Sept 2004 doc IEEE 802 11 040 abcr
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 HNS Proposal for 802. 11 n Physical Layer Mustafa Eroz, Feng-Wen Sun, & Lin-Nan Lee meroz@hns. com fsun@hns. com llee@hns. com Hughes Network Systems 11717 Exploration Lane Germantown, MD 20876 Submission 1 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Proposal Topics • • • PHY and Air Interface Description Supported Rate Set (mandatory/optional) Proposed Scheme Preamble Design Approach Spectral Mask with non-linear model Short Block Length LDPC Performance Curves Submission 2 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 PHY and Air Interface • The air interface is built upon IEEE 802. 11 a (1999) PHY specifications and associated overhead – OFDM Modulation with PSK and QAM – (20/64) MHz subcarrier spacing, 52 Sub-carrier set • 48 data carriers and 4 pilots (center location not used) – Preamble modified for MIMO • Compatible with 802. 11 a air-interface – 1, 2, 3 and 4 TX antenna for high throughput modes – One TX Antenna mode for legacy STA support – PHY-MAC maximum efficiency of 60% assumed • In AP-STA test, 100 Mbps at MSDU 167 Mbps at PHY Submission 3 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 802. 11 n Rate Set Supported No. of TX Antennas Modulation Type 4 BPSK 3 Info. Bytes per channel. use PHY Info Rate (Mbps) MAC Info Rate (Mbps) @60% of PHY Rate 1/2 12 24 14. 4 2/3 18 36 21. 6 384 1/2 24 48 28. 8 8 -PSK 576 1/2 36 72 43. 2 16 -QAM 768 1/2 48 96 57. 6 32 -QAM 960 1/2 60 120 72 64 -QAM 1152 1/2 72 144 86. 4 2/3 96 192 115. 2 1/2 18 36 21. 6 2/3 24 48 28. 8 1/2 36 72 43. 2 2/3 48 96 57. 6 1/2 56 112 67. 2 2/3 72 144 86. 4 16 -QAM 64 -QAM Submission 192 Code Rate QPSK 2 Transmit bits per channel use 288 576 864 BPSK 96 1/2 6 12 7. 2 QPSK 192 1/2 12 24 14. 4 8 -PSK 288 1/2 18 36 21. 6 16 -QAM 384 1/2 24 48 28. 8 32 -QAM 480 1/2 30 60 36 64 -QAM 576 1/2 36 72 43. 2 2/3 48 96 57. 6 4 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Proposed PHY Layer Block Diagram (Tx) Information bits In x = [x 1 x 2… xn]T MIMO LDPC Block Formatter MIMO Preambles x 1 LDPC Encoder Insert Pilots PSK/QAM Modulator OFDM Symbol Generator (frequency domain) Submission PA = Rapp’s model, p=3 IFFT Prefix Digital-RF-PA Preamble Attachment & 1: n OFDM Symbol Demux xn 5 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Proposed PHY Layer Block Diagram (Rx) y = [y 1… ym]T LDPC DECODER FFT Remove P/fix RF-Digital y 1 OFDM Demod MAP Detector Reconstruct PSDU ym out Information bits Submission Channel Estimates Prefix Timing/Channel Estimation/Symbol Timing / Frequency/Phase Acquisition/Tracking 6 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Key Elements of the Physical Layer Proposal • A family of high-performance FEC codes optimized for the application – Capable of decoding at information rate close to 200 Mbps with modest implementation complexity – Exceptional performance in fading channel at near 10 -2 packet error rate – Flexibility to support short as well as long packets without compromise in throughput at MAC layer • An 802. 11 a/b/g compatible preamble design supports up to 4 Tx antennas Submission 7 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Considerations for FEC Code Selection • With their inherent parallel architecture, Low-Density Parity Check (LDPC) decoders are more suitable for high-speed operation than turbo decoders • LDPC codes with block length equal to integer number of OFDM channel uses maximize efficiency by eliminating unnecessary padding or shortening of a code block • At one (1) percent or higher block error rates, the performance gap between short and long block codes diminishes • Longer codes are extremely inefficient for the transmission of short bursts or the last block of a long burst due to need of padding or shortening • Short burst traffic cannot be ignored, as applications such as Vo. IP and video games are important • Decoders for short LDPC codes are much simpler to implement than long LDPC codes Submission 8 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Our FEC Choice • A base LDPC code of block length 192 bits (4 x number of data carriers in an OFDM symbol) • A simple means to extend block length with minimal performance compromises to any length in increment of 192 bits. Submission 9 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 LDPC Details • Code rates of 1/2 and 2/3 are sufficient to cover a broad range of throughput due to various choice of modulation schemes such as QPSK, 8 -PSK, 16 -QAM, 32 -QAM and 64 -QAM. • Base LDPC codes have a coded block length of 192 bits with the following parity check matrix format which ensures simple encoding where B Submission é 1 ù ê ú ê 1 1 ú ê ú 1 1 =ê ú 1 1 ê ú ê 1 1 ú ê ú 1 1ûú ëê 0 0 10 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 LDPC Details Parity check on k bits • The A sub-matrix has a constant column weight of 3. • The small column weight ensures simpler decoding while performance is not sacrificed on the fading channel. • Larger block sizes are supported by simply concatenating base LDPC codes and adding one extra base block of parity check on select LDPC bits. Submission x x x x LDPC Block 1 x x x x LDPC Block 2 x x x x LDPC Block 3 : : : k < or = m x x x x LDPC Block m x x x x Parity Check Block 11 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Preamble/ Pilot Approach to HNS PHY Proposal • We base our approach on the 802. 11 a OFDM Specifications – There are 53 frequency bins in 802. 11 a OFDM • Indexed -26, -25, …-1, 0, 1 … 25 and 26. • The zero index (frequency location) is not used. – -21, -7, 7 and 21 are used as Pilots during data transmission • Modulated by 127 bit long PN code (x 7 + x 4 + 1) on the ‘ 1 st’ Antenna • Use the same frequency set on each of the TX Antennas • Use different phase of the 127 bit PN (quasi-orthogonal) on each of the other Antennas – 48 remaining bins are used for data transmission • Each TX antenna uses the same 48 sub-carrier set but with different data stream • The transmission commences with an 802. 11 a specified preamble called the PLCP preamble – – Submission 8 usec ‘short’ preamble with only 12 sub-carriers active 8 usec ‘long’ preamble all sub-carriers active per a specified 52 bit sequence Short preamble empty bins are used by secondary antennas 4 TX supported 52 bits of the Long preamble are transmitted sequentially over the TX antenna set 12 Mustafa Eroz, Hughes Network Systems
Preamble Duration = 8 usec Sept 2004 Preamble Approach for Multiple TX Antennas 1+ j -1 - j 1+ j -1 - j 1+ j Δf IEEE 802. 11 a Standard Short Training Preamble (i. e. first 8 usec) from one TX Antenna - 26 Preamble Duration = 8 usec doc. : IEEE 802. 11 -04/0 abcr 0 + 26 First Antena (s 0) Other Antennas (s 1, s 2 and s 3) 1+ j -1 - j 1+ j 1. 0 -1 - j 1+ j Preamble duration = 8 usec Δf Proposed: Short Training Preamble (First 8 usec) over one ‘First’ and Three ‘Other’ Antennas 1 1 -1 -1 1 1. . . (-26) . . . 0. 3125 MHz L-26, 26 per section 17. 3. 3 Std 802. 11 a -1999 . . . -1 1 1 (26) Δf Proposed: Long Preamble Sequence Spread Sequentially over the Four TX Antennas Submission 13 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Simulation Conditions • 2, 3 and 4 TX antenna cases simulated • AWGN with recommended channel matrices simulated • NLOS Model for B, D and E used in simulation • Florescent light effects included for Model D&E • Antenna Spacing of half-wavelength used Submission 14 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Transmit Spectrum of the OFDM Signal Through PA Model OFDM Signal 16 -QAM after Non-linear Amplifier IBO = 8 d. B OFDM Signal 16 -QAM after Non-linear Amplifier IBO = 3 d. B • Fully compliant with spectral mask • Essentially the same spectral density for 64 -QAM Submission 15 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Simulation Methodology • Coding and BB TX module – Information bits encoded into 192 bit LDPC code blocks – LDPC code blocks extended to longer code blocks as described previously – generate PSK/QAM modulation symbols • OFDM and Channel Model – Arranges into transmission vector for 2, 3 or 4 TX antennas – Converts modulation symbol stream into OFDM symbols with cyclic prefix, 4 usec/OFDM Symbol – Runs through channel model – Detects OFDM signals on each of the Rx antenna – Delivers demodulated samples from each Rx antenna to MAP detector Submission 16 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Performance for Channel Model B 1. 0 E+00 Packet Error Rate QPSK R=1/2 3 x 3, QPSK R=2/3 16 QAM R=1/2 4 x 4 2 x 2 1. 0 E-01 2 x 2 3 x 3 2 x 2 1. 0 E-02 4 x 4, 8 PSK R=1/2 3 x 3, 16 QAM R=2/3 64 QAM, R=2/3 1. 0 E-03 2. 0 Submission 6. 0 10. 0 14. 0 18. 0 Es/No (d. B) 17 22. 0 26. 0 30. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Performance for Channel Model D Packet Error Rate 1. 0 E+00 3 x 3, QPSK 16 QAM 2 x 2 QPSK R=2/3 R=1/2 3 x 3 1. 0 E-01 2 x 2 4 x 4 1. 0 E-02 4 x 4, 8 PSK R=1/2 3 x 3, 16 QAM R=2/3 64 QAM R=2/3 2 x 2 1. 0 E-03 4 x 4 2. 0 Submission 6. 0 10. 0 14. 0 18. 0 Es/No (d. B) 18 22. 0 26. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Performance for Channel Model E 1. 0 E+00 Packet Error Rate 4 x 4 QPSK R=1/2 1. 0 E-01 3 x 3, QPSK R=2/3 16 QAM R=1/2 4 x 4 2 x 2 1. 0 E-02 4 x 4, 8 PSK R=1/2 3 x 3 4 x 4, 64 QAM R=2/3 2 x 2 1. 0 E-03 2. 0 Submission 3 x 3, 16 QAM R=2/3 6. 0 10. 0 14. 0 18. 0 Es/No (d. B) 19 22. 0 26. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 AWGN Channel Performance Submission 20 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Channel Model B 1. 0 E+00 4 x 4, QPSK R=1/2 Packet Error Rate One LDPC Block Append a parity block for every 10 LDPC block 1. 0 E-01 1. 0 E-02 1. 0 E-03 6. 0 Submission 7. 0 8. 0 9. 0 10. 0 Es/No (d. B) 21 11. 0 12. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Channel Model D Packet Error Rate 1. 0 E+00 4 x 4, QPSK R=1/2 One LDPC block 1. 0 E-01 Append a parity block for every 10 LDPC block 1. 0 E-02 1. 0 E-03 1. 0 E-04 4. 0 Submission 5. 0 6. 0 7. 0 8. 0 Es/No (d. B) 22 9. 0 10. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Channel Model E Packet Error Rate 1. 0 E+00 4 x 4, QPSK R=1/2 One LDPC block Append a parity block for every 10 LDPC block 1. 0 E-01 1. 0 E-02 1. 0 E-03 4. 0 Submission 5. 0 6. 0 7. 0 8. 0 Es/No (d. B) 23 9. 0 10. 0 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Required Es/No vs PHY Data Speed Submission 24 Mustafa Eroz, Hughes Network Systems
Sept 2004 doc. : IEEE 802. 11 -04/0 abcr 0 Conclusion • All the design requirements of 802. 11 n met with the PHY partial proposal – FEC and MIMO alone achieve the goal – Compatible with current MAC, expect to be compatible with any MAC proposal. – In the interest of best overall proposal, PHY needs to be evaluated separately and then combined with the best MAC. • Capable of supporting both 1 x and 2 x 20 MHz approaches. • Extremely simple to implement • Highly efficient due to its flexible construction technique Submission 25 Mustafa Eroz, Hughes Network Systems
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