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DecaWave Proposal for TG3c Alternative PHY

This document presents an alternative PHY proposal for TG3c, focusing on a single carrier system, adaptive phased antenna array, low complexity, and multi-national regulatory compliance.

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DecaWave Proposal for TG3c Alternative PHY

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [DecaWave Proposal for TG3c Alternative PHY] Date Submitted: [2007-May-7th] Source: [Brian Gaffney, Michael Mc Laughlin] Company [DecaWave] Address [25 Meadowfield, Sandyford, Dublin 18, Ireland] Voice:[+353 87 688 2514], FAX: [none], E-Mail:[michael.mclaughlin@decawave.com, brian.gaffney@decawave.com] Re: [Response to Call for Proposals 15-07-0586-02-003c-tg3c-call-proposals.doc] Abstract: [Alternative PHY Proposal for TG3c] Purpose: [To assist TG3c in selecting a mm Wave PHY] 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. Gaffney, Mc Laughlin, DecaWave

  2. DecaWave 3c Proposal Gaffney, Mc Laughlin, DecaWave

  3. Proposal Outline • Single Carrier system. • Adaptive Phased Antenna Array to boost SNR at receiver and provide spatial multiple access • Low complexity • Multi-national regulatory compliance. Gaffney, Mc Laughlin, DecaWave

  4. Proposed Band Plan U.S. Japan 1.6Ghz 57 59 64 66 f(Ghz) ~2.2Ghz Gaffney, Mc Laughlin, DecaWave

  5. Modulation Scheme Q • 8-QAM • Used in the V.29 modem standard due to resilience to phase noise. • Higher bandwidth efficiency than QPSK. • More resilient to phase noise and power amplifier problems than higher order constellations (16-QAM). • Allows for Non-Coherent reception • Only two levels I R1 R0 Gaffney, Mc Laughlin, DecaWave

  6. Error Correction Coding • Outer systematic Reed Solomon block code. • Inner systematic Convolutional code. • Constraint length K = 5 and rate 1/3. • One information bit in produces 3 bits out (the information bit and two parity bits) which are mapped to a symbol in the 8-QAM constellation. • Systematic to allow for Non-Coherent Reception for low complexity receivers • File Transfer and Kiosk usage scenarios Gaffney, Mc Laughlin, DecaWave

  7. Outer Reed Solomon • The systematic Reed Solomon code is over the Galois field GF(26) and is given as RS(63,55). • Input of 55 symbols creates 8 parity symbols for a rate 0.87 code. • Systematic gives the option of ignoring the parity symbols in low complexity receivers. • Used in the 802.15.4a standard. • Interleaved output before input to inner code improves performance by separating burst errors at the receiver. Gaffney, Mc Laughlin, DecaWave

  8. Convolutional Code • Generator Polynomial: g1=208, g2 = 278, g3 =328. + + Gaffney, Mc Laughlin, DecaWave

  9. Convolutional Code • With K=5, there are only 16 possible states. • 8 branch metrics need to be calculated per symbol • Other coding techniques, which achieve better performance, such as LDPC codes were investigated, but the convolutional code was chosen because it is easier to implement at the high data rates of interest. Gaffney, Mc Laughlin, DecaWave

  10. Convolutional Code • Systematic code gives the option of ignoring the parity bits • Important for Non-Coherent receiver. To be covered later. • However, systematic codes are known to perform worse than non-systematic. • We have developed the previous code in conjunction with a bit to symbol mapping which approaches the performance of a Gray coded constellation with maximum free distance non-systematic code. Gaffney, Mc Laughlin, DecaWave

  11. 8-QAM Constellation 001 100 101 000 010 111 110 011 Gaffney, Mc Laughlin, DecaWave

  12. Our 8-QAM versus Gray Coded Gaffney, Mc Laughlin, DecaWave

  13. Data Modes • Four Data Modes: • Base mode 1.4Gbps • High data rate mode 2.8Gbps • Very High data rate mode 4.2Gbps • Low rate (67Mbps) back channel mode obtained by sending a direct sequence code Gaffney, Mc Laughlin, DecaWave

  14. Base Mode – 1.4Gbps • Base mode • One bit per symbol. • Pulse Repetition Frequency (PRF) = Bandwidth (B) • Data rate = 0.87*B Gbs • Inner and Outer coding • Interleave RS output • Spatial multiple access Gaffney, Mc Laughlin, DecaWave

  15. Base Mode – 1.4Gbps Gaffney, Mc Laughlin, DecaWave

  16. High Data Rate Mode – 2.8Gbps • High Data Rate mode • Two bits per symbol • Punctured Base mode • PRF = B • Interleave RS output • Data rate = 2*0.87*B Gbs Not transmitted From convolutional coder s1 s2 s3 s4 s5 s6 Gaffney, Mc Laughlin, DecaWave

  17. High Data Rate Mode – 2.8Gbps Gaffney, Mc Laughlin, DecaWave

  18. Very High Data Rate Mode – 4.2Gbps • Very High Data Rate mode • No convolutional code • Reed Solomon RS(63,55) • Interleave RS output • Data rate = 3*0.87*B Gbs Gaffney, Mc Laughlin, DecaWave

  19. Very High Data Rate Mode – 4.2Gbps

  20. Low Data Rate Mode – 67Mbps • Low data rate back channel mode. • Length 21 Ipatov ternary sequence. • +00−++−0+0+−+++++−−0− • Golay Merit Factor of 5.3 • Gives the option of 67Mbs (base mode) or 133Mbs (high data mode) which is more resistant to errors Gaffney, Mc Laughlin, DecaWave

  21. Non Coherent Reception • The Non Coherent receiver is ideal for File Transfer or the Kiosk modes • The systematic bit decides which “ring” the transmitted symbol is on. Therefore, by using a simple energy detector receiver we can decode the systematic bit from any base mode signal. • The Outer Reed Solomon code then gives some optional error correcting capabilities Gaffney, Mc Laughlin, DecaWave

  22. Non Coherent Reception to RS decoder from antenna LPF exp(j2πfct) Gaffney, Mc Laughlin, DecaWave

  23. Non Coherent Reception • Used with a directional antenna, we can achieve a data rate of 0.87*B Gbs at short range • Enables a very low cost implementation • Ideal for integration into media players, phones, cameras etc. Gaffney, Mc Laughlin, DecaWave

  24. Non Coherent Reception Gaffney, Mc Laughlin, DecaWave

  25. Phased Antenna Array • We propose using a phased antenna array to boost the signal to noise ratio at the receiver input and provide spatial multiple access. • The phased antenna array can adapt to any direction of arrival (assuming omni directional elements) • The phased antenna array offers a low complexity solution Gaffney, Mc Laughlin, DecaWave

  26. Phased Antenna Array + Gaffney, Mc Laughlin, DecaWave

  27. Phased Antenna Array • For omni directional antenna elements, the phased antenna array can achieve a high gain in any given direction. For example, ten elements (uniform linear array) can give a gain of 10dBi • To achieve higher gains, directive elements need to be applied which require some physical alignment of Tx and Rx • The non-coherent mode could have a single highly directive element and assume the user will align the Tx and Rx Gaffney, Mc Laughlin, DecaWave

  28. Hidden Node Problems • Major problem with directive antenna systems is finding Nodes. • To combat this problem, we propose using a single element mode. • For omni-directional antenna elements, we can now “see” in every direction. • For directive antenna elements, we can only “see” in the direction we can adapt in. Gaffney, Mc Laughlin, DecaWave

  29. Hidden Node Problems • However, the path loss is so high at 60Ghz, a very weak signal is received when we are not using the antenna array gain • The Solution: • Compensate for the lack of antenna array gain at Tx and Rx by spreading the signal to obtain an equal or higher processing gain • Much lower data rate, but not so important at the start of communication Gaffney, Mc Laughlin, DecaWave

  30. Ternary Spreading Sequence • Ipatov Sequence • Perfect Periodic Autocorrelation properties. • Allows for accurate channel estimation for Channel Matched Filtering (CMF) and Antenna Array adaptation. • Used in 802.15.4a • For example, a length 183 sequence is equivalent to an antenna array gain of approximately 22.2 dBi • Many such sequences allows separate piconets to co-exist • Example length 183 Ipatov Sequence: +−−−+0+−−−−−++−−+++++++−−++0+−+−+−+−−00−−+−+−++−−++−−+−0−−−++−−0−++−0−−+++−+++−−+−+−−+−+++++0−−++−−++−+−−−0+0+++0+−0−−−−−+−++−−0++++−+−−−−+++−+−+−−++−++−+0−++++−+−++++−++−+++++++−+−−+ Gaffney, Mc Laughlin, DecaWave

  31. Ternary Spreading Sequence Periodic Auto Correlation of Length 183 Ipatov Sequence Gaffney, Mc Laughlin, DecaWave

  32. Ternary Spreading Sequence • With the perfect autocorrelation we can obtain an excellent estimate of the channel for the Channel Matched Filter (CMF) • Send 16 times before each packet • However, inter symbol interference (ISI) due to multipath in the channels without a dominant single path is not combated by the CMF • Instead of equalization, we want to use the antenna to point in a direction which gives a useable channel Gaffney, Mc Laughlin, DecaWave

  33. Interference & susceptibility • All out of band interference filtered out. • Adjacent channel interference is filtered out. • However, power amplifier backoff will affect this and will be addressed fully at future meetings. • Co-channel interference is avoided by spatial multiple access. • Narrowband interference rejection with digital notch filter • Tones can be detected at the A/D output. • A simple notch filter either at the input or output of the matched filter can then remove this completely with no loss in performance (if notch is narrow enough). Gaffney, Mc Laughlin, DecaWave

  34. Link Budget (LOS) Gaffney, Mc Laughlin, DecaWave

  35. Link Budget (NLOS) Gaffney, Mc Laughlin, DecaWave

  36. Link Budget Summary Gaffney, Mc Laughlin, DecaWave

  37. Base Mode CM 1.3 Gaffney, Mc Laughlin, DecaWave

  38. Base Mode CM 2.3 (NLOS) Gaffney, Mc Laughlin, DecaWave

  39. Base Mode CM 3.1 Gaffney, Mc Laughlin, DecaWave

  40. High Data Rate CM 1.3 Gaffney, Mc Laughlin, DecaWave

  41. Performance Summary Gaffney, Mc Laughlin, DecaWave

  42. Summary of our proposal • 8-QAM modulation scheme • 4 Data rates • Base mode of 1.4Gps obtained with outer RS (rate 0.87) and inner convolutional (rate 1/3) coding • High data rate mode of 2.8Gps obtained by puncturing base mode signal • Very high data rate mode of 4.2Gps obtained by using only RS code • Lower rate for back channel using Direct Sequence code • Systematic code developed specifically for the 8-QAM constellation which enables a Non-coherent receiver architecture • Node discovery and channel adaptation with omni directional antenna mode with spreading gain from long ternary sequence Gaffney, Mc Laughlin, DecaWave

  43. Advantages • Low complexity solution • Constellation resilient to RF impairments • Simple Non-coherent mode • Ideal for low cost receiver e.g. for media player • Single carrier • potential common signalling mode operation • More resistant to multipath • Ternary sequences and omni-directional antenna mode allow easy node discovery • Multi-national regulatory compliance Gaffney, Mc Laughlin, DecaWave

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