OBSS issue and simulation scenarios in TGac Month Year doc.: IEEE 802.11-yy/xxxxr0 November 2009 OBSS issue and simulation scenarios in TGac Authors: Yasushi Takatori (NTT) John Doe, Some Company

November 2009 Outline Background Measured propagation loss in a typical Japanese apartment Difference between OBSS issue in TGac and that in TGaa OBSS simulation scenarios in TGac Video Streaming with 11ac devices Yasushi Takatori (NTT)

November 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 video streaming[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 video streaming but also for other traffic. Yasushi Takatori (NTT)

Measured propagation loss in a typical Japanese apartment November 2009 Measured propagation loss in a typical Japanese apartment Yasushi Takatori (NTT)

Measurement place 6 1 2 3 4 5 7 3.0 m 7.3 m November 2009 Yasushi Takatori (NTT)

Layout of each room in the measurement place November 2009 7.3 m S1 1 S2 S5 3.0 m S3 S4 2 AP　 Number of antennas = 8, Linear array (Spacing 0.5λ) STA　 Number of antennas = 4, Linear array (Spacing 0.5λ) S * Yasushi Takatori (NTT)

Measurement equipment November 2009 4x8 MIMO channel measurement was carried out for SDMA evaluation. Long preamble signal is continuously transmitted. Interference between two APs or AP/STA is assumed in this measurement. Rx (AP) : 8 element h = 2.12 m Tx (STA) : 4 element h = 2.12/0.9, 0.75 m AGC Down-conv. LNA HPA Up-conv. D/A A/D AGC Down-conv. LNA Up-conv. HPA D/A A/D AGC Up-conv. Down-conv. LNA D/A HPA A/D HPA Up-conv. D/A AGC Down-conv. LNA A/D Channel estimator TCP-IP Yasushi Takatori (NTT)

Image of interference from OBSS November 2009 Image of interference from OBSS (other person’s room) (my room) AP AP (OBSS) (desired) Measured path STA (OBSS) (desired) STA Yasushi Takatori (NTT)

Measurement parameters November 2009 Measurement parameters Frequency 4.85 GHz Bandwidth 40 MHz (20MHz x 2) Signal OFDM signal Number of FFT 128 Number of subcarrier 96 (Legacy .11a mode) Antenna height 2.12 m (Rx side) 0.75m (Tx side) Yasushi Takatori (NTT)

Results on Interference power November 2009 Results on Interference power ~ Horizontal neighborhood rooms~ AP (Case 1) (Case 1) [dBm] -74.46 -68.28 -63.52 -56.89 -50.18 3m Averaged. -76.54 -69.18 -64.63 -56.23 -45.79 height = 2.12 m (Case 2) AP (Case 2) [dBm] -78.61 -69.98 -65.73 -55.57 -41.39 3m height = 0.9 m Yasushi Takatori (NTT)

Measurement result agrees with the path-loss model in TGn [2]. November 2009 -22 -32 -42 -52 -62 -72 -82 -92 TGn Model [3] Measurement Result Measurement result agrees with the path-loss model in TGn [2]. Relative Received Power [dB] Indoor propagation loss formula (11n) *, F in MHz, d in feet For d<16.5ft Lp = – 38 + 20 log F + 20 log d + Wall/Floor loss (Free Space formula) For d>16.5ft Lp = – 38 + 20 log F + 20 log 16.5 + 35 log (d/16.5) + Wall/Floor Loss Yasushi Takatori (NTT)

Summary for measured propagation loss November 2009 Summary for measured propagation loss When considering the interference betweens rooms on horizontal direction, interference seems to be almost the same with the TGn model.[2] Hence, the model in TGn seems to be reasonable in the evaluation of OBSS in the apartment. As well as described in [2], this result shows the influence on the interference by OBSSs is serious problem in Japanese apartment. OBSS in TGac would be a serious problem because 80MHz bandwidth is likely to be used. Slide 12 K.Nishimori, T. Murakami, R.Kudo, Y.Takatori, Y.Asai (NTT) Yasushi Takatori (NTT)

Difference between OBSS issue in TGac and that in TGaa November 2009 Difference between OBSS issue in TGac and that in TGaa Yasushi Takatori (NTT)

November 2009 July xx, 2009 OBSS issue in TGaa [2][3] OBSS issue in TGaa is focusing on video streaming. Frequency channel assignment and time sharing mechanism have been developed to support video streaming in OBSS. Simple competition among general 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 14 Yasushi Takatori (NTT) Names

Frequency band allocation in Japan OBSS Issue in TGac November 2009 OBSS issue is important in TGac because frequency channel shortage is expected. OBSS issue in TGac is not only for video streaming but also for other traffic. Frequency channel assignment algorithm using TGaa approach may mitigate OBSS effect. However, TGaa approach seems not to be directly applicable to 11ac because TGac should take into account other traffic also. 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)

November 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 information 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 November 2009 Possible Interference Management Frequency domain: Access mechanism that enables frequency channel assignment would be devised to use 80MHz bandwidth for all 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 already have beamforming capability to enable MU-MIMO. Yasushi Takatori (NTT)

Basic flow to mitigate influence of OBSS November 2009 Basic flow to mitigate influence of OBSS (1) OBSS detection Carrier Sensing Others (2) Exchanging control messages RTS/CTS mechanism TRM/Sounding signals (Advertisement of Qload) (3) Resource allocation NAV setting (Frequency channel selection) (TPC/Beamforming ) (4) Data transmission (5) ACK (1) (3) (1) (3) (2) AP-1 AP-2 (2) (2) (2) (2) (4) (4) (5) (5) (2) STA-11 STA-21 Yasushi Takatori (NTT)

Summary of possible approaches November 2009 OBSS issue is important in TGac because frequency channel shortage is expected. It is not only for video streaming but also for other traffic. TGaa has addressed OBSS issue to support video streaming in OBSS. Other general traffic is not taken into account. Frequency channel assignment and time sharing mechanism have been developed in TGaa to support video streaming 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)

OBSS Simulation Scenario in TGac November 2009 OBSS Simulation Scenario in TGac There two scenarios, enterprise scenario [6] and home network scenario [7]. The following slides explain home network scenario with OBSS. Yasushi Takatori (NTT)

Home Network Evaluation Scenario November 2009 Home Network Evaluation Scenario To simplify OBSS scenario, the following effects are focused on. Overlapping with 11ac Overlapping with 11n Effect of hidden terminals in OBSS Throughput degradation from isolated Home Entertainment scenario Evaluation model BSS A: In-Home entertainment application BSS B: 11ac with 3 STAs BSS C: 11n with 3 STAs Room walls are inserted to evaluate effect of hidden terminals Yasushi Takatori (NTT)

November 2009 AP and STA locations Attenuation factors of room wall and outside wall are TBD. 11n In-home entertainment application 11ac Yasushi Takatori (NTT)

Channel Assignment BSS A,B BSS C Case 1 Frequency 80MHz BSS A,B BSS C November 2009 Channel Assignment BSS A is identical to the BSS in TGac scenario #3 BSS B is an 11ac BSS BSS C is a upper 40MHz 802.11n BSS Both 11ac have the same bandwidth (40MHz or 80MHz) BSS A,B BSS C Case 1 Frequency 80MHz BSS A,B BSS C Case 2 Frequency 80MHz Yasushi Takatori (NTT)

Traffic flow at overlapping BSS B November 2009 Traffic flow at overlapping BSS B Flow number 1 and 12 in simulation scenario #3 are considered. Flow No. STAs (Source/Sink) Source Location (meters) Sink Location Channel Model Application (Forward Traffice / Backward Traffic) Application Load (Mbps) (Forward / Backward) Rate Distribution MSDU Size (B) Max. Delay (ms) Max. PLR 1 AP / STA1 (0,0) (0,5) C LC Video / VoD control channel 150.00 / 0.06 Constant, UDP / Constant UDP 1500 / 64 10 / 100  10^-7 / 10^-2 12 STA4 / STA10  (-7,7)  (10,10) Local file transfer Max. 1Gbps TCP 300 Inf.  N/A Yasushi Takatori (NTT)

Traffic flow at overlapping BSS C November 2009 Traffic flow at overlapping BSS C Flow No.1 in BSS B is changed to Flow No.1 of 802.11n scenario #1. Flow No. STAs (Source/Sink) Source Location (meters) Sink Location Channel Model Application (Forward Traffice / Backward Traffic) Application Load (Mbps) (Forward / Backward) Rate Distribution MSDU Size (B) Max. Delay (ms) Max. PLR 1 AP / STA1 (0,0) (0,5) C HDTV(Video / Audio) / VoD control channel 19.2 / 0.06 Constant, UDP / Constant UDP 1500 / 64 200 / 100  10^-7 / 10^-2 12 STA4 / STA10  (-7,7)  (10,10) Local file transfer Max. 1Gbps TCP 300 Inf.  N/A Yasushi Takatori (NTT)

November 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. [6] Brian Hart, Enterprise Simulation Scenario, IEEE 802.11-09/816r5, Sept. 22, 2009. [7] Yasushi Takatori, et al., Home Network Simulation Scenario with OBSS, Doc. IEEE802.11-09/1076r0. Yasushi Takatori (NTT)

November 2009 Video Streaming in 11ac There seems to be three possibilities to support video streaming services with 11ac devices. (A) 11aa + 11ac: Simple combination (B) 11aa+ + 11ac: Creation of new standard, 11aa+ (C) 11ac only: Basic functions of 11aa are supported by 11ac Question: Which one is suitable for video streaming services with 11ac devices? (A) 11aa + 11ac: (B) 11aa+ + 11ac: (C) 11ac only: Yasushi Takatori (NTT)