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

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: STM_CEA-LETI_CWC_AETHERWIRE 15.4aCFP response Date Submitted: January 4th, 2005 Source: Ian Oppermann (1), Mark Jamtgaard (2), Laurent Ouvry (3), Philippe Rouzet (4) Companies:
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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
  • Submission Title:STM_CEA-LETI_CWC_AETHERWIRE 15.4aCFP response
  • Date Submitted: January 4th, 2005
  • Source: Ian Oppermann (1), Mark Jamtgaard (2), Laurent Ouvry (3), Philippe Rouzet (4)
  • Companies:
  • (1) CWC-University of Oulu, Tutkijantie 2 E, 90570 Oulu, FINLAND
  • (2) Æther Wire & Location, Inc., 520 E. Weddell Drive, Suite 5, Sunnyvale, CA 94089, USA
  • (3) CEA-LETI, 17 rue des Martyrs 38054, Grenoble Cedex, FRANCE
  • (4) STMicroelectronics, CH-1228, Geneva, Plan-les-Ouates,SWITZERLAND
  • Voice: (1) +358 407 076 344, (2) 408 400 0785 (3) +33 4 38 78 93 88, (4) +41 22 929 58 66
  • E-Mail: (1) ian@ee.oulu.fi, (2) mark@aetherwire.com(3) laurent.ouvry@cea.fr, (4) philippe.rouzet@st.com,
  • Abstract: UWB proposal for 802.15.4a alt-PHY
  • Purpose: Proposal based on UWB impulse radio for the IEEE 802.15.4a CFP
  • 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 contributors acknowledge and accept that this contribution becomes the property of IEEE and may be made publicly available by P802.15
  • List of Authors
  • CWC– Ian Oppermann, Alberto Rabbachin (1)
  • AetherWire – Mark Jamtgaard, Patrick Houghton (2)
  • CEA-LETI – Laurent Ouvry, Samuel Dubouloz, Sébastien de Rivaz, Benoit Denis, Michael Pelissier, Manuel Pezzin et al. (3)
  • STMicroelectronics – Gian Mario Maggio, Chiara Cattaneo, Philippe Rouzet & al. (4)
  • Outline
  • Introduction
  • Transmitter
  • Receiver architectures
  • System performances
  • Link budget
  • Framing, throughput
  • Power Saving
  • Ranging
  • Proof of concept
  • Conclusions
  • Introduction (1/2)
  • Proposal main features:
  • Impulse-radio based (pulse-shape independent)
  • Support for different receiver architectures (coherent/non-coherent)
  • Flexible modulation format
  • Support for multiple rates
  • Enables accurate ranging/positioning
  • Support for multiple SOP
  • Introduction (2/2)
  • Motivation for (2-4):
  • Supports homogenous and heterogeneous network architectures
  • Different classes of nodes, with different reliability requirements (and cost) must inter-work
  • Commonalities with Other Proposals
  • Many commonalities exist between the CWC/Aetherwire/LETI/STM proposal and other proposals, including FT and Mitsubishi:
  • UWB technology
  • Modulation features
  • Bandwidth usage
  • Ranging approach
  • Discussions are under way for future collaborations and merging
  • UWB Technology
  • Impulse-Radio (IR) based:
  • Very short pulses  Reduced ISI
  • Robustness against fading
  • Episodic transmission (for LDR) allowing long sleep-mode periods and energy saving
  • Low-complexity implementation
  • Modulation Features
  • Simple, scalable modulation format
  • Flexibility for system designer
  • Modulation compatible with multiple coherent/non-coherent receiver schemes
  • Time hopping (TH) to achieve multiple access
  • Bandwidth Usage (1/2)
  • Flexible use of (multi-)bands depending on application and regulatory environment
  • Use of TH and/or polarity randomization for spectral smoothing
  • Noise-like interference towards existing radio services
  • Bandwidth Usage (2/2)ISM BandISM BandUpper Band 3Upper Band 1Upper Band 2Lower band 0.96 3.1 5.1 6.0 8.0 8.1 10.1 GHzRanging Approach
  • Signal bandwidth ≥ 1GHz for very good location accuracy
  • Two-way ranging protocol to avoid synchronization between nodes
  • Location based on ranging from several nodes on a higher layer
  • Preliminaries (1/2)
  • Definitions:
  • Coherent RX: The phase of the received carrier waveform is known, and utilized for demodulation
  • Differentially-coherent RX: The carrier phase of the previous signaling interval is used as phase reference for demodulation
  • Non-coherent RX: The phase information (e.g. pulse polarity) is unknown at the receiver -operates as an energy collector
  • Preliminaries (2/2)
  • Pros (+) and cons (-) of RX architectures:
  • Coherent
  • + : Sensitivity
  • + : Use of polarity to carry data
  • + : Optimal processing gain achievable
  • - : Complexity of channel estimation and RAKE receiver
  • - : Longer acquisition time
  • Differential (or using Transmitted Reference)
  • + : Gives a reference for faster channel estimation (coherent approach)
  • + : No channel estimation (non-coherent approach)
  • - : Asymptotic loss of 3dB for transmitted reference (not for DPSK)
  • Non-coherent
  • + : Low complexity
  • + : Acquisition speed
  • - : Sensitivity, robustness to SOP and interferers
  • ½ PRP½ PRPTX: Modulation FormatsPRP« 1 »OOK« 0 »D« 1 »TR-BPSK« 0 »« 1 »DBPSK (one pulse per PRP ) « 0 »« 1 »BPPM« 0 »½ PRP½ PRPTX: Multi-pulse Modulation FormatsPRP« 1 »OOK« 0 »Scope for Adding more information with multi-pulseD« 1 »TR-BPSK« 0 »« 1 »DBPSK« 0 »« 1 »BPPM« 0 »Transmitted Reference (TR)
  • TR schemes simplify the channel estimation process
  • Reference waveform available for synchronisation
  • Potentially more robust (than non-coherent) under SOP operation
  • Supports both coherent/differentially-coherent demodulation
  • Reference waveform averaging (non-coherent integration);
  • see also GLRT [Franz, Mitra; Globecom’03, pp. 744-748, Dec 2003]
  • Implementation challenges:
  • Analogue: Implementing delay value,
  • delay mismatch, jitter
  • DTR Schemes (1/3)
  • GTR (Generalized Transmitted Reference) BPSK
  • Extension to N-ary TRD« A »« B »« C »« D »PRP
  • Concept: Multi-level version of the TR scheme, where the energy associated with the reference pulse is “shared” to improve efficiency
  • D1TR Schemes (2/3)
  • TR-BPPM (with/without BPAM)
  • Extension to N-ary TR« A »D2« B »« C »CoherentDetection« D »PRP
  • Concept: Transmitted-reference version of BPPM, with BPAM [Zasowski, Althaus and Wittneben, Proc. IWUWBS/UWBST’04, Kyoto, Japan]
  • TR-BPPM (non-coherent): Binary symbols restricted to “A” and “B”
  • D½ PRP½ PRPTR Schemes (3/3)
  • TR-PCTH (pseudo-chaotic time hopping)
  • [Maggio, Reggiani, Rulkov; IEEE Trans. CAS-I, v. 48, no. 12, p. 1424, Dec 2001]
  • Random inter-pulse intervalExtension to N-ary TR« 0 »« 1 »
  • Concept: Random TH  Smoothes spectral lines in the PSD
  • Modulation: Pulses in the first ½ PRP correspond to “0” and vice versa for“1”
  • Demodulation: Similar to PPM, but more flexible (threshold or Viterbi detector)
  • Transmission
  • Combine BPPM with more sophisticated TR scheme
  • Non-coherent receiver sees BPPM with pulse stream per bit
  • More sophisticated receiver sees BPPM (1 bit) plus bits carried in more sophisticated modulation scheme (e.g. extended TR)
  • Advantages:
  • Differential and non-coherent receiver may coexist
  • reference can be used for synch and threshold estimation
  • Concept can be generalized to N-ary TR-BPSK
  • Design Parameters (1/6)
  • Motivation:
  • Flexible waveform
  • Still simple
  • Compatible with multiple coherent/non-coherent receiver schemes
  • Limitations (compliant with FCC)
  • Increased Bandwidth (pros/cons)
  • (+) High transmit power
  • (+) High time resolution
  • (-) Increased design complexity
  • (-) Less stringent requirements on out of band interference filtering
  • Signal BW of 500 MHz - 2 GHz in Upper bands
  • Signal BW of 700 MHz in 0 to 960 MHz Lower band (low band)
  • Increased Pulse Repetition Period (pros/cons)
  • (+) more energy per pulse (easier to detect single pulse)
  • (+) Lower inter-channel interference due to channel delay spread
  • (-) Transmitter peak voltage compatible with technology
  • (-) Acquisition time
  •  PRP (chip period) Between 250ns and 500nsTX: Design Parameters (2/6)
  • Simple modulation schemes:
  • BPPM combined with Transmitted Reference
  • min 1 bit/symbol for non-coherent, 2 bits/symbol for TR (more for GTR)
  • Channelization :
  • Coherent schemes: Use of TH codes and polarity codes
  • Non-coherent schemes: Use of TH codes (polarity codes for spectrum smoothing only)
  • Increased TH code length (pros/cons):
  • (+) higher processing gain, robustness to SOP operation
  • (-) Lower bit-rate
  • (-) Faster acquisition, shorter frame size (synch. phase)
  • TH code length 8 or 16
  • TX: Design Parameters (3/6)
  • Basic Mode - Upper-bands (XH0=250 Kbps):
  • PRP = 250 ns, binary modulation, TH code length of 16chips
  • N pulses per symbol (1 < N < 124)
  • PHY-SAP payload bit rate (Xo) is 250 kbps
  • Enhanced Mode 1 - Upper-bands (XH1=500 Kbps):
  • PRP = 250 ns, 4-level modulation, TH code length of 16chips
  • N pulses per symbol (1 < N < 124)
  • PHY-SAP payload bit rate (Xo) is 500 kbps
  • Enhanced Mode 2 - Upper-bands (XH2=1000 Kbps):
  • PRP = 250 ns, 8-level modulation, TH code length of 16chips
  • N pulses per symbol (1 < N < 40)
  • PHY-SAP payload bit rate (Xo) is 1000 kbps
  • D« 1 1 »« 1 0 »Enhanced Mode 1«0 1 »«0 0 »« 1 1 1 1»« 1 0 1 0 »Enhanced Mode 2½ PRP½ PRPTX: Design Parameters (4/6)« 1 »Basic Mode« 0 »Need not fill entire slot« 1 »Basic Mode(as seen by receiver)« 1 1 »Enhanced Mode 1 (randomising code)TX: Design Parameters (5/6)« 1 1 »Enhanced Mode 1« 1 0 »Position Swap, polarity invertTH PatternTH Code 1,1 1,1 0,1 0,0 1,0 0,1Data 1,1 1,1 1,1 1,1 1,1 1,1TX: Design Parameters (6/6)
  • Basic Mode - Lower-band (XL0=250 Kbps):
  • PRP = 500 ns, binary modulation, TH code length of 8 chips
  • N pulses per symbol (1 < N < 120)
  • PHY-SAP payload bit rate (Xo) is 250 kbps
  • Enhanced Mode 1 - Lower-band (XL1=500 Kbps):
  • PRP = 500 ns, 4-level modulation, TH code length of 8 chips
  • N pulses per symbol (1 < N < 120)
  • PHY-SAP payload bit rate (Xo) is 500 kbps
  • Enhanced Mode 2 - Lower-band (XL2=1000 Kbps):
  • PRP = 500 ns, 8-level modulation, TH code length of 8 chips
  • N pulses per symbol (1 < N < 40)
  • PHY-SAP payload bit rate (Xo) is 1000 kbps
  • SynchronizationClock TrackingThresholds settingChannel EstimationTrigADCBand MatchedBPFBufferLNAThresholdIntegration / DecisionEstimated CIRCoefficientsCoherent Receiver ArchitectureBand MatchedADCADCBPFADCDumpLatchTRDelayControlledIntegratorBPPM Synch TriggerTR Demodulation branchDifferentially-Coherent/Non-Coherent Receiver Architecture Basic Mode and Enhanced Mode 1BPPM Demodulation branchControlledIntegratorr(t)LNADumpLatch x2RAZRAZDUMPSynchroTrackingThresholds settingTHRESHOLDRanging branchComparatorTriggerIntegratorTime baseRecyle this branch for Enhanced Mode 2Band MatchedBand MatchedADCADCBPFBPFDe-spreading TH CodesTH Sequence Matched Filterr(t)Bit Demodulation LNACase I - Coherent TH despreadingTH Sequence Matched Filterb(t) soft infoBit Demodulation r(t)LNACase II – Non-coherent / differential TH despreadingPreamble(32 bits)SFD(8 bits)LEN(8 bits)MHR+MSDU(240 bits)CRC(16 bits)PER in 15.4a Channel Model Non-Coherent (Energy Collection) BPPMFraming format:
  • Simulations over 1000 channel responses
  • BW = 2GHz – Integration Time = 80ns
  • Implementation loss + Noise figure margin : 11 dB
  • Max range is determined from:
  • Required Eb/N0,
  • Implementation margin
  • Path loss characteristics
  • Case I: 250 kbps – PRP 250 ns with 16 pre-integrations = 4 µsCase II: 250 kbps – PRP 500 ns with 8 post-integrationsDBPSK – PER vs. Eb/N0 – 15.4a Channel Models 010X1X2X3X4-110PER-210-3101011121314151617181920Eb/N (dB)0 PER/BER in 15.4a Channel Model DBPSK (RAKE)Theoretical BER Curves – Integration Time = 50 nsImplementation loss and Noise figure margin : 11 dBCase I: 250 kbps – PRP 250 ns with 16 pre-integration = 4 µsCase II: 250 kbps – PRP 500 ns with 8 post-integrationsLink Budget: Non-Coherent (Energy Collection) BPPMLink Budget: DBPSK (RAKE)BP : Beacon PeriodCAP : Contention Access PeriodCFP : Contention Free PeriodIP : Inactive Period (optional)Beacon slotCAP slotCFP slotOctets411320123456789101112131415PHY layerPreambleSFDFrame lengthPSDU = MPDUBPCAPCFPIPSHRPHRPSDU (PHY Service Data Unit)Superframe DurationBeacon IntervalPPDU (PHY Protocol Data Unit)Framing – 802.15.4 CompatibleBytes4115PHY layerPreambleSFDFrame lengthPSDUSHRPHRPSDUPPDU (PHY Protocol Data Unit)Bytes41132PHY layerPreambleSFDFrame lengthPSDU = MPDUSHRPHRPSDU (PHY Service Data Unit)PPDU (PHY Protocol Data Unit)ThroughputData Frame (32 octet PSDU) ACK Frame (5 octet PSDU) TdataT_ACKTackIFS
  • Numerical example (high-band)
  • Preamble + SFD + PHR = 6 octets
  • Tdata = 1.216 ms
  • T_ACK = 50 ms (turn around time requested by IEEE 802.15.4 is 192ms)
  • Tack = 0.352 ms
  • IFS = 100μs
  • Throughput = 32 octets/1.718 ms = 149 kb/s
  • Average data-rate at receiver PHY-SAP 250 kb/s (Basic Mode)
  • Power Saving techniques achieved by combining advantages offered at 3 levels:Technology (best if CMOS)Architecture (flexible schemes provided by the TH+pulse modulation)System level (framing, protocol usage)Selected techniques used in one existing realization (see proof of concept slides) Low-duty cycle Episodic transmission/receptionScheduled wake-up80ms RTOS tickAd-hoc networking using multi-hopSpecial rapid acquisition codes / algorithmMatchmaking further reduces acquisition timeMulti-stage time-of-day clockSynchronous counter / current mode logic for highest speed stagesRipple counter / static CMOS for lowest speed stagesCompute-intensive correlation done in hardwareSaving PowerRanging
  • Motivation :
  • Benefit from high time resolution (thanks to signal bandwidth):
  • Theoretically: 2GHz provides less than 20cm resolution
  • Practically: Impairments, low cost/complexity devices should support ~50cm accuracy with simple detection strategies (better with high resolution techniques)
  • Approach :
  • Use Two Way Ranging between 2 devices with no network constraint (preferred); no need for time synchronization among nodes
  • Use One Way Ranging and TDOA under some network constraints (if supported)
  • TOF EstimationRequestTwo Way Ranging (TWR)T1ToTerminal A TX/RXTerminal B RX/TXTOFTOFTReplyTerminal APrescribed Protocol Delay and/or Processing TimeTerminal BMain Limitations / Impact of Clock Drift on Perceived TimeTwo Way Ranging (TWR)Is the frequency offset relative to the nominal ideal frequency
  • Range estimation is affected by :
  • Relative clock drift between A and B
  • Prescribed response delay
  • Clock accuracy in A and B
  • Channel response (weak direct path)
  • Example using Imm-ACK SIFS of 15.4 and 15.3
  • Relaxing constraints on clock accuracy is possible by
  • Performing fine drift estimation/compensation
  • Benefiting from cooperative transactions (estimated clock ratios …)
  • Adjusting protocol durations(time stamp…)
  • 20dB SNR, 3ns Integration Non-Coherent Energy DetectionTOA estimation with serial search. Parameters: uncertainty region of 13 ns, search region 20 ns, integration window 3 ns, SNR of 20 dB, CM1 (802.15.3a)TOA Error CDF (CM1 802.15.3a)TOA error CDF for serial search. Integration window of 3 and 4 ns.55 mm40 mmAntenna FeasibilityCapacitive Dipole and Various Bowtie AntennasBowtie antennaCWC Oulu“Proof-of-Concept” (1) Non-coherent TransceiverNon-coherent, Energy Collection Receiver5 Mbps BPPM 350 ps pulse train with long scrambling codeCWC Oulu“Proof-of-Concept” (2) Non-coherent TransceiverUWB-IR BPPM Non-Coherent Transceiver ImplementationUWB Transmitter400 μm x 400 μm 0.35 μm CMOSUWB TransceiverTest architecture <10 mm20.35 μm SiGe Bi-CMOSP-Channel DriversN-Channel DriversN-CDelayBuffers“Proof-of-Concept” (3): Transmitter - Lower Band UWB Transmitter chip for generating impulse doubletsLF RTCDACsHigh-FrequencyReal Time ClockCodeSequenceGeneratorsDACsPLL Loop Filter32 Time-IntegratingCorrelators“Rails” for testing analog circuitsVGC Amp“Proof-of-Concept” (4): Receiver - Lower Band Coherent UWB Receiver withmultiple time integrating correlators“Proof-of-Concept” (5) High Speed Coherent Circuit ElementsRF front end chips in CMOS 0.13mm, 1.2V20 GHz digitizer for UWB20 GHz DLL for UWB3-5 GHz LNAChip and layoutConclusions
  • Proposal based upon UWB impulse radio
  • High time resolution suitable for precise ranging using TOA
  • Modulation:
  • Pulse-shape independent
  • Robust under SOP operation
  • Facilitates synchronization/tracking
  • Supports multiple coherent/non-coherent RX architectures
  • System tradeoffs
  • Modulation optimized for several aspects (requirements, performances, flexibility, technology)
  • Trade-off complexity/performance RX
  • Flexible implementation of the receiver
  • Coherent, differential, non-coherent (energy collection)
  • Analogue, digital
  • Fits with multiple technologies
  • Easy implementation in CMOS
  • Very low power solution (technology, architecture, system level)
  • Backup Slides-110-210BER-310-410-510567891011121314151617181920 Eb/N0 BER Performance in AWGN ChannelMRC Solution (coherent)Differential SolutionEnergy Collection solution in OOKTransmitted Reference (one pulse)-3 dB : the “reference” is not in the same PRP !PER = 1% with 32 bytes PSDU  acceptable BER 4x10-5 with no channel codingBER Performance in AWGN Channelzantenna hat Ø 24 mmq7 mmyjground plane Ø 80 mmxAntenna Practicality
  • Bandwidth: 3 GHz-10 GHz
  • Form factor
  • Omni-directional
  • Info T2 IsochronousInfo T3Info T3TDOAEstimationInfo T2TOAEstimationTime Difference Of Arrival (TDOA) & One Way Ranging (OWR)TDOAEstimationMobile TXTOAEstimationToTOF,1Anchor 1Anchor 1 RXT1TOF,2Anchor 2 RXT2MobileTOF,3Anchor 3 RXAnchor 2T3Anchor 3Passive LocationIsochronousAnchor 3 (xA3,yA3)Anchor 2 (xA2,yA2)Mobile (xm,ym)Estimated PositionMeasurementsAnchor 1 (xA1,yA1)Positioning from TDOA3 anchors with known positions (at least) are required to find a 2D-position from a couple of TDOAsSpecific Positioning Algorithms
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