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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: France Telecom / CEA / Thales final proposal Date Submitted: May 4th, 2009 Source: Jean Schwoerer (1), Laurent Ouvry (2), Arnaud Tonnerre(3) Companies:

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slide1

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

  • Submission Title: France Telecom / CEA / Thales final proposal
  • Date Submitted: May 4th, 2009
  • Source: Jean Schwoerer (1), Laurent Ouvry (2), Arnaud Tonnerre(3)
  • Companies:
    • (1) France Telecom R&d, 28 chemin du vieux chênes, 38240 Meylan, Cedex, FRANCE
    • (2) CEA-LETI, 17 rue des Martyrs 38054, Grenoble Cedex, FRANCE
    • (3) THALES, 146 boulevard de Valmy, 92704 Colombes, France
  • Voice: (1) +33 4 76 76 44 83, (2) +33 4 38 78 93 88, (3) +33 1 46 13 28 50
  • E-Mail: (1) jean.schwoerer@orange-ftgroup.com, (2) laurent.ouvry@cea.fr, (3) arnaud.tonnerre@fr.thalesgroup.com,
  • Abstract: Response to IEEE 802.15.6 call for proposals
  • Purpose: PHY and MAC proposal based on UWB impulse radio for the IEEE 802.15.6 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
List of Authors
  • France Telecom – Jean Schwoerer, Benoit Miscopein, Stephane Mebaley-Ekome (1)
  • CEA-LETI – Laurent Ouvry, Raffaele D’Errico, François Dehmas, Mickael Maman, Benoit Denis, Manuel Pezzin (2)
  • THALES – Arnaud Tonnerre (3)
  • University of Surrey, UK– Ehsan Z. Hamadani
  • INSA-Lyon, FR – Jean-Marie Gorce
outline
Outline
  • Introduction
  • PHY proposal
    • Advantages of UWB
    • Band Plan and PLL reference diagram
    • Pulse Repetition Frequency, Preamble, Modulation
    • Variable bit rate & throughput
    • Link Budget, Performances
    • Feasibility examples
  • MAC elements proposal
    • Beacon-based mode: Evolution of IEEE 802.15.4 MAC
    • Beacon-disabled mode: Preamble sampling approach
    • Upper layers responsibility
  • Conclusions & References
introduction
Introduction
  • Proposal main features:
    • Based on IEEE802.15.4a-2007 where a very reduced set of mode is selected for the BAN context
    • UWB Impulse-radio based
    • Support for different receiver architectures (coherent/non-coherent)
    • Flexible modulation format
    • Support for multiple rates
    • Support for multiple SOP
advantages of uwb
Advantages of UWB

Low radiated power

Low PSD, low interference, low SAR

High co-existence with existing 802.x standards

Real potential for low power consumption

Large bandwidth worldwide

Spectrum is worldwide available

Robust to multipath and fast varying channels

Flexible, scalable (e.g. data rates, users)

Low complexity HW/SW solutions in advanced development (eg 802.15.4a)

complexity vs data rate coverage
Complexity vs. data rate & coverage

Complexity / Power

Coherent Rake IR-UWB

EQ IR-UWB

Non coherentIR-UWB

Coherent IR-UWB

FM-UWB

Non coherentIR-UWB

LDR

MDR

HDR

Applications

Coverage

band plan selection from 15 4a
Band plan (selection from 15.4a)
  • Comparison with 15.4a :
  • Only 500 MHz bandwidth channels
  • No sub-GHz band
pll reference diagram
PLL Reference Diagram

Oscillator

Phase

Detector

LPF

VCO

fcomp

fc

XTAL

fX

÷ N

÷ M

fs = 499.2 MHz

For channels 5,6,8,9,10,12,13,14 (high band), the factor N becomes respectively 13,14,15,16,17,18,19,20

pulse repetition frequency
Pulse Repetition Frequency
  • Selected value
    • 15.6 MHz PRF (64.10 ns of pulse repetition period PRP)
    • Use of binary codes, No bursts => mean PRF = peak PRF
  • Rationale
    • Typical channel delay spread for indoor applications below 25 ns in 90% of channel realizations => very limited ISI (or IPI)
    • Integer relationship with base frequency of the bandplan (499.2 MHz / 32) => no fractional PLL
    • Maximized Pulse amplitude
      • => better for transmitter power consumption (between-pulses duty cycling)
      • => better for pulse detectability in the receiver
      • => better for threshold crossing receivers
      • => compatible with low voltage CMOS technologies without I/O « tricks » (around 780 mVp-p)
    • A single value => simplicity
    • Compatible with bit rate scalability with short spreading factors
    • No high speed clock / long FIRs filters to generate or correlate with bursts of pulses
preamble
Preamble
  • PRF is the same as one of the mean PRF in 15.4a
  • Sp code duration:
    • Example with N=31 : Tpsym = 31 * PRP = 1.9871 us
    • To be checked if enough for a correct (Pd,Pfa) versus complexity
  • Number of Sp codes in the preamble
    • Example with Nsp = 16 : Tsync = 16 * Tpsym = 31.7936 us
    • This is probably a maximum value
    • To be checked if enough for a correct (Pd,Pfa) versus overhead

Sp code : binary. Length TBD. Unique.

PRP = 64.10 ns

Sp code duration N*PRP

modulation
Modulation

Sd = +1 +1 +1 −1 −1 +1 −1

Symbol : +1

PRP = 64.10 ns

Symbol : -1

  • PRF is ~ the same as one of the mean PRF in 15.4a
  • Spreading code length Sd
    • Example with N=7 (BARKER CODE) : Symbol duration Ts = 7 * PRP = 0.4488 us
  • Modulation : 1 bit per symbol + second bit used for redundancy OR non coherent demod
    • DBPSK : BPSK with differential encoding (at symbol level)
      • Sub-optimal but easier to implement and less sensitive to clock drift
    • DBPSK + PPM : the whole S code can be shifted within the PRP with ½ the PRP value
      • Does not affect the mean PRF value and the spectrum shape, Is simple to implement (though a little more complex than pure DPBSK), Is compatible with non coherent / threshold crossing detectors, Is ISI compatible in the BAN context
    • DBPSK + chip-PPM : each chip of the code is shifted according to the chip value => selected option

Symbol duration =

7 pulses ~ 448.8 ns

Objective: to afford (differential) coherent and non coherent receivers

variable bit rates
Variable bit rates
  • Bit rates
    • Bit rate is adjusted with the number of pulses per symbol keeping a constant mean PRF
    • 2.22 Mbit/s is the default uncoded data rate
    • 5.2 and 15.6 Mbit/s are mandatory => No additional complexity & allows to reduce channel use
    • 31.2 Mbit/s is proposed optionally for coherent receiver (uses both PPM & DPBSK)
    • Proposed FEC : systematic RS (63,55) as in 15.4a (maximum efficiency ~0.87)
    • The lowest rate is a compromise between “Tx_on time” and range (+clock drift compensation requirements).
performances analysis methodology and channel models
Performances analysis methodology and channel models
  • Goal:
    • Get/discuss performances at a link budget / outage probability level with the different channel models at the default 2.2 Mbps rate before digging into the design level performances
  • Methodology:
    • Perform extra measurements at CEA-Leti (for UWB 3-5GHz but also for 2.4 GHz)
    • Complement the IEEE802.15.6 CM3 UWB channel model with extra measurements and models and compare channel models with each other
    • Move towards a scenario based approach
      • Scenario = [at least] given (Tx,Rx) couple + given generic environment + given generic movement
      • Justified by the huge dispersion of the BAN radio channel
    • Calculate outage probabilities given the path loss and shadowing statistics
performances channel path loss models
Performances: channel path loss models
  • Available CM3 UWB channel models as in TG6 document :
    • A (source NICT)
      • Indoor and anechoic
    • B (source IMEC)
      • Anechoic
    • C (source Samsung)
      • Indoor and anechoic
  • Conclusion
    • Huge dispersion (tens of dBs) between models
    • Distance is not a relevant parameter to get a path loss model
    • Coming back to the scenario based channel characterization is proposed
  • Reference
    • Roblin C.; D'Errico R.; Gorce J.M.; Laheurte J.M ; Ouvry L., « Propagation channel models for BANs: an overview », COST 2100, 16/02/2009 - 18/02/2009, Braunschweig , Germany
performances extra channel measurements
Performances: extra channel measurements
  • 2-5 GHz, indoor and anechoic, 7 subjects, standing/walking/running, scenarios as depicted below
  • Log normal path loss model. Shadowing and small scale fading modeled separately.
  • Reference : D'Errico R.; Ouvry L.,“Time-variant BAN channel characterization” TD(09)879, COST2100, 18-19/05/2009, Valencia, Spain (Measurement set up details available on request)
performances extra channel measurements1
Performances: extra channel measurements
  • On previous page:
    • Error bar @ 1 std of mean channel gain over subjects
    • Without the slow shadowing std
    • 2.4 GHz and 3-5 GHz for comparison
  • On this page
    • UWB 3-5 GHz only
    • Error bar @ 2 stds of mean channel gain and slow shadowing (95% confidence interval)
  • Conclusions
    • 2.5% outage probability @ ~-70dB channel loss for the 8 scenarios in indoor conditions
    • Higher outage in anechoic chamber depending on the scenario (not shown here)
performances outage probability
Performances : outage probability
  • Starting from:
    • The link budget
      • PTx + antenna = -20.5 dBm
      • Sensitivity = -90.5 dBm
        • Includes 6dB NF, 5dB I.L. and 9dB min required EbN0
      • 70dB total link margin
    • The different scenario based path loss models
      • CM3 UWB A back to the scenarios
      • CM3 UWB C back to the scenarios
      • CEA-Leti’s measurements
  • Get the outage probability performance for an EbN0
    • Probability that the received power is higher than the receiver sensitivity
    • from the proposed -90.5dBm sensibility (2.2 Mbps)
    • through to -87.8dBm (5.2 Mbps)
    • and to -82dBm (15.6 Mbps)
performances outage probability1
Performances : outage probability

5% of channel realizations threshold

Area where target PER is obtained

X legend : sensitivity (dBm)

2.2 Mbps proposed sensibility

5.2 Mbps proposed sensibility

performances outage probability2
Performances : outage probability

5% of channel realizations threshold

Area where target PER is obtained

X legend : sensitivity (dBm)

2.2 Mbps proposed sensibility

5.2 Mbps proposed sensibility

performances scenario based outage probability
Performances : scenario based outage probability
  • Tentative consolidation of
    • CM3 A (NICT)
    • CM3 C (Samsung)
    • CEA-Leti’s measurements

for four indoor scenarios :

    • Hip-left ear
    • Hip-right wrist
    • Hip-thigh
    • Hip-chest
    • (others available as well, including anechoic chamber cases)
  • Needs further update to refine comparisons, but aims at opening discussions
performance ebn0 requirements dbpsk
Performance : EbN0 requirements (DBPSK)
  • Conditions: DBPSK, 20 bytes PSDU, CM3 A channel
  • Same results (with better PER floor in highest rate) for 256 bytes

Note: Input uncoded BER to reach the target PER :

5e-5 for PER=10% with 256 bytes PSDU

6e-5 for PER = 1% with 20 bytes PSDU (15.4/4a)

conclusions on link performances on the different channel
Conclusions on link performances on the different channel
  • The proposed link budget and system specification makes the UWB proposal feasible for most of the scenarios
    • outage of 5% as in TRD
    • 1e-2 PER for 20 bytes PSDU, or
    • 1e-1 PER for 256 bytes PSDU
    • Actual EbN0 requirement still to refine (current simulation with realistic receiver on CM3 gives 13dB after RS decoding, within the proposed IL values, but the CM3 multipath model is questionable)
  • However, large variations between the different models (CM3 A is optimistic, CM3 C is pessimistic, CM3 B and CEA-Leti’s measurement are median)
  • Further analysis in the 7.25-8.5 GHz band is necessary
background design know how see references

Transmitter 4.5 GHz

Receiver 4.5 GHz

Max amplitude

Min Mean PRF

Modulations

Power consumption

: 700mVpp

: 3.9MHz

: OOK, PPM, BPSK

: 0.7mW

S11

IIP3

Input BW

Max sensitivity

Power consumption (analogue + digital RF)

: <-15dB

: -15dBm

: 850MHz

: -78dBm

: 17mW

Background design know-how (see references)
  • RF part only
    • Total Power consumption: 34mW (Rx:17 + Tx:0.7 + I/O:16.3)
    • Max data rate: 31Mb/s (@ max PRF)
    • RF receiver energy efficiency : 1.1nJ/b @ 31Mb/s
    • RF transmitter energy efficiency : 23pJ/b @ 31Mb/s
  • Overall transceiver
    • DBPSK Digital BB: 347 kbps - 1 Mbps
    • Total RX power consumption:
      • 44mW peak in synchronization mode(RF=17 + BB=27)
      • 25mW in demodulation mode(RF=17 + BB=8)
conclusions
Conclusions
  • Proposal based upon UWB impulse radio alt-PHY of 15.4a
    • Advantage
      • Early implementations exist: experienced proposal
      • Selection of the most relevant modes and their adaptation to the BAN context (note: 15.4a mandatory mode is NOT the selected option for 15.6)
      • A standard exists which will speed up the 15.6 standard drafting steps
    • Modulation:
      • DBPSK provide robustness for a limited complexity & 2PPM allow several receiver implementations
      • RS FEC help to improve link budgets and parity bit will improve robustness of the DBPSK receiver
  • System tradeoffs
    • Variable bit rates allow to accommodate all applications envisaged in TG6
    • Minimizing talk time improve energy consumption, SOP performances, and regulatory compliance
  • Flexible implementation of the receiver
    • Compatible with a lot of UWB detectors (coherent, differential, energy, threshold crossing)
    • FEC decoder is optional
  • Fits with multiple technologies
    • Compatible with implementation in low voltage CMOS
    • Very low power integrated solutions already proven (thus to be adapted)
  • The very low transmit power is a very attractive feature for the UWB PHY adoption

Will permit good compromises between cost, performances and energy consumption

mac layer
MAC layer
  • BANs may be coordinated most of the time
    • The coordinator can allocate a negotiated bandwidth to QoS demanding nodes (data rate, BER, latency)
    • A beacon based approach is adapted
  • Some applications imply a lower channel load
    • A beacon-free mode is more efficient
  • An IEEE 802.15.4-like MAC layer is a good base for BANs
    • With a beacon-enabled mode including TDMA and Slotted-ALOHA (for UWB) with relaying
    • With an enhanced beacon-free mode by using Preamble Sampling
beacon based mac mode
Beacon-based MAC mode
  • BAN requires above all:
    • Relaying capability: to cope with low-power emission and severe NLOS conditions
      • Would be limited to 2-hops in the BAN context
    • Reliability: high level of QoS for critical / vital traffic flows
  • Proposed architecture
    • Mesh network centralized on the gateway
      • Full mesh topology based on a scheduling tree
      • Guaranteed access for management and data messages (real TDMA)
beacon based mac mode1

Control portion

Data portion

Beacon

period

Request

period

Topo mgmt

period

CAP

CFP

Inactive

Beacon-based MAC mode
  • Superframe structure
    • Based on 802.15.4
    • Inclusion of a control portion for management messages
      • The control portion shall be large enough to allow dynamic changes of topology
    • The CAP is minimized, mostly used for association using slotted ALOHA
beacon based mac mode2
Beacon-based MAC mode
  • Fine structure
    • Superframe is divided equally into slots
    • Use of Minislots in the Control portion
      • Provides flexibility: adaptation to different frame durations
    • Guaranteed Time MiniSlot (GTMS) shall be introduced in CFP
beacon based mac mode3
Beacon-based MAC mode
  • Control portion structure
    • Beacon period
      • The beacons are relayed along the Scheduling Tree
      • The beacon-frame length shall be minimized
      • Beacon alignment procedure shall be used
    • Request period
      • Request period is a set of GTS dedicated to allocation demands
      • Transmission from the leaves to the coordinator
    • Topology management period
      • Hello frames, for advanced link state procedure
      • Scheduling tree based update
beacon free mac mode
Beacon-free MAC mode
  • However, some situations might not require a beacon-enabled MAC protocol (see references.)
    • Symmetric or asymmetric network, low communication rate and small packets
    • Network set-up, coordinator disappearance, etc
  • In such conditions, the downlink is an issue : nodes must be powered-up to receive data from the coordinator (e.g. polling/by-invitation MAC scheme)
  • We propose a Preamble Sampling MAC protocol for UWB
beacon free mac mode1
Beacon-free MAC mode
  • Preamble Sampling principles:
    • Nodes periodically listen to the channel. If it is clear, they go back to sleep; conversly, they keep on listening until data
    • Nodes are not synchronized but share the wake up period (TCI)
    • A packet is transmitted with a preamble as long as TCI
beacon free mode
Beacon-free mode
  • Preamble sampling protocols are known to be the most energy efficient uncoordinated MAC protocols
  • TCI depends on the traffic load and the TRX consumption (TX/RX/listen modes)
  • Can be of the order of 100 ms
  • The preamble is a network specific sequence
    • Either a typical wake-up signal
    • Or a preamble with modulated fields (e.g. @, time left to data)
beacon free mac mode2
Beacon-free MAC mode
  • To comply with LDC regulation in the lower band (e.g. Europe), the preamble can be relayed by the BAN nodes (up to 5ms long bursts)
beacon free mac mode3
Beacon-free MAC mode
  • Mode 0: only one burst per device is emitted
  • Mode 1: burst is re-emitted by a device, under the LDC limit, until a neighbour relays
  • Mode 2: same as mode 1 + former relays, with emission credits left, can relay again
upper layers responsibility
Upper Layers responsibility
  • Enabling/disabling beacons switching procedure
    • From beacon-free to beacon-based mode
      • BAN formation (coordinator election)
      • New coordinator election if former coordinator leaves
      • Can be triggered by a user requesting a link with high QoS
    • From beacon-based to beacon-free mode
      • Fallback mode if the coordinator leaves
      • If the required BW (rate of GTS requests) is below a given threshold and requested QoS is adequate
conclusions on mac
Conclusions on MAC
  • Propose a combination of
    • A Beacon-based true TDMA mode including fast relaying and mesh support
    • A Beacon-free mode using preamble sampling and extra features adapted to UWB
references
References
  • 15-08-0644-09-0006-tg6-technical-requirements-document.doc
  • M. Pezzin, D. Lachartre, « A Fully Integrated LDR IR-UWB CMOS Transceiver Based on "1.5-bit" Direct Sampling », ICUWB 2007, Singapore, September 2007
  • D.Lachartre, B. Denis, D. Morche, L. Ouvry, M. Pezzin, B.Piaget, J. Prouvée, P. Vincent, « A 1.1nJ/b 802.15.4a-Compliant Fully Integrated UWB Transceiver in 0.13μm CMOS», ISSCC 2009, San Francisco, February 2009
  • European ICT PULSERS II and ICT EUWB projects deliverables
  • French ANR "BANET" project
  • Roblin C.; D'Errico R.; Gorce J.M.; Laheurte J.M ; Ouvry L., « Propagation channel models for BANs: an overview », COST 2100, 16-18/02/2009, Braunschweig , Germany
  • D'Errico R.; Ouvry L.,“Time-variant BAN channel characterization” TD(09)879, COST2100, 18-19/05/2009, Valencia, Spain
  • European ICT SMART-Net project deliverables
  • Timmons, N.F.   Scanlon, W.G.   "Analysis of the performance of IEEE 802.15.4 for medical sensor body area networking", IEEE SECON 2004, Santa Clara, Ca, October 2004
beacon free mac mode4
Beacon-free MAC mode
  • In this collaborative scheme, the preamble burst can composed of
    • Destination adress (compuls.)
    • Time left to data (compuls.)
    • Packet length
    • Source adress
  • Need for a relaying collision resolution policy
    • Based on the wake-up instant during the burst (priority is given to the node which has detected the burst first)
beacon free mac mode5
Beacon-free MAC mode
  • Relationship between wake-up instant in the burst and back-off length can be of any kind (linear, logarithmic, exponential…)
beacon free mac mode6
Beacon-free MAC mode
  • Collaborative scheme is very flexible
    • Nodes can relay once or up to the emission maximum duration (50 ms in Europe)
    • If the source listens to the relays, it can get the wake-up schedules of its neighboors
    • The destinator can emit a specific burst to notify the source
      • Possibility to stop the relay process
      • Reduction of the latency because the source can anticipate the payload emission
beacon free mac mode7
Beacon-free MAC mode
  • Exemple of latency reduction
upper layers responsibility1
Upper layers responsibility
  • Management of cooperative transmissions
    • One way relay channel (OWRC)

A single source node transmits data to a single destination node with the help of some relay nodes

    • Two way relay channel (TWRC)

Two nodes like to communicate to each other through the help of a relay

upper layers responsibility2
Upper layers responsibility
  • Cooperation possibilities
    • Low data rate transmission
      • Complexity of involved nodes and power consumption are the main issues
      • Low complexity cooperative techniques may be used
    • High data rate transmission
      • Increasing data rate and channel availability are more important
      • Decode and forward schemes in OWRC or even network coding with TWRC are more suitable