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HDR 802.11a solution using MIMO-OFDM

HDR 802.11a solution using MIMO-OFDM. Heejung Yu ETRI Wireless LAN Research Team Heejung@etri.re.kr. Contents. System and signal model Optimal detection ZF and MMSE receiver Layered architecture using ZF and MMSE Simulation results Conclusion. Rayleigh Fading Channel. IFFT. S/P.

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HDR 802.11a solution using MIMO-OFDM

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  1. HDR 802.11a solution using MIMO-OFDM Heejung Yu ETRI Wireless LAN Research Team Heejung@etri.re.kr Heejung Yu, ETRI

  2. Contents • System and signal model • Optimal detection • ZF and MMSE receiver • Layered architecture using ZF and MMSE • Simulation results • Conclusion Heejung Yu, ETRI

  3. Rayleigh Fading Channel IFFT S/P Add CP Remove CP FFT Det. P/S Tx ant 1 Rx ant 1 IFFT Remove CP FFT Add CP Tx ant 2 Rx ant 2 Mapping Demap IFFT Remove CP FFT Add CP Tx ant N Rx ant M System model Heejung Yu, ETRI

  4. Signal model • Received Signal for one subcarrier • H : Frequency domain channel matrix • (hi,j : channel from j-th Tx antenna to i-th Rx antenna) • P : Total Tx power • N : Total # of Tx antenna • x : Tx signal vector (1 x N) • y : Rx signal vector (1 x M) • n : AWGN noise vector (1 x M) Heejung Yu, ETRI

  5. Optimal receiver • Detect signal maximizing likelihood function • Exhaustive search : AN candidates (A : # of constellation) • Advantage • Diversity order = # of receiver antennas • Can be applied in case of N>M • The best performance • Disadvantage • Implementation complexity increases exponentially Heejung Yu, ETRI

  6. ZF receiver • Only need channel matrix • Exit the noise enhancement problem • Diversity order : M-N+1 ( )+ : Pseudo-inverse Heejung Yu, ETRI

  7. MMSE receiver • Consider noise power : achieve better performance than ZF • In High SNR, MMSE receiver  ZF receiver • Diversity order : M-N+1 Heejung Yu, ETRI

  8. Layered receiver(1) • 1. Find signal with minimum noise enhancement(using H) • 2. Make a decision statistic • 3. Decision Heejung Yu, ETRI

  9. Layered receiver(2) • 4. Reconstruct signal and cancel it • 5. Update H (zero-forcing the kth column of current H) • 6. Return to step 1. until deciding all symbols. Heejung Yu, ETRI

  10. Example of Layered Arch. • N = M = 3 (BPSK) • 1. • 2. Heejung Yu, ETRI

  11. Example of Layered Arch. • 3. Hard decision[0.8333] • 4. • 5. Heejung Yu, ETRI

  12. Example of Layered Arch. • 6. • 7. • 8. Hard decision[0.4000] Heejung Yu, ETRI

  13. Example of Layered Arch. • 9. • 10. • 11. Heejung Yu, ETRI

  14. Example of Layered Arch. • 12. • 13. Hard decision[-1.633] • 14. Heejung Yu, ETRI

  15. Simulation Environment • Modulation : OFDM (the same as 802.11a) • Mapping : BPSK, QPSK, 16-QAM, 64-QAM • Coding : No coding • Channel : Exponentially decaying Rayleigh fading channel with 100nsec RMS delay spread • # of Tx and Rx antennas : 4 x 4 • BW = 20MHz Heejung Yu, ETRI

  16. Simulation results (BPSK) 48Mbps 12Mbps Heejung Yu, ETRI

  17. Simulation results (QPSK) 96Mbps 24Mbps Heejung Yu, ETRI

  18. Simulation results (16-QAM) 192Mbps 48Mbps Heejung Yu, ETRI

  19. Simulation results (64-QAM) 288Mbps 72Mbps Heejung Yu, ETRI

  20. Conclusions • We can achieve more than 100Mbps using MIMO-OFDM with a small performance degradation. • In BPSK and QPSK modulation, we can achieve better performance than SISO case • In 16 and 64-QAM, performance degradations due to MIMO are about 0.5 and 2dB, respectively. • We can get the high spectral efficiency by using MIMO-OFDM • MIMO-OFDM is a good solution for HDR 802.11a Heejung Yu, ETRI

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