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Enhanced E16 Code with Offset QPSK for 802.15.4b High Rate Alt-PHY

This proposal presents an enhanced E16 code with offset QPSK modulation for the IEEE 802.15.4b high rate alternative PHY standard, providing improved transmission efficiency and reduced implementation complexity.

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Enhanced E16 Code with Offset QPSK for 802.15.4b High Rate Alt-PHY

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Enhanced E16 Code with Offset QPSK for 802.15.4b High Rate Alt-PHY] Date Submitted: [13 Jan, 2004] Source: [Liang Zhang, Hongyu Gu, Liang Li, Yafei Tian, Chenyang Yang, Zhijian Hu, Yong Guan] Company: [WXZJ Inc.] Address: [2 Xinxi St, Building D, Haidian District, Beijing, China 100085 ] Voice:[86-10-139-11895301], E-Mail:[liang_1@yahoo.com] Re: [Response to the call for proposal of IEEE 802.15.4b] Abstract: [This presentation compares all proposals for the IEEE802.15.4b PHY standard.] Purpose: [Proposal to IEEE 802.15.4b Task Group] 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, WXZJ

  2. Motivation Choose DSSS code sequences that will lead to efficient transmission and low implementation complexity. Liang Li, WXZJ

  3. Six desirable properties of DSSS code sequences • All sequences contain equal number of ones and zeros • All sequences contain equal number of ones and zeros in the even numbered chips (I phase) • All sequences contain equal number of ones and zeros in the odd numbered chips (Q phase) • Total phase rotation in I / Q plane accumulates to 0 degree over a complete symbol period • The first 8 symbols are shifted versions of each other • The last 8 symbols have inverted odd numbered chips (Q phase); when compared to the 8 first symbols, have the exact inverted baseband phase Liang Li, WXZJ

  4. Decimal Symbol Binary Symbol Chip Values 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 1 2 0 1 0 0 0 0 0 0 0 1 1 1 0 1 1 1 0 1 1 1 3 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 0 0 1 0 4 0 0 1 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 5 1 0 1 0 0 1 1 0 1 1 1 0 0 0 0 1 1 1 1 0 6 1 1 1 0 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0 7 0 1 1 1 0 1 0 1 1 1 0 1 0 0 1 0 1 1 0 1 8 0 0 0 1 0 0 1 1 0 1 0 0 1 0 1 1 1 0 1 1 9 1 0 0 1 0 1 1 0 0 0 0 1 1 1 1 0 1 1 1 0 10 0 1 0 1 0 0 0 0 0 1 1 1 1 0 0 0 1 0 0 0 11 1 1 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 1 0 1 12 0 0 1 1 0 0 1 1 1 0 1 1 1 0 1 1 0 1 0 0 13 1 0 1 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 0 1 14 0 1 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 1 15 1 1 1 1 0 1 0 1 1 1 0 1 1 1 0 1 0 0 1 0 Issue: Non-zero DC value of E16 DSSS Sequence DC values Total DC values = -16 • Source doc.: IEEE 802.15-04-0314-02-004b Liang Li, WXZJ

  5. Attachment I: generation of E16 Walsh matrix W is Liang Li, WXZJ

  6. Attachment I: generation of E16 • Local sequence is 0 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0 ; • E16 is generated by correlating local sequence with Walsh Matrix W; Liang Li, WXZJ

  7. Proposed Symbol-to-Chip Mapping (Enhanced 16-chip Code Set W16) Liang Li, WXZJ

  8. Attachment II: generation of W16 Modified Walsh matrix W’ is Liang Li, WXZJ

  9. Attachment II: generation of W16 • Local sequence is 0 0 1 1 1 1 1 0 0 0 1 0 0 1 0 1 ; • W16 is generated by correlating local sequence with modified Walsh Matrix W’; Liang Li, WXZJ

  10. The Features of W16 Sequences lHaving same features of DSSS sequences of 802.15.4 std: • 1. Equal number of “0”s and “1”s in preamble sequence; • 2.The first chip is not always 0 or 1; • 3. Total DC value is 0, even though not always 0 in every sequence; • 4. The phase comes back to 0 after one symbol period. lMaintaining good characteristics of E16 sequences: • 1.Orthogonality characteristics introduced by Walsh conversion; • 2.Performance similar to that of E16 orthogonal sequences; • 3.Low complexity of correlation decoder implementation. Liang Li, WXZJ

  11. Key Parameters of W16 (1) • Bit rate of 250 kBit/s • Better orthogonal characteristic • 16 sequences for 4 bits mapping • Each consisting of 16 chips • Chip rate = 1Mchips per second • Center frequency = 915MHz; • Bandwidth, pulse shape,PAPR, frequency offset • The 1st null-null bandwidth 1.5MHz; • Half-sine pulse shape; • 0dB PAPR, same MSK scheme as 15.4, constant modulus and continuous phase,lower out-of-band emission; • PSD: 30dB lower over 2MHz-wide bandwidth, conforming to 802.15.4 std; • Frequency offset tolerance over 40ppm; Liang Li, WXZJ

  12. Key Parameters of W16 (2) • Multipath fading robustness • Achieving PER<10-2 in multipath channels of 250ns rms delay spread (channel model suggested by Paul) • Support of current RF • Support 2 MHz-wide channels as allocated in the USA and other countries • Low cost and low power consumption Liang Li, WXZJ

  13. PSD of W16 • Bandwidth, Pulse shape: • The 1st null-null bandwidth 1.5MHz; Half-sine pulse shape: • MSK modulation offers constant modulus and continuous phase; • PSD 30dB lower at 1.5MHz from center frequency. Liang Li, WXZJ

  14. W16 PSD characteristic • PSD of W16 is not affected by sampling error. • Low out-of-band emission: no need for Tx filter • Satisfies the IEEE 802.15.4 PSD requirements Source: IEEE 802.15.4 Standard Liang Li, WXZJ

  15. Auto-correlation performance Synchronization performance of W16 based on simulations: • Auto-correlation characteristics with MSK modulation in 2x sampling rate • Synchronization performance in the presence of frequency offset Liang Li, WXZJ

  16. The Auto-Correlation of W16 and En- Cobi 16 En-Cobi 16 W16 In this test, the correlations are calculated after spreading sequences are OQPSK modulated with half-sine pulse shaping. Liang Li, WXZJ

  17. Cross-correlation of received Signals of W16 and En-Cobi16 W16 En-Cobi16 (2x over sampling rate) Liang Li, WXZJ

  18. Frequency offset performance Simulation parameters & assumptions: • Rayleigh Channel model as suggested at TG4 discussions • O-QPSK + half-sine pulse shaping • 2M sampling rate (1M chips/sec) • Frequency offset from 0ppm to 40ppm • Center frequency = 915MHz • Average over 1 million Monte-Carlo simulations Notes: • Synchronization is achieved by correlating local PN with received preamble impaired by frequency offset. • Throughout this document, the perfect synchronization (no error) in a multipath environment is defined as the receiver being synchronized to the strongest path. Liang Li, WXZJ

  19. Frequency offset performance: simulations Sync performance BER performance Frequency offset affects the sync and decoding performance significantly. So, frequency offset should be considered in 154b system. Liang Li, WXZJ

  20. Proposal for preamble Preamble of 15.4 standard: The preamble field proposed here consists of at least 4 octets (prefer 6 octets). Preamble here proposed for 15.4b: Liang Li, WXZJ

  21. System performance comparison between W16 and COBI16 Simulation parameters & assumptions: • 250ns rms delay spread Rayleigh Channel model • O-QPSK modulation + half sine pulse • without frequency offset • without synchronization error • 20 octets in each packet • 10,000 packets for Monte-Carlo simulation • Non-coherent demodulation • No SFDdetection • No fading • The solid curve indicates the performance of W16andthe dash one indicates the performance of COBI16 Liang Li, WXZJ

  22. System Simulation Models Discrete exponential channel model: – Sampled version of diffuse channel model offer by Paul with 4MHz sampling rate; –At least 10000 random channel realizations; –PER calculated on 20 bytes PPDUs with preamble. Liang Li, WXZJ

  23. AWGN: Ideal Sync. vs. Correlation Sync. Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Frame Detection: No SFD: No Liang Li, WXZJ

  24. Multipath channel: no fading + correlation sync (1) Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Frame Detection: No Phase noise :No SFD: No Sync.: Correlation Down sampling error: No Liang Li, WXZJ

  25. Multipath channel: no fading + correlation sync (2) Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Frame Detection: No Phase noise :No SFD: No Sync.: Correlation Down sampling error: Yes Liang Li, WXZJ

  26. Multipath channel: no fading + correlation sync (3) Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: Yes Frame Detection: No Phase noise :No SFD: No Sync.: Correlation Down sampling error: No Liang Li, WXZJ

  27. Multipath channel: no fading + correlation sync (4) Frame Detection: No Phase noise :YES SFD: No Sync.: Correlation Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  28. Multipath channel: no fading + correlation sync (5) Frame Detection: No Phase noise :YES SFD: YES Sync.: Correlation Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  29. Multipath channel: no fading + correlation sync (6) Frame Detection: YES Phase noise :YES SFD: Yes Sync.: Correlation Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  30. Multipath channel: no fading + correlation sync (7) Frame Detection: YES Phase noise :YES SFD: Yes Sync.: Correlation Down sampling error: Yes Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  31. Multipath channel: no fading + correlation sync (8) Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: Yes Frame Detection: YES Phase noise :YES SFD: Yes Sync.: Correlation Down sampling error: Yes Liang Li, WXZJ

  32. Multipath channel without Fading + Correlation Sync. (frequency offset estimation) Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: Yes Frame Detection: YES Phase noise :YES SFD: Yes Sync.: Correlation Down sampling error: Yes Liang Li, WXZJ

  33. Multipath channelwith fading + correlation Sync (1) Frame Detection: No Phase noise: No SFD: No Sync.: Correlation Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  34. Multipath channelwith fading + correlation Sync (2) Frame Detection: Yes Phase noise :Yes SFD: Yes Sync.: Correlation Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  35. Nonlinear PA Characteristics Liang Li, WXZJ

  36. Impact of PA Nonlinearity: 2x sampling rate (1) Tx PSD without PA (2) Tx PSD with PA For the constant module and continuous phase in our proposal, the Tx PSD is not affected by nonlinear PA. Liang Li, WXZJ

  37. AWGN: Ideal Sync. Among E16, W16 and COBI16 Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Frame Detection: No SFD: No Liang Li, WXZJ

  38. Multipath channelwith fadingAmong E16, W16 and COBI16 Frame Detection: No Phase noise: No SFD: No Sync.: Ideal Down sampling error: No Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Time offset: No Liang Li, WXZJ

  39. Summary • Enhanced W16 can satisfy the some criteria • 1. Equal number of “0”s and “1”s in preamble sequence; • 2.The first chip is not always 0 or 1; • 3. Total DC value is 0, even though not always 0 in I or Q route of every sequence; • 4. The phase comes back to 0 after one symbol period. • No spikes in frequency spectrum • The sync performance using correlation method is the same as the En-COBI16 , and the performance of demodulation is about 0.5db better than that of En-COBI16(d1) • The system PER performance of W16 is about 0.5dB better than that of En-COBI16(d1),especially in condition of large delay spread Liang Li, WXZJ

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