1. TGn Simulation Methodology Ad Hoc Overview
Month 2004
doc.: IEEE /0170r2
TGn Simulation Methodology Ad Hoc Overview
Jeff Gilbert Atheros Communications
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications

2. Month 2004
doc.: IEEE /0170r2
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) – Albuquerque
Large consensus in 1/6/04 FRCC telecon. of need
H.Bonneville and B.Jechoux (Mitsubishi) Vancouver – 1/15/04 TGn straw polls and votes
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications

3. Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

4. PHY Abstraction problem
Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

5. Goals Goals of a common phy / MAC interface:
Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

6. Risks of not specifying Abstraction
Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

7. Some PHY Abstraction-Related Work
Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

8. Goals of the Ad Hoc Committee
Month 2004
doc.: IEEE /0170r2
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
J.Gilbert, Atheros Communications

9. Process of the Ad Hoc Committee
Month 2004
doc.: IEEE /0170r2
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, :00 Pacific Time
Feb 19, :00 Pacific Time
Mar 04, :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/ to reflector by Feb 16) will be discussed
During the 3rd call, proposal(s) to be presented to the TGn body (posted w/ by Mar 1) will be selected and refined
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications

10. Methodology Requirements
Month 2004
doc.: IEEE /0170r2
Methodology Requirements
These requirements were discussed on the first conference call and updated on the calls and/or s.
These have not been ranked / approved by the group. The requirements are to accurately model:
Beamforming gains
Bit / packet errors
Channel variation and resulting varying PER
Interference effects
MIMO MAC operation with multiple independent data streams
PHY impairments
Rate adaptation interactions with the PHY
Additional metric for comparison is compute resource requirements: CPU cycles and storage
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications

11. Sample TGn Technologies
Month 2004
doc.: IEEE /0170r2
Sample TGn Technologies
By considering the variety technologies to be proposed for TGn, the methodologies can make sure that they can adequately represent performance.
This list was discussed on the first call and will be updated as new suggestions come on the calls or s.
These have not been ranked / approved by the group:
Adaptive bit-loading
Closed loop
Many more coding rates
Beamforming / nulling
LDPC / other coding methods
MIMO / Multiple data streams
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications

12. Month 2004
doc.: IEEE /0170r2
Simulation Tools Used
This page lists the simulation tools used by members. This is informative only and does not imply that a particular tool or tools are mandated or recommended by the ad hoc.
This list was discussed on the 1st conference call and updated from new information on the calls and s:
Opnet + C-models (7): Intel, Mitsubishi, Nortel, NTT, Samsung Electronics, TI, Toshiba
MLDesigner (1): Caller not present on call
NS (6): Airgo, Atheros, Fujitsu, Marvell, Qualcomm, ST Microelectronics
QualNet: UCLA
J.Gilbert, Atheros Communications
J.Gilbert, Atheros Communications