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Partial Proposal for 802.11n: ITRI Preamble Specification

This proposal presents the system block diagram and the proposed preamble structure for the 802.11n standard. It includes the construction and purposes of short and long training symbols, as well as numerical results. The proposal also considers backward compatibility and discusses the construction of short training symbols.

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Partial Proposal for 802.11n: ITRI Preamble Specification

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  1. Partial Proposal for 802.11n: ITRI Preamble Specification Yung-Yih Jian, Pangan Ting, Wei-Ping Chuang, Chun-Chun Kuo, Chang-Lung Hsiao Industrial Technology Research Institute (ITRI) Computer and Communications Research Laboratories (CCL) Bldg.14, 195 Sec. 4, Chung Hsing Rd. Chutung, Hsinchu, Taiwan 310, R.O.C Phone : +886-3-5914707 Fax : +886-3-5820371 e-Mail: {yyjian, pating, joeChuang, godeman, clhsiao}@itri.org.tw Wei-De Wu National Tsing Hua University Institute of Communications Engineering welder@micro.ee.nthu.edu.tw Chih-Kai Chen Stanford University Department of Electrical Engineering chihkai@stanford.edu Pangan Ting, CCL/ITRI

  2. Outline • System block diagram • Proposed preamble structure • Short training symbol • Purpose of short training symbol • Construction of short training symbol • Numerical Results • Long training symbol • Purpose of long training symbol • Construction of long training symbol • Numerical Results • Conclusion Pangan Ting, CCL/ITRI

  3. IFFT IFFT CP CP Remove CP Remove CP FFT FFT System block diagram ( 2 x 2 case ) Pangan Ting, CCL/ITRI

  4. IFFT IFFT IFFT CP CP CP Remove CP Remove CP Remove CP FFT FFT FFT System block diagram ( 3 x 3 case ) Pangan Ting, CCL/ITRI

  5. IFFT IFFT IFFT IFFT CP CP CP CP Remove CP Remove CP Remove CP Remove CP FFT FFT FFT FFT System block diagram ( 4 x 4 case ) Pangan Ting, CCL/ITRI

  6. 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n LTS31 802.11n LTS32 802.11n LTS33 802.11n LTS34 Tx3 MIMO frame detect, MIMO AGC Coarse freq.offset estimation, MIMO timingsynchronization Channel estimation, fine frequency offset estimation 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n LTS31 802.11n LTS32 802.11n LTS33 802.11n LTS34 Tx1 Proposed Preamble Structure ( 2 x 2 case ) 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n LTS11 802.11n LTS12 Tx1 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n LTS21 802.11n LTS22 Tx2 MIMO frame detect, MIMO AGC Coarse freq. offset estimation, MIMO timingsynchronization Channel estimation, fine frequency offset estimation Proposed Preamble Structure ( 3 x 3 case ) 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n LTS31 802.11n LTS32 802.11n LTS33 802.11n LTS34 Tx2 Pangan Ting, CCL/ITRI

  7. 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n STS3 802.11n LTS31 802.11n LTS32 802.11n LTS33 802.11n LTS34 Tx3 MIMO frame detect, MIMO AGC Coarse freq.offset estimation, MIMO timingsynchronization Channel estimation, fine frequency offset estimation Proposed Preamble Structure ( 4 x 4 case ) 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n STS1 802.11n LTS11 802.11n LTS12 802.11n LTS13 802.11n LTS14 Tx1 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n STS2 802.11n LTS21 802.11n LTS22 802.11n LTS23 802.11n LTS24 Tx2 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n STS4 802.11n LTS41 802.11n LTS42 802.11n LTS43 802.11n LTS44 Tx4 Overlapped preambles structure is proposed Lower overhead caused by preamble Pangan Ting, CCL/ITRI

  8. Preamble Parameters Pangan Ting, CCL/ITRI

  9. Short Training Symbol (STS) • Purposes of STS • Frame detection, AGC and Coarse frequency offset estimation • The new STSs from different Tx antenna have zero cross-correlation. • The preamble consists of several concatenated copies. • Backward compatibility • Assume there exists a protection mechanism similar to the case of 11g and 11b. • We propose that the new STSs should not be detected by legacy systems. • The new STS should have the period longer than the legacy systems. Pangan Ting, CCL/ITRI

  10. Received short training symbol: ( )* ( )* ( )* ( )* X X X X + Find the STSs such that when received by 11a STA Backward Compatibility Consideration • Without considering channel and noise, the STSs of MIMO packet received by 11a system can be written as • Low detection probability for 11a systems Conventional frame detection algorithm of 11a systems Where Mt denotes the number of transmit antenna Pangan Ting, CCL/ITRI

  11. Construction of Short Training Symbols • The properties of the proposed STSs • Period of 32 samples • Zero cross-correlation of the STSs • Low detection probability for 11a systems • The short training symbols are designed in frequency domain. • Time domain waveform of the ith STS is obtained by Pangan Ting, CCL/ITRI

  12. Proposed Short Training Symbol ( 3x3 case ) Pangan Ting, CCL/ITRI

  13. Proposed Short Training Symbol ( 4x4 case ) Pangan Ting, CCL/ITRI

  14. Proposed Time-Domain STS (1/2) Pangan Ting, CCL/ITRI

  15. Proposed Time-Domain STS (2/2) Pangan Ting, CCL/ITRI

  16. Numerical Results • Since the nonzero tones of the STSs are disjoint, the cross-correlation of each pair of STSs is 0. • Each STS has a period of 32 samples ( 1.6 us ) in time domain. Pangan Ting, CCL/ITRI

  17. ( )* ( )* ( )* ( )* X X X X + Frame Detection Scenarios (1/2) Received short training symbol: Decision Moving Average Threshold Conventional frame detection algorithm of 11a systems Pangan Ting, CCL/ITRI

  18. Frame Detection Scenarios (2/2) Decision Pangan Ting, CCL/ITRI

  19. Numerical Results The detection probability of the proposed STSs ( 3 x 3 mode ) in a 11a receiver over channel B,D and E which is tested over 1000 channel realizations. The detection probability of the proposed STSs ( 4 x 4 mode ) in a 11a receiver over channel B,D and E which is tested over 1000 channel realizations. Pangan Ting, CCL/ITRI

  20. Numerical Results The detection probability of the proposed STSs ( 3 x 3 mode ) in a 11n receiver over channel B,D and E which is tested over 1000 channel realizations. The detection probability of the proposed STSs ( 4 x 4 mode ) in a 11n receiver over channel B,D and E which is tested over 1000 channel realizations. Pangan Ting, CCL/ITRI

  21. Long Training Symbol (LTS) • Purposes of LTS • fine frequency offset estimation, Channel estimation • The proposed LTS • 2 x 2 system: the LTS occupies 2 OFDM symbol periods • 3 x 3 system: the LTS occupies 4 OFDM symbol periods • 4 x 4 system: the LTS occupies 4 OFDM symbol periods Pangan Ting, CCL/ITRI

  22. L f 2 x 2 Mode: 0.8 µs 3.2 µs 0.8 µs 3.2 µs Tx 1 CP IFFT(L) CP IFFT(L) CP IFFT(L) CP IFFT(L) CP IFFT(L) CP IFFT(L) t Tx 2 CP IFFT(L) CP W21IFFT(L) CP IFFT(L) CP W41IFFT(L) CP W42IFFT(L) CP W43IFFT(L) CP IFFT(L) CP W42IFFT(L) CP W44IFFT(L) CP W46IFFT(L) 3 x 3 Mode: Tx 1 0.8 µs 3.2 µs Tx 2 t Tx 3 CP IFFT(L) CP IFFT(L) CP IFFT(L) CP IFFT(L) CP IFFT(L) CP W41IFFT(L) CP W42IFFT(L) CP W43IFFT(L) 4 x 4 Mode: CP IFFT(L) CP W42IFFT(L) CP W44IFFT(L) CP W46IFFT(L) CP IFFT(L) CP W43IFFT(L) CP W46IFFT(L) CP W49IFFT(L) Tx 1 Tx 2 Tx 3 t Tx 4 The Structure of Proposed LTS Pangan Ting, CCL/ITRI

  23. Long Training Symbol (LTS) • The proposed LTSs are constructed with a basis sequence L. • We choose L the same as the long training sequence described in 11a • The properties of the proposed LTSs are determined by L. • With the proposed LTSs, the receiver can effectively and efficiently estimate the frequency domain responses of MIMO channel. Pangan Ting, CCL/ITRI

  24. Proposed Frequency-Domain LTS Pangan Ting, CCL/ITRI

  25. Proposed Time-Domain LTS (w/o CP) Pangan Ting, CCL/ITRI

  26. Proposed Time-Domain LTS (w/ CP) Pangan Ting, CCL/ITRI

  27. 0 0 10 10 -1 -1 10 10 -2 -2 10 10 -3 -3 10 10 -4 -4 10 10 5 10 15 20 25 30 35 5 10 15 20 25 30 35 Numerical Results The MSE of the channel estimates with proposed LTSs for 3x3 mode over channel B, D and E. The MSE of the channel estimates with proposed LTSs for 4x4 mode over channel B, D and E. 11n Channel B for 3x3 system 11n Channel B for 4x4 system 11n Channel D for 3x3 system 11n Channel D for 4x4 system 11n Channel E for 3x3 system 11n Channel E for 4x4 system MSE per nonzero subcarrier MSE per nonzero subcarrier averaged received SNR averaged received SNR Pangan Ting, CCL/ITRI

  28. Conclusion • We propose STSs with the properties of • Period of 32 samples • Zero cross-correlation of the STSs • Low detection probability for 11a systems • With the proposed LTSs, the receiver can effectively and efficiently estimate the frequency domain responses of MIMO channel. Pangan Ting, CCL/ITRI

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