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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: [ Extended Common Signaling Mode ] Date Submitted: [July 15, 2004 ] Source: [ Matt Welborn ] Company [ Freescale Semi, Inc ] Address [8133 Leesburg Pike]

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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: [Extended Common Signaling Mode] Date Submitted: [July 15, 2004] Source: [Matt Welborn] Company [Freescale Semi, Inc] Address [8133 Leesburg Pike] Voice:[703-269-3000], FAX: [703-249-3092] Re: [] Abstract: [This document provides an overview some possible extensions for the proposed Common Signaling Mode that would allow the inter-operation or MB-OFDM and DS-UWB devices at data rates as high as 110 Mbps.] Purpose: [Promote further discussion and compromise activities to advance the development of the TG3a Higher rate PHY standard.] 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, Freescale Semi

  2. Background • Initial TG3a discussions on a “Common Signaling Mode” (CSM) began some months ago • A few ad hoc meetings during January TG3a Interim • Ad hoc meeting in February • Several presentations in March Plenary • Other attempts at compromise to allow forward progress in TG3a not successful • ~50/50 split in TG3a voter support for two PHY proposals • Little support for two optional independent PHYs • Can we re-examine some of the ideas for a single multi-mode UWB PHY as a path for progress? Welborn, Freescale Semi

  3. The CSM Vision • A single PHY with multiple modes to provide a complete solution for TG3a • Base mode that is required in all devices, used for control signaling: “CSM” for beacons and control signaling • Higher rate modes also required to support 110+ Mbps • Compliant device can implement either DS-UWB or MB-OFDM (or both) • Interoperability between all compliant devices at high rates • All devices work through the same 802.15.3 MAC • User/device only sees common MAC interface • Hides the actual PHY waveform in use • Effectively only one PHY – with multiple modes Welborn, Freescale Semi

  4. Talking with each other: Basic Requirements • Each class of UWB devices (MB-OFDM or DS-UWB) needs a way to send control/data to the other type • MB-OFDM  DS-UWB • DS-UWB MB-OFDM • Goal: Minimize additional complexity for each type of device while enabling this extra form of communications • Use existing RF components & DSP blocks to transmit message to “other-class” devices • Also need to enable low-complexity receivers • Data rates need to support full piconet operation without impacting throughput/capacity or robustness Welborn, Freescale Semi

  5. UWB Consumer Electronics Applications Home Entertainment Computing Mobile Devices Welborn, Freescale Semi

  6. Interoperation with a Common Signaling Mode Images from camera to storage/network Print from handheld Exchange your music & data Stream DV or MPEG to display Stream presentationfrom laptop/ PDA to projector MP3 titles to music player Welborn, Freescale Semi

  7. No Interoperation: Tragedy of the Commons Images from camera to storage/network Print from handheld Stream DV or MPEG to display Stream presentationfrom laptop/ PDA to projector MP3 titles to music player Welborn, Freescale Semi

  8. Interoperability Signal Generation • One waveform possible for either class of device is a BPSK signal centered in the middle of the “low band” at ~ 4GHz • Such a signal could be generated by both MB-OFDM and DS-UWB devices using existing RF and digital blocks • MB-OFDM device contains a DAC nominally operating at 528 MHz • A 528 MHz BSPK (3 dB BW) signal is too wide for MB-OFDM band filters • DAC an be driven at slightly lower clock rate to produce a BPSK signal that will fit the MB-OFDM Tx filter • Result: 500 MHz BPSK signal that DS-UWB device can receive & demodulate • DS-UWB device contains a pulse generator • Use this to generate a 500 MHz BPSK signal at lower chip rate • This signal would fit MB-OFDM baseband Rx filter and could be demodulated by the MB-OFDM receiver Welborn, Freescale Semi

  9. Issues & Solutions for CSM • Common frequency band • Solution: Use MB-OFDM Band #2 • Passed by MB-OFDM FE with hopping stopped • Common FEC • Solution: Each receiver uses native FEC (e.g. k=6/7 Viterbi) • Every transmitter can encode for both codes – low complexity • Common clock frequency (“chip rate”) • Close, but final resolution still TBD • Initial CSM rates were too low for some applications • Add extensions to higher rates (at slightly reduced ranges) • As high as 110-220 Mbps for interoperability, depending on desired level of receiver complexity Welborn, Freescale Semi

  10. MB-OFDM & DS-UWB Signal Spectrum with CSM Compromise Solution MB-OFDM (3-band) Theoretical Spectrum Relative PSD (dB) Proposed Common Signaling Mode Band (500 MHz bandwidth) DS-UWB Low Band Pulse Shape (RRC) 0 -3 -20 3432 3960 4488 Frequency (MHz) 3100 5100 FCC Mask Welborn, Freescale Semi

  11. Interoperability Signal Overview • MB-OFDM band 2 center frequency for common signaling band • Centered at 3960 MHz with approximately 500 MHz bandwidth • BPSK chip rate easily derived from carrier: chip = carrier frequency / 9 • Frequency synthesis circuitry already present in MB-OFDM radio • 500 MHz BPSK is similar to original “pulsed-multiband” signals • Proposed by several companies in response to TG3a CFP • Better energy collection (fewer rake fingers) than wideband DS-UWB • More moderate fading effects than for MB-OFDM (needs less margin) • Relatively long symbol intervals (10-55 ns) avoids/minimizes ISI • Equalization is relatively simple in multipath channels • Not necessary for lowest (default) CSM control/beacon rates • Use different CSM spreading codes for each piconet • Each DEV can differentiate beacons of different piconets • Provides processing gain for robust performance: signal BW is much greater than data rate Welborn, Freescale Semi

  12. Packets For Two-FEC Support • FEC used in CSM modes to increase robustness • Each device can use native FEC decoder (e.g k=7 or 6) • For multi-recipient packets (beacons, command frames) • Packets are short, duplicate payload for two FEC types adds little overhead to piconet • For directed packets (capabilities of other DEV known) • Packets only contain single payload with appropriate FEC • FEC type(s) & data rate for each field indicated in header fields CSM PHY Preamble Headers FEC 1 Payload FEC 2 Payload Welborn, Freescale Semi

  13. Data Rates Possible for CSM Welborn, Freescale Semi

  14. Implementation • Mandatory/optional modes determined by TG to meet performance & complexity goals for applications • Implementations do not need “optimal” receivers • Sufficient margins for moderate range interoperability • Shorter codes for higher rates can be based on “sparse” codes (e.g. “1-0-0-0”) • Eliminate need for transmit power back-off • Peak-to-average still supports low-voltage implementation • Equalizers desirable at higher CSM rates (>20 Mbps?) • Complexity is very low (a few K-gates), and works great • Other transceiver blocks (Analog FE, ADC/DAC, Viterbi decoder, digital correlators, etc.) already in radio Welborn, Freescale Semi

  15. CSM Link Budgets with DS-UWB FEC Welborn, Freescale Semi

  16. CSM Link Budgets with MB-OFDM FEC Welborn, Freescale Semi

  17. Concerns • A “two PHY” solution will confuse the market • PHY waveform is transparent to application • This “multi-mode PHY” solution allows interoperability with high functionality and prevents interference/QoS breakdown • Even a “single PHY” solution will have multiple modes & allows devices with different capability levels • CSM interoperability data rates can be high enough to meet PAR (110 Mbps) -- even between dissimilar device classes • Complexity: CSM additional complexity can be very low and doesn’t require optimal receivers • Higher rates benefit from simple equalizers and/or digital rake • “I would really like to continue attending TG3a meetings indefinitely!” • Are you crazy? Welborn, Freescale Semi

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