Post on 05-Jan-2016
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