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Simulation Effort Required to Satisfy the 802.11n Comparison Criteria

This study examines the significant simulation effort required for the 802.11n Comparison Criteria, including both PHY layer and system simulations. The study provides estimates of CPU time needed for each simulation type and suggests ways to reduce the simulation effort without compromising quality.

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Simulation Effort Required to Satisfy the 802.11n Comparison Criteria

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  1. Simulation Effort Required to Satisfy the 802.11n Comparison Criteria Bjorn A. Bjerke, John Ketchum, and Irina Medvedev Qualcomm, Inc. bbjerke@qualcomm.com Bjorn Bjerke et al., Qualcomm, Inc

  2. Simulation Effort • Significant simulation effort required to satisfy the current version of the 802.11n Comparison Criteria • Two types of simulations: • PHY layer sims: typically implemented in C • System sims: typically implemented in NS2 or similar Bjorn Bjerke et al., Qualcomm, Inc

  3. CCs Involving Simulations • System sims: • CC15 • CC18 • CC19 • CC20 • (CC24) • CC27 • CC28 • CC58 • PHY sims: CC59 CC67 CC67.1 CC67.2 Bjorn Bjerke et al., Qualcomm, Inc

  4. PHY Sims: Assumptions • NxN MIMO system  N*N possible system configurations • PER vs SNR evaluated for 10 SNR values • 100 packet errors collected per point • CPU time per point: 1 hour  CPU time per curve: 10 hours Bjorn Bjerke et al., Qualcomm, Inc

  5. PHY Sims: CPU Time Estimate • CC59 (PER vs SNR with fixed channel): • 5 representative data rates • Example: N=4  16 system configurations • CPU time = 16*5*10 hours = 800 hours • CC67 (PER vs SNR with fading channels): • 5 representative data rates • 16 system configurations • 3 channel models (B, D, F) • Channel D w/fluorescent lights and highest rate • CPU time = (16*5*3+16)*10 hours = 2560 hours Bjorn Bjerke et al., Qualcomm, Inc

  6. PHY Sims: CPU Time Estimate • CC67.1 (Rate vs SNR with fading channels): • 16 system configurations • 3 channel models (B, D, F) • Channel D w/fluorescent lights • CPU time = 16*4*10 hours = 640 hours • CC67.2 (PER for 2 SNR values with frequency offset): • 16 system configurations • Example: 5 representative freq. offset values • 2 SNR values (1 hour each) • CPU time = 16*5*2 hours = 160 hours Bjorn Bjerke et al., Qualcomm, Inc

  7. PHY Sims: CPU Time Estimate • Total CPU time needed for PHY sims: 800+2560+640+160 hours = 4160 hours • With 8 CPUs running continuously, this will take 4160/(24*8) days = 22 days • Assume 100% overhead  44 days Bjorn Bjerke et al., Qualcomm, Inc

  8. System Sims: Assumptions • Simulation Scenario 1 (baseline): • 40 secs. of simulated time to reach steady state; < 1 hour of CPU time to simulate • Assume CPU time goes as the square of the number of STAs Bjorn Bjerke et al., Qualcomm, Inc

  9. System Sims: CPU Time Estimate • CC15: • SS17: 1 AP, 1 STA, 1 channel model; < 1 hour • SS18: 1 AP, 1 STA, 1 channel model; < 1 hour • SS19: 1 AP, 2 STA, 1 channel model; < 1 hour • CCs 18, 19, 20, 24 • SS1:  1 AP, 11 STA --  1 hour • SS4:  1 AP, 30 STA -- 7 hours • SS6:  1 AP, 52 STA  -- 20 hours • SS9:  1 AP, 6 STA --  1 hour • SS11: 2 AP, 12 STA -- 2 hours Bjorn Bjerke et al., Qualcomm, Inc

  10. System Sims: CPU Time Estimate • CCs 27, 28, 58 • Need to run SS16 for each of the two channel models, B and D. • SS16: 1 AP, 1 STA, repeated for various locations of the STA    • Total: 4 hours • Total CPU time for system sims: < 40 hours  • Add 100% overhead: < 80 hours Bjorn Bjerke et al., Qualcomm, Inc

  11. The Simulation Effort May Be Reduced Without Compromising Quality • PHY sims represent the majority share of the effort  focus on PHY sims: • Limit the number of required system configurations to a set of 5 representative, e.g., 1xN, Nx1, N1xN1, N1xN2, and N2xN2 • Let proposer choose between CC67 and CC67.1, i.e., make CC67 mandatory for fixed rate systems, and make CC67.1 mandatory for rate-adaptive systems • Total CPU time required drops to 1100 hours and 500 hours, respectively (or 1300 hours if all versions of CC67 are mandatory) Bjorn Bjerke et al., Qualcomm, Inc

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