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 Characteristics Multi Access Spread spectrum Technology Channel Coding Interleave Technology
WCDMA wireless technology
Radio propagation charactistics
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
Characteristics of Radio Propagation Interference
dithering 0
2τ
delay
τ
σ
Sending signal
σ+τ
Accepting signal
fading 0dB
0
σ
3τ
Sending signal
Accepting signal
Sending signal
τ
-25dB
σ+τ
Accepting signal
Sending signal
Accepting signal
Frequency Frequencyoff-set off-setcaused causedby bythe the movement movementof ofmobile mobile , , that thatis is Doppler Doppler effect effect
Radio propagation charactistics
Multi-Path Effects
sending signal
strength
receiving signal 0
time
Content The basic principles of wireless communication Radio Propagation Characteristics Multi Access Spread spectrum Technology Channel Coding Interleave Technology
WCDMA wireless technology
Multiple access
Multiple Access Frequency division multiple access technology
FDMA
Channels in different frequency are allocated to different users, e.g. TACS 、 AMPS 。
Power
Time division multiple access technology
TDMA
channels in different time are allocated to different users, e.g. GSM 、 DAMPS 。
Power
T im
e
Tim
e
Code division multiple access technology
CDMA
Users distinguished by scramble code, e.g. CDMA
Power Tim e
y nc e u eq Fr
e qu Fre
eq Fr
y nc
y nc e u
Content The basic principles of wireless communication Radio Propagation Characteristics Multi Access Spread spectrum Technology Channel Coding Interleave Technology
WCDMA wireless technology
Spreading technology
Principle of Spreading spectrum
A technology of transmission technology after spreading frequency of signal.
Theoretical Basis: Shannon theory C=Wlog2(1+S/N) Wideband Signal
Slow Information Sent
Slow Information Recovered
TX
Fast Spreading Sequence
RX
Fast Spreading Sequence
Spreading technology
Sketch Map of Spreading S(f)
S(f) signal
signal f0
f0
f
Before spreading
f
After spreading
S(f)
S(f)
White noise
signal White noise
signal f0
f
Before despreading
signal
interference
f0
f
After despreading
White noise
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 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
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
Content The basic principles of wireless communication Radio Propagation Characteristics Multi Access Spread spectrum Technology Channel Coding Interleave Technology
WCDMA wireless technology
Channel coding
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
?CCDDMMA
WCDMA
WWCCDDMMAA
W
TURBO
T T UURRBBOO
A
SPEAK
S S PPEEAAKK
T T U
?RRBBO
O S S PPEEA
?KK
Channel coding
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 No correct coding: BER
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