umts radio theory.pdf

UMTS Radio Theory

ZTE University

Content

The Basic Principles of Wireless Communication

3G services

Multiple Access Technologies

Spectrum Planning

Spreading Technology

Coding And Interleave Technology

Modulation

UMTS Radio mechanism

Radio Transmission Technology

Requirements

Data：

144 kbps High speed and driving

384 kbps Modest speed and walking

2 Mbps Low speed and indoor

Voice

4.75Kb/s -- 12.2Kb/s

64kb/s (Video Phone)

Information transmission at variable rate

according to bandwidth requirements；

Delay requirements of different service

3G services

Delay

Bit Error

Different QOS requirements

3G services

Categories Actual Service Delay (One-way) Bearer Speed

conversational

Voice <150ms 12.2kbps

Video Call <150ms 64kbps

VoIP <150ms 15.3~39.6kbps

Interaction

Game

<250ms N/A

Streaming

Real-time Voice

Streaming

<2s 4.7~25kbps

Real-time Video

Streaming

<2s 64kbps~2Mbps

Interaction

Web Browsing <4s N/A

WAP Browsing <4s N/A

E-commerce <4s N/A

Background FTP No strict N/A

E-mail No strict N/A

Content


3G services


Spectrum Planning



Modulation


Duplex mode

TDD mode－uplink and downlink

has the same frequency

Adaptable to any frequency

band

Suitable for both asymmetric

and symmetric services

FDD mode－uplink and downlink

has the different frequency

Paired frequency bands are

needed

Suitable for symmetric

services

TDD ( Time division

duplex,Such as TD-SCDMA)

D D D D U U U U

FDD（Frequency division

duplex, Such as WCDMA

and CDMA2000）

D D D D D D D D

U U U U U U U U

Why Multiple Access?

Increased capacity: serve more users

Reduced capital requirements since

fewer media can carry the traffic

Decreased per-user expense

Types of Transmission Medium:

Twisted pair

Coaxial cable

Fiber optic cable

Air interface (radio signals)

Three methods are frequently used:

FDMA

TDMA

CDMA

Each pair of users enjoys

a dedicated, private circuit

through the transmission

medium, unaware that the

other users exist.

Transmission

Medium

Multiple access technologies enable various users access public communication line but without interference.


Users are using

different frequency Time

Frequency

FDMA

FDMA (Frequency Division Multiple Access)

FDMA

Traffic channels are assigned to different users at

different frequency band, such as TACS, AMPS.

Time

Frequency

TDMA

Users are using

different time slot

TDMA (Time Division Multiple Access)

TDMA

Traffic channels are assigned to different users at

different time, such as GSM, DAMPS.

Time

Frequency

CDMA

Code

Users are using different

orthogonal code sequence

CDMA (Code Division Multiple Access)

CDMA

Traffic channels are assigned to users at same time,

same frequency band, but with different code.

Freq. 1

Freq. 1

BS1

BS2

Code D

CDMA Application

Users are distinguished by scrambling codes and OVSF

codes

Self-interference system

CDMA system is restricted to interference (GSM system is

restricted to frequency resources)

Content


3G services


Spectrum Planning



Modulation


GSM900/1800: 3G (WCDMA):

Single Frequency Network

IMT-2000 Spectrum Allocation

1850 1900 1950 2000 2050 2100 2150 2200

ITU

Europe

USA MSS

PCS

A D B B C D C E F A F E MSS Reserve Broadcast auxiliary

2165 MHz 1990 MHz

1850 1900 1950 2000 2050 2100 2150 2200

UMTS GSM 1800 DECT MSS

1885 MHz 2025 MHz

2010 MHz

IMT 2000

MSS UMTS

Japan MSS IMT 2000 MSS IMT 2000 PHS

IMT 2000

2110 MHz 2170 MHz

MSS MSS

FDD MSS MSS TDD TDD

19

80

GSM

1800 FDD

19

20

China

18

80

1865

1870

1885

1890

1910

1930

1945

1965

1970

1975

3G Spectrum Allocation in China

60 MHz 30

MHz

FDD TDD

100 MHz 15

MHz

40

MHz

155MHz

1785 1850 1755 1880 1920 1980 2010 2025 2110 2170 2200 2400

Satellite Empty Satellite

2300

3G Spectrum Planning in China

Main Operating Frequency Band：

FDD mode：1920-1980 MHz / 2110-2170 MHz

TDD mode：1880-1920MHz、2010-2025 MHz

Supplementary Operating Frequency Band：

FDD mode：1755-1785 MHz / 1850-1880 MHz

TDD mode：2300-2400MHz

Frequency Band for Satellite Mobile Communication System：

1980-2010 MHz / 2170-2200 MHz

The frequency bands, 825 - 835 MHz / 870 - 880 MHz, 885 - 915 MHz

/ 930 - 960 MHz and 1710 - 1755 MHz / 1805 - 1850 MHz, which are

currently allocated to public mobile communication system are also

allocated to expanded frequency bands of 3G public communication

system, but frequency using mode remains the same for both uplink

and downlink.

Content


3G services


Spectrum Planning



Modulation


SHANON Formula

C = Blog2(1+S/N)

Spread Spectrum Principles

Where,

C is capacity of channel, b/s

B is signal bandwidth, Hz

S is average power for signal, W

N is average power for noise, W

It is the basic principle and theory for spread spectrum

communications.


5 MHz

12 KHz

Power is “Spread” Over a Larger Bandwidth

radio channel

Receiver Transmitter

Spreading

Despreading

Noise


User information bits are spread over a wide

bandwidth by multiplying high speed spread

code(chip)

Spread signal bandwidth W wider than original

signal bandwidth Rb

f

S（f）

f0

Before spreading

signal

S（f）

f f0

After spreading

signal

S（f）

f f0

After despreading

signal

White noise

f

S（f）

f0

Before despreading

signal

White noise

signal interference White noise


Spreading Mode

Direct sequence spread spectrum（DS-SS）

Base band data is spread by multiplication of pseudo-noise sequence and base-band pulse, the pseudo-noise sequence generated by the pseudo-noise generator

BER subject to Multiple Access Interference and near-far effect

Power control can overcome the near-far effect, but it is limited by power detection accuracy

WCDMA uses DS-SS

Frequency hopping spread spectrum（FH-SS）

Data is transmitted in the random channel by the carrier frequency hopping

Before FH again, data is transmitted using traditional narrowband modulation

No near-far effect

DS-SS communication system

A technology of transmission after spreading

signal spectrum.

Fast Spreading Sequence

Slow Information

Sent

TX

Slow Information Recovered

RX

Fast Spreading Sequence

Wideband Signal


Many code channels are individually

“spread” and then added together to

create a “composite signal”

Unwanted Power from

Other Resoures


Any Code Channel can be extracted from the received

composite signal by using the “right” orthogonal code

Energy for transmitting signal can be lower than

interference and noise

Processing Gain

Broadband

Interference

Concept of orthogonal code

Orthogonal—

the result of multiplying

and sum is 0

Code1 +1 -1 +1 +1 -1 +1 -1 -1

Code2 -1 +1 +1 -1 -1 +1 +1 -1

Mul -1 -1 +1 -1 +1 +1 -1 +1

Sum 0

Orthogonal

Code1 +1 -1 +1 -1 -1 +1 -1 -1

Code2 +1 +1 -1 +1 -1 -1 +1 -1

Mul +1 -1 -1 -1 +1 -1 -1 +1

Sum -2

Non-orthogonal

-1 1 -1 1 -1 -1 1 1 -1 -1 1 1 -1 1 -1 1 MUL

-1 1 -1 1 -1 -1 1 1

1 -1 1 -1

-4 4

0 0 Judge

-1 1

1 -1 1 -1

-1 1 MUL

Integral

1 1 1 1 -1 -1 -1 -1

Example of orthogonal code

S1

S2

S1xC1

S2XC2

W Spreading

Despreading

(S1xC1)+(S2xC2)

Air Interface

[S1xC1+S2xC2]xC2

=S2

[S1xC1+S2xC2]xC1

=S1 N

S

C1xC2=0,

C1,C2,orthogonal

Direct spread technique

Spreading code =

1 -1 -1 1 -1 1 1 -1

( SF = 8 )

Symbol

Spreading

Despreading

1 -1

1 -1 1 -1

1 -1

1 -1

Data=010010

Spreading code

Spread signal = Data × code

Data = Spread signal × Spreading code

Chip

Sketch map of Spreading and Despreading

Characteristics of Spreading Communication

High anti-multi-path- interference capability

Anti-sudden-pulse

High security

Lower transmitting power

Easy to implement large-capacity Multiple Access

Communication

Occupy band wide

Complex realization

Content


3G services


Spectrum Planning



Modulation


Purpose of Channel Coding

By adding redundant information in the original

data stream, receivers can detect and correct the

error signal, and improve data transmission rates.

No correct coding: BER<10-1 ~ 10-2 Can not satisfy

the communication

Convolutional coding：BER<10-3 Can satisfy the

speech communication

Turbo coding： BER<10-6 Can satisfy the

data communication

Principle of Channel Coding

Channel coding

Error-correcting ability obtains by adding redundancy in the

original data

Convolutional coding and Turbo coding （1/2，1/3） are

widely applied.

Increase noneffective load and transmission time

Suitable to correct few non-continuous errors

W C D M A

T U R B O

S P E A K

W W C C D D M M A A

T T U U R R B B O O

S S P P E E A A K K

W ? C C D D M M A A

T T ? U R R B B O O

S S P P E E A ? K K

Decoding

Encoding

Principle of Interleave Technology

advantage

Interleave is to change the sequence of data to random the

unexpected errors

Advance the correcting validity

disadvantage

Increase the processing delay

Especially, Several independent random errors may intertwined for

the unexpected error.

x1 x6 x11 x16 x21

x2 x7 … x22

x3 x8 … x23

x4 x9 … x24

x5 x10 … x25

Data input

A = (x1 x2 x3 x4 x5 … x25)

Data output

A’= (x1 x6 x11 x16… x25)

e.g.

Encoding and Interleaving

W C D M A

T U R B O

S P E A K

W W C C D D M M A A

T T U U R R B B O O

S S P P E E A A K K

W T S W T S

C U P C U P

D R E D R E

M B A M B A

A O K A O K

W ? ? C D D M M A ?

T ? ? U R ? ? B O O

S ? ? P ? E A A K K

Encoding Interleaving

W T S ? ? ?

? ? ? C U P

D R ? D ? E

M ? A M B A

A O K ? O K

Deinterleaving Decoding

Encoding + Interleaving can correct both

continuous and non-continuous errors

Content


3G services


Spectrum Planning



Modulation


Principle of Modulation

Definition

Modulation is the process where the amplitude,

frequency, or phase of an electronic or optical signal

carrier is changed in order to transmit information.

Using symbol stand for one or more bits to improve

communication effectiveness

Classification

Analog Modulation

Digital Modulation

Symbol bit Modulation

Analog Modulation

The purpose of analog modulation is to impress

an information-bearing analog waveform onto a

carrier for transmission.

Common analog modulation methods include:

Amplitude modulation (AM)

Frequency modulation (FM)

Phase modulation (PM)

Digital Modulation

The purpose of digital modulation is to convert an

information-bearing discrete-time symbol

sequence into a continuous-time waveform

(perhaps impressed on a carrier).

Basic analog modulation methods include

Amplitude shift Keying (ASK)

Frequency shift Keying (FSK)

Phase shift Keying (PSK)

Content



UMTS Data transmission Procedure

Channel Coding of UMTS

Spreading Technology of UMTS

Modulation of UMTS

WCDMA Data transmission Procedure

RF Receiving Demodulation Despreading

Decoding &

De-inteleaving UE Data

UE Data Spreading

RF Transmitting

Modulation

Baseband

demodulation

Baseband

modulation

Encoding &

Interleaving

Content






Modulation of UMTS

Mainly used in the voice channel and control signal channel

Coding rate is ½ and 1/3.

Output 0

G 0 = 557 (octal)

Input

D D D D D D D D

Output 1

G 1 = 663 (octal)

Output 2

G 2 = 711 (octal)

Rate 1/3 convolutional coder

Convolutional Code

Easy decode

Short delay

Generally use the Viterbi Algorithm

Channel bit error rate is 10－3 magnitude

Suitable to realtime service

e.g. speech and video service.

Characteristics of Convolutional code

Used in Data service channel

Code Rate is 1/3

Can be implemented in the transmission for large block and long

delay services

Turbo coding structure is based on two or more weak error

control code combinations. The information bits are interleaved in

the two Encoder, and generate two information flow. At last, this

information can be multiplexed and punctured

Decoding needs cycle iterative calculation

Interleaver

Encoder 1

Encoder 2

Mu

ltip

lex

input output

Turbo Code

Complex decoding

Use the LOG-MAP arithmetic

Channel bit error rate is 10－6 magnitude

Very suitable to non-realtime package service

which is BER sensitive & delay insensitive,

e.g. WWW, FTP, E_mail, multimedia

transmission.

Characteristics of Turbo Codes

Content






Modulation of UMTS

Symbol rate × SF = Chip rate=3.84Mcps

For UMTS，SF of uplink channelization code：4~256

SF of downlink channelization code: 4~512

OVSF: Orthogonal Variable Spreading Factor

OVSF Code Scrambling Code

Data Spread Data

Spreading Process of UMTS

Symbol Chip

3.84Mcps

3.84Mcps

Channelization Code

Adopt OVSF code

Definition: Cch,SF,k, describe channelization code, where

SF : spread factor， k : code number, 0 < k<SF-1

SF = 1 SF = 2 SF = 4

C ch,1,0 = (1)

C ch,2,0 = (1,1)

C ch,2,1 = (1,-1)

C ch,4,0 =(1,1,1,1)

C ch,4,1 = (1,1, - 1, - 1)

C ch,4,2 = (1, - 1 ,1, - 1)

C ch,4,3 = (1, - 1, - 1, 1)

Scrambling Code

UMTS Scrambling code is pseudo random binary

sequence

It has similar noise array character, seemingly random

but with regularity.

Can make the user data further random , strengthened

by scrambling a code to keep secret the user data, at

the same time easy to carry out multiple access

communication.

UMTS scrambling code is generated from Gold sequence

Gold sequence has excellent self-correlation.

Cross-correlation is very week between two codes.

It is used to identify cell and user for multiple access.

Characteristic of Scrambling code

There are 224 Uplink Scrambling Codes, they are

used to distinguish different users in one cell.

There are 218-1 Downlink Scrambling Codes,

used to distinguish different cells

Scrambling codes usually used are the first 8192 codes,

which are code 0，1，……，8191. They are divided

into 512 aggregations，each aggregation has 1 primary

scrambling code (PSC) and 15 secondary scrambling

codes (SSC).

The 512 primary scrambling codes are divided further

into 64 primary scrambling code groups , with 8 primary

scrambling codes in each group.

Numbering rule for Downlink Scrambling

Codes

…

218

-1 Downlink Scrambling Codes in all

(0..262142)

No. 511 Scrambling Code

Group

8176

8177

8191

8176：PSC

8177：SSC

…

8191：SSC


Group

8160

8161

8175

8160：主扰码

8161：辅扰码

…

8175：辅扰码


Group

8064

8065

8079

8064：主扰码

8065：辅扰码

…

8079：辅扰码

…


Group

112

113

127

8176：PSC

8177：辅扰码

…

8191：辅扰码


Group

16

17

31

16：PSC

17：SSC

…

31：SSC


Group

0

1

15

0：PSC

1：SSC

…

15：SSC

No.63 Primary Scrambling Code Group … …

No.0 Primary Scrambling Code Group

Code Functions

Channelization code ---- for separation of physical

channels in the uplink and separation of users in

the downlink

Scrambling code ---- for separation of

users/terminals in the uplink and cells/sectors in

the downlink.

Air Interface

2chc

3chc

1chc

scramblingc Modulation

Spreading code & scrambling code

Cch：spread code

Relative to service rate，extended to 3.84Mchips/s

A kind of orthogonal code

Cscrambling：scrambling code

Have no effect on signal bandwidth

Downlink for identifier cell，uplink identifier terminal

A pseudo-random sequence

f

P

W

Processing

Gain

Rb

Despreading

Processing Gain

PG=Wc/Rb (Wc : Chip rate , Rb : Service bit rate)

Transmitter/receiver can obtain gain after

spread/despread

The narrower original signal bandwidth, the larger Pg ,

the better

The higher PG, the more anti-interference capability system has.

b

c

R

WGain Processing

Eb = Signal Power

Bit Rate =

S

R

E / t

B / t = N0 =

Noise Power

Bandwidth =

N

W

Eb

N0 =

S

R

N

W

= S

R X W

N =

S

N X W

R

Signal to Noise

Processing Gain

The more the expansion multiples, the higher the

processing gain, the stronger the anti-jamming capability

Relation between Eb/N0 and PG

Despreading procedure

Method of despreading

Input signal

Local PN code

When T=Ts, judge

Output after despreading

integral

0

Ts

(*)dt

Content






Modulation of UMTS

Modulation Methods in UMTS

BPSK (Binary Phase Shift Keying) in Uplink channles

QPSK (Quadrature Phase Shift Keying) in Downlink channels

16QAM (16-state Quadrature Amplitude Modulation) in HSDPA

Physical Channel Spread-Spectrum

Modulation Process-Downlink

∑ ∑

Separation

of real

Parts

And

Imaginary

parts

Pulse

Forming

Pulse

Forming

Serial

Parallel

Switch

Serial

Parallel

Switch

……

……

Downlink physical channel 1

Cch,SF,m

j

I+jQ Sdl,n

G1

Cch,SF,m

j

I+jQ

Sdl,n

G2 Downlink physical

channel 2

Gp

Gp

P-SCH

S-SCH

cos(wt)

-sin(wt)

Re(T)

Im(T)

Physical Channel Spread-Spectrum

Modulation Process-Uplink

Separation

of real

Parts

And

Imaginary

parts

Pulse

Forming

Pulse

Forming

cos(wt)

-sin(wt)

Sdpch,n

Re(S)

Im(S)

∑

Cd,1 βd

I

cc

Q

j

I+jQ

∑

∑

DPDCH1 Cd,3 βd

DPDCH3 Cd,5 βd

DPDCH5

Cd,2 βd DPDCH2

Cd,4 βd

DPDCH4 Cd,6 βd

DPDCH6

cc Cc βc

DPCCH

Q

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