doc.: IEEE /0637r0 Submission May 2014 James Wang et. al., MediaTekSlide 1 Spatial Reuse and Coexistence with Legacy Devices Date: Authors:

doc.: IEEE /0637r0 Submission Background Several contributions [references 1-10] show that significant network throughput improvements can be achieved via spatial re-use using higher CCA, TPC, DSC, or combination of these. However, some co-existence issues are observed from the simulation results –Starvation of legacy devices, when legacy devices co-exist with the spatial reuse devices –Higher collision This contribution analyze these issues and explore the fairness basis for co-existence with legacy devices May 2014 Slide 2 James Wang et al, MediaTek

doc.: IEEE /0637r0 Submission Channel Access Issues in Dense Environment Ref 11 provides a real life scenario of a dense deployment campus network which shows high channel busy condition (low likelihood of channel access) despite high percentage (>50%) of STAs transmit with highest MCS May 2014 James Wang(MediaTek)Slide 3

doc.: IEEE /0637r0 Submission Starvation of Legacy Devices STA3 and STA4 use spatial re-use during TXOP 1 to access the channel, it delays the legacy STAs channel access window from the end of TXOP1 to the end of TXOP 2. STA3 and STA4 have unfair advantage (over legacy devices) for channel access  the starvation of legacy devices during co-existence. May 2014 Slide 4 James Wang et al, MediaTek

doc.: IEEE /0637r0 Submission Fairness to Legacy Devices The fairness issue during spatial re-use can be addressed with the medium sharing rules (from 11ah Clause ) which mandates spatial-reuse TXOP (TXOP2) to end at or before the expiration of TXOP 1. May 2014 Slide 5James Wang et al, Mediatek

doc.: IEEE /0637r0 Submission Higher Collision Issue Spatial reuse STA using higher CCA levels can transmit in the middle of a TXOP owned by a legacy STA, which operates at lower CCA levels, potentially causing collision to legacy STA, resulting in –higher power consumption due to re-transmission –reduced throughput May 2014 Slide 6James Wang et al, Mediatek Legacy STA1 Legacy STA2 STA 3 Spatial Reuse The spatial re-use STAs should reduce its transmit power level during spatial reuse to prevent causing collisions to legacy STAs.

doc.: IEEE /0637r0 Submission TPC during Spatial Re-use A reasonable transmit power level for the spatial reuse device is to reduce TX PWR by CCI (co-channel interference) This transmit control is only used during spatial re-use and is based on the received CCI. (Note that spatial reuse STA needs to operate at high noise level (CCA+CCI)) Noise floor CCA Space Loss CCI AP STA Spatial re-use STA CCI May 2014 Slide 7 AP TX Pwr Noise floor CCA Space Loss TX PWR Reduction = CCI TPC James Wang et al, MediaTek CCI

doc.: IEEE /0637r0 Submission Spatial Detection Window Since there are two STAs involved in a frame exchange, the spatial re-use STA should consider CCIs from both STAs involved in the frame exchange. TPC power level for spatial re-use STAs should be TX PWR reduction = max(CCI1, CCI2) Spatial reuse STA uses a spatial detection window to measure CCI 1 and CCI 2 before transmission May 2014 Slide 8James Wang et al, Mediatek Legacy STA1 Legacy STA2 STA 3 Spatial Reuse CCI 1 CCI2 CCI 1 CCI 2

doc.: IEEE /0637r0 Submission Conclusions and Future Works This contribution discusses the legacy device starvation issues due to spatial re-use as observed from previous contributions This contribution proposes mechanisms to achieve fairness for co-existence with legacy STAs when spatial re-use is used. –Spatial re-use should have independent channel contention and its TXOP should be confined within the duration original TXOP –Transmit power of the spatial reuse STAs should be constrained as described in Slide 7 (or 6) Future work –Simulation results for the use case scenarios will be presented –Further investigation of transmit power control mechanism for spatial re- use May 2014 Slide 9James Wang et al, Mediatek

doc.: IEEE /0637r0 Submission References 1.Ron Porat, Broadcom, Improved Spatial Reuse Feasibility - Part I 2.Jinjing Jiang, Marvell, System level simulations on increased spatial reuse 3.Graham Smith, DSP Group, Dynamic Sensitivity Control for HEW 4.Graham Smith, DSP Group, 11-14, Dynamic Sensitivity Control Channel Selection and Legacy Sharing 5.Imad Jamil, Orange, ax Mac Simulation Results for DSC and TPC 6.Graham Smith, DSP Group, Dense Apartment Complex Throughput Calculations 7.Graham Smith, DSP Group, E-Education Analysis 8.Graham Smith, DSP Group, Pico Cell Use Case Analysis 9.Graham Smith, DSP Group, Airport Capacity Analysis 10.Graham Smith, DSP Group, Apartment Capacity - DSC and Channel Selection 11.Chingwa Yeh, MediaTek, Performance Observation of a Dense Campus Network r0 May 2014 Slide 10 James Wang et al, Mediatek