#8 Adaptive Modulation Coding

Transcription

1 06 Q Wireless Communication Engineering #8 Adaptive Modulation Coding Kei Sakaguchi sakaguchi@mobile.ee. July 5, 06

2 Course Schedule () Date Text Contents #7 July Error correction coding #8 July 5 Adaptive modulation coding #9 July 4.3 Inter symbol interference and adaptive equalizer #0 July 3.6, 4.5 Spread spectrum and code division multiple access (CDMA) # July Orthogonal frequency division multiple access (OFDM) # July 9 Array signal processing and MIMO spatial multiplexing #3 TBD all Final examination July 5, 06 Wireless Communication Engineering

3 From revious Lecture n Convolutional coding & Viterbi decoding m(t) n Error rate of Viterbi decoding e < d = d Z min d-d Z min ( d) x ( t) x ( t) n Interleaver & time diversity Hard detection: Soft detection: Avoiding burst error by interleaving d d k ( d) = e ( e ) k = d + k c ( d) erfc( γd ) = July 5, 06 Wireless Communication Engineering 3 T x A = [,] [0,0] t t t 3 t4 [ 0,0 [0,0] 0,0] A A A A B [,] [0,] [ ] B [0,0] B [0,0] B C D [,] [,] [, ] [,0] [,0 ] [0,] [0,] [,0] C D [,] [0,] [0,] [,0] d ( d) = erfc γ i i= [,0] C D d k

4 Contents Throughput of higher order modulation Throughput in fading channel Adaptive modulation Adaptive modulation coding July 5, 06 Wireless Communication Engineering 4

5 Higher Order Modulation BSK QSK log M = log M = 6QAM 64QAM log M = 4 log M = 6 July 5, 06 Wireless Communication Engineering 5

6 BER of Higher Order Modulation BSK modulation eb ( γ ) = erfc ( γ ) γ = h σ BER of QAM modulation BSK QSK 6QAM 64QAM QAM modulation eb ( γ ) = log M erfc 3γ M ( M ) Bit Error Rate Average SNR per antenna [db] July 5, 06 Wireless Communication Engineering 6

7 Throughput of Higher Order Modulation Frame structure reamble Data Data length acket Error Rate (ER) ( γ ) = ( ( γ )) L ep Throughput eb L Throughput [bits/s/hz] Throughput of QAM modulation BSK QSK 6QAM 64QAM T ( γ ) log M ( ( γ )) L = [bits/s/hz] eb Average SNR per antenna [db] July 5, 06 Wireless Communication Engineering 7

8 BER in Fading Channel BER of BSK modulation eb ( γ ) = erfc ( γ ) γ = h σ Rayleigh fading channel DF of Rayleigh fading channel f ( γ ) γ = exp γ γ γ h( t) E σ = Average BER Error events eb ( γ ) = eb ( γ ) f ( γ ) dγ = γ + γ July 5, 06 Wireless Communication Engineering 8

9 BER in Fading Channel BER performance BSK QSK 6QAM 64QAM Bit Error Rate Average BER performance BSK QSK 6QAM 64QAM Average SNR per antenna [db] Rayleigh fading Bit Error Rate Average SNR [db] July 5, 06 Wireless Communication Engineering 9

10 Throughput in Fading Channel Throughput [bits/s/hz] Throughput performance BSK QSK 6QAM 64QAM Average SNR per antenna [db] Rayleigh fading Average throughput performance Throughput [bits/s/hz] BSK QSK 6QAM 64QAM Average SNR [db] July 5, 06 Wireless Communication Engineering 0

11 Structure of Rate Adaptation Fading channel Conv. coding QAM mod. QAM demod. Viterbi dec. Coding rate r Adaptive control Modulation order M Training sequence Feedback channel ˆM Channel quality est. rˆ Adaptive control Maximization of transmit data rate by adaptive control of modulation order of QAM and coding rate of channel coder in accordance with the channel variation (by using feedback channel) Channel quality estimation One of receiver function to estimate optimal transmit rate (modulation order, coding rate) based on instantaneous SNR estimated using training sequence and to tell transmitter about their optimal values via feedback channel July 5, 06 Wireless Communication Engineering

12 SNR estimation hˆ( t) γ ( t ) = σ Throughput estimation T BSK QAM eb ( γ ) = Adaptive Modulation ( ) γ, M = log M ( γ ) eb ( γ ) erfc ( γ ) Adaptive modulation ( Mˆ = arg max T γ, M ) M ( ) L eb = log M erfc 3γ M ( M ) Optimal modulation order Table for adaptive modulation July 5, 06 Wireless Communication Engineering

13 Throughput of Adaptive Modulation Average throughput T( γ, M f ( γ ) ) = DF of Rayleigh fading γ = exp γ γ f ( γ ) T( γ, M γ ) dγ h( t) E σ = Average throughput of adaptive modulation T( γ ) γ = f ( γ ) T( γ,)dγ γ = γ = γ = 0 γ + f ( γ ) T( γ,64)dγ Inst. SNR Modulation - 9.5dB BSK 9.5dB 6dB 6dB.5dB.5dB QSK 6QAM 64QAM July 5, 06 Wireless Communication Engineering 3 Table of adaptive modulation SNR threshold

14 Adaptive Modulation in Fading Channel Fixed modulations & Adaptive modulation July 5, 06 Wireless Communication Engineering 4

15 Convolutional Coding & uncture Convolutional coding (constraint length 7) Input data Encoded data with puncture /3 3/4 A B uncture matrix R=/ d free 0 R=/3 0 d free R=3/4 d free R=4/5 000 d free R=5/6 d free July 5, 06 Wireless Communication Engineering 5

16 BER of Convolutional Coding Bit Error Rate BER performance in AWGN channel BSK / BSK 3/4 BSK no code QSK / QSK 3/4 QSK no code 6QAM / 6QM 3/4 6QAM no code 64QAM / 64QAM 3/4 64QAM no code Average SNR [db] July 5, 06 Wireless Communication Engineering 6

17 Throughput of Convolutional Coding Throughput [Mbps] Throughput performance in AWGN channel BSK / BSK 3/4 BSK no code QSK / QSK 3/4 QSK no code 6QAM / 6QAM 3/4 6QAM no code 64QAM / 64QAM 3/4 64QAM no code Average SNR [db] July 5, 06 Wireless Communication Engineering 7

18 Adaptive Modulation Coding in Fading Channel erformance in Rayleigh fading channel July 5, 06 Wireless Communication Engineering 8

19 Summ n Throughput against modulation order T ( ) L ( ) γ, M = log M ( γ ) eb SNR Table for AMC n Adaptive modulation Mˆ = arg max T M ( γ, M ) n Throughput performance of AMC T ( γ ) γ 0 = f ( γ ) T( γ,)dγ + + f ( γ ) T( γ,64)dγ γ 3 July 5, 06 Wireless Communication Engineering 9