GORA: Goodput Optimal Rate Adaptation for 802.11 using Medium Status Estimation

1. Estimated Pcoll and Perr, SNR=20 dB Single user 9 interferes SNR=10dB 3 interferes GORA: Goodput Optimal Rate Adaptation for 802.11 using Medium Status Estimation Nicola Baldo, Federico Maguolo, Simone Merlin, Andrea Zanella, Michele Zorzi Diego Melpignano, David Siorpaes 802.11 Rate Adaptation However… Aim • Choosing the 802.11 PHY rate R that maximizes saturation throughput • Most well-known Rate-Adaptation schemes (ARF, AARF, RBAR, MBLAS) are designed for single user scenarios • MPDU-Based Link Adaptation Scheme (MBLAS) choose the PHY rate that achieves the best througput • RBAR & MBLAS are often considered optimal In realistic scenarios we have Throughput and MBLAS SNR thresholds, 1 user Throughput and MBLAS SNR thresholds, 6 users • Multiple users • Collisions and prolonged backoff time • MBLAS and RBAR are not optimal any longer! • Other schemes have been proposed (e.g. CARA) State of the art and hence Goodput Optimal Rate Adaptation Goal Features Method • No overhead • RTS/CTS not required • Standard compliancy • Terminal-centric • No cooperation among STAs • Dynamically estimate medium status • Estimate expected gooudput for different R • Choose R that max. expected goodput • Adapt PHY rate to actual channel conditions: • quality of the radio signal • Level of contention for the medium access • medium access delay Goodput Model Medium Status Estimation Definition • Medium Status  =< Pcoll,  ,SNR> where: • Pcoll : Collision probability •  : Average tick period • SNR : Signal to Noise Ratio Estimate • From MAC counters and measures we get Scenario Performance Evaluation • Reference “Ideal” schemes • GORA with real SNR (instead of estimated SNR) • MBLAS (MPDU-Based Link Adaptation Scheme) • Schemes suitable for implementation: • GORA with estimated SNR • MBLAS with RTS-CTS • Still suffer from SNR measurement issues • Non-standard protocol • Auto Rate Fallback (ARF) Results • Single user scenario • MBLAS with no RTS-CTS and GORA achive optimum performance • Multi user scenarios: • MBLAS is suboptimal because it does not take into account losses due to collisions • GORA achieves the best throughput, especially whether the SNR is known