IEEE 802.19 Coexistence TAG

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Project IEEE P802.19 Coexistence TAG Submission
Title Coexistence Metrics for Wireless
Systems Date Submitted 11 Sep 2002 Source
Jim Lansford Company Mobilian
Corporation Address 7431 NE Evergreen Rd,
Suite 220, Hillsboro, OR 97124 Voice(405)
377-6170, FAX [phone],
E-Mailjimlans_at_mobilian.com Re
Abstract This presentation is based on work
in progress by the authors for PHY-based metrics
for determining coexistence. Metrics based on
physical layer characteristics provide a relative
measure of the interference between systems that
establishes a bound on degradation. More
detailed models that take MAC characteristics
into account can provide more fidelity, but are
much more difficult to develop and
verify. Purpose Propose possible metrics to
quantify the level of coexistence between two
wireless systems. Notice This document has
been prepared to assist the IEEE P802.19. 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 P802.19.
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Coexistence Metric (CM)for Wireless Systems
Jim Lansford Jim.Lansford_at_mobilian.com Rob
Poor r_at_ember.com

• PHY models are good first order approximations
  to quantify interference
• Parameters are well defined and lead to models
  that are relatively easy to compute
• Can give reasonably good estimates of BER/PFR
• Do not have the fidelity of PHYMAC models
• Cannot be used to evaluate latency and jitter

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Terms

• Coexistence?
• the effects of interference among wireless
  devices that are physically near one another
• Two wireless devices are said to coexist if they
  can be brought near one another without
  significant degradation in their performance
• The term significant is open to interpretation
• What is a coexistence metric?
• A number, typically derived from a model, that
  quantifies the extent to which device A is
  expected to interfere with and be interfered by
  device B.
• The level of detail required in the model is
  debatable, but simple is desirable.

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Goals of a Coex Metric

• Quantitative, rather than qualitative
• Simple framework
• Allows others to use the model easily
• Produces intuitive results
• Builds upon previous work
• Particularly TG2
• Establishes a bound
• A relatively simple model should be somewhat
  pessimistic
• More detailed models (e.g., including MAC) should
  improve results
• Use a portable, widely supported framework
• Java or Matlab
• Open process
• Consensus-based
• Frequent feedback and revision

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A Physical Model

• Similar to TG2
• Provides BER/FER
• No MAC behavior
• Doesnt give latency/jitter performance
• Doesnt give detailed throughput, but a bound

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Model parameters

• Interference is assumed to appear as AWGN at the
  detector
• Can refine this over time
• Signal power
• Interference power
• Path loss
• Spectral coupling (called spectrum factor in TG2)
• Signal-to-interference ratio derived from
  parameters
• Bit error rate derived from SIR and modulation
  type
• Frame error rate derived from BER and frame
  structure of victim

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Path loss

• At 2.4GHz, can use TG2 model
• L 20 log(4?d/?) 40.23 20 log(d) d 8m
  58.3 33 log(d/8) d gt 8m

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Spectral coupling
Area AI
Area AF
Receiver Passband
Coupled power
Interferer
Spectral Coupling Area AF / Area AI

• Combined effect of Tx mask of interferer and Rx
  passband of victim
• Quantifies power from interferer that couples to
  victims detector
• For FH systems, there would be multiple offsets

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Status

• Java applet has been coded
• Future work to incorporate
• Compare model to measured results and refine
• Add other radios such as UWB
• Incorporate effects of duty cycle