Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
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November 2002 - PowerPoint PPT Presentation

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ UWB Coexistence Issues ] Date Submitted: [ 12 November 2002 ] Source: [ Matthew Welborn ] Company [ XtremeSpectrum, Inc. ] Address [ 8133 Leesburg Pike, Ste 700, Vienna, VA 22182 ]

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

Submission Title: [UWB Coexistence Issues]

Date Submitted: [12 November 2002]

Source: [Matthew Welborn] Company [XtremeSpectrum, Inc.]

Address [8133 Leesburg Pike, Ste 700, Vienna, VA 22182]

Voice:[703-269-3000], FAX: [703-269-3092], E-Mail:[[email protected]]

Re: [.]

Abstract: [Discussion of interference and coexistence considerations involved for the 15.3a ALT PHY]

Purpose: [Provide information to help committee evaluate coexistence criteria for 802.15.3a ALT PHY]

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.

Matt Welborn, XtremeSpectrum Inc.

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Overview Area Networks (WPANs)

  • UWB effects on other systems

    • Licensed and unlicensed spectrum

  • Other system’s effects on UWB

Matt Welborn, XtremeSpectrum Inc.

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UWB Effects on Licensed Systems Area Networks (WPANs)

  • This is the set of cases that the FCC studied in proceedings 98-153

    • Result: R&O with emissions and usage limitations

    • Conclusion is that rules are very conservative, no interference to licensed systems

    • Analyzed many systems, commercial and federal

      • GPS, PCS, DARS, radars, satellites, aviation and navigation, etc.

      • Emission limits below 3.1 GHz are significantly lower than Class B levels to protect GPS, aviation and radars

Matt Welborn, XtremeSpectrum Inc.

Uwb effects on unlicensed systems l.jpg
UWB Effects on Unlicensed Systems Area Networks (WPANs)

  • ISM and U-NII band systems (IEEE, BT, HomeRF, cordless phones, etc.)

  • Nearly all such systems are out-of-band for UWB communications applications

    • Low O.O.B. limits provide significant protection for such systems

    • Additional protection can be provided

      • Engineering cost/benefit trade-off (example: indoor versus handheld limits)

Matt Welborn, XtremeSpectrum Inc.

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Interference and Coexistence Area Networks (WPANs)

  • Biggest design issue is to determine desired level of “co-existence”

  • Different analysis techniques to determine potential for interference/coexistence

    • Noise-floor analysis

      • Estimate effect of UWB on thermal noise floor

      • Relies on assumptions about real-world effects

      • Most conservative approach

      • Can lead to overly-restrictive/unrealistic results

    • SNR-based approaches

      • Determine when emissions will actually affect operation

      • Real-world factors (e.g. RFI, noise, CCI) also affect system

Matt Welborn, XtremeSpectrum Inc.

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Specific Example: 802.11a WLAN Area Networks (WPANs)

  • Active coexistence

    • Coordination at PHY/MAC or higher layer to improve coexistence performance

    • 802.15.3 MAC provides several mechanisms

      • Child and neighbor piconets capabilities

      • Piconet maximum transmit power limits

      • Transmit power control

  • Passive coexistence: no explicit interaction at higher layers

    • Implicit: scanning for best available channel

    • Uncoordinated, simultaneous use of the channel

Matt Welborn, XtremeSpectrum Inc.

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Geometry, Duty Cycle & Power Control Area Networks (WPANs)

UWB range = 10 m

  • Relative size- few WLAN devices see UWB effects

    • Many WLAN devices far from UWB piconet, no effects

  • Duty cycle effects: reduced probability of collision

    • e.g. 30% duty cycle = 10% impact

  • Power control: UWB Tx power minimized

    • ½ range UWB = 6 dB lower Tx power  better WLAN SNR

If WLAN range = 30/50/100 m

then UWB area = 10/4/1%

Matt Welborn, XtremeSpectrum Inc.

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Interference of UNII System on UWB Area Networks (WPANs)

  • Back-of-the-envelope example:

    • Assume 11a device has +17 dBm Tx power

    • Assume UWB has 4 GHz BW  -5 dBm Tx power

    • (4000/100 MHz) possible processing gain = 16 dB

    • Direct approach: (-6 dB) SIR at output of MF

  • Conclusion: 100 Mbps operation with WLAN < 10 m requires some rejection of interference energy

  • Two issues: MF output SIR and front end protection

Matt Welborn, XtremeSpectrum Inc.

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Three Choices for UNII Protection Area Networks (WPANs)

  • Never (provide no explicit protection)

    • If interference occurs, system uses existing mechanisms (FEC, processing gain, re-transmit at MAC or higher layer)

    • Simplest to build, but impact is potentially large

      (2) Always (static protection from UNII interferer)

    • Assume that UNII protection is always needed

    • Potential impact on performance

      (3) Sometimes (dynamic protection from UNII interferer)

    • Determine presence/frequency of interferer

    • Provide adaptive interference rejection mechanism

    • Trades implementation complexity for potential performance gains when interferer is not present

Matt Welborn, XtremeSpectrum Inc.

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Non-UNII, In-band Interference Area Networks (WPANs)

  • Most other in-band systems are outdoors, LOS, use directional (high-gain) antennas, and are subject to site planning

    • Unlikely to cause/receive UWB interference under normal conditions

    • High EIRP required to have same effect as UNII WLAN:

Matt Welborn, XtremeSpectrum Inc.

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Conclusions Area Networks (WPANs)

  • UWB effects on other systems

    • Licensed systems analyzed by FCC- no problem

    • Unlicensed systems: UNII band is primary issue

      • Many factors affect likelihood for interference in the real world: geometry, duty cycle, power control, RFI, etc.

  • Other system’s effects on UWB

    • UWB will require some mechanism for rejecting UNII band interference, or performance will suffer

    • Protection method is an engineering trade-off

Matt Welborn, XtremeSpectrum Inc.