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    doc.: IEEE 802.15-04-0337-00-004b

    Submission

    July 2004

    Paul Gorday, MotorolaSlide 1

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

    Submission Title: [802.15.4 Multipath]

    Date Submitted: [July 2004]

    Source: [Paul Gorday] Company: [Motorola]

    Address: [8000 W. Sunrise Blvd., Plantation, FL, 33322, USA]

    Voice:[+1 561 723 4047], E-Mail:[[email protected]]

    Re: [ IEEE 802.15.4 ]

    Abstract: [This contribution presents simulated performance of a simple 802.15.4 (2.4 GHz PHY)

    receiver in multipath channel conditions.]

    Purpose: [To encourage discussion.]

    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 ofIEEE and may be made publicly available by P802.15.

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    Motivation

    Proposed modifications to 868/915 MHz PHY

    consider additional multipath tolerance for long-

    range applications.

    Provide benchmark simulation results for the 2.4

    GHz PHY, which would also apply to the

    proposed down-banded version.

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    2.4 GHz PHY Simulation

    Floating point simulation of optimum non-coherent

    demodulator.

    Detection based on largest correlation peak (largest path) No RAKE or equalizer.

    Assume channel is constant throughout packet (quasi-

    static) and uncorrelated from packet to packet.

    Record average packet error rate (PER) vs. Eb/No.

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    2.4 GHz Channel Model

    No channel model was specified by 802.15.4

    Commonly used diffuse exponential model

    802.11 Handbook [1]

    802.15.3a Narrowband Model [2]

    ETSI BRAN, HIPERLAN/2 [3]

    Many textbooks [e.g., 4]

    Detailed channel models are being developed by 802.15.4afor a variety of environments, but are not finished.

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    Diffuse Exponential Model

    0 2 4 6 8 10 12 14 16 18 200

    0.05

    0.1

    0.15

    0.2

    0.25 Diffuseeach delay bin

    contains multipath energy

    Exponentialaverage power

    decays exponentially

    Fading - each delay bin has

    independent Rayleigh fading

    Single Parameter:- RMS delay spread = - Mean excess delay

    - Max excess delay (10 dB) 2.5

    - Max excess delay (20 dB) 5k (Bin #)

    NormalizedAveragePower 0,)(

    /

    kCekf s

    kT

    C = Normalization Constant

    Ts = Simulation Sample Period

    Depicted: = 4Ts

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    0 5 10 15 20 25 30 35 4010

    -3

    10-2

    10-1

    100

    Eb/No (dB)

    PER

    No Fading

    = 0 ns

    = 100 ns

    = 200 ns

    = 300 ns

    = 400 ns

    = 500 ns

    Results for 2.4 GHz PHY

    Acceptable performance

    for 400 ns

    RMS delay spread = 400 ns

    Mean excess delay 400 nsMax excess delay (10 dB) 1 s

    Max excess delay (20 dB) 2 s

    Results scale with chip rate

    half-rate at 915 MHz would

    tolerate RMS delay spreads

    up to 800 ns

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    802.11a/HIPERLAN/2 Models [3]

    Channel EnvironmentRMS Delay

    Spread (ns)

    A Typical office (NLOS) 50B Typical large open space (NLOS) 100

    C Large open space indoor (NLOS) 150

    D Large open space indoor/outdoor (LOS) 140

    E Large open space outdoor (NLOS) 250

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    IEEE 802.11 Handbook[1]

    EnvironmentRMS Delay

    Spread (ns)

    Typical Home < 50

    Typical Office ~ 100

    Typical Manufacturing 200-300

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    Factory/Office Measurements [4]

    Tx-Rx separation < 30 m

    Location Type

    Mean RMS

    Delay Spread

    (ns)

    Max RMS

    Delay Spread

    (ns)

    A Factory 16 40

    B Factory 29 60

    C Factory 52 152

    D Factory 73 150

    E Factory 33 146

    F Office 16 48

    G Office 39 55

    H Office 55 146

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    Conclusions

    802.15.4 (2.4 GHz PHY) with simple non-coherent demodulator can tolerate RMS delayspreads up to 400 ns sufficient for most WLAN

    applications, more than enough for WPANapplications.

    Down-banded, half-rate 2.4 GHz PHY wouldtolerate RMS delay spreads up to 800 ns.

    Additional delay spread tolerance may beachievable with some increase in demodulatorcomplexity.

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    References

    [1] B. OHara and A. Petrick,IEEE 802.11 HandbookA

    Designers Companion, IEEE Press, 1999.

    [2] J. Foester, Channel Modeling Sub-committee Report

    (Final), IEEE P802.15-02/490r1-SG3a, Feb. 2003.

    [3] J. Medbo and P. Schramm, Channel Models for

    HIPERLAN/2, ETSI/BRAN doc. No. 3ERI085B, 1998.

    [4] K. Pahlavan and A. Levesque, Wireless Information

    Networks, John Wiley & Sons, 1995.