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Dynamic subcarrier allocation with ESINR metric in correlated SM-OFDMA

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R. Nordin, S. Armour, J.P. McGeehan, “Dynamic subcarrier allocation with ESINR metric in correlated SM-OFDMA”, Proceedings of 2010 6th Conference on Wireless Advanced (WiAD), pp.1-5, June 2010

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Dynamic subcarrier allocation with ESINR metric in correlated SM-OFDMA

  1. 1. Dynamic Subcarrier Allocation with ESINR Metric in Correlated SM-OFDMA Wireless Advanced 2010 Rosdiadee Nordin, Prof. Joe McGeehan & Dr. Simon University of Bristol Centre for Communications Research
  2. 2. Presentation Outline Self-interference DSA-ESINR Simulation Parameters Results & Analysis Conclusion Centre for Communications Research
  3. 3. 3 Correlation in MIMO Correlation occurs due to:  antenna location/spacing  lack of scatterers  angular spread. Resulting in self-interference. Retransmissions and equalisation do notimprove the BER performance.
  4. 4. 4 Self-Interference MIMO only works when the channel is inlow correlation. In practice: h’ s0 h’ r0 r0=r1=h’(s0+s1) BS h’ MS Scenario: all spatial layers ` h’ are fully correlated s1 r1 Mathematically: If h’ coefficients are correlated, then [H] is [S] =[H]-1[R] ill-conditioned matrix and difficult to invert
  5. 5. 5 ESINR Metric Is the performance metric to determine thesubcarrier allocation. MMSE filter q= spatial layer Main spatial layer Gk H k qq 2 Es q   N ESINR k Gk H k qj, j  q 2 2 2 E s  Gk qq  Gk qj, j  q Knowledge of self-interference k= subcarrier index
  6. 6. 6 DSA-ESINR Involves sorting, comparing and simplearithmetic. Ranks users from lowest to highest ESINR. Fairness: Allow poor users to have the next‘best’ subcarriers. Prevents users from sharing the samesubcarrier with the adjacent layer (interferer).
  7. 7. 7 System Model X1 Tx1 Rx1 H1 X1 With Index 1 Transmitter at Base Station OFDM H3 X1User k Input With Index 2 Data Scrambling/ FEC/ Symbol Serial to Parallel& DSA H2 Rx2 X1X2 Puncturing/ Interleaving Mapping Spatial Multiplexing mapping X2 Tx2 With Index 3 H4 X2 X2 OFDM With Index 4 Uplink process Index 1 2 3 4 Downlink process Index 4 ESINR and channel Index 1 DSA Index 2 } DSA-ESINR gain feedback from other users Scheme Index 3 Index 2 Index 3 Index 1 Index 4 } DSA-Scheme 1 ESINR1 ESINR2 [ H3 ] [ H4 ] ESINR calculation Receiver at Mobile Station k [ H1 H3 ] [ H2 H4 ] S1 Y1 DSA OFDM User k Deinterleaving/ S1 S2 Parallel to MMSE [ H1 H3 ] Demapping Symbol Output Depuncturing/ Viterbi Serial& De- Linear Demapping Data Decoding/ Descrambling Multiplexing Detection Y2 DSA S2 [ H2 H4 ] Demapping OFDM
  8. 8. 8 Compared against… Maximum Gain Sort-Swap (MGSS):  Sort subcarriers pairs by metric of total perceived gain.  Swap subcarriers between users.  Two parts: initial allocation and iteration. ESINR metric is used to improve theallocation process.
  9. 9. 9 Simulation Setup Simulated under BPSK, ½ rate based on V-BLAST (2×2). Nsub= 768, NFFT= 1024 for 16 users, 48subcarriers per user. 1 0.93GPP-SCM ‘Urban Micro’: 0.8 0.7• RMS delay spread= 251 ns Normalised power 0.6• Excess delay= 1200 ns 0.5 0.4• 2000 i.i.d Rayleigh 0.3 0.2 0.1 200 300 400 500 600 700 800 900 1000 Excess delay (ns)
  10. 10. 10 Correlation Model Kronecker product, RMIMO=RMSRBS Uncorrelated = ideal channel environment Fully correlated = worst case, i.e. dominatedby self-interference Correlation Modes RBS RMS Uncorrelated 0.00 0.00 Fully Correlated 0.99 0.99
  11. 11. 11 Example of Spatial Correlation RMIMO= 0.00 (uncorrelated) RMIMO= 0.85 10 10 5 5 0 0 -5 Transmit Power (dB) -5Transmit Power (dB) -10 -10 -15 -15 -20 -20 -25 h -25 h11 11 h h12 -30 12 -30 h h21 21 -35 -35 h 22 h22 -40 0 100 200 300 400 500 600 700 -40 0 100 200 300 400 500 600 700 Subcarrier Subcarrier 10 5 Transmit power (dB) 0 RMIMO= 0.99 -5 h11 -10 h12 h21 h22 -15 0 100 200 300 400 500 600 700 Subcarrier
  12. 12. 12BER Performance 0 0 10 10 -1 10 -1 10 -2 10 -2 10 -3BER BER 10 -3 10 -4 10 -4 -5 MGSS-ESINR 10 MGSS-ESINR 10 MGSS-ChG MGSS-ChG DSA-ESINR DSA-ESINR DSA-ChG DSA-ChG -6 -5 10 10 -10 0 10 20 30 -10 0 10 20 30 SNR(dB) SNR(dB) Uncorrelated channel Fully correlated channel
  13. 13. 13Allocated Subcarriers 10 0 Channel Gain (dB) -10 -20 -30 Source Interferer ESINR Metric -40 DSA-ESINR DSA-ChG DSA-ChG (Interferer) -50 0 100 200 300 400 500 600 700 Subcarrier Uncorrelated channel
  14. 14. 14Allocated Subcarriers10 5 Channel Gain (dB) 0 -5 Source Interferer -10 ESINR Metric DSA-ESINR DSA-ChG DSA-ChG (Interferer) -15 0 100 200 300 400 500 600 700 Subcarrier Fully correlated channel
  15. 15. 15 Effective Correlation 1 1 0.8 0.8 0.6 0.6 0.4 0.4Effective Correlation Effective Correlation 0.2 0.2 0 0 -0.2 -0.2 -0.4 -0.4 -0.6 DSA-ESINR -0.6 DSA-ESINR MGSS-ESINR MGSS-ESINR -0.8 h &h -0.8 h11&h22 11 12 DSA-ChG DSA-ChG -1 -1 1 11 21 1 11 21 SNR (dB) SNR (dB) Uncorrelated channel Fully correlated channel
  16. 16. 16 Pdf distribution at SNR= 0 dB 3 2.5 DSA-ChG DSA-ESINR DSA-ESINR MGSS-ESINR MGSS-ESINR DSA-ChG 2.5 h11&h12 2 p(correlation coefficient)p(correlation coefficient) 2 1.5 1.5 1 1 0.5 0.5 0 0 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 correlation coefficient correlation coefficient Uncorrelated channel Fully correlated channel
  17. 17. 17 Pdf distribution across SNR 1.8 2 SNR= 10 dB SNR= 10 dB 1.6 SNR= 20 dB 1.8 SNR= 20 dB SNR= 30 dB SNR= 30 dB 1.4 1.6p(correlation coefficient) 1.4 p(correlation coefficient) 1.2 1.2 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 correlation coefficient correlation coefficient DSA-ESINR MGSS-ESINR
  18. 18. 18 Conclusions ESINR with a combination of DSA can minimise the effect of self-interference. Outperforms other forms of suboptimal allocation by 3 dB at BER=10-3 and known as MGSS . Allocation improves as SNR increase.
  19. 19. Thank You!Centre for Communications Research

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