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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 、 diffracti
on and scattering
Signal attenuation:
Path loss : Loss of electromagnetic waves in large scope of the spre
ad 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 w
avelength 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 ,, thatha
t is Doppler effectt is Doppler effect
Frequency Frequency off-setoff-set caused by the movement of mobile caused by the movement of mobile ,, thatha
t is Doppler effectt 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
FrequencyTime
Power
FrequencyTime
Power
FrequencyTime
Power
FDMA
TDMA
CDMA
Frequency division multiple access technology Channels in different frequency are allocated to different users, e.g. TACS 、 AMPS 。
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 。
Time division multiple access technologychannels in different time are allocated to different users, e.g. GSM 、 DAMPS 。
Code division multiple access technology
Users distinguished by scramble code, e.g. CDMA
Code division multiple access technology
Users 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 freque
ncy of signal.
Theoretical Basis: Shannon theory C=Wlog2(1+S/N)
FastSpreadingSequence
SlowInformation
Sent
TX
SlowInformationRecovered
RX
FastSpreadingSequence
WidebandSignal
Spreading technology
f
S ( f )
f0
Before spreading
signal
S ( f )
ff0
After spreading
signal
S ( f )
ff0
After despreading
signal
White noise
f
S ( f )
f0
Before despreading
signal
White 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 sequ
ence 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 ( FH-SS ) Data is transmitted in the random channel by the carrier frequency
hopping Before FH again, data is transmitted using traditional narrowband m
odulation 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 Communicati
on
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 improv
e data transmission rates.
Error-correcting ability obtains by adding redundancy in the o
riginal data
Channel coding
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
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<10-1 ~ 10-2Can not satisfy
the communication
Convolutional coding : BER<10-3Can satisfy the
speech communication
Turbo coding : BER<10-6Can satisfy the
data communication
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 t
he 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.
Interleaving technology
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 A
T ? ? U R R B B O O
S ? ? P E E A A K K
Encoding Interleaving
W T S ? ? ?
? ? ? C U P
D R E D R E
M B A M B A
A O K A O K
DeinterleavingDecoding
Interleaving technology
Content
The basic principles of wireless communication
WCDMA wireless technology
UE DataEncoding & Interleaving
Spreading&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 ½ 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
Mu
ltip
lex
inputoutput
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 sen
sitive & 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 DataEncoding & Interleaving
Spreading&Scrambling Modulation
RF Transmission
RF ReceivingDemodulationDespreading&Descrambling
Decoding & Deinteleaving
UE Data
Data transmission Procedure
WCDMA wireless technology
Symbol rate × SF = 3.84McpsSymbol rate × SF = 3.84Mcps
WCDMAWCDMA ,, SF of uplink channelized codeSF of uplink channelized code :: 4~2564~256
SF of downlink channelized code:4~512SF of downlink channelized code:4~512
OVSF: Orthogonal Variable Spreading Factor OVSF: Orthogonal Variable Spreading Factor
Symbol rate × SF = 3.84McpsSymbol rate × SF = 3.84Mcps
WCDMAWCDMA ,, SF of uplink channelized codeSF of uplink channelized code :: 4~2564~256
SF of downlink channelized code:4~512SF of downlink channelized code:4~512
OVSF: 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
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
OrthogonalCode1 +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
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-1
WCDMA wireless technology
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 d
ownwards subtree
Result of code allocation: block all low rate SC in subtree and high rate in upwards ro
ot 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 sc
rambling operation. This is needed to separate terminals or base statio
ns from each other. Scrambling is used on top of spreading, so it does
not change the signal bandwidth but only makes the signals from differ
ent 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 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 bu
t cyclicity binary system array. Can make the user data a further randomizati
on , strengthened by scrambling a code to keep secret the function, at the s
ame time easy to carry out multiple access communication.
WCDMA Scrambling code is pseudo random binary sequence (PN code)
It has similar noise array character , is that one kind is seemingly random bu
t cyclicity binary system array. Can make the user data a further randomizati
on , strengthened by scrambling a code to keep secret the function, at the s
ame 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 differe
nt users in one cell.
Uplink Scrambling codes include long scrambling codes and short scramblin
g codes. The Short Scrambling codes are used for multi-user detecting
There are 218-1 Downlink Scrambling Codes, used to distinguish different c
ells
Scrambling codes in common use are 0 , 1 ,……, 8191 , they are divided i
nto 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 ,th
ere is 8 primary scrambling in each group.
WCDMA wireless technology
UE DataEncoding & Interleaving
Spreading&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 techn
ology purpose.
WCDMA adopts( ) and( )channel coding technology. th
e 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 dist
inguish different( ) in one cell.
There are ( ) Downlink Scrambling Codes, used to distingui
sh( )
WCDMA modulation technology include ( ) and ( )