Download - 02 WCDMA Wireless Principle
-
8/14/2019 02 WCDMA Wireless Principle
1/30
-
8/14/2019 02 WCDMA Wireless Principle
2/30
B :- Gaurav Kumar
The Basic Principles of Wireless CommunicationRadio Propagation CharacteristicsSpreading TechnologyChannel CodingInterleave TechnologyModulation
Content
-
8/14/2019 02 WCDMA Wireless Principle
3/30
B :- Gaurav Kumar
Multi-path characteristics of radio channel
Electromagnetic propagation:--direct radiation reflection diffraction and scatteringSignal attenuation:
Path loss Loss of electromagnetic waves in large scope of thespread reflects the trend of the received signal in the spreading Slow fading Loss because of being blocked by the building andhill in the propagation pathFast fading Electromagnetic signals rapidly decline in a fewdozens wavelength ranges
Description of Fast fading distributionRayleigh distribution non line-of sight(NLOS) transmissionRician distribution line-of sight(LOS) transmission
-
8/14/2019 02 WCDMA Wireless Principle
4/30
B :- Gaurav Kumar
Multi-Path Effects
receiving signal
time
strength
0
sending signal
-
8/14/2019 02 WCDMA Wireless Principle
5/30
B :- Gaurav Kumar
Frequency off -se t caused by the mo vement of mo bi le tha t
is Dopp ler effect
Sending signal Accepting signal
Interference
0dB
Sending signal
-25dB
Accepting signal
fading
0 +
Sending signal Accepting signal
delay
0 2 3 +
Sending signal Accepting signal
dithering
Characteristics of Radio Propagation
-
8/14/2019 02 WCDMA Wireless Principle
6/30
-
8/14/2019 02 WCDMA Wireless Principle
7/30 B :- Gaurav Kumar
SHA NON Form ula
C = Blog 2(1+S/N)
Spread Spectrum Principles
Where,C is capacity of channel, b/sB is signal bandwidth, HzS is average power for signal, WN is average power for noise, W
It is the basic principle and theory for spread spectrumcommunications.
-
8/14/2019 02 WCDMA Wireless Principle
8/30 B :- Gaurav Kumar
Spread Spectrum Principles
5 MHz30 KHz
Power is Spread Over a Larger Bandwidth
-
8/14/2019 02 WCDMA Wireless Principle
9/30 B :- Gaurav Kumar
radio channel
ReceiverTransmitter
SpreadingDespreading
Noise
Spread Spectrum Principles
User information bits are spread over a widebandwidth by multiplying high speed spreadcode(chip)Spread signal bandwidth W wider than original signalbandwidth RbFor WCDMA, W=3.84Mchip/s Rb(voice)=12kbit/s
-
8/14/2019 02 WCDMA Wireless Principle
10/30 B :- Gaurav Kumar
f
S f
f0
Before spreading
signal
S f
ff0
After spreading
signal
S f
ff0After despreading
signal
White noise
f
S f
f0
Before despreading
signal
White noise
signal interference White noise
Spread Spectrum Principles
-
8/14/2019 02 WCDMA Wireless Principle
11/30 B :- Gaurav Kumar
Spreading Mode
Direct sequence spread spectrum DS-SS Base band data is spread by multiplication of pseudo-noisesequence and base-band pulse, the pseudo-noise sequencegenerated by the pseudo-noise generatorBER subject to Multiple Access Interference and near-far effect
Power control can overcome the near-far effect, but it is limited bypower detection accuracy WCDMA uses DS-SS
Frequency hopping spread spectrum FH-SS
Data is transmitted in the random channel by the carrier frequencyhoppingBefore FH again, data is transmitted using traditional narrowbandmodulationNo near-far effect
-
8/14/2019 02 WCDMA Wireless Principle
12/30 B :- Gaurav Kumar
DS-SS communication system
A technology of transmission after spreading signalspectrum.
FastSpreadingSequence
SlowInformation
Sent
TX
SlowInformat ionRecovered
RX
FastSpreadingSequence
WidebandSignal
-
8/14/2019 02 WCDMA Wireless Principle
13/30 B :- Gaurav Kumar
Spread Spectrum Principles
Many code channels are individuallyspread and then added together tocreate a composite signal
-
8/14/2019 02 WCDMA Wireless Principle
14/30 B :- Gaurav Kumar
Unwanted Power fromOther Resoures
Spread Spectrum Principles
Any Code Channel can be extracted from the receivedcomposite signal by using the right orthogonal code Energy for transmitting signal can be lower thaninterference and noise
Processing Gain
BroadbandInterference
-
8/14/2019 02 WCDMA Wireless Principle
15/30 B :- Gaurav Kumar
Concept of orthogonal code
Orthogonal
the result of multiplyingand sum is 0
Code1 +1 -1 +1 +1 -1 +1 -1 -1Code2 -1 +1 +1 -1 -1 +1 +1 -1Mul -1 -1 +1 -1 +1 +1 -1 +1
Sum 0
Orthogonal
Code1 +1 -1 +1 -1 -1 +1 -1 -1Code2 +1 +1 -1 +1 -1 -1 +1 -1Mul +1 -1 -1 -1 +1 -1 -1 +1Sum -2
Non-orthogonal
-
8/14/2019 02 WCDMA Wireless Principle
16/30 B :- Gaurav Kumar
-1 1 -11-1 -11 1 -1 -1 11-1 1-1 1MU
-1 1 -11-1 -11 1
1 -1 1 -1
-4 40 0
Judge -1 1
1 -1 1 -1
-1 1 MU
Integral
1 1 1 1-1 -1 -1 -1
Example of orthogonal code
-
8/14/2019 02 WCDMA Wireless Principle
17/30 B :- Gaurav Kumar
S1
S2
S1xC1
S2XC2
W Spreading
Despreading
(S1xC1)+(S2xC2)
Air Interface
[S1xC1+S2xC2]xC2=S2
[S1xC1+S2xC2]xC1=S1N
S
C1xC2=0,C1,C2,orthogonal
Direct spread technique
-
8/14/2019 02 WCDMA Wireless Principle
18/30 B :- Gaurav Kumar
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
-
8/14/2019 02 WCDMA Wireless Principle
19/30 B :- Gaurav Kumar
Characteristics of Spreading Communication
High anti-multi-path- interference capability Anti-sudden-pulseHigh security
Lower transmitting powerEasy to implement large-capacity Multiple AccessCommunicationOccupy band wideComplex realization
-
8/14/2019 02 WCDMA Wireless Principle
20/30 B :- Gaurav Kumar
The Basic Principles of Wireless CommunicationRadio Propagation CharacteristicsSpreading TechnologyChannel CodingInterleave TechnologyModulation
Content
-
8/14/2019 02 WCDMA Wireless Principle
21/30
-
8/14/2019 02 WCDMA Wireless Principle
22/30 B :- Gaurav Kumar
Principle of Channel Coding
Channel codingError-correcting ability obtains by adding redundancy in theoriginal dataConvolution coding and Turbo coding 1/2 1/3 are widelyapplied.Increase no effective load and transmission timeSuitable 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
Encod ing
-
8/14/2019 02 WCDMA Wireless Principle
23/30 B :- Gaurav Kumar
The Basic Principles of Wireless CommunicationRadio Propagation CharacteristicsSpreading TechnologyChannel CodingInterleave TechnologyModulation
Content
-
8/14/2019 02 WCDMA Wireless Principle
24/30 B :- Gaurav Kumar
Principle of Interleave Technology
advantageInterleave is to change the sequence of data to random theunexpected errors Advance the correcting validity
disadvantage Increase the processing delayEspecially, Several independent random errors may intertwined forthe unexpected error .
x1 x6 x11 x16 x21x2 x7 x22
x3 x8 x23
x4 x9 x24
x5 x1 x25
Data input A = (x1 x2 x3 x4 x5 x25)
Data output A= (x1 x6 x11 x16 x25)
e.g.
-
8/14/2019 02 WCDMA Wireless Principle
25/30 B :- Gaurav Kumar
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 AA 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
DeinterleavingDecoding
Encod ing + Inter leaving can c orrect bothcont inuo us and non-con t inuous e r rors
-
8/14/2019 02 WCDMA Wireless Principle
26/30 B :- Gaurav Kumar
The Basic Principles of Wireless CommunicationRadio Propagation CharacteristicsSpreading TechnologyChannel CodingInterleave TechnologyModulation
Content
-
8/14/2019 02 WCDMA Wireless Principle
27/30
-
8/14/2019 02 WCDMA Wireless Principle
28/30 B :- Gaurav Kumar
Analog Modulation
The purpose of analog modulation is to impress aninformation-bearing analog waveform onto acarrier for transmission.
Common analog modulation methods include: Amplitude modulation (AM)
Frequency modulation (FM)
Phase modulation (PM)
-
8/14/2019 02 WCDMA Wireless Principle
29/30
B :- Gaurav Kumar
Digital Modulation
The purpose of digital modulation is to convert aninformation-bearing discrete-time symbol sequence into acontinuous-time waveform (perhaps impressed on acarrier).
Basic analog modulation methods include Amplitude shift Keying (ASK)Frequency shift Keying (FSK)Phase shift Keying (PSK)
-
8/14/2019 02 WCDMA Wireless Principle
30/30