent by the UE

The UE moves

Target BSSource BS

Time


The UE moves

Target BSSource BS

No “GAP” of communication


Hard Handover

The UE moves

Target BSSource BS

Time


The UE moves

Target BSSource BS

Time


“GAP” of communication


Contents







Technical Specifications of WCDMA FDDTechnical Specifications of WCDMA FDD

Modulation mode: QPSK for both the uplink and the downlink

Speech coding: AMR

Channel coding: convolutional code and Turbo code

Demodulation mode: coherence demodulation assisted by pilots

Transmit diversity mode: TSTD, STTD, and FBTD

Power control: uplink and downlink closed and open loop power control

BS synchronous mode: supports asynchronous and synchronous BS operation

Signal bandwidth: 5 MHz; chip rate: 3.84 Mcps


Adopts AMR speech coding and supports the voice quality of 4.75

kbit/s to 12.2 kbit/s

Adopts soft handover and transmit diversity to improve the capacity

Provides high-fidelity voice modes

Supports fast power control

Speech Evolution of the WCDMA SystemSpeech Evolution of the WCDMA System


Supports up to 14.4 Mbit/s data services (HSDPA)

Supports packet switching

Evolves from the ATM platform to All-IP gradually

Provides QoS control

Better supports Internet packet services (HSDPA) through the CPCH

and DSCH.

Provides mobile IP services (dynamic assignment of IP addresses)

Determines dynamic data rates provided by the TFCI domain.

Provides high quality support for symmetric uplink and downlink data

services, including the voice, videophone, and video conference.

Data Evolution of the WCDMA SystemData Evolution of the WCDMA System


Summary

This course introduces the WCDMA system briefly.

The course contents include the basic key technologies of mobile

communication systems, basic principles of the CDMA system,

and the FDD mode of the WCDMA system.

After studying this course, you can have a general understanding

of the 3G system, thus make a good foundation for further study.

Thank you!

www.huawei.com

gsm-fesfrsgrdgdgciples of the wcdma system_v1.0

Documents