Consideration on Interference Management in OBSS Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2009 Consideration on Interference Management in OBSS Authors: Yasushi Takatori (NTT) John Doe, Some Company

July 2009 Background TGac agrees that it is important to see how 11ac devices behave in OBSS [1]. TGaa has addressed OBSS issue for video streaming. Frequency channel assignment and time sharing mechanism have been developed to support QoS in OBSS [2]. OBSS in TGac is caused by both possible frequency band enlargement and increase in the number of WLAN devices. The behavior of 11ac devices in OBSS should be examined not only for QoS traffic but also for non-QoS traffic. Yasushi Takatori (NTT)

July 2009 July xx, 2009 OBSS issue in TGaa [2][3] OBSS issue in TGaa is focusing on QoS support. Frequency channel assignment and time sharing mechanism have been developed to support QoS in OBSS. Simple competition among non-QoS traffic is considered to be sufficient. Information of QoS traffic load is advertised among multiple BSSs. QAP-1 QAP-2 Qload EDCA or HCCA EDCA or HCCA Frequency Channel K1 Frequency Channel K2 STA-11 STA-21 Slide 3 Yasushi Takatori (NTT) Names

Frequency band allocation in Japan OBSS Issue in TGac July 2009 OBSS issue is important in TGac because frequency channel shortage is expected. OBSS issue in TGac is not only for QoS traffic but also for non-QoS traffic. Frequency channel assignment algorithm using TGaa approach may mitigate OBSS effect. However, TGaa approach cannot be directly applied because TGac should take into account non-QoS traffic. Frequency band allocation in Japan 20MHz mode 5150 5190 5230 5250 5270 5310 5350[MHz] 40MHz mode (80MHz mode) 5470 5510 5550 5590 5630 5670 5710 5725[MHz] Yasushi Takatori (NTT)

July 2009 Direction Time resource is fairly shared by CSMA/CA with RTS/CTS mechanism [2]. SDMA scheme in 11ac should not degrade this level of fairness. Sharing scheduling among multiple BSSs may improve the throughput [5]. Interference management has a potential to achieve further throughput improvement in OBSS. It has been also addressed in TGaa [2][3][4]. Yasushi Takatori (NTT)

Possible Interference Management July 2009 Possible Interference Management Frequency domain: Access mechanism that enables frequency channel assignment would be devised to use 80MHz bandwidth for QoS/non-QoS traffic. (For 11aa case, see [2]) Falling back to narrowband mode, e.g. 20/40MHz mode, can be one of the practical solutions. (For 11aa case, see [3]) Spatial domain.: Transmission power control (TPC) might be effective to decrease the number of OBSSs. (TGh addressed TPC to avoid interference to other systems. Although it is effective in an apartment scenario, TPC might cause range limitation in other scenarios [4].) Beamforming might be also useful because 11ac devices might already have beamforming capability to enable MU-MIMO. Yasushi Takatori (NTT)

Basic Flow for OBSS in Downlink July 2009 Basic Flow for OBSS in Downlink (1) OBSS detection Carrier Sensing Others (2) Exchanging control messages RTS/CTS mechanism Advertisement of Qload (3) Resource allocation NAV setting Frequency/Space channel allocation (4) Broadcasting allocated resources/scheduling (5) Data transmission (6) ACK (1) (3) (1) (3) (2) AP-1 AP-2 (2) (2) (2) (2) (4) (4) (6) (6) (5) (5) (2) STA-11 STA-21 Yasushi Takatori (NTT)

Summary July 2009 OBSS issue is important in TGac because frequency channel shortage is expected. It is not only for QoS traffic but also for non-QoS traffic. TGaa has addressed OBSS issue to support QoS in OBSS. Non-QoS traffic is not taken into account. Frequency channel assignment and time sharing mechanism have been developed in TGaa to support QoS in OBSS. The following interference management approaches are suggested. Frequency domain approach: Modification of TGaa mechanism is one of the possible approaches. Frequency channel assignment / Falling back to narrow band modes Spatial domain approach: Interference management with TPC / Beamforming Yasushi Takatori (NTT)

July 2009 References [1] Yasushi Takatori, “Importance of Overlapped BSS issue in 802.11ac,” Doc. IEEE802.11-09/0630r1. [2] Graham Smith, “TGaa OBSS Background,” Doc. IEEE802.11-09/0762/r0. [3] Graham Smith, “20/40MHz Channel Selection,” Doc. IEEE802.11-09/0740/r0. [4] Graham Smith, et al., “Overlapping BSS Proposed Solution,” Doc. IEEE802.11-08/0457/r3. [5] Yuichi Morioka, “Two Levels of OBSS Control in 11ac ,” Doc.IEEE802.11-09/0833/r0. Yasushi Takatori (NTT)