doc.: IEEE 802.11-14/0637r0

Submission

May 2014

James Wang et. al., MediaTekSlide 1

Spatial Reuse and Coexistence with Legacy Devices

Date: 2014-05-13

Name Affiliations Address Phone email

James Wang

MediaTek

2860 Junction Ave., San Jose, CA 95134

USA

+1-408-526-1899-88109

james.wang@mediatek.com

Jianhan Liu jianhan.liu@mediatek.com

Thomas Pare thomas.pare@mediatek.com

James Yee james.yee@mediatek.com

Chingwa Yu chingwa.yu@mediatek.com

Alvin Hsu Alvin.hsu@mediatek.com

Authors:

doc.: IEEE 802.11-14/0637r0

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 802.11-14/0637r0

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 802.11-14/0637r0

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 802.11-14/0637r0

Submission

Fairness to Legacy Devices

• The fairness issue during spatial re-use can be addressed with the medium sharing rules (from 11ah Clause 9.48.4) which mandates spatial-reuse TXOP (TXOP2) to end at or before the expiration of TXOP 1.

May 2014

Slide 5 James Wang et al, Mediatek

doc.: IEEE 802.11-14/0637r0

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 6 James 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 802.11-14/0637r0

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 floorCCA

Space Loss

CCI

AP

STA

Spatial re-use STA

CCI

May 2014

Slide 7

AP TX Pwr

Noise floorCCA

Space Loss

TX PWR Reduction = CCITPC

James Wang et al, MediaTek

CCI

doc.: IEEE 802.11-14/0637r0

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 8 James Wang et al, Mediatek

Legacy STA1

Legacy STA2

STA 3

Spatial Reuse

CCI 1

CCI2

CCI 1

CCI 2

doc.: IEEE 802.11-14/0637r0

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 9 James Wang et al, Mediatek

doc.: IEEE 802.11-14/0637r0

Submission

References

1. Ron Porat, Broadcom, 11-14-0082-00 Improved Spatial Reuse Feasibility - Part I

2. Jinjing Jiang, Marvell, 11-14-0372-00 System level simulations on increased spatial reuse

3. Graham Smith, DSP Group, 11-14-1290-01 Dynamic Sensitivity Control for HEW

4. Graham Smith, DSP Group, 11-14,0294-02 Dynamic Sensitivity Control Channel Selection and Legacy Sharing

5. Imad Jamil, Orange, 11-14-0523-00-00ax Mac Simulation Results for DSC and TPC

6. Graham Smith, DSP Group, 11-14-0328-02 Dense Apartment Complex Throughput Calculations

7. Graham Smith, DSP Group, 11-14-0045-02 E-Education Analysis

8. Graham Smith, DSP Group, 11-14-0058-01 Pico Cell Use Case Analysis

9. Graham Smith, DSP Group, 11-13-1489-05 Airport Capacity Analysis

10. Graham Smith, DSP Group, 11-13-1487-02 Apartment Capacity - DSC and Channel Selection

11. Chingwa Yeh, MediaTek, 11-14-0648-00 Performance Observation of a Dense Campus Network r0

May 2014

Slide 10 James Wang et al, Mediatek