wcdma radio theory
DESCRIPTION
Understanding Basic Radio theoryTRANSCRIPT
WCDMA Radio Theory
ZTE UniversityTD&W&PCS BSS Course Team
1G(Analog)
NMT
AMPS
TACS
3G(Wideband)
IMT-2000
2G(Digital)
GSM900/1800/1900
CDMA IS-95
TDMA IS-136
PDC
Evolution of Mobile Communications
Birth of IMT2000
1985, FPLMTS being put forward FPLMTS: Future Public Land Mobile Telecommunication System
1996, renamed by IMT-2000 IMT2000: International Mobile Telecommunication 2000
Meaning of ‘2000’ frequency spectrum around 2000MHz
putting into business about 2002
data rate up to 2000kbps
Frequency Range 1992
1885-2025MHz(uplink),2110-2200MHz(downlink)
Mainly: 1920~1980 2110~2170
May,2000, spread frequency range 806-960MHz,1710-1885MHz & 2500-2690MHz
The Goal of 3G
Higher transmit rate
Rich and colorful service
Good voice quality
Larger capacity
Lower cost
Good secret performance
High frequency efficiency
Max rate up to 2Mb/s
Easy to transition from 2G
Duplex Mode
Downlink
Uplink
5 MHz channelFDD mode
Fq. 1
Fq. 2
Uplink and Downlink
5 MHz channel
. .. . ..TDD mode
Multiplexing ( Multiplex Access Technology ): Transmit two or more voice signals through one pair of cables without mutual interference at the same time.
• Each carrier frequency equals one traffic channel• Voice is transmitted continuously in time domain
USER
1 USER
2 USER
3
Time
FrequencyFDMA
FDMA
• Increase frequency spectrum efficiency• Voice is transmitted uncontinuously in time domain• System synchronous is very import
USER1
USER2
USER3
Frequency
Time
TDMA
• Large capacity• High voice quality• Soft hand-over• Low sensitive to radio fading
USER2
USER3
USER1
CDMA Frequency
TimeCode
CDMA
UE Data Encoding & Interleaving
Spreading
RF Transmission
RF ReceivingDemodulationDespreading
Decoding & Deinteleaving
UE Data
Data transmission Procedure
ModulationBaseband modulation
Baseband
demodulation
Channel encoding
Purpose:
Inserting redundant information into data stream to make
the detect and correction of transmission error possible.
UnusableNon-coding : BER<10-1 ~ 10-2
Convolutional coding : BER<10-3Voice
services
Turbo coding : BER<10-6Data
services
Principle of channel encoding
Inserting redundant information into original data to make
correction.
Convolutional encoding and Turbo encoding(1/2,1/3).
Increase noneffective load and transmission time.
Correct incontinuous error.
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
Interleaving
Purpose:
Break original data alignment and realign according to new
rule to decrease influence of short term fading.
May transform continuous error into random error.
Disadvantage:
Bring additional transmission time.
x1 x6 x11 x16 x21
x2 x7 … x22
x3 x8 … x23
x4 x9 … x24
x5 x10 … x25
Input Data A = (x1 x2 x3 x4 x5 … x25)
Output data A’= (x1 x6 x11 x16… x25)
e.g :
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
UE Data Encoding & Interleaving Spreading Modulation
RF Transmission
RF ReceivingDemodulationDespreading
Decoding & Deinteleaving
UE Data
Data transmission Procedure
SHANON Formula
C = Blog2(1+S/N)
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.
Spread Spectrum Principles
radio channel
ReceiverTransmitter
spread De-spread
Noise
Extend wideband
User information bits are spread over a wide bandwidth by
multiplying high speed spread code(chip)
Spreading signal bandwidth wider than original signal
bandwidth W=3.84Mchip/s 、 Rvoice=12.2kbit/s
Channelization Code
Adopt OVSF code
Definition: C ch,SF,k, describe channelization code, SF:spread , 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)
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
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
S1xC1
S2XC2
W
S1
S2
spread
De-spread(S1xC1)+(S2xC2)
Air-IF air interface
[S1xC1+S2xC2]xC1=S1
[S1xC1+S2xC2]xC2
=S2
N
S
C1xC2=0,C1,C2,orthogonal
Direct spread technique
EXAMPLE
-1 1 -11-1 -11 1 -1 -1 11-1 1-1 1Dispread-1 1 -11-1 -11 1
1 -1 1 -1
-4 40 0
Judge -1 1
1 -1 1 -1
-1 1 Spread
Integral
1 1 1 1-1 -1 -1 -1
1 1 1 1 -11-11
Spread Spectrum Flow
f
S ( f )
f0Signal spectrum before spreading
Signal
S ( f )
ff0Signal spectrum after spreading
Signal
S ( f )
ff0Signal spectrum after dispreading
SignalNoise
f
S ( f )
f0Signal spectrum before dispreading
SignalNoise
Signal Pulse noise noise
Spread Spectrum Principles
Many code channels are individually“spread” and then added together tocreate a “composite signal”
Spread Spectrum Principles
UNWANTED POWERFROM OTHER SOURCES
Using the “right” mathematicalsequences any Code Channelcan be extracted from the receivedcomposite signal
Eb/No
PG
PG = 25dBPG = 25dB
Voice 12.2 kbpsVoice 12.2 kbps Data 64 kbpsData 64 kbps Data 384 kbpsData 384 kbpsNodeBNodeB
PG = 18dBPG = 18dB
PG = 10dBPG = 10dB
Processing Gain
Processing gain
Processing gain = Chip rate/Bit rate (PG = W/R)
Different services have dissimilar processing gains. As a
result, their service coverage radiuses are different.
WCDMA Coverage Estimation
Eb/No
• Eb/No Power spectrumPower spectrum
Eb/No Eb/No requiredrequired
Subscriber 1Subscriber 1NoiseNoise Subscriber 2Subscriber 2Subscriber 3Subscriber 3
Eb/No = = S R X W
N SN
X W R
= SN
X PG
Eb indicates the signal energy per bit, that is, Eb = S/R where S indicates signal
energy and R indicates service bit rate.
No indicates the noise power spectrum density, that is No = N/W where W
indicates bandwidth (3.84 M) and N indicates noise (total receiving power except
the signal itself).
WCDMA Coverage Estimation
Eb/No
Channel
Rate
(kbit/s)
Required
Error Block
Rate
Recommended
Value by 3GPP
12.2 <10-1 n.a
<10-2 5.1 dB
64 <10-1 1.5 dB
<10-2 1.7 dB
144 <10-1 0.8 dB
<10-2 0.9 dB
384 <10-1 0.9 dB
<10-2 1.0 dB
Static propagation condition Multi-path channel 1 Multi-path channel 2
Channel Rate
(kbit/s)
Required
Error Block
Rate
Recommended
Value by 3GPP
12.2 <10-1 n.a
<10-2 11.9 dB
64 <10-1 6.2 dB
<10-2 9.2 dB
144 <10-1 5.4 dB
<10-2 8.4 dB
384 <10-1 5.8 dB
<10-2 8.8 dB
Channel Rate
(kbit/s)
Required
Error Block
Rate
Recommended
Value by 3GPP
12.2 <10-1 n.a
<10-2 9.0 dB
64 <10-1 4.3 dB
<10-2 6.4 dB
144 <10-1 3.7 dB
<10-2 5.6 dB
384 <10-1 4.1 dB
<10-2 6.1 dB
Eb/No Values Under Different Channel Environments in 3GPP
Eb/No is related to the service type, moving speed, coding/decoding algorithm,
antenna diversify, power control, and multi-path environment
WCDMA Coverage Estimation
DATA
Orthogonal Variable Spreading Factor (OVSF)---Channelization code Scrambling code
Symbol rate Chip rate3.84Mcps
Chip rate3.84Mcps
Spreading process of WCDMA
Symbol rate × SF = 3.84Mcps Uplink SF range : 4~256 Downlink SF range : 4~512
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.
Channelization code Resource
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
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
Scrambling code reuse
114
13
121
8
7
6 3
9
10
5 2114
13
121
8
7
6 3
9
10
5 2
114
13
121
8
7
6 3
9
10
5 2
114
13
121
8
7
6 3
9
10
5 2
114
13
121
8
7
6 3
9
10
5 2114
13
121
8
7
6 3
9
10
5 2
114
13
121
8
7
6 3
9
10
5 2
UE Data Encoding & Interleaving Spreading Modulation
RF Transmission
RF ReceivingDemodulationDespreading
Decoding & Deinteleaving
UE Data
Data transmission Procedure
WCDMA Modulation
Principles of WCDMA
Principle of WCDMA All users are simultaneously transmitting in the same frequency
bands
Each user interferes with each other
Adjacent cells use the same frequencies
Cell, users (terminals), and physical channels are separated by
code
Codes Channelization codes for separation of physical channels in the
uplink and separation of users in the downlink
Scrambling codes for separation of users/terminals in the uplink
and cells/sectors in the downlink.