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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ I 2 R CFP Presentation for 802.15.3a UWB Alt-PHY ] Date Submitted: [ 5 May, 2003 ]

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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: [I2R CFP Presentation for 802.15.3a UWB Alt-PHY] Date Submitted: [5 May, 2003] Source: [Francois Chin, Madhukumar, Xiaoming Peng, Sivanand] Company [Institiute for Infocomm Research (Singapore)] Address [20 Science Park Road, #02-34/37 Teletech Park, Singapore 117674] Voice:[(65)6870-9309], FAX: [(65)6779-5441], E-Mail:[chinfrancois@i2r.a-star.edu.sg] Abstract: [This contribution describes a proposal for high-rate wireless personal area network PHY layer approach based on sub-band hopping system architecture. The system has variable data / sampling rates to address numerous application / power / complexity requirements; flexible spectrum management techniques to adapt, to different regulatory environments; good performance in the presence of multipath and multiple access interference especially with channel equalisation.] Purpose: [This contribution is submitted to the IEEE 802.15.3a task group for consideration as a possible solution for high-rate, short-range WPAN applications.] 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. Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  2. Outline • Key features • Multi-band plan • Variable pulse rate Multi-band PHY • Frame structure & Preamble • RF & Baseband Architecture • Performance Analysis • Implementation feasibility • Coexistence & Interference Plans • Self evaluation Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  3. Key Features • Uses multiband approach • Available spectrum is divided into multiple bands • PNC ID based Time-frequency sub-band hopping sequence for uncoordinated piconets • Frequency agility for interference mitigation • Flexible spectrum usage • Compatible with existing wireless PAN/LAN standards • High spectral efficiency • QPSK modulation for data within each band • Reed-Solomon outer code + Quadrature M-ary Orthogonal Keying (QMOK) inner code • Multi-channel equaliser per subband to suppress ISI and interference from simultaneously operating piconets (SOP) • Variable pulse rate transmission • Variable data / sampling rates to cater to different power / complexity requirements Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  4. Multiband Approach • Divide spectrum into multiple bands • 13 subbands • Lower frequency group has 7 subbands • Higher frequency group has 6 subbands • Reference clock as 11 MHz • Chip rate per subband is 308 MHz (= 28*11) • Chip duration ~3.25 ns • Rectified cosine pulse shaping filter • ~ 622 MHz wide bands to best utilize the spectrum • Inter-band spacing is 539 MHz (= 1.75*308) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  5. Low frequency group High Frequency Group 5 6 0 1 2 3 4 7 8 9 10 11 12 ~ ~ ~ ~ Band Allocation Plan Sacrifice one band for WLAN coexistence (depending on geographical location) Possible interferences: 802.11 interference in Japan (4.9-5.25 GHz) (Band 2) andin Europe/US (5.15-5.825 GHz) (Band 3 & 4) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  6. Band Allocation Plan • 13 active frequency bands for transmission • Divided into lower (band 0-6) and upper (band 7-12) frequency groups • One band in the lower group is avoided for co-existence with 802.11a WLAN • Centre frequencies selected for ease of implementation • Both groups can be used in parallel to increase the bit rate Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  7. Transmit Pulse Shape • Rectified cosine pulse as pulse shape filter • Pulse width ~ 3.25 ns (=1/ 308 MHz = 1/(28*11MHz)) • ~ 622 MHz wide bands to best utilize the spectrum Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  8. Time-Frequency Hopping Sequence for Multiple Access • Length 6 time-frequency sequence • Random sequences can be used • Possible number of hopping sequence is 720 (= 6!) • Various degree of collision from multiple devices will be resolved using oversampling multi-channel equalizer • Sequence can be determined by piconet coordinator’s (PNC) ID • Faster piconet establishment • Linear congruency design is an good method to design sequences that will minimise impact of multiple access interference • All Beacons will have a fixed TF Hopping Sequence for easy detection Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  9. Variable pulse rate Multi-band PHY • Supports 3 pulse rates • 77/154/308 MHz • Sampling frequency is 4*PRF (Pulse Repetition Frequency) • Independent of total number of subband available, few subbands means shorter PRI • Adaptive sampling rates for better power utilization • Oversampling for multi-channel equalisation to provide effective ISI suppression when operating in channels with large delay spread and interference suppression when operating under simultaneous operating piconets Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  10. Variable pulse rate (for 6-band) • PRl/subband is inversely proportional to chip rates • 19.5 ns: 6 pulses, each with pulse width ~3.25 ns for 308 Mcps • 39 ns: 6 pulses, each with pulse width ~3.25 ns for 154 Mcps • 78 ns: 6 pulses, each with pulse width ~3.25 ns for 77 Mcps • Sampling frequency changes with chip rate (= 4*chip rate) so as to reduce ADC power consumption at lower data rate Sampling instance Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  11. Operation Modes and Payload Bit Rates • Mode 0 for beacons & headers, with same information in all subbands • PHY header data rate field mapped to Operation mode index • In each operation mode, different number of sub-bands can be used, and the payload bit rate will be proportional to #subbands used Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  12. Preamble Modulation & Symbol Rate • Preamble has same pulse rate as payload information Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  13. Frame structure • Features • Preamble: CAZAC symbols repeated on all subbands • Headers: Fixed pulse rate at 154 Mpps • Payload bits: RS outer coded + QMOK inner coded • No structural change for existing 15.3 frame definition • Same MAC header and HCS definition • PHY header data rate field mapped to Operation mode index Packet overhead parameters for data throughput comparison Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  14. 10 CAZAC Sequences 5 CAZAC Sequences 1 inverted CAZAC Sequence Preamble Definition • 16 CAZAC sequences • CCA/packet detection • Timing acquisition • Channel estimation • Channel equalisation • SIR estimation / Link quality assessment • End of preamble delimiter Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  15. Preamble Sequence • Use cyclic shifted CAZAC sequence for preamble on different subbands for rapid acquisition Subband # 3.25ns CAZAC Sequence: Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  16. Quadrature orthogonal keying RS coding Coding & Interleaving • Inner code: Reed-Solomon Code (221, 255) • To overcome burst errors • Outer code: Quadrature M-ary Orthogonal Keying (QMOK) • 4/8 rate and ¾ rate selection • Power efficient modulation • Walsh-Hadamard Orthogonal code • Fast Hadamard Transforms exist with low latency and low complexity • Scrambler • Same as that in 15.3 standard To RF Data Block Interleaver Scrambling code Preamble Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  17. A A B consists of 4 bits A A A B B B i 6 0 4 2 0 6 4 2 I A A A A A A A A Mapping 4 4 4 4 8 8 8 8 3 7 6 5 4 2 1 0 4 4 4 4 4 4 4 4 Mapping 4 4 4 4 8 8 8 8 Q A B A A A B B B 5 7 7 3 1 5 3 1 Quadrature M-ary Orthogonal Keying(example 4/8 rate code) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  18. 90o 90o PNC ID based TF Subband Hopping Seq. LO 2 LO 1 RF Transmitter Architecture Lower frequency band Data I • Upper frequency band may be in parallel to achieve high data rate Data Q Bit sequence from QMOK encoder Subband select De-MUX Data I Data Q Upper frequency band (Optional) Subband select Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  19. Gain Control Antenna Quad. Mixer LPF BPF I LNA VGA -90° LPF Q LO Receiver RF Architecture & Noise Figure (Frequency depends on subband selector) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  20. DeInt. P/S Adaptive MMSE Adaptive MMSE ADC Receiver Baseband Architecture Scrambling code Multi-channel Equalizer From RF QMOKDemap RS decoding W Multichannel Equalizer: For Subband #1 Demux. Into Subbandeqr W For Subband #6 Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  21. Multi-Channel Equalizer • Each of the parallel subband has a multi-channel MMSE Equalizer • Each equalizer takes in the 4 oversamples within each Pulse Repetition Interval, and combine with a 4-tap weight to give a output complex symbol • Each equaliser can suppress self-interference due to same sub-band • upto 3 inter-pulse interference under large channel delay spread • ~60 ns for CM1 & CM2 • ~120 ns for CM3 • ~240 ns for CM4 • Each equaliser can suppress upto 3 simultaneously operating piconets (SOP) interferers using the same sub-band • Recursive Least Square (RLS) adaptive algorithm is a good candidate for the mutli-channel MMSE equalizer • Fast convergence • Efficient implementation Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  22. Multi-Channel Equalizer - Complexity • Each of the parallel subband has a multi-channel MMSE Equalizer with Recursive Least Square (RLS) adaptive algorithm • RLS can be implemented using systolic array structure • Each array cell can be implemented in pipeline fashion RLS Systolic array structure Array Cell pipelined structure Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  23. Performance analysis • Link Budget • PHY-SAP Throughput • System Performance • Simultaneously Operating Piconets Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  24. Link budget (6-band) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  25. Frame Duration & PHY-SAP Throughput Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  26. System Performance • Mode 1 (67Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 100 CM4 channels / 6-Band / NF = 7dB / Imp. Loss = 5dB Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  27. System Performance • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 100 CM3 channels / 6-Band / NF = 7dB / Imp. Loss = 5dB Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  28. System Performance • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 100 CM4 channels / 6-Band / NF = 7dB / Imp. Loss = 5dB Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  29. System Performance • Mode 5 (267Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 100 CM2 channels / 6-Band / NF = 7dB / Imp. Loss = 5dB Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  30. System Performance • Mode 7 (533Mbps payload, QPSK, RS (255,221)) • 100 CM1 channels / 6-Band / NF = 7dB / Imp. Loss = 5dB Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  31. System PerformanceEqualiser vs RAKE (Mode 1 & 3) Mode 1 (67Mbps) Mode 3 (133Mbps) • Performance gap widens when channel delay spread increases • MMSE equaliser can better suppress ISI Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  32. System Performance Equaliser vs RAKE (Mode 5 & 7) Mode 5 (267Mbps) Mode 7 (533Mbps) • RAKE receiver performance is ISI-limited (cannot achieve 8% FER however short the link distance is) • Performance gap widens when channel delay spread increases and Eb/No requirement increases (as in Mode 7) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  33. Simultaneously Operating Piconets • Objective: evaluate the multipath performance in the presence of multiple uncoordinated piconets under the effects of • Choice of Time-Frequency Hopping Sequence • MMSE channel equalisation vs RAKE • Performance Results • dint/dref for each reference link in a given CM, each reference link over each interfering link in another given CM • e.g. 25 dint/dref values for 5 ref CM3 x 5 int CM4 (as backup materials) • PER vs. dint/dref, averaged over all reference links in a given CM, each reference link over all interfering links in another given CM • e.g. 1 set of PER vs. dint/dref values for 5 ref CM3 x 5 int CM4 (as backup materials) • the minimum value of dint/dref for which the average PER is 8%, averaged over all reference links in a given CM, each reference link over all interfering links in another given CM • e.g. 1 dint/dref value for 5 ref CM3 x 5 int CM4 Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  34. Simultaneously Operating Piconets • All reference and interference links are normalised to unit energy • Reference link distance (dref) was half the 8% PER distance (notionally giving 6 dB margin) • Interfering link distance (dint) was varied from 8* dref to dref /8 • Measure PER as a function of the ratio of dint to dref Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  35. Simultaneously Operating Piconets • Ref. and interference link • Reference link: Channel 1-5 from each CM 1-4 • 1st interference link: Channel 6-10 from each CM 1-4 • 2nd interference link: Channel 11-15 from each CM 1-4 • 3rd interference link: Channel 16-20 from each CM 1-4 • 2nd and 3rd interference link do not use AWGN channels as stated in selection criteria, as it may not be realistic enough • 5 sets of Interference link channels • Channel 6,11,16 of each interfering CMs represents first set • Channel 7,12,17 of each interfering CMs represents second set, etc • E.g. When N=2, channel 6&11 will be used for 1st and 2nd interference links for first SOP interference scenario; channel 7&12 for second SOP interference scenario, etc Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  36. Simultaneously Operating PiconetsEffect of TF Hopping Sequence Collision 5 collision patterns • '1 x N' - desired piconet has full collision (from all SOP) in only 1 specific subband • 'B x 1' - desired piconet has at most one collision in each sub-band • 'B x N' - desired piconet has full collisions in all subbands (worst case) • 'B x 1/2' - desired piconet has “1/2” collision (by ringing down subband transmitted one PRI earlier in another SOP) in all subbands • 'B x 1/3' - desired piconet has “1/3” collision (by ringing down subband transmitted two PRI earlier in another SOP) in all subbands '1 x N' Piconet # ‘B x 1' Piconet # Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  37. Simultaneously Operating PiconetsEffect of TF Hopping Sequence Collision ‘B x N' ‘B x 1/3' Piconet # Piconet # ‘B x 1/2' Piconet # Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  38. Simultaneously Operating Piconets • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 5 CM3 ref. Channels x 5 sets of CM1 int. Channels Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  39. Simultaneously Operating Piconets • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 5 CM3 ref. Channels x 5 sets of CM2 int. Channels Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  40. Simultaneously Operating Piconets • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 5 CM3 ref. Channels x 5 sets of CM3 int. Channels Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  41. Simultaneously Operating Piconets • Mode 3 (133Mbps payload, QPSK, RS (255,221) + 4/8-rate QMOK) • 5 CM3 ref. Channels x 5 sets of CM4 int. Channels Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  42. SOP – Performance Analysis • # interfering SOP • Performance gets worse when # interfering SOP increases • Equaliser vs RAKE • Considerable performance gap • 5x difference in dint/dref for CM1,CM2 • 3x difference in dint/dref for CM3,CM4 • Each sub-band equaliser can suppress self-interference due to same sub-band • Each sub-band equaliser can suppress upto 3 simultaneously operating piconets (SOP) interferers using the same sub-band • Effect of TF Hopping Sequence collision • ‘B x N’ worst performance • ‘1 x N’, ‘B x 1’, ‘B x 1/2 ‘ similar performance • ‘B x 1/3’ > ‘1 x N’, ‘B x 1’, ‘B x 1/2‘ > ‘B x N’ Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  43. SOP performance analysis– impact on system design • Adaptive equaliser • Activate adaptive multi-channel equalisation algorithm in the presence of SOP to improve performance • Choice of Time-Frequency Hopping Sequence • Avoid ‘B x N’ full collision from SOP in all subbands • Random Time-Frequency Hopping Sequence based on PNC’s ID is sufficient Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  44. Implementation Feasibility • The proposed multi-band approach is designed to reduce the complexity and power consumption • Re-use of same circuitry for different sub-bands leads to lesser silicon area due to non-overlapped timing between sub-bands • Shared LO, ADC, equalizer, etc.. • ADCs with lower sampling rate due for lower pulse rate, for lower data rate • reduction in number of bits requirement for ADC • 4-tap equalizer and ‘QMOK decoding/despreading processing’ allows the system to work satisfactorily even with four-bit ADCs Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  45. Scalability • Power consumption • ADC sampling rate is proportional to pulse rate, thus lower power at lower date rate • Data rate increases with the number of bands used in the transceiver, while system complexity remains the same • Simultaneous transmission in low and high frequency groups to double data rate • Increases the cost of transmitter and receiver due to the presence of a second local oscillator and an additional receiver chain Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  46. Coexistence Plans • Static control • Frequency band for the devices should be configurable through software based on the geographic locations • Dynamic control • UWB device will detect possible narrowband interference and avoid the corresponding bands • WLAN 802.11a bands • Respective bands are avoided • E.g: In Japan (4.9-5.25 GHz) in Europe/US (5.15-5.825 GHz) Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  47. Narrowband Interference Plans • Sub-bands should be scanned periodically to detect narrowband interference • Rely on adjacent channel rejection of filters + receiver signal processing (e.g. multi-channel equaliser) to overcome • Robust RF front end design • Antenna • Filters • Component linearity requirements Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  48. Flexibility • Individual devices are adapted to interference without coordination with other devices • Easy adaptation for different regulatory environments • Simply avoid the affected sub-band within geographical area Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  49. Location awareness • Accuracy and precision of ranging using UWB devices • Is independent of “turn-around time” of the transmitter/receiver. • Can rely on sub-ns transceiver clocking circuits. • Is nearly independent of chosen UWB pulse width. • Location information is calculated based on simultaneous exchange of two messages between devices • Time differences between sending and receiving messages are computed for both the devices • The physical distance between devices are proportional to the time difference Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

  50. Summary • Features of I2R’s Proposal on UWB multi-band system • Spectrum flexibility • Adapting to different regulatory requirements • Coexistence with narrowband systems • scalability in terms of number of bands employed • Good performance with multipath and simultaneously operating piconets • Better interference suppression with the use of equaliser • Minimum performance degradation even with random time-frequency hopping sequence • Low power / complexity solution • Sampling rate and pulse rate proportional to data rate • Minimal MAC supplements Francois Chin, Madhukumar, Xiaoming Peng, Sivanand, I2R

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