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Scaling TG3a PHY Proposals for High Data Rates

Explore complex increases necessary for DS-UWB and MB-OFDM proposals to support 480+ Mbps applications. Technical information provided to TG3a voters regarding PHY proposals.

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Scaling TG3a PHY Proposals for High Data Rates

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Scaling-TG3a-PHY-Proposals-for-High-Aggregate-Data-Rates] Date Submitted: [18 March 2004] Source: [Matt Welborn] Company [Motorola] Address [8133 Leesburg Pike Vienna, VA USA] Voice:[703-269-3000], E-Mail:[mwelborn@xtremespectrum.com] Re: [] Abstract: [The DS-UWB offers 110 Mbps at 10m in the low band, and only drops to 7m in the high band. The newest OFDM band plan ranges scale to 3m in the high band groups. Applications that need 480+ Mbps support need to consider the complexity increases necessary over the baseline modes for both the DS-UWB and MB-OFDM proposals.] Purpose: [Provide technical information to the TG3a voters regarding PHY proposals.] 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. Welborn Motorola

  2. Outline • Scaling baseline PHY modes • Higher frequency bands • Higher data rates Welborn Motorola

  3. DS-UWB Operating Bands Low Band High Band 3 4 5 6 7 8 9 10 11 3 4 5 6 7 8 9 10 11 GHz GHz MB-OFDM Operating Bands Welborn Motorola

  4. Multi-piconet Overview • DS-UWB low band and high band • 2x center frequency & BW in high band • Support for 6 piconets in each of low band and high band • MB-OFDM has added full FDM support for multiple piconets using band groups • New band groups have higher frequencies • All use same TFCs • For both proposals, higher frequency bands will experience worse RF losses • Likely higher receiver noise figures Welborn Motorola

  5. Assumptions for Comparison • Assumptions for multiple piconet support • All piconets >5GHz assumed to have +2dB NF • Assume multipath ranges reduced by 20*Log(Fc ratio) • All piconets are outside UNII except Band Group 2 • UNII devices ~30dB higher transmit power • 802.11a, cordless phone, TDWR, DSRC… • Typical UNII device within about 100-200m of BG2 piconet will degrade sensitivity 6dB (~½ range) • Assumes erasure decoding present to partially mitigate UNII RFI • Dynamic UNII protection may increase NF/BOM (03/141r3, p.12) • Seems unlikely that this would be acceptable to user/OEM • Does not meet selection criteria of <1 m for 802.11a separation • Assumptions about acceptable distance ratio, 2 cases • Distance ratio of <=1.5 is required for multi-piconet support • Distance ratio of <=1.0 is required for multi-piconet support • Assumes adequate adjacent band/band group isolation Welborn Motorola

  6. Multipath Ranges for 110 Mbps * * Band group 5 has 2 bands  rate or range is lower Welborn Motorola

  7. Piconets & Multipath Range Band Group 2 shown degraded 6 dB (UNII Device at 100-200 m) Band Group 4 With 2 “piconets” Comparison of piconet support for distance ratios < 1.5 Welborn Motorola

  8. Piconets & Multipath Range Band Group 2 shown degraded 6 dB (UNII Device at 100-200 m) Band Group 4 With 1 “piconet” Comparison of piconet support for distance ratios < 1.0 Welborn Motorola

  9. DS-UWB scaling to Higher Rates • There is significant interest in “cable replacement” applications that require high speed operation (480+ Mbps) at short range • DS-UWB operation at 500 Mbps uses L=2 code & ¾ FEC • Complexity is similar DS-UWB receiver for 110 & 220 Mbps • Same ADC bit widths & clock rates • Same rake bit width & complexity • Fewer rake taps available (only 2/3 as many as for 220 Mbps) • Viterbi decoder for k=6, rate ¾ likely 2x gates  45k gate increase • Operation at 660 Mbps also supported with un-coded operation • 4.9 m range in fully impaired AWGN simulation • Eliminates requirement for high speed Viterbi decoder • Complete, fully impaired multipath simulations for 500-1000 Mbps DS-UWB are underway Welborn Motorola

  10. MB-OFDM scaling to Higher Rates • Currently available complexity estimates for MB-OFDM implementations do not support operation at > 200 Mbps • Document 267r5, p. 35 • Estimated MB-OFDM receiver complexity scaling for 480 Mbps • 5-bit ADC required instead of 4-bit ADC at lower rates (Doc# 03/267) • Increased bit-width for internal FFT processing • 45 bits is 25% increase  assume 25% higher gate count (conservative) • This scales FFT engine from 70-100k gates to 90-125k gates @ 85 MHz • 25k gate increase over current estimates for 200 Mbps implementation • K=7 Viterbi decoder does not operate at 480 Mbps • SiWorks (Document 03/213r0) estimates that 480 Mbps, k=7 operation would be possible, but would require a 4-wide parallel implementation • SiWorks estimate for 200 Mbps k=7 Viterbi is 75k gates at 100 MHz • Equivalent to 88 k gates at 85.5 MHz • SiWorks estimate for 480 Mbps is 110K gates at 120 MHz  154k gates at 85.5 MHz (about 2x the <=200 Mbps Viterbi complexity) • K=7 Viterbi decoder would require an increase of 80k gates @ 85MHz Welborn Motorola

  11. DS-UWB & MB-OFDM Complexity Scaling • Complexity increase for MB-OFDM receiver • Increase for FFT & Viterbi is >100k gates @ 85 MHz • Total complexity now >550 k gates at 85.5 MHz • Based on estimate of 295k gates at 132 MHz for <= 200 Mbps • Complexity increase for DS-UWB receiver • Increase in gate count due only to Viterbi decoder, 54k gates • Total receiver complexity now ~230 k gates at 85.5 Mhz • For un-coded operation at 660 Mbps, no Viterbi decoder • Power consumption equivalent to 130 k gates at 85.5 MHz • DS-UWB digital baseband complexity is only ~30-40% of the equivalent MB-OFDM implementation Welborn Motorola

  12. Conclusions • Both PHY proposals support scaling the baseline modes to operation in higher bands • Use full FDM • Higher losses in higher bands • Receiver complexity scaling at higher rates is important to consider for some applications • Viterbi decoders, FFT engines and ADC requirements can be different for higher rates • In general, complexity is higher at high rates Welborn Motorola

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