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Proposed Technologies for >200Mbps in PHY

This proposal presents various technologies for achieving data rates of over 200Mbps in the physical layer of next-generation wireless LAN. The technologies include MIMO-OFDM, dual-band operation, and high-order modulation. Simulation results and conclusions are also provided.

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Proposed Technologies for >200Mbps in PHY

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  1. ETRI Proposalto IEEE 802.11 TGn Heejung Yu, Taehyun Jeon, Sok-Kyu Lee, Myung-Soon Kim, Eun-young Choi, Seung-Ku Hwang Next Generation Wireless LAN Research Team ETRI {heejung, thjeon, sk-lee, mskim75, eychoi, skhwang}@etri.re.kr Heejung Yu, ETRI

  2. Contents • Proposed technologies for >200Mbps in PHY • MIMO-OFDM • Dual band • Detail Standard • Simulation Results • Conclusions Heejung Yu, ETRI

  3. Proposed technologies for >200Mbps in PHY Heejung Yu, ETRI

  4. Candidate technologies • Legacy IEEE 802.11a => 20MHz BW, 54Mbps • To achieve more than 100Mbps at the top of the MAC SAP, we need x3 or x4 data rate. • Depending on MAC efficiency • To extend x4 transmission • MIMO (improve spectral efficiency) • Bandwidth extension • High order modulation • High rate coding Heejung Yu, ETRI

  5. MIMO • Data rate can be increased with the number of Tx antennas. • We have some problem in using 3 and more stream. • Implementation complexity • Limitation on antenna spacing, high MIMO channel correlation can be a problem. • So, we cannot fully rely on the MIMO technology for 3 or 4x data rate. Heejung Yu, ETRI

  6. 64 subcarrier 64 subcarrier 64 subcarrier 64 subcarrier 40MHz xxx subcarrier 40MHz 40MHz Bandwidth Extension • Clock doubling • Dual band • New OFDM parameter 20MHz Heejung Yu, ETRI

  7. Bandwidth Extension • Clock doubling • 802.11a modem with clock switching function • Protection mechanism for compatibility • Dual band • 802.11a modem (2 units) or 802.11a modem with some change( using 128 point FFT) • Compatible with legacy 802.11a (refer specification part) • New OFDM parameter • 802.11a + new modem with new OFDM parameters( # of subcarrier, # of CP, etc.) • Protection mechanism for compatibility Heejung Yu, ETRI

  8. Dual-band • Merits • More flexible implementation • We extend threefold, fourfold BW systematically by increasing number of FFT or FFT size. • Compatible preamble and SIGNAL field is possible. • More robust to DC-offset (11 DC-carrier) • Demerits • Reduce the number of channel • In some countries, only 20MHz channel usage is allowed Heejung Yu, ETRI

  9. Max. data rate (mandatory) • # of Tx and Rx antennas = 3 • We use 2 Tx antennas out of 3 antennas (include Tx antenna selection option) • # of Tx streams (MIMO gain) = 2 • Dual-band (data rate gain) = 2 • Achievable Data Rate = 2 x 2 x (legacy rate) = 216Mbps • In optional mode, 288Mbps (256-QAM, 3/4 code rate) is possible. Heejung Yu, ETRI

  10. Details of ETRI PHY specification Heejung Yu, ETRI

  11. Main features • Compatible with IEEE 802.11a • Bandwidth : 20 or 40MHz • Multiple antennas : 2 Tx antennas • 3 Rx antennas are recommended. • Tx antenna selection is available. • Modulation : Legacy OFDM, SDM-OFDM, STBC-OFDM • Data Rate • 20MHz BW:6,9,12,18,24,36,48,54,72,96,108,128,144 Mbps • 40MHz BW : doubled Heejung Yu, ETRI

  12. TXVECTOR, RXVECTOR • BANDWIDTH and MODE are added in TX/RX VECTOR • BANDWIDTH : PHY can use consecutive two 20MHz band for higher data rate. • MODE : transmission scheme • Legacy OFDM • SDM-OFDM (Spatial Division Multiplexing) • STBC-OFDM (Space-Time Block Code) Heejung Yu, ETRI

  13. Frame Format • Legacy OFDM • STBC-OFDM, SDM-OFDM Heejung Yu, ETRI

  14. PCLP Preambles • Legacy OFDM • STBC-OFDM, SDM-OFDM Even Even Even Odd Odd Odd Odd Even Heejung Yu, ETRI

  15. Preamble Pattern(Single Antenna Single Band) • Short preamble • Long preamble Heejung Yu, ETRI

  16. Preamble Pattern(Dual Antenna Single Band) • Short preamble • (Ant 0 : even subcarriers, Ant 1 : odd subcarriers) • Ant 0 • Ant 1 • Long preamble • (Ant 0 : even subcarriers, Ant 1 : odd subcarriers) • Ant 0 • Ant 1 Heejung Yu, ETRI

  17. Preamble Pattern(Single Antenna Dual Band) • Short preamble (concatenation of single band preambles) • Long preamble (concatenation of single band preambles) Heejung Yu, ETRI

  18. Preamble Pattern(Dual Antenna Dual Band) • Short preamble (concatenation of single band preambles) • Ant 0 • Ant 1 • Long preamble (concatenation of single band preambles) • Ant 0 • Ant 1 Heejung Yu, ETRI

  19. Preamble Properties • Repetition property is maintained • Same auto-correlation property • PAPR for single band preamble • Legacy-OFDM mode : 2.09dB (short), 3.17dB(long) • SDM/STBC-OFDM mode • Antenna 0 : 4.69dB(short), 5.58dB(long) • Antenna 1 : 4.69dB(short), 5.85dB(long) • PAPR for dual band preamble • Legacy-OFDM mode : 5.10dB (short), 6.18dB(long) • SDM/STBC-OFDM mode • Antenna 0 : 5.80dB(short), 7.05dB(long) • Antenna 1 : 5.80dB(short), 8.86dB(long) • Cross correlation between Tx antenna • Orthogonal preamble by using subcarriers alternatively Heejung Yu, ETRI

  20. SIGNAL bit assignment • 802.11n device uses the R4 to distinguish the legacy and multi-antenna • R4 = 1 : legacy OFDM • R4 = 0 : multi-antenna (STBC-OFDM, SDM-OFDM) • 802.11n device uses the reserved bit to distinguish STBC-OFDM and SDM-OFDM. • For legacy device, discard • For Alamouti code, A = 0 • For SDM, A = 1 Heejung Yu, ETRI

  21. RATE and ANTENNA field definitionRate-dependant parameters Heejung Yu, ETRI

  22. RATE and ANTENNA field definitionRate-dependant parameters Heejung Yu, ETRI

  23. RATE and ANTENNA field definitionRate-dependant parameters • These parameters are based on single band. • NBPSC : Coded bits per subcarrier • NCBPS : Coded bits per OFDM symbol • NDBPS : Data bits per OFDM symbol Heejung Yu, ETRI

  24. SIGNAL Field Modulation • Single Antenna single band (same as 802.11a) • Subcarrier allocation : • Dual antenna single band • Subcarrier allocation : • Single antenna dual band • Subcarrier allocation : • Dual antenna dual band • Subcarrier allocation : Heejung Yu, ETRI

  25. DATA Field (changed parts)Pad bits, Data arbitrator • Pad bits • To make DATA bits to be an integer multiple of NDBPS (Legacy OFDM, SDM-OFDM), or 2NDBPS(STBC-OFDM). • Data arbitrator • Receive one byte from MAC, even numbered 4 bits directed to scrambler(channel) 0 and odd numbered 4 bits to scrambler(channel) 1. Heejung Yu, ETRI

  26. DATA Field (changed parts)Interleaving • Interleaver : block interleaver • Interleaver size : NCBPS(single band), 2NCBPS(dual band) • Interleaver (Single band. In dual band, all NCBPS’sare replaced with 2NCBPS) • Deinterleaver(Single band. In dual band, all NCBPS’sare replaced with 2NCBPS) Heejung Yu, ETRI

  27. DATA Field (changed parts)Modulation mapping • Optional 256-QAM is added to 802.11a modulations • Kmod = Heejung Yu, ETRI

  28. DATA Field (changed parts)Antenna arbitration • Legacy OFDM • Single band case • Dual band case Heejung Yu, ETRI

  29. DATA Field (changed parts)Antenna arbitration • STBC-OFDM • Single band case • Ant 0 • Ant 1 • Dual band case • Ant 0 Ant1 Heejung Yu, ETRI

  30. DATA Field (changed parts)Antenna arbitration • SDM-OFDM • Single band case • Ant 0 • Ant 0 • Dual band case • Ant 0 • Ant 1 Heejung Yu, ETRI

  31. DATA Field (changed parts)OFDM Modulation • OFDM modulation for i-th antenna j-th channel • One OFDM symbol modulation • Concatenation of multiple OFDM symbols • OFDM modulation for dual band Heejung Yu, ETRI

  32. Transmitter structure • Using one 128 (I)FFT structure Heejung Yu, ETRI

  33. Transmitter structure • Modified structure with 64 point FFT Heejung Yu, ETRI

  34. Transmit spectrum • Tx spectrum for dual band is the extended version of legacy 11a spectrum Heejung Yu, ETRI

  35. Simulation Results Heejung Yu, ETRI

  36. Detection Method • In Legacy OFDM, Maximal Ratio Combining method is used. • In SDM-OFDM, Zero Forcing scheme is used. • The simplest and reasonable method considering both implementation complexity and performance • In higher order modulation and smaller number of Nt case, SNR loss between ZF and ML (Maximum Likelihood) becomes lower. Heejung Yu, ETRI

  37. AWGN performance • 1 Tx, 1 Rx antenna (only for Legacy mode) Heejung Yu, ETRI

  38. AWGN performance • 2 Tx, 2 Rx antennas Heejung Yu, ETRI

  39. AWGN performance • 2 (out of 3) Tx, 3 Rx antennas (We select 2 antennas out of 3 Tx antennas.) Heejung Yu, ETRI

  40. AWGN performance • 2 (out of 4) Tx, 4 Rx antennas (We select 2 antennas out of 4 Tx antennas.) In AWGN channel, Nr  => detection SNR  (no diversity gain) => (Nr = 4) has 3dB gain over (Nr = 2). Nt , SNR per info. bit  (to normalize total Tx power) => 54Mbps has 3dB gain over 108Mbps. Heejung Yu, ETRI

  41. Non-AWGN performance • 2 Tx and 3 Rx antennas are used. • In Legacy mode, randomly selected single Tx antenna is used. • Antenna spacing • Tx spacing : 1 wavelength (2 out of 3 antennas are used.) • Rx spacing : ½ wavelength (3 antennas) • Power amplifier backoff : 10dB (p=3 RAPP mode) • CFO and timing offset : -13.675ppm • Channel model : B, D (with fluorescent effect), and E (NLOS) • Packet size : 1000 bytes Heejung Yu, ETRI

  42. Non-AWGN performance • Channel model B (NLOS) Heejung Yu, ETRI

  43. Non-AWGN performance • Channel Model D (NLOS) Heejung Yu, ETRI

  44. Non-AWGN performance • Channel model E (NLOS) Heejung Yu, ETRI

  45. Offset effect • Channel E (NLOS) Solid : offset compensation performance Dash : zero offset performance CFO and timing tracking loop coefficients are optimized for high data rates. Heejung Yu, ETRI

  46. Offset effect • Channel E (LOS), at 50dB SNR • Constellation of 108Mbps mode with different offset values 40ppm 20ppm -20ppm -40ppm Heejung Yu, ETRI

  47. Offset effect • Channel E (LOS), at 50dB SNR • Constellation of 6Mbps mode with different offset values 40ppm 10ppm -10ppm -40ppm Heejung Yu, ETRI

  48. Conclusions Heejung Yu, ETRI

  49. Conclusions • In this proposal, MIMO-OFDM with 2 transmit antennas and dual band scheme are used for higher data rate (throughput). • SDM-OFDM : double data rate • Dual band : double data rate • STBC-OFDM : increase link reliability (optional) • To satisfy the FR (100Mbps throughput in 20MBz), 256-QAM is added (144Mbps in 20MHz band) • Compatible with 802.11a (Preamble and SINGAL structure) Heejung Yu, ETRI

  50. Appendix Heejung Yu, ETRI

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