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Simulation Methodology Ad Hoc Overview by Jeff Gilbert

Explore the development of a unified approach for modeling PHY error rate in MAC/System simulations, its history, goals, risks, and related work, as presented by Jeff Gilbert from Atheros Communications.

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Simulation Methodology Ad Hoc Overview by Jeff Gilbert

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  1. TGn Simulation Methodology Ad Hoc Overview Jeff GilbertAtheros Communications J.Gilbert, Atheros Communications

  2. History • Simulations methodology ad hoc has been formed based on the belief by the majority of the TGn body that we need a unified way of modeling the PHY error rate in MAC / System simulations • Issue has been raised: • J.Gilbert (Atheros) - 11-03-0888 – Albuquerque • Large consensus in 1/6/04 FRCC telecon. of need • H.Bonneville and B.Jechoux (Mitsubishi) 11-04-0120 Vancouver – 1/15/04 TGn straw polls and votes J.Gilbert, Atheros Communications

  3. Charter • Simulation Methodology Ad hoc was discussed and approved in the TGn session on 1/15/04 and announced at the 1/16/04 closing plenary • Bi-weekly conference calls to be held • Ad Hoc chartered through March Plenary (w/ extension by TGn vote if nec.) to define a PHY-MAC interface to be used in MAC simulations generating results reported in the CC matrix • Following the sub-committee's completion there will be a TGn vote to determine whether the methodology will be mandatory or optional J.Gilbert, Atheros Communications

  4. PHY Abstraction problem • PHY / MAC interface can dramatically impact overall results: • Time varying channel creates time varying PER • Affects overall delay, jitter, and goodput • Challenges • Properly model PHY characteristics in MAC sims • Keep flexibility to readily adapt to different proposals’ PHYs • Keep simulation effort reasonable J.Gilbert, Atheros Communications

  5. Goals • Goals of a common phy / MAC interface: • Allow fair comparison of MAC / system results • Facilitate verification / cross-checking of results • Intermediate results to simplify process • Possible other goals to be discussed: • Ability to merge MAC and PHY from different proposers • Ability to simulate MAC-only modifications with known PHY J.Gilbert, Atheros Communications

  6. Risks of not specifying Abstraction • Without common PHY/MAC interface, results could depend more on simulation methodology than proposal • Possible interpretations: • Idealized PHY • Distance -> fixed PER (based on theoretical values) • Distance -> mean SNR (w, w/o interference) -> PER • Distance -> fading SNR (w, w/o interference) -> PER • Distance -> fading SNR -> capacity formula -> PER • Fully accurate PHY model w/rate adaptation -> PER lookup • Approximate PHY based on SNR profile in MAC simulation • Full PHY simulation per packet in MAC simulation • Standardizing the abstraction could save significant time during the proposal evaluation selection process J.Gilbert, Atheros Communications

  7. Some PHY Abstraction-Related Work • Black-box PHY methods • Use full accuracy of PHY sims w/ rate adapt encapsulated in tables • Tight coupling of channel & PHY models, looser coupling w/ MAC • Example from Mitsubishi /Atheros (11-04/0172) • PHY integrated into MAC methods • Parametric version of PHY incorporated in system simulations • Looser coupling of channel & PHY models, tighter coupling w/ MAC • Example from Intel (11-03/0863) • “Channel Capacity to determine PERs” method • Markov model for channel capacity mapped to PERs • Channel capacity links Markov channel model and per-rate PERs • Example from from ST Microelectronics (11-04/0064) • Challenges: • Accurately model channel variation, MAC interactions, arbitrary PHYs J.Gilbert, Atheros Communications

  8. Goals of the Ad Hoc Committee • Determine a methodology that the TGn body will choose to adopt to allow fair comparisons • If we cannot arrive at a single methodology, refine 2-3 to be selected from at the March 2004 session • All members of ad hoc should provide positive feedback to improve the various approaches and focus on consensus J.Gilbert, Atheros Communications

  9. Process of the Ad Hoc Committee • It is critical that we move quickly in order to have conclusions to present at the March 2004 session • There will be 3 calls prior to the March 2004 session: • Feb 05, 2004 08:00 Pacific Time • Feb 19, 2004 00:00 Pacific Time • Mar 04, 2004 16:00 Pacific Time • Proposed Agenda: • During the 1st call, the goal of the group and overview of different approaches will be discussed • During the 2nd call, specific proposed methodologies (posted on server w/ email to reflector by Feb 16) will be discussed • During the 3rd call, proposal(s) to be presented to the TGn body (posted w/email by Mar 1) will be selected and refined J.Gilbert, Atheros Communications

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