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Date: 2014-04-17

MAC simulation results for Dynamic sensitivity control (DSC - CCA adaptation) and transmit power control (TPC). Date: 2014-04-17. Authors:. Context. In dense environments, CSMA-CA parameters (especially CCA physical carrier sensing) as defined in the standard are quite conservative.

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Date: 2014-04-17

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  1. MAC simulation results for Dynamic sensitivity control (DSC - CCA adaptation) and transmit power control (TPC) Date: 2014-04-17 Authors: Imad Jamil (Orange)

  2. Context • In dense environments, CSMA-CA parameters (especially CCA physical carrier sensing) as defined in the standard are quite conservative. • reducing reuse between neighboring cells • Several presentations have takled this problem: • adaptation of this CCA (dynamic sensitivity control) • adaptation of transmit power • In this presentation, we run a set of simulations to confirm/infirm first insights regarding these schemes • MAC system simulator with simple PHY abstraction Imad Jamil (Orange)

  3. co-channel interference (CCI) from neighboring cells UsefulRx power • In scenarios where the useful receive power is always sufficiently higher than interference, reuse between neighboring cells is possible • but currently prevented by CCA threshold Min SINR to receiveMCSx (sensitivity) CCI CCI Co-Channel interference (CCI) CCA Noise floor AP Simultaneous transmission STA STA Interfering AP Imad Jamil (Orange)

  4. How to enable reuse UsefulRx Power 1: Transmit power control 2: CCA control (DSC) Min SINR to receiveMCSx (sensitivity) CCI Co-Channel interference (CCI) Co-Channel interference (CCI) Simultaneous transmission Simultaneous transmission STA STA AP AP UsefulRx Power STA STA Min SINR to receiveMCSx (sensitivity) CCA CCI CCI CCA Interfering AP Interfering AP Noise floor Noise floor Imad Jamil (Orange)

  5. Simulate simple algorithms • DSC (CCA control): • each STA adjust CCA to CCA = UsefulRx Power – Margin • TP control: • eachreceiverrequeststransmitter to adjustTP sothatitreceives the UsefulRx Power at Margin dB aboveclassical CCA (-82dBm) • In each case, the margin has a strongrelationshipwith the min SINR experienced by STAs • we are not discussinganyprotocol in here tune CCA level AP tune CCA level (and receiver sensitivity) STA tune TP AP STA Imad Jamil (Orange)

  6. Simulation scenario BSS Cluster 3 Imad Jamil (Orange)

  7. Simulation scenario Close to scenario 3 - First tier only (7 BSSs), 8 STAs per BSS, Single channel for reuse 3 Tx : 15 dBm [21 m] [7 m] Tx :15 dBm Imad Jamil (Orange)

  8. Simulation scenario • PHY • IEEE 802.11n • Path Loss: ITU UMi (23.3+36.7log10(d)+ 21log10(2400/900MHz)) • Band: 5 Ghz • Channel: 20 MHz • Tx power: 15 dBm • Traffic • Full buffer UDP traffic • DL (AP->STA) • UL (STA->AP) • Simple metric • Aggregate throughput • Fixed MCS or rate adaptation AARF Parameters Imad Jamil (Orange)

  9. Fixed MCS7 – DSC and TPC Different margin (10-15-20-25-30-35-40-50) No DSC No TPC DSC TPC Imad Jamil (Orange)

  10. Rate control – DSC and TPC • Different set of MCSs for rate control: • all MCSs, MCS 2-7, MCS 3-7, MCS 4-7, MCS 5-7, MCS 6-7 No DSC No TPC DSC TPC Imad Jamil (Orange)

  11. First observations • CCA and TPC are strongly increasing reuse and aggregate throughput • Margin optimization • Weak rate control algorithms make aggregate throughput collapse • The margin gives an indication on min SINR • if used for suppression of MCS usage below this min SINR • it leads to strong improvement of rate control efficiency and to aggregate throughput gains Imad Jamil (Orange)

  12. Impact of legacy devices • mix of legacy (not implementing DSC or TPC) and DSC/TPC-capable STAs (implementing DSC or TPC) • 1 legacy STA per BSS Imad Jamil (Orange)

  13. Rate control – DSC– mix with legacy devices All DSC-capable STAs DSC-capable STAs + 7 legacy STAs No DSC DSC No DSC DSC Imad Jamil (Orange)

  14. Rate control - TPC – mix with legacy devices All TPC-capable STAs TPC-capable STAs + 7 legacy STAs No TPC TPC No TPC TPC Imad Jamil (Orange)

  15. First observations for mix with legacy • As expected, the impact of legacydevices on aggregatethroughputiswaystrongerwith TPC thanwith DSC • with TPC, thoselegacy are disablinganyreusepossibility • with TPC, thoselegacy are alsodisturbing the relationshipbetween the margin and the min SINR and cancels MCS suppression benefits in rate control algorithms Imad Jamil (Orange)

  16. Conclusion/next steps • Preliminaryresultswith MAC system simulator are showing • very good per user throughput gains both for TPC and DSC • additionalbenefit of the « margin » for rate adaptation improvementthroughdesabling the use of lowMCSs • strong impact of legacydevices on TPC reuseefficiency • Nextsteps • simulator evolution (calibrated) • different scenarios • analysis of potentialstarvation of legacydevices in case of DSC • analysis of RTS/CTS impact Imad Jamil (Orange)

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