01 wr bt1002 e01_1 wcdma wireless principle-49

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01 wr bt1002 e01_1 wcdma wireless principle-49

  1. 1. WCDMA Wireless Principle ZTE University
  2. 2. Content  The Basic Principles of Wireless Communication       Radio Propagation Characteristics Spreading Technology Channel Coding Interleave Technology Modulation WCDMA Radio mechanism
  3. 3. Multi-path characteristics of radio channel  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(NLOS) transmission  Rician distribution:line-of –sight(LOS) transmission
  4. 4. Multi-Path Effects sending signal strength receiving signal 0 time
  5. 5. Characteristics of Radio Propagation Interference dithering 0 2 3 delay  Sending signal +  Accepting signal fading 0dB 0  Sending signal Accepting signal Sending signal   -25dB +  Accepting signal Sending signal Accepting signal Frequency off-set caused by the movement of mobile ,that is Doppler effect
  6. 6. Content  The Basic Principles of Wireless Communication       Radio Propagation Characteristics Spreading Technology Channel Coding Interleave Technology Modulation WCDMA Radio mechanism
  7. 7. Spread Spectrum Principles 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.
  8. 8. Spread Spectrum Principles Power is “Spread” Over a Larger Bandwidth 30 KHz 1.25 MHz
  9. 9. Spread Spectrum Principles Despreading Spreading radio channel Noise Transmitter    Receiver User information bits are spread over a wide bandwidth by multiplying high speed spread code(chip) Spread signal bandwidth W wider than original signal bandwidth Rb For WCDMA, W=3.84Mchip/s、 Rb(voice)=12kbit/s
  10. 10. Spread Spectrum Principles S(f) S(f) signal signal f0 Before spreading S(f) f f0 f After spreading S(f) White noise signal White noise signal f0 f Before despreading signal interference f0 After despreading f White noise
  11. 11. Spreading Mode  Direct sequence spread spectrum(DS-SS)      Base band data is spread 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 spectrum(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
  12. 12. DS-SS communication system  A technology of transmission after spreading signal spectrum. Wideband Signal Slow Information Sent Slow Information Recovered TX Fast Spreading Sequence RX Fast Spreading Sequence
  13. 13. Spread Spectrum Principles Many code channels are individually “spread” and then added together to create a “composite signal”
  14. 14. Spread Spectrum Principles   Any Code Channel can be extracted from the received composite signal by using the ―right‖ orthogonal code Energy for transmitting signal can be lower than interference and noise Processing Gain Broadband Interference Unwanted Power from Other Resoures
  15. 15. Concept of orthogonal code Code1 +1 -1 +1 +1 -1 +1 -1 -1 Code1 +1 -1 +1 -1 -1 +1 -1 -1 Code2 -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 Mul +1 -1 -1 -1 +1 -1 -1 +1 Sum 0 Orthogonal Sum -2 Non-orthogonal Orthogonal— the result of multiplying and sum is 0
  16. 16. Example of orthogonal code -1 1 MUL -1 1 -1 1 1 -1 1 -1 -1 -1 -1 -1 1 1 1 1 1 -1 1 -1 Integral MUL -1 -1 -1 -1 1 1 1 1 -1 1 -1 1 1 -1 1 -1 1 -1 1 -1 -4 4 0 0 Judge -1 1
  17. 17. Direct spread technique S1xC1 S1 Spreading W S2 S2XC2 Air Interface S N [S1xC1+S2xC2]xC1 =S1 (S1xC1)+(S2xC2) Despreading [S1xC1+S2xC2]xC2 =S2 C1xC2=0, C1,C2,orthogonal
  18. 18. Sketch map of Spreading and Despreading Symbol Data=010010 Chip Spreading code = 1 -1 -1 1 -1 1 1 -1 ( SF = 8 ) 1 -1 Spreading 1 -1 1 -1 Spread signal = Data × code Despreading Spreading code 1 -1 1 -1 Data = Spread signal × Spreading code
  19. 19. Characteristics of Spreading Communication        High anti-multi-path- interference capability Anti-sudden-pulse High security Lower transmitting power Easy to implement large-capacity Multiple Access Communication Occupy band wide Complex realization
  20. 20. Content  The Basic Principles of Wireless Communication       Radio Propagation Characteristics Spreading Technology Channel Coding Interleave Technology Modulation WCDMA Radio mechanism
  21. 21. Purpose of Channel Coding  By adding redundant information in the original data stream, receivers can detect and correct the error signal, and improve data transmission rates. No correct coding: BER<10-1 ~ 10-2 Convolutional coding:BER<10-3 Turbo coding: BER<10-6 Can not satisfy the communication Can satisfy the speech communication Can satisfy the data communication
  22. 22. Principle of Channel Coding  Channel coding     Error-correcting ability obtains by adding redundancy in the original data Convolutional coding and Turbo coding (1/2,1/3) are widely applied. Increase noneffective load and transmission time Suitable to correct few non-continuous errors WCDMA W W C C D D M MAA W ? C C D D M MAA TURBO T T UURRBBOO T T ? URRBBOO S S PPE EAAK K S S PPEE A? KK SPEAK Encoding Decoding
  23. 23. Content  The Basic Principles of Wireless Communication       Radio Propagation Characteristics Spreading Technology Channel Coding Interleave Technology Modulation WCDMA Radio mechanism
  24. 24. Principle of Interleave Technology   advantage  Interleave is to change the sequence of data to random the unexpected errors  Advance the correcting validity disadvantage:  Increase the processing delay  Especially, Several independent random errors may intertwined for the unexpected error . e.g. x1 x6 x11 x16 x21 Data input A = (x1 x2 x3 x4 x5 … x25) x2 x7 … x22 x3 x8 … x23 x4 x9 … x24 x5 x10 … x25 Data output A’= (x1 x6 x11 x16… x25)
  25. 25. Encoding and Interleaving WCDMA Encoding W W C C D D M MAA TURBO T T UURRBBOO SPEAK WTSWTS Interleaving S S PPE EAAK K CUPCUP DREDRE MBAMBA Encoding + Interleaving can correct both continuous and non-continuous errors Decoding W??CDDMMA? T ? ?UR??BOO S ? ? P? EAAK K AOKAOK WTS??? Deinterleaving ? ? ?CUP DR?D?E M?AMBA AOK?OK
  26. 26. Content  The Basic Principles of Wireless Communication       Radio Propagation Characteristics Spreading Technology Channel Coding Interleave Technology Modulation WCDMA Radio mechanism
  27. 27. Principle of Modulation  Definition   Modulation is the process where the amplitude, frequency, or phase of an electronic or optical signal carrier is changed in order to transmit information. Using symbol stand for one or more bits to improve communication effectiveness bit  Classification   Analog Modulation Digital Modulation Modulation Symbol
  28. 28. Analog Modulation  The purpose of analog modulation is to impress an information-bearing analog waveform onto a carrier for transmission.  Common analog modulation methods include:    Amplitude modulation (AM) Frequency modulation (FM) Phase modulation (PM)
  29. 29. Digital Modulation  The purpose of digital modulation is to convert an information-bearing discrete-time symbol sequence into a continuous-time waveform (perhaps impressed on a carrier).  Basic analog modulation methods include    Amplitude shift Keying (ASK) Frequency shift Keying (FSK) Phase shift Keying (PSK)
  30. 30. Content  The Basic Principles of Wireless Communication  WCDMA Radio mechanism     WCDMA Data transmission Procedure Channel Coding of WCDMA Spreading Technology of WCDMA Modulation of WCDMA
  31. 31. WCDMA Data transmission Procedure UE Data Encoding & Interleaving Baseband modulation Spreading Modulation RF Transmitting Despreading Baseband demodulation Demodulation RF Receiving Decoding & De-inteleaving UE Data
  32. 32. Content  The Basic Principles of Wireless Communication  WCDMA Radio mechanism     WCDMA Data transmission Procedure Channel Coding of WCDMA Spreading Technology of WCDMA Modulation of WCDMA
  33. 33. Convolutional Code  Characteristics       Mainly used in the voice channel and control signal channel Coding rate : 1/2 & 1/3 Channel bit error rate is 10-3 magnitude Easy decoding Short delay Suitable for realtime service  e.g. speech and video service.
  34. 34. Turbo Code  Characteristics       Used in Data service channel Code Rate is 1/3 Channel bit error rate is 10-6 magnitude Can be implemented in the transmission for large block and long delay services Complex decoding, needs cycle iterative calculation Very suitable for non-realtime package service which is BER sensitive & delay insensitive  e.g. WWW, FTP, E-mail , multimedia transmission .
  35. 35. Content  The Basic Principles of Wireless Communication  WCDMA Radio mechanism     WCDMA Data transmission Procedure Channel Coding of WCDMA Spreading Technology of WCDMA Modulation of WCDMA
  36. 36. Spreading Process of WCDMA Symbol Chip Spread Data Data 3.84Mcps 3.84Mcps OVSF Code Scrambling Code Symbol rate × SF = Chip rate=3.84Mcps For WCDMA,SF of uplink channelization code:4~256 SF of downlink channelization code: 4~512 OVSF: Orthogonal Variable Spreading Factor
  37. 37. Channelization Code  Adopt OVSF code  Definition: Cch,SF,k, describe channelization code, where SF : spread factor, k : code number, 0 < k<SF-1 C ch,4,0 =(1,1,1,1) C ch,2,0 = (1,1) C ch,4,1 = (1,1, -1, - 1) C ch,1,0 = (1) C ch,4,2 = (1, - 1 ,1, - 1) C ch,2,1 = (1,-1) C ch,4,3 = (1, - 1, - 1, 1) SF = 1 SF = 2 SF = 4
  38. 38. Scrambling Code  WCDMA Scrambling code is pseudo random binary sequence (PN code)    It has similar noise array character, seemingly random but with regularity. Can make the user data further random , strengthened by scrambling a code to keep secret the user data, at the same time easy to carry out multiple access communication. WCDMA scrambling code is generated from Gold sequence    Gold sequence has excellent self-correlation. Cross-correlation is very week between two codes. It is used to identify cell and user for multiple access.
  39. 39. Characteristic of Scrambling code  There are 224 Uplink Scrambling Codes, they are used to distinguish different users in one cell.  There are 218-1 Downlink Scrambling Codes, used to distinguish different cells   Scrambling codes usually used are the first 8192 codes, which are code 0,1,……,8191. They are divided into 512 aggregations,each aggregation has 1 primary scrambling code (PSC) and 15 secondary scrambling codes (SSC). The 512 primary scrambling codes are divided further into 64 primary scrambling code groups , with 8 primary scrambling codes in each group.
  40. 40. Numbering rule for Downlink Scrambling Codes 18 2 -1 Downlink Scrambling Codes in all (0..262142) No.63 Primary Scrambling Code Group …… No. 511 Scrambling Code No.0 Primary Scrambling Code Group Group No. 7 Scrambling Code No. 510 Scrambling Code 8176:PSC Group … Group 8177:SSC No. 1 Scrambling Code Scrambling Code … No. 504 112 8176:PSC 8160 8160:主扰码 Group … Group No. 0 Scrambling Code 8191 8191:SSC 113 8177:辅扰码 8161 8161:辅扰码 Group … 16 16:PSC … 8064:主扰码 8064 127 8191:辅扰码 17 17:SSC 8175:辅扰码 81758065 8065:辅扰码 0 0:PSC … 1 1:SSC … 31 31:SSC … 8079 8079:辅扰码 15 15:SSC 8176 8177
  41. 41. Code Functions  Channelization code ---- for separation of physical channels in the uplink and separation of users in the downlink  Scrambling code ---- for separation of users/terminals in the uplink and cells/sectors in the downlink.
  42. 42. Spreading code & scrambling code cch1 cch 2 Air Interface cscrambling cch 3  Cch:spread code    Relative to service rate,extended to 3.84Mchips/s A kind of orthogonal code Cscrambling:scrambling code  Have no effect on signal bandwidth  downlink for identifier cell,uplink identifier terminal  A pseudo-random sequence Modulation
  43. 43. Processing Gain P Processing Gain Processing Gain  Wc Rb Despreading W  Rb PG=Wc/Rb (Wc : Chip rate , Rb : Service bit rate)   Transmitter/receiver can obtain gain after spread/despread The narrower original signal bandwidth, the larger Pg , the better The higher PG, the more anti-interference capability system has. f
  44. 44. Question What’s the Processing Gain for voice service in WCDMA system?  Given: Voice data rate = 12.2kbps  PG=10lg(Wc/ Rb) , dB units     Wc: 3.84Mchip/s Rb: 12.2kbps So for voice service,  PG=10lg(3.84* 106 /12.2* 103)= 25 dB
  45. 45. Despreading procedure  Method of despreading Input signal Output after despreading Ts (*)dt 0 When T=Ts, judge integral Local PN code
  46. 46. Content  The Basic Principles of Wireless Communication  WCDMA Radio mechanism     WCDMA Data transmission Procedure Channel Coding of WCDMA Spreading Technology of WCDMA Modulation of WCDMA
  47. 47. Modulation Methods in WCDMA    BPSK (Binary Phase Shift Keying) in Uplink channles QPSK (Quadrature Phase Shift Keying) in Downlink channels 16QAM (16-state Quadrature Amplitude Modulation) in HSDPA
  48. 48. summary  Principle of WCDMA      Channel coding    Convolutional code Turbo code Codes    All users are simultaneously transmitted in the same frequency band Users interfere with each other Adjacent cells use the same frequency Cells, users (terminals), and physical channels are separated by codes Channelization code Scrambling code Modulation    BPSK QPSK 16QAM

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