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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: [DS-UWB Proposal Update] Date Submitted: [July 2004]

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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: [DS-UWB Proposal Update] Date Submitted: [July 2004] Source: [Reed Fisher(1), Ryuji Kohno(2), Hiroyo Ogawa(2), Honggang Zhang(2), Kenichi Takizawa(2)] Company [ (1) Oki Industry Co.,Inc.,(2)National Institute of Information and Communications Technology (NICT) & NICT-UWB Consortium ]Connector’s  Address [(1)2415E. Maddox Rd., Buford, GA 30519,USA, (2)3-4, Hikarino-oka, Yokosuka, 239-0847, Japan] Voice:[(1)+1-770-271-0529, (2)+81-468-47-5101], FAX: [(2)+81-468-47-5431], E-Mail:[(1)reedfisher@juno.com, (2)kohno@nict.go.jp, honggang@nict.go.jp, takizawa@nict.go.jp ] Source: [Michael Mc Laughlin] Company [decaWave, Ltd.] Voice:[+353-1-295-4937], FAX: [-], E-Mail:[michael@decawave.com] Source: [Matt Welborn] Company [Freescale Semiconductor, Inc] Address [8133 Leesburg Pike Vienna, VA USA] Voice:[703-269-3000], E-Mail:[matt.welborn@freescal.com] Re: [] Abstract: [Technical update on DS-UWB (Merger #2) Proposal] Purpose: [Provide technical information to the TG3a voters regarding DS-UWB (Merger #2) Proposal] 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. Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  2. Outline • Merger #2 Proposal Overview • DS-UWB + Common Signaling Mode (CSM) + MB-OFDM • Complexity/Scalability of UWB implementations • Spectral control options for DS-UWB • Performance Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  3. Overview of DS-UWB Proposal • Merged Proposal #2 has a fundamental goal of DS-UWB and MB-OFDM harmonization & interoperability through a Common Signaling Mode (CSM) • High rate modes using either DS-UWB or MB-OFDM • Best characteristics of both approaches with most flexibility • A piconet could have a pair of DS and a pair of MB devices • CSM waveform provides control & interoperation between DS-UWB and MB-OFDM • All devices work through an 802.15.3 MAC • User/device only sees common MAC interface • Hides the actual PHY waveform in use Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  4. The Common Signaling Mode:What Is The Goal? • The common signaling mode (CSM) allows the 802.15.3 MAC to arbitrate between multiple UWB PHYs • It is an “etiquette” to manage peaceful coexistence between the different UWB PHYs • Multiple UWB PHYs will exist in the world • DS-UWB & MB-OFDM are first examples • CSM improves the case for international regulatory approval • Common control mechanism for a multitude of applications • Planned cooperation (i.e. CSM) gives far better QoS and throughput than allowing un-coordinated operation and interference • CSM provides flexibility/extensibility within the IEEE standard • Allows future growth & scalability • Provides options to meet diverse application needs • Enables interoperability and controls interference Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  5. What Does CSM Look Like?One of the MB-OFDM bands! Proposed Common Signaling Mode Band (500+ MHz bandwidth) 9-cycles per BPSK “chip” DS-UWB Low Band Pulse Shape (RRC) 3-cycles per BPSK “chip” 3978 Frequency (MHz) 3100 5100 MB-OFDM (3-band) Theoretical Spectrum Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  6. CSM Specifics • We have designed a specific waveform for the CSM • BPSK modulation for simple and reliable performance • Length 24 spreading codes using 442 MHz chip rate • Harmonically related center frequency of 3978 MHz • Rate ½ convolutional code with k=6 • Provides 9.2 Mbps throughput • Extendable up to 110 Mbps using variable code and FEC rates • 802.15.3 MAC works great with CSM • CSM can be used for control and beaconing • Negligible impact on piconet throughput (beacons are <1%) • Requires negligible additional cost/complexity for either radio • MB-OFDM already has a DS mode that is used for synchronization • This proposal is based on both MB-OFDM and DS-UWB operating with a 26 MHz cell-phone crystal • Very low cost yet terrific phase-noise and accuracy (see GSM spec) Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  7. Overview of DS-UWB Proposal • DS-UWB proposed as a radio for handheld with • low-cost, • ultra high-rate, • ultra low-power, • BPSK modulation using variable length spreading codes • Scales to 1+ Gbps with low power - essential for mobile & handheld applications • Much lower complexity and power consumption Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  8. 1 1 … … -1 -1 Overview of DS-UWB Proposal • Two wide 50%-bandwidth contiguous bands • Each captures unique propagation benefits of UWB • Bandwidth and Center Frequency Programmable • Low band provides long wavelet • High band provides short wavelet • Wavelet = 3 cycles, packed back-to-back 3 4 5 6 7 8 9 10 11 GHz • Wavelets are modulated with BPSK or QPSK • Symbol is made with an N-chip code sequence • Code is ternary (+1, 0, -1) N-chips • Result is Not-spiky in either Time or Frequency Domain volts time Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  9. DS-UWB Signal Generation Input Data Scrambler K=6 FEC Encoder Conv. Bit Interleaver Bit-to-Code Mapping Pulse Shaping Static Center Frequency Gray or Natural mapping K=4 FEC Encoder 4-BOK Mapper Transmitter blocks required to support optional modes • Data scrambler using 15-bit LFSR (same as 802.15.3) • Constraint-length k=6 convolutional code • K=4 encoder can be used for lower complexity at high rates or to support iterative decoding for enhanced performance (e.g. CIDD) • Convolutional bit interleaver protects against burst errors • Variable length codes provide scalable data rates using BPSK • Support for optional 4-BOK modes with little added complexity Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  10. Data Rates Supported by DS-UWB Similar Modes defined for high band Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  11. 1-16 Rake Fingers (or more) Variable Equalizer Span Variable Rate FEC (or no FEC) 1 to 3 bits ADC Resolution Pre-Select ADC at Chip Rate GA/ VGA Filter LPF De-interleave & FEC Decode LNA DFE Rake ADC at Chip Rate GA/ VGA LPF Cos Agile Clock Synch/ Track Logic Sin DS-UWB Architecture Is Highly Scaleable • DS-UWB provides low & scalable receiver complexity • ADC can range from 3 bits to 1 bit for super-low power implementation • Rake pipeline & DFE can be optimized to trade off power & cost in multipath • 16 fingers @ 220, 5 fingers @ 500, 2 fingers @ 1326Mbps • Time duration of DFE scales (shrinks) at shorter range – higher rates. • FEC can scale w/data rate (k=6 & k=4) or be turned-off for ultra low power • DFE effectiveness and simplicity proven in shipping chips – 3% of area Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  12. UWB System Complexity & Power Consumption • Two primary factors drive complexity & power consumption • Processing needed to compensate for multipath channel • Modulation requirements (e.g. low-order versus high-order) • DS-UWB designed to operate with simple BPSK modulation for all rates • Receiver functions operate at the symbol rate • Optional 4-BOK has same complexity and BER performance • MB-OFDM operates at fixed 640 Mbps (raw) • Designed to operate at high rate, then use carrier diversity (redundancy) and/or strong FEC to combat multipath fading • Diversity not used above 200 Mbps Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  13. Fundamental Design Approach Differences • Signal bandwidth leads to different operating regimes • DS-UWB uses 1.326 GHz bandwidth • MB-OFDM data BW is 412.5 MHz (100 tones x 4.125 MHz/tone) • Modulation bandwidth induces different fading statistics • DS-UWB (single carrier UWB) results in frequency-selective fading with relatively low power fluctuation (variance) • MB-OFDM (multi-carrier) creates a bank of parallel channels that experience flat fading with a Rayleigh distribution (deep fades) • Motivations for different choices • Different energy capture mechanism (rake vs. FFT) • Different ISI compensation (time vs. frequency domain EQ) • These fundamental differences affect both complexity & flexibility • Significant impact on implementation, especially at high rates Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  14. Analog Complexity • Equivalent analog components have similar complexity Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  15. Implications of Switchable UNII Filter(slide copied from Doc 03/141r3,p12) • MB-OFDM is proposed to use the UNII band for Band Group 2 • If the operating BW includes the U-NII band, then interference mitigation strategies have to be included in the receiver design to prevent analog front-end saturation. • Example: Switchable filter architecture. • When no U-NII interference is present, use standard pre-select filter. • When U-NII interference is present, pass the receive signal through a different filter (notch filter) that suppresses the entire U-NII band. • Problems with this approach: • Extra switches  more insertion loss in RX/TX chain. • More external components  higher BOM cost. • More testing time. Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  16. Band-Select Filter Complexity DS-UWB Filter Bandwidth of DS-UWB > 1500 MHz Uses single fixed bandwidth – filter provides rejection for OOB noise & RFI • MB-OFDM filter complexity • depends on requirements to reject • adjacent-band signal energy • Depends on whether design • is using the guard tones for • real data or just PN modulated • noise Data tones Guard tones Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  17. MB-OFDM Band-Select Filter Complexity Tight filter constraint • If guard tones are used for useful data, band filter must have very steep cut-off • Transition region is very narrow • Only 5 un-modulated tones between bands (~21 MHz) • SOP performance also affected by filter design – rejection of adjacent band MAI for SOP • If guard tones not used for data, then filter constraint is relaxed • Transition region is a wider (15 tones ~62 MHz) • Energy in guard band is distorted (not useful) • May not meet FCC UWB requirement for 500 MHz Filter must reject MAI for SOP Relaxed filter constraint Data tones Guard tones Filter response Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  18. Comparison of DS-UWB to MB-OFDM Digital Baseband Complexity for PHY • Gate count estimates are based on MB-OFDM proposal team methodology detailed in IEEE Document 03/449r2 • Gate counts converted to common clock (85.5 MHz) for comparison • Explicit MB-OFDM gates counts have only been reported by proposers for a 110/200 Mbps implementation • Other estimates of MB-OFDM Viterbi decoder and FFT engine are provided in IEEE Document 03/343r0 • Estimates for MB-OFDM 480 Mbps mode complexity are based on scaling of FFT engine, equalizer and Viterbi decoder • MB-OFDM estimates of 480 Mbps power available in 03/268r3 • Details available in IEEE Document 04/164r0 • Estimates for MB-OFDM 960 Mbps mode details are based on linear scaling of decoder and FFT engine to 960 Mbps • Assumes 6-bit ADC for 16-QAM operation • DS-UWB gate estimates are detailed in IEEE Document 03/099r4 • Methodology for estimating complexity of 16-finger rake, equalizer and synchronization blocks are per MB-OFDM methodology Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  19. DS-UWB & MB-OFDM Digital Baseband Complexity • Gate counts are normalized to 85.5 MHz Clock speeds to allow comparison • Based on methodology presented by MB-OFDM proposal team (03/449r3) • Other details of gate count computations in Documents 04/099 and 04/256r0 Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  20. Digital Baseband Complexity Comparison at ~1 Gbps Assumptions: MB-OFDM using 6-bit ADC, FFT is 2.25x & Viterbi is 4x of low rate. *DS-UWB operating with no FEC at 1.362 Gbps Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  21. p(t) D w0 w1 x(t) Optional Improvement for Interference Mitigation (Approach 1):Analog type of SSA- Notch generation by using a simple analog delay line: • Example： Just Two taps delay line The output signal x(t) is given by where p(t) is a pulse signal , and d is delayed time by a delay line D. By assuming that coefficients w0 and w1 is time- invariant, then its signal in frequency domain is given by ＋ Now, we set w0=1 and w1=a (a is in real value), we obtain A notch is generated at a frequency fnwhere |X(fn)|2=0, then The solutions are given by , however,the coefficient a can take only real value. Therefore, （m=1,2,3,…） As you can see, the coefficient a takes +1 or -1. It leads simple implementation. The right figure is an example; a is set to 1 and d is set at 0.116nsec. Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  22. Optional Improvement for Interference Mitigation (Approach 2): Analog type of SSA- Notch generation by using a spreading code • DS-UWB systems Tx model 2 Tx model 1 b(t) x(t) x(t) b(t) X X X X X X X c(t) fc c(t) fc cl(t) p(t) p(t) long code Spreading code Pulse signal Carrier frequency (Scrambler) Spreading code Pulse signal Carrier frequency Assumption: Chip rate of a long code is the same as bit rate. c(t)=[-1 -1 -1 1 1 -1 1 1] cl(t), c(t)=[-1 -1 -1 1 1 -1 1 1] Example: Example: • 　Narrow and Repetitive • 　Narrow and Repetitive 4.3GHz (EES) 4.3GHz (EES) Note: These notches are diminished by a bi-phase modulation. Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  23. Optimization of coding rate and spreading factor • Original VS-DS-UWB (Have you already optimized the combinations ?) > >= • The other combinations FEC Rate=1/2: [53,75] FEC Rate=1/3: [47,53,75] Constraint length is fixed to 6 FEC Rate=1/4: [53,67,71,75] Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  24. Multipath Performance for 110 Mbps Simulation Includes: 16 finger rake with coefficients quantized to 3-bits 3-bit A/D (I and Q channels) RRC pulse shaping DFE trained in < 5us in noisy channel Front-end filter for Tx/Rx + 6.6 dB Noise Figure Packet loss due to acquisition failure Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  25. Multipath Performance for 220 Mbps Simulation Includes: 8 finger (16 finger) rake with coefficients quantized to 3-bits 3-bit A/D (I and Q channels) RRC pulse shaping DFE trained in < 5us in noisy channel Front-end filter for Tx/Rx + 6.6 dB Noise Figure Packet loss due to acquisition failure Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  26. Multipath Performance for 500 Mbps Simulation Includes: 16 finger rake with coefficients quantized to 3-bits 3-bit A/D (I and Q channels) RRC pulse shaping DFE trained in < 5us in noisy channel Front-end filter for Tx/Rx + 6.6 dB Noise Figure Packet loss due to acquisition failure Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  27. AWGN SOP Distance Ratios • AWGN distances for low band • High band ratios expected to be lower • Operates with 2x bandwidth, so 3 dB more processing gain Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  28. Multipath SOP Distance Ratios Test Transmitter: Channels 1-5 Single Interferer: Channels 6-10 Second Interferer: Channel 99 Third Interferer: Channel 100 • High band ratios expected to be lower (3 dB more processing gain) Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  29. Conclusions • Our 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 & 200+ Mbps: • Compliant device can implement either DS-UWB or MB-OFDM (or both) • Increases options for innovation and regulatory flexibility to better address all applications and markets • DS-UWB is shown to have equal or better performance to MB-OFDM in all modes and multipath conditions – for a fraction of the complexity & power Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  30. Back-up slides Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  31. Notch generation by using a spreading code • DS-UWB systems Tx model Frequency domain b(t) x(t) X X X c(t) fc p(t) Output spectrum is given by convolution Carrier Spreading code Pulse signal Spectrum of a spreading code Example: Convolution Spectrum of a pulse signal Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  32. Notch generation by using a spreading code • Experimental result by UWB Test bed MATLAB results UWB testbed outputs Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  33. All-Digital Architecture DS-UWB Receiver 1-16 Rake Fingers (or more) Variable Equalizer Span Variable Rate FEC (or no FEC) 1 to 3 bits ADC Resolution • DS-UWB Digital architecture provides scalable receiver complexity • ADC can range from 3 bits to 1 bit for super-low power implementation • Rake & DFE can be optimized to trade off power & cost in multipath • FEC can scale data rate or be turned-off for low power operation • DFE effectiveness and simplicity proven in shipping chips Pre-Select ADC at Chip Rate GA/ VGA Filter LPF De-interleave & FEC Decode LNA DFE Rake ADC at Chip Rate GA/ VGA LPF Cos Agile Clock Synch/ Track Logic Sin Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  34. Scalability to Varying Multipath Conditions • Critical for handheld (battery operated) devices • Support operation in severe channel conditions, but also… • Ability to use less processing (& battery power) in less severe environments • Multipath conditions determine the processing required for acceptable performance • Collection of time-dispersed signal energy (using either FFT or rake processing) • Forward error correction decoding & Signal equalization • Poor: receiver always operates using worst-case assumptions for multipath • Performs far more processing than necessary when conditions are less severe • Likely unable to provide low-power operation at high data rates (500-1000+ Mbps) • DS-UWB device • Energy capture (rake) and equalization are performed at symbol rate • Processing in receiver can be scaled to match existing multipath conditions • MB-OFDM device • Always requires full FFT computation – regardless of multipath conditions • Channel fading has Rayleigh distribution – even in very short channels • CP length is chosen at design time, fixed at 60 ns, regardless of actual multipath Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  35. Interference Issues (1) • Hopped versus non-hopped signal characteristics • ITS and FCC studies are underway • Goal is to see if interference characteristics of MB-OFDM are acceptable for certification (using DS-UWB/noise/IR for comparison) • Use of PN-modulation to meet 500 MHz BW • Recent statements by NTIA emphasize importance of minimum • Desire is to ensure protection for restricted bands • DS-UWB bandwidth is determined by pulse shape and pulse modulation • Spectrum exceeds 1500 MHz • MB-OFDM bandwidth for data and pilot tones is 466 MHz, guard tones are used to increase bandwidth to 507 MHz • Guard tones “carry no useful information”, only to meet BW req’t. • See authors statements in 802.15-03/267r1 (July 2003, page 12) Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  36. NTIA Comments on Using Noise to meet FCC 500 MHz BW Requirement • NTIA comments specifically on the possibility that manufacturer would intentionally add noise to a signal in order to meet the minimum FCC UBW 500 MHz bandwidth requirements: “Furthermore, the intentional addition of unnecessary noise to a signal would violate the Commission’s long-standing rules that devices be constructed in accordance with good engineering design and manufacturing practice.” • And: • “It is NTIA’s opinion that a device where noise is intentionally injected into the signal should never be certified by the Commission.” • Source: NTIA Comments (UWB FNPRM) filed January 16, 2004 available at http://www.ntia.doc.gov/reports.html Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

  37. FCC Rules Regarding Unnecessary Emissions • FCC Rules in 47 CFR Part 15 to which NTIA refers: “§ 15.15 General technical requirements. (a) An intentional or unintentional radiator shall be constructed in accordance with good engineering design and manufacturing practice. Emanations from the device shall be suppressed as much as practicable, but in no case shall the emanations exceed the levels specified in these rules.” Kohno NICT, Welborn Freescale, Mc Laughlin decaWave

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