WCDMA Radio Theory ZTE University TD&W&PCS BSS Course Team
WCDMA Radio Theory
ZTE University
TD&W&PCS BSS Course Team
Course Objectives
At the end of this course, you will be able to: Master channel encoding of WCDMA Master spread spectrum principle of WCDMA Master modulation of WCDMA
Content
The basic principles of wireless communication
Radio Propagation CharacteristicsRadio Propagation Characteristics
Multi AccessMulti Access
Spread spSpread spectrum ectrum TechnologyTechnology
Channel CodingChannel Coding
InterleavInterleavee Technology Technology
WCDMA wireless technology
Characteristic of Radio Propagation Electromagnetic propagation: direct
radiation reflection diffraction and scattering
Signal attenuation: Path loss Loss of electromagnetic waves in large scope of the
spread reflects the trend of the received signal in the spreading
Slow fading Loss because of being blocked by the building and hill in
the propagation path
Fast fading Electromagnetic signals rapidly decline in a few dozens
wavelength ranges
Description of Fast fading distribution Rayleigh distribution non line-of sight transmission
Rice distribution line-of sight transmission
Radio propagation charactistics
Frequency Frequency off-setoff-set caused by the movement of mobile caused by the movement of mobile that is Doppler effectthat is Doppler effect
Sending signal Accepting signal
Interference Interference
0dB
Sending signal
-25dB
Accepting signal
fadingfading
0 + Sending signal Accepting signal
delaydelay
0 2 3 + Sending signal Accepting signal
ditheringdithering
Characteristics of Radio Propagation
Radio propagation charactistics
Multi-Path Effects
receiving signalreceiving signal
timetime
strengthstrength
00
sending signalsending signal
Radio propagation charactistics
Content
The basic principles of wireless communication
Radio Propagation CharacteristicsRadio Propagation Characteristics
Multi AccessMulti Access
SpreadSpread spectrum spectrum Technology Technology
Channel CodingChannel Coding
Interleave TechnologyInterleave Technology
WCDMA wireless technology
Freque
ncyTime
Power
Freque
ncyTime
Power
Freque
ncyTime
Power
FDMA
TDMA
CDMA
Frequency division multiple access technology Channels in different frequency are allocated to different users, e.g. TACS AMPS
Time division multiple access technologychannels in different time are allocated to different users, e.g. GSM DAMPS
Code division multiple access technologyUsers distinguished by scramble code, e.g. CDMA
Multiple Access
Multiple access
Content
The basic principles of wireless communication
Radio Propagation CharacteristicsRadio Propagation Characteristics
Multi AccessMulti Access
SpreadSpread spectrum spectrum Technology Technology
Channel CodingChannel Coding
Interleave TechnologyInterleave Technology
WCDMA wireless technology
Principle of Spreading spectrum
A technology of transmission technology after spreading
frequency of signal.
Theoretical Basis: Shannon theory C=Wlog2(1+S/N)
FastSpreadingSequence
SlowInformation
Sent
TX
SlowInformationRecovered
RX
FastSpreadingSequence
WidebandSignal
Spreading technology
fS f
f0Before spreading
signal
S f
ff0After spreading
signal
S f
ff0After despreading
signalWhite noise
f
S f
f0
Before despreading
signalWhite noise
signal interference White noise
Sketch Map of Spreading
Spreading technology
Spreading Mode
Direct sequence spread DS SS Base band data is spreaded 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 accuracyWCDMA uses DS-SS
Frequency hopping spread 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
Spreading technology
Characteristics of Spreading Communication
High anti-multi-path- interference capability
High security
Lower transmitting power
Easy to implement large-capacity Multiple Access
Communication
Occupy band wide
Complex realization
Spreading technology
Content
The basic principles of wireless communication
Radio Propagation CharacteristicsRadio Propagation Characteristics
Multi AccessMulti Access
Spread spectrum TechnologySpread spectrum Technology
Channel CodingChannel Coding
Interleave TechnologyInterleave Technology
WCDMA wireless technology
Purpose of Channel Coding
purpose:
By adding redundant information in the original data stream,
receivers can detect and correct the error signal, and
improve data transmission rates.
Error-correcting ability obtains by adding redundancy in the
original data
Channel coding
W C D M AT U R B OS P E A K
W W C C D D M M A AT T U U R R B B O OS 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
Principle of Channel Coding
Channel coding
Convolutional coding and Turbo coding 1/2 1/3 are widely applied.
Increase redundancy and transmission time
Suitable to correct few non-continuous errors
Channel coding
No correct coding: BER
Content
The basic principles of wireless communication
Radio Propagation CharacteristicsRadio Propagation Characteristics
Multi AccessMulti Access
SpreadSpread spectrum spectrum Technology Technology
Channel CodingChannel Coding
Interleave TechnologyInterleave Technology
WCDMA wireless technology
Principle of Interleave Technology advantage
Interleave is to change the sequence of data to discretize the burst
continuous 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 x21x2 x7 x22x3 x8 x23x4 x9 x24x5 x10 x25
Data input A = (x1 x2 x3 x4 x5 x25)
Data output A= (x1 x6 x11 x16 x25)
e.g.
Interleaving technology
Encoding and Interleaving
W C D M AT U R B OS P E A K
W W C C D D M M A AT T U U R R B B O OS S P P E E A A K K
W T S W T SC U P C U PD R E D R EM B A M B AA O K A O K
W ? ? C D D M M A AT ? ? U R R B B O O
S ? ? P E E A A K K
Encoding Interleaving
W T S ? ? ?? ? ? C U PD R E D R EM B A M B AA O K A O K
DeinterleavingDecoding
Interleaving technology
Content
The basic principles of wireless communication
WCDMA wireless technology
UE Data Encoding & InterleavingSpreading&Scrambling
RF Transmission
RF ReceivingDemodulationDespreading&Descrambling
Decoding & Deinteleaving
UE Data
Data transmission Procedure
Modulation
Baseband
demodulation
WCDMA wireless technology
Convolutional Code
Mainly used in the voice channel and control signal channel
Coding rate is and 1/3
Output 0 G0 = 557 (octal)
Input D D D D D D D D
Output 1 G1 = 663 (octal)
Output 2 G2 = 711 (octal)
Rate 1/3 convolutional coder
WCDMA wireless technology
Characteristics of 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.
WCDMA wireless technology
Turbo 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. 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 The information bits are interleaved in the two Encoder, and generate two information
flow. At last, this information can be multiplexed and puncturedflow. At last, this information can be multiplexed and punctured
Decoding needs cycle iterative calculationDecoding needs cycle iterative calculation
InterleaverEncoder 1
Encoder 2
Mul
tiple
xinputoutput
WCDMA wireless technology
Characteristics of Turbo Codes
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 .
WCDMA wireless technology
Interleaving Technology of WCDMA
Intra-frame interleave
Bits transform in the internal frame
Inter-frame interleave
Data transform among the frames
Intra-Turbo codes interleave
Complex nesting of intra-frame and inter-frame interleave
WCDMA wireless technology
UE Data Encoding & InterleavingSpreading&Scrambling Modulation
RF Transmission
RF ReceivingDemodulationDespreading&Descrambling
Decoding & Deinteleaving
UE Data
Data transmission Procedure
WCDMA wireless technology
Symbol rate SF = 3.84McpsSymbol rate SF = 3.84McpsWCDMAWCDMA SF of uplink channelized codeSF of uplink channelized code 4~2564~256
SF of downlink channelized code:4~512SF of downlink channelized code:4~512OVSF: Orthogonal Variable Spreading Factor OVSF: Orthogonal Variable Spreading Factor
OVSF Code Scramble Code
Data bitChip after Spreadin
g
Spreading of WCDMA
WCDMA wireless technology
Despreading of WCDMA
Method of despreading
Input signal
Local PN code
When T=Ts, judge
Output after despreading
integral
0
Ts(*)dt
WCDMA wireless technology
Symbol
Spreading
Despreading
1-1
1-1
1
-1
1-1
1-1
Data = 010010
Spreading code
Spread signal= Data code
Spreading code =1 -1 -1 1 -1 1 1 -1 ( SF = 8 )
Data = Spread signal Spread code
Chip
Spreading and Despreading
WCDMA wireless technology
Concept of orthogonal code
Orthogonal
the result of multiplying and sum is 0-1-1+1-1+1+1-1+1Mul
0Sum
Orthogonal
-1+1+1-1-1+1+1-1Code2
+1-1+1+1-1+1-1-1Code1
+1-1-1-1+1-1-1+1Mul
-2Sum
Non-orthogonal
+1+1-1+1-1-1+1-1Code2
+1-1+1-1-1+1-1-1Code1
WCDMA wireless technology
Code Resource Allocation
Channelization code:
Channelization codes are based on the orthogonal variable
spreading factor (OVSF) technology. Transmission from a
single source are separated by channelization codes.
Scrambling code:
Scrambling codes are used after spreading, which will not
change the signal bandwidth. They are only used to
differentiate different UEs or Node Bs.
In WCDMA, code resources are mainly divided into channelization codes and scrambling codes.
WCDMA wireless technology
Channelization Code
Adopt OVSF code C ch,SF,k describe channelization code,
SF spread factor
k code number, 0 < k
SF=8
SF=32
SF=16
Characteristic of channelization code
Premise of code allocation:ensure not occupied for the code in the root direction and
downwards subtree
Result of code allocation:block all low rate SC in subtree and high rate in upwards
root direction
WCDMA wireless technology
Example
SF=64
SF=32
SF=16
SF= 8
0 1 2 3 4 5 6 7` ` ` `
` `0 1 2 3
` 0 1
0
SF=64
SF=32
SF=16
SF= 8
0 1 2 3 4 5 6 7` ` ` `
` `0 1 2 3
` 0 1
0
0 1 2 3 4 5 6 7` ` ` `
` `0 1 2 3
` 0 1
0
0 1 2 3 4 5 6 7` ` ` `
` `0 1 2 3
` 0 1
0
(a) (b)
(c) (d)
`
Idle
Allocated
Blocked
WCDMA wireless technology
OVSF Code Scramble Code
Data bitChip after Spreadin
g
Scrambling code
In addition to spreading, part of the process in the transmitter is the
scrambling operation. This is needed to separate terminals or base
stations from each other. Scrambling is used on top of spreading, so it
does not change the signal bandwidth but only makes the signals from
different sources separable from each other.
WCDMA wireless technology
Scrambling code of WCDMA
WCDMA scrambling code is generated from Gold sequence Gold has excellent self_correlation, Mutual_correlation is very small between subsection serial. It is used to identify cell and user for multiple address.
WCDMA Scrambling code is pseudo random binary sequence (PN code)
It has similar noise array character , is that one kind is seemingly random but cyclicity binary system array. Can make the user data a further randomization , strengthened by scrambling a code to keep secret the function, at the same time easy to carry out multiple access communication.
WCDMA wireless technology
Characteristic of Scrambling code
There are 224 Uplink Scrambling Codes, they are used to distinguish
different users in one cell.
Uplink Scrambling codes include long scrambling codes and short
scrambling codes. The Short Scrambling codes are used for multi-user
detecting
There are 218-1 Downlink Scrambling Codes, used to distinguish different
cells Scrambling codes in common use are 0 1 8191 they are divided
into 512 aggregations each aggregation has 1primary scrambling code and
15 secondary scrambling codes.
512 primary scrambling codes can be divided into 64 scrambling code groups
,there is 8 primary scrambling in each group.
WCDMA wireless technology
UE Data Encoding & InterleavingSpreading&Scrambling Modulation
RF Transmission
RF ReceivingDemodulationDespreading&Descrambling
Decoding & Deinteleaving
UE Data
Data transmission Procedure
WCDMA wireless technology
WCDMA Modulation
UL: BPSK
DL:QPSK HSDPA introduce 16QAM
WCDMA wireless technology
Exercise multiple access technolog include ?
pls describe the channel coding purpose and interleaving technology purpose.
WCDMA adopts( ) and( )channel coding technology. the coding rate is( ) ( )
the spreading code of WCDMA is ( ), the sf of ul channelize code is ( ), and the dl is ( )
There are ( ) Uplink Scrambling Codes, they are used to distinguish different( ) in one cell.
There are ( ) Downlink Scrambling Codes, used to distinguish( )
WCDMA modulation technology include ( ) and ( )