doc.: IEEE /1207r0 Submission Imad Jamil (Orange)Slide 1 OBSS reuse mechanism which preserves fairness Date: Authors: September 2014

doc.: IEEE /1207r0 Submission Context It has been shown in many presentations that CCA adaptation (DSC, fixed CCA) can lead to very strong per-user throughput increase in dense environments (multiple x-times improvements) We look at it for a planned freq reuse 3 deployment (close to scenario 3), In 523r0, we demonstrated the benefits of DSC, but show some fairness warning (even for 11ax devices) In this presentation –We present fairness analysis with different CCA adaptation (DSC, fixed CCA), with TPC –We propose a mode that optimizes both area throughput and fairness Imad Jamil (Orange)Slide 2 September 2014

doc.: IEEE /1207r0 Submission DSC algorithm DSC (CCA control): –each STA adjust its CCA to CCA = Useful Rx Power – Margin –AP adjust its CCA to CCA = Useful Rx Power from further STA - Margin CCA adapation is caped by max CCA value (upper limit) Imad Jamil (Orange)Slide 3 STAs at 3m: CCA=-50dBm STAs at 5m: CCA =-60dBm APs: CCA =-60dBm margin 20dB Max CCA -50dBm STAs at 3m: CCA=-40dBm STAs at 5m: CCA =-60dBm APs: CCA =-60dBm margin 20dB Max CCA -40dBm September 2014

doc.: IEEE /1207r0 Submission TPC algorithm TPC (Transmit Power control): –each receiving STA requests transmitting STA to adjust its TP so that Rx Power = CCA + Margin We took a margin of 20dB Imad Jamil (Orange)Slide 4 September 2014

doc.: IEEE /1207r0 Submission Tx :15 dBm [21 m] Close to scenario 3 - First tier only (7 BSSs), 8 STAs per BSS, frequency reuse 3 pattern Simulation scenario Imad Jamil (Orange)Slide 5 [7 m] September 2014

doc.: IEEE /1207r0 Submission Parameters PHY o IEEE n o Path Loss: ITU UMi ( log10(d)+ 21log10(2400/900MHz) ) o Band: 5 Ghz o Channel: 20 MHz o Tx power: 15 dBm Traffic o Full buffer UDP traffic o DL (AP->STA): 4Mbps per STA o UL (STA->AP): 4Mbps per STA Metric Aggregate throughput, per user throughput CDF Rate adaptation AARF with selection of set of MCSs (link adaptation) Simulation scenario Imad Jamil (Orange)Slide 6 September 2014

doc.: IEEE /1207r0 Submission How to improve fairness (1/2) with CCA adaptation DSC presents unfairness issues at saturation state, linked to the fact that different users have different CCA parameters How to improve fairness? –1: DSC unfairness can be improved by tuning the max CCA threshold –2: CCA can also be fixed for the entire zone We propose to compare these approaches and evaluate fairness –between 11ax STAs –with regards to legacy STAs Slide 7 September 2014

doc.: IEEE /1207r0 Submission 1 - DSC fairness improvements with max CCA threshold optimization Slide 8 Unfairness between STAs at different range in UL We changed the max CCA threshold to limit the CCA difference between STAs, which limits the unfairness STAs at 3m: CCA=-50dBm STAs at 5m: CCA =-60dBm APs: CCA =-60dBm margin 20dB Max CCA -50dBm STAs at 3m: CCA=-40dBm STAs at 5m: CCA =-60dBm APs: CCA =-60dBm margin 20dB Max CCA -40dBm September 2014

doc.: IEEE /1207r0 Submission 2 - Fairness comparison with Fixed CCA Slide 9 Same simulation scenario (7 11ax, 1 legacy per AP), comparing: –fixed CCA: -82, -70, -60, -50dBm –DSC with max CCA threshold (-50dBm): (STAs at 3m: CCA=-50dBm, STAs at 5m: CCA =-60dBm, APs: CCA =-60dBm) 11ax STAslegacy STAs : best fixed CCA -50 CCAC: DSC UL User throughput CDF results for 11ax devices: Curve slope is a good indication of fairness September 2014

doc.: IEEE /1207r0 Submission 2 - Fairness comparison with Fixed CCA Slide 10 Conclusion: at saturation state: –fixed CCA is not more fair than DSC between 11ax STAs –fixed CCA is unfair with legacy devices Without legacy STAsWith legacy STAs September 2014

doc.: IEEE /1207r0 Submission How to improve fairness (2/2) joint CCA/TPC adaptation DSC and TPC both present unfairness issues, linked to the fact that different users have different CCA/TP parameters –CCA control favors 11ax, TP control favors legacy STAs How to improve fairness? –propose a scheme that adapts both CCA and TP, following a specific rule in order that each mechanism (CCAC and TPC) counteracts the unfairness from the other Slide 11 September 2014

doc.: IEEE /1207r0 Submission Reuse scheme: balanced CCAC/TPC Example with an equal modification of CCA and TP Slide 12 STA calculates a Delta_x value, which is the amount of dB by which CCA and TP will be changed –this delta_x value would be equal to delta_CCA if CCA adaptation only is performed and to delta_TP if TPC only is performed –if the STA uses the concept of DSC on this first Delta_x calculation, we have: Delta_x = Rx_power – Margin – standard_CCA (ex: Margin= 20dB, standard_CCA = -79dBm for 40MHz) STA applies a specific formula for the calculation of delta_CCA and delta_TP, based on Delta_x –in our example, we considered the rule as being an equal change of CCA and TP Delta_CCA=Delta_TP=Delta_x / 2 STA applies CCA adaptation using Delta_CCA STA requests AP to apply TP adaptation using Delta_TP –or applies TP adaptation using Delta_TP September 2014

doc.: IEEE /1207r0 Submission Fairness comparison with balanced CCAC/TPC (1/4) Slide 13 Same simulation scenario, comparing: –best fixed CCA: -60 dBm –DSC with max CCA threshold (-50dBm): (STAs at 3m: CCA=-50dBm, STAs at 5m: CCA =-60dBm, APs: CCA =-60dBm) –TPC –balanced CCAC/TPC (equal change between CCA and TP) Aggregate throughput results, with and without legacy devies: All solutions present similar results (expect TPC, which collapses in the presence of legacy devices TPC in presence of legacy devices September 2014

doc.: IEEE /1207r0 Submission Slide 14 Same simulation scenario, comparing: –best fixed CCA: -60 dBm –DSC with max CCA threshold (-50dBm): (STAs at 3m: CCA=-50dBm, STAs at 5m: CCA =-60dBm, APs: CCA =-60dBm) –TPC –balanced CCAC/TPC (equal change between CCA and TP) Without legacy STAs (8 11ax STA per AP) With legacy STAs (7 11ax STA and 1 legacy STA per AP Balanced CCAC/TPC and TPC DSC and fixed CCA Balanced CCAC/TPC DSC and fixed CCA UL User throughput CDF results for 11ax devices: Curve slope is a good indication of fairness Fairness comparison with balanced CCAC/TPC (2/4) September 2014

doc.: IEEE /1207r0 Submission Slide 15 Same simulation scenario, comparing: –best fixed CCA: -60 dBm –DSC with max CCA threshold (-50dBm): (STAs at 3m: CCA=-50dBm, STAs at 5m: CCA =-60dBm, APs: CCA =-60dBm) –balanced CCAC/TPC (equal change between CCA and TP) legacy STAs throughput (7 11ax STA and 1 legacy STA per AP) Balanced CCAC/TPC DSC Legacy throughput are better preserved than with DSC UL User throughput CDF results for legacy devices: Fairness comparison with balanced CCAC/TPC (3/4) September 2014

doc.: IEEE /1207r0 Submission Slide 16 Conclusion: –Balanced CCAC/TPC seems the best solution with regards to fairness between 11ax and with legacy devices –It gives equal area throughput gains than CCAC (DSC, fixed CCA..) and TPC Further advantages: –It preserves the benefit of being directly beneficial for the STA to implement (compared to TPC) –It can be very simple to define in 11ax: we can define in 11ax only the proportion rule to respect between Delta_CCA and Delta_TPC: gives every STA the possibility to use its own algorithm (need to see what proportion rule is the optimum) this proportion rule could be parametrized in case of a managed network (need simulations to evaluate if different proportion rules are required depending on the environments, or depending on the proportion of legacy/11ax devices) Note that such proportion rule would need to be adapted when combined with UL OFDMA and UL MU-MIMO, as TP adaptation will be required also for those schemes. Fairness comparison with balanced CCAC/TPC (4/4) September 2014

doc.: IEEE /1207r0 Submission Conclusion Fairness has to be considered for OBSS reuse mechanisms –even if it only arises at saturation state Fairness analysis with CCA control –We previously showed fairness issues with DSC –fixed CCA is not more fair than DSC between 11ax STAs –fixed CCA is unfair with legacy devices New solution to consider: balanced CCAC/TPC –in our simulation scenario, Balanced CCAC/TPC performs way better with regards to fairness between 11ax and with legacy devices –and It gives equal area throughput gains than CCAC (DSC, fixed CCA..) and TPC –Need to evaluate it on other scenarios, and to optimize the ratio between CCAC and TPC Imad Jamil (Orange)Slide 17 September 2014