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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [MPSK Modulation for PHY Layer Proposal for Chinese Band] Date Submitted: [25−Oct−2007] Source: [Liang Li, T.T. Liu, ChenYang Yang, Pei Liu, Bill Zhang] Company: [Vinno Technologies Inc, Hisilicon Inc. ASTRI Inc.] Address: [Suite 402, Building D, No.2 Shangdi Xinxi Lu, Beijing 100085, China] Voice:[8610-82782373], FAX: [8610-82893004] E−Mail: [liangli@vinnotech.com, cyyangbuaa@vip.sina.com] Re: [802.15.4c] Abstract: [ ] Purpose: [To encourage discussion in 802.15.4c] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Liang Li (Vinno), C.Y. Yang (BUAA)

  2. Proposal • A new PHY Proposal for low-rate WPAN that employs the MPSK modulation scheme with new DSSS sequences: • The MPSK tech is adopted as the basic modulation of communication in LR-WPAN at 780mhz • New DSSS sequences: 16 sequences for 4-bit mapping. • Data rate = 250Kbps. • Channel separation = 2MHz. The 1st null-null bandwidth = 750KHz. • Pt < 10mw. Liang Li (Vinno), C.Y. Yang (BUAA)

  3. The Important Operation Coefficients Fc=780, 782, 784, 786 MHz The Transmit Path (I or Q Paths) Liang Li (Vinno), C.Y. Yang (BUAA)

  4. DSSS Mapping (Symbol to Chips) • The Direct Sequence Spread Spectrum (DSSS) tech is applied • 16 orthogonal spreading sequences are designed to map 4 information bits. The base sequence is a 16-length chirp sequence and the other 15 sequences are its cyclic shifts. Liang Li (Vinno), C.Y. Yang (BUAA)

  5. Pre-Processing • Remove DC component The DC component of one base sequence is • Subtract ADC from each chip directly in the processing, all DC components of PPDU can be mitigated. Liang Li (Vinno), C.Y. Yang (BUAA)

  6. PPDY Packet • The Preamble sequence is defined as: 8 symbols [0X00 0X00 0X00 0X00](128s), • The SFD sequence is defined as: 2 symbols [0XA7](32s). Liang Li (Vinno), C.Y. Yang (BUAA)

  7. 1 0.9 0.8 0.7 0.6 0.5 Auto-Correlation Property 0.4 0.3 0.2 0.1 0 -8 -6 -4 -2 0 2 4 6 8 t/Tc Spreading Sequences Advantage(1) • Distinguish auto-correlation property • Obtain better synchronization performance. • Reduce inter-chip interference in multipath environments. Liang Li (Vinno), C.Y. Yang (BUAA)

  8. Spreading Sequences Advantage(2) • The correlation characteristic with frequency offset s(t) —preamble — time delay f—frequency offset Liang Li (Vinno), C.Y. Yang (BUAA)

  9. Spreading Sequences Advantage(2) • Distinguish correlation characteristic • The Frequency offset is consist of to integral frequency offset and fractional frequency offset; • The correlation characteristic is repeated on integral frequency offsets; • The impact of integral frequency offset may be treated as that of the time delay, and have no effect on the timing; • Only the fractional frequency offset affects the correlation characteristic. where kf1 is the integer frequency offset Liang Li (Vinno), C.Y. Yang (BUAA)

  10. 0 1 0.8 -10 0.6 -20 Pluse Shape 0.4 PSD (dB) -30 0.2 -40 0 -50 -0.2 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 -60 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 t [Tc] f [MHz] Pulse Shaping Filter The Pulse Shaping Filter on I and Q paths is Raised-Cosine (α=0.5 ): Liang Li (Vinno), C.Y. Yang (BUAA)

  11. 1 0.5 Real 0 -0.5 -1 0 2 4 6 8 10 12 14 16 t / Tc 1 0.5 Imag 0 MPSK RC-0.5 0 PSD MASK -36dBm -0.5 -1 -10 0 2 4 6 8 10 12 14 16 t / Tc (f) [dBm] -20 BW=100KHz -30 PSD -40 -50 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 f [MHz] Promoted Communication Tech in LR-WPAN • The Transmit Waveforms (I and Q) and Spectrum are: • ( Condition: RC shaping filter, Random chip sequence, 100 kHz resolution band width, 0 dBm TX-power ) Liang Li (Vinno), C.Y. Yang (BUAA)

  12. PSD in the Band • PSD Requirements in Band • Minimum Receiver Jamming Resistance Requirement Liang Li (Vinno), C.Y. Yang (BUAA)

  13. EVM, and Crest factor • The Envelop is non-constant. • The EVM and Crest Factor are: (RC-0.5-pulse shaping ): Liang Li (Vinno), C.Y. Yang (BUAA)

  14. 0 10 -1 10 -2 10 -3 Sync Error Rate 10 -4 10 -5 10 -6 10 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 E /n b 0 Performance: Synchronization Performance Simulation Condition: In AWGN channel, 20 data octets in each packet, sliding-correlation algorithm is used for sync . Liang Li (Vinno), C.Y. Yang (BUAA)

  15. 0 10 MPSK (Coherent Detect) MPSK (Non-Coherent Detect) -1 10 -2 PER 10 -3 10 -4 10 4 5 6 7 8 9 10 E /N b 0 Performance: Demodulation Performance Simulation Condition: In AWGN channel, ideal synchronization, Correlation demodulation, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  16. Coherent Detect 0 10 MPSK (ideal) MPSK (Sync) O-QPSK (ideal) O-QPSK (Sync) -1 10 -2 PER 10 -3 10 -4 10 4 5 6 7 8 9 10 E /N b 0 Performance Comparison Simulation Condition: In AWGN channel, Coherent Correlation demodulation, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  17. Non-Coherent Detect 0 10 MPSK (ideal) MPSK (Sync) O-QPSK (ideal) O-QPSK (Sync) -1 10 -2 PER 10 -3 10 -4 10 4 5 6 7 8 9 10 E /N b 0 Performance Comparison Simulation Condition: In AWGN channel, Non-coherent Correlation demodulation, 20-octe data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  18. 0 10 MPSK 0ppm MPSK 20ppm MPSK 40ppm MPSK 60ppm -1 10 -2 PER 10 -3 10 -4 10 4 5 6 7 8 9 10 E /N b 0 Performance: Performance under Sync and Freq-offset Simulation Condition: In AWGN channel, sliding correlationsync method and fractional freq-offset estimation and correction, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  19. Performance in Multipath Channel • Tapped-Delay-Line Channel Model • IEEE P802.15 Working Group for WPANs, Multipath Simulation Models for Sub-GHz PHY Evaluation, 15-04-0585-00-004b, Oct. 2004. • Power delay profile is exponentially declined. • Each path is independently Rayleigh fading. • The average power of the channel response over many packets is 1, but in each packet the power is varied. • Flat Fading Channel • Without rake receiver • Frequency Selective Channel • Without rake receiver Liang Li (Vinno), C.Y. Yang (BUAA)

  20. 0 10 -1 10 -2 PER 10 -3 10 -4 10 5 10 15 20 25 30 35 40 E /N b 0 Performance: Under Flat Fading Channel Simulation Condition: In the Rayleigh fading channel, Delay Spread RMS = 0ns, with synchronization, 0ppm frequency offset, Non-coherent demodulation, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  21. 0 10 -1 10 -2 PER 10 -3 10 -4 10 5 10 15 20 25 30 35 40 E /N b 0 Performance: Under Multipath Channel Simulation Condition: In the Rayleigh multipath channel, Delay Spread RMS = 250ns, with synchronization, 0ppm frequency offset, Non-coherent demodulation, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  22. 0 10 -1 10 -2 PER 10 t MPSK = 0ns rms t MPSK = 250ns rms t O-QPSK = 0ns rms -3 10 t O-QPSK = 250ns rms -4 10 5 10 15 20 25 30 35 40 E /N b 0 Performance Comparison Simulation Condition: In the Rayleigh multipath channel, Delay Spread RMS = 250ns, with synchronization, 0ppm frequency offset, Non-coherent demodulation, 20-octet data in each packet Liang Li (Vinno), C.Y. Yang (BUAA)

  23. PICS Table C.4 Radio Frequencies Liang Li (Vinno), C.Y. Yang (BUAA)

  24. Summary • Regulatory rules for China may require reduced side lobes: -36 dBm outside of the 779-787 MHz Band. • The non-coherent demodulation of MPSK-RC can achieve same performance with differential MSK-type detectors, i.e. performance is same as the OQPSK mode @ 900 MHz. • RC shaping is recommended w.r.t. EVM < 35% • The MPSK modulation are recommended as one of proposals to implement the PHY layer operation in LR-WPAN. Liang Li (Vinno), C.Y. Yang (BUAA)

  25. Backup Slides Liang Li (Vinno), C.Y. Yang (BUAA)

  26. MPSK RC-0.5 0 MPSK RC-0.8 PSD MASK -36dBm -10 a = 0.5 1 (f) [dBm] a = 0.8 -20 0.5 Real 0 BW=100KHz -0.5 -30 -1 PSD 0 2 4 6 8 10 12 14 16 -40 t / Tc 1 -50 0.5 Imag 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 f [MHz] -0.5 -1 0 2 4 6 8 10 12 14 16 t / Tc Promoted Communication Tech in LR-WPAN • The Transmit Waveforms (I and Q) and Spectrum are: • ( Condition: RC shaping filter, Random chip sequence, 100 kHz resolution band width, 0 dBm TX-power ) MPSK-RC-0.5: Crest factor (2.87dB), MPSK-RC-0.8: Crest factor (3.05dB) Liang Li (Vinno), C.Y. Yang (BUAA)

  27. Spreading Sequences Property of OQPSK • The correlation characteristicof OQPSK ones with frequency offset s(t) —preamble —time delay f—frequency offset Liang Li (Vinno), C.Y. Yang (BUAA)

  28. 0 10 -1 10 -2 PER 10 MPSK 0ppm MPSK 20ppm MPSK 40ppm MPSK 60ppm -3 10 O-QPSK 0ppm O-QPSK 20ppm O-QPSK 40ppm O-QPSK 60ppm -4 10 4 5 6 7 8 9 10 E /N b 0 Performance Comparison Simulation Condition: In AWGN channel, with sync and freq-offset estimation and correction,20 data octets in each packet Traditional freq-offset estimation method: Liang Li (Vinno), C.Y. Yang (BUAA)

  29. +1.0 1 In the linear area Vout Saturated area of PA 0.9 In the saturated area 0.8 0.7 0.6 Correlation Property Linear area of PA 0.5 0.4 0 -1.0 +1.0 Vin 0.3 0.2 0.1 0 -8 -6 -4 -2 0 2 4 6 8 t/Tc -1.0 Performance under Non-linear Power Amplifier • Correlation property with non-linear power amplifier • The model of nonlinear PA was proposed by 15.4b group in 2004 Liang Li (Vinno), C.Y. Yang (BUAA)

  30. Promoted Communication Tech in LR-WPAN • The PSD before and after PA: After PA Before PA Liang Li (Vinno), C.Y. Yang (BUAA)

  31. 0 10 MPSK (Rake) O-QPSK (Rake) MPSK (NoRake) O-QPSK (NoRake) -1 10 -2 PER 10 -3 10 -4 10 5 10 15 20 25 30 35 40 E /N b 0 Performance: In Multipath Channel Simulation Condition: In the Rayleigh multipath channel, Delay Spread RMS = 250ns, with synchronization, Non-coherent demodulation, 20 data octets in each packet Liang Li (Vinno), C.Y. Yang (BUAA)