OBSS Mitigation Date: 2013-05-11 Authors: May 2013 Month Year doc.: IEEE 802.11-yy/XXXXr0 May 2013 OBSS Mitigation Date: 2013-05-11 Authors: Name Affiliations Address Phone Email Shoukang Zheng I2R 1 Fusionopolis Way, Singapore +65 6408 2252 skzheng@i2r.a-star.edu.sg Zander Lei Li Chia Choo Haiguang Wang Yuan Zhou Yeow Wai Leong Huai-Rong Shao Samsung Chiu Ngo chiu.ngo@samsung.com ChaoChun Wang MediaTek San Jose, CA, USA +1-408-526-1899 chaochun.wang@mediatek.com James Wang james.wang@mediatek.com Jianhan Liu jianhan.liu@mediatek.com James Yee Hsinchu, Taiwan james.yee@mediatek.com Thomas Pare thomas.pare@mediatek.com Kiran Uln kiran.uln@mediatek.com Eric Wong Broadcom Sunnyvale, CA, USA +1-408-922-6672 ewong@broadcom.com Matthew Fischer +1-408-543-3370 mfischer@broadcom.com Minyoung Park Intel Hillsboro, OR, USA +1-503-712-4705 minyoung.park@intel.com Tom Tetzlaff thomas.a.tetzlaff@intel.com Emily Qi emily.h.qi@intel.com Chao-Chun Wang, MediaTek Shoukang ZHENG et. al, I2R, Singapore

Authors: March 2013 Name Affiliations Address Phone Email Hongyuan Zhang Marvell Santa Clara, CA, USA +1-408-222-1837 hongyuan@marvell.com Su Khiong Yong skyong@marvell.com Sudhir Srinivasa sudhirs@marvell.com George Calcev Huawei Rolling Meadows, IL, USA george.calcev@huawei.com Osama Aboul Magd Ottawa, Canada osama.aboulmagd@huawei.com Young Hoon Kwon San Diego, CA, USA younghoon.kwon@huawei.com Betty Zhao Beijing, China +86-10-59728332 betty.zhao@huawei.com David Xun Yangxun Shenzhen, China david.yangxun@huawei.com Bin Zhen zhenbin@huawei.com Yongho Seok LG Electronics LG R&D Complex, Anyang, Korea +82-42-450-1947 yongho.seok@lge.com Jeongki Kim Anyang, Korea jeongki.kim@lge.com Jinsoo Choi jinsoo.choi@lge.com Hangyu Cho hg.cho@lge.com Sun, Bo         ZTE Xi’an, China sun.bo1@zte.com.cn Lv, Kaiying         lv.kaiying@zte.com Simone Merlin Qualcomm +1-858-845-1243 smerlin@qti.qualcomm.com Santosh Abraham sabraham@qti.qualcomm.com Menzo Wentink Breukelen, Netherlands mwentink@qca.qualcomm.com Alfred Asterjadhi aasterja@qti.qualcomm.com Amin Jafarian jafarian@qti.qualcomm.com Hemanth Sampath hsampath@qti.qualcomm.com VK jones vkjones@qca.qualcomm.com Bin Tian George Cherian Chao-Chun Wang, MediaTek

Authors: March 2013 Name Affiliations Address Phone Email Sayantan Choudhury Nokia Berkeley, CA, USA sayantan.choudhury@nokia.com Klaus Doppler klaus.doppler@nokia.com Chittabrata Ghosh +1-650-200-7566 chittabrata.ghosh@nokia.com Esa Tuomaala Ken Mori Panasonic Osaka, Japan mori.ken1@jp.panasonic.com Rojan Chitrakar Tai Seng Ave, Singapore +65-6550-5347 rojan.chitrakar@sg.panasonic.com Minho Cheong ETRI 138 Gajeong-no, Yuseong-gu, Daejeon, Korea +82-42-560-5635 minho@etri.re.kr Hyoung Jin Kwon Daejeon, Korea +82-42-860-1698 kwonjin@etri.re.kr Jae Seung Lee +82-42-860-1326 jasonlee@etri.re.kr Jae Woo Park +82-42-860-5723 parkjw@etri.re.kr Sok-kyu Lee +82-42-860-5919 sk-lee@etri.re.kr Anna Pantelidou Renesas Mobile Oulu, Finland +358-50-410-5316 anna.pantelidou@renesasmobile.com Juho Pirskanen +358-50-363-6632 juho.pirskanen@renesasmobile.com Timo Koskela +358-50-487-6991 timo.koskela@renesasmobile.com Liwen Chu STMicroelectronics Santa Clara, CA, USA +1-408-467-8436 liwen.chu@st.com George Vlantis +1-408-893-9357 george.vlantis@st.com Chao-Chun Wang, MediaTek

May 2013 11ah OBSS issue A long range BSS may enclose and overlap spatially with several short range BSSs An STAL associated with the long range APL that is not within the coverage of one or more short range BSSs. An STAO associated with the long range APL that is also overlapped within the coverage of a short range BSS. An STAS is associated with a short range APS that is also within the coverage of a long range BSS APL STAL APS STAS APS STAS STAO Shoukang Zheng, I2R

11ah OBSS issue - Continue May 2013 11ah OBSS issue - Continue A long range BSS has a coverage area radius that is multiples of that of a short range BSS. A long range BSS has narrow 1 or 2 MHz channel bandwidth, while a short range BSS has wider bandwidth, such as 2, 4, 8 MHz A STAS is capable of receiving 1 and 2 MHz frames and a STAL is capable of receiving 1 MHz frames only Without loss of generality, we assume the long range BSS occupies a 2 MHz channel and each short range BSS occupy 8 MHz band, consisting of four 2 MHz band. In the short range BSS, the protection period is set up by using duplicate RTS/CTS The RTS/CTS has range covering the short range BSS only Chao-Chun Wang, MediaTek

Setting TXOP for STAs using duplicate RTS/CTS May 2013 Setting TXOP for STAs using duplicate RTS/CTS A transmitting STAs sends duplicate RTS frames to all 2 MHz sub-channels, primary and secondary. In response, duplicate CTS frames are sent to all usable 2MHz sub-channels The receiver decides the best usable channel bandwidth based on the channel measurements prior to the receiving of duplicate RTSs The transmitter exchanges frames with the receiver by using the bandwidth indicated in the duplicate CTS. Duplicate ACKs are returned on primary and all usable secondary channels Chao-Chun Wang, MediaTek

May 2013 Problem Statement - 1 Non-overlapping (in frequency domain) long range BSSs enclosing multiple non-overlapping (in spatial domain) short range BSSs A short range BSS and a long range BSS that share the primary channel co-exist according to the current channel access rule. The APss and STAss will hear the traffic of a long range BSS sharing the primary channel and set up a NAV for collision avoidance scheme accordingly. The APLs and STALs on the secondary channels may not hear the traffic or TXOP set up in a short range BSS sharing the primary channel and may interfere with the traffic in the short range BSS. Chao-Chun Wang, MediaTek

May 2013 Problem Statement - 2 Long range BSSs on the secondary channels of a short range BSS may not hear TXOP set up of the short range BSS and will access channel according to CCA rules As a result, the traffic in the long range BSSs occupying secondary channels may collide with the traffic in short range BSSs and causes data loss. In response, the STAS and STAL may re-transmit and continue to collide. With information about the condition of secondary channels, the re-transmission process will converge faster STAL and STAS need to co-exist fairly Chao-Chun Wang, MediaTek

Secondary Channel Interference May 2013 Secondary Channel Interference Long range STALs exchange RTS/CTS in a 1 or 2 MHz channel to set up a TXOP in a secondary channel. The TXOP of the long range BSS overlaps with the TXOP set up by the short range BSSs Long range STALs and short range STASs exchange frames around the same time. The collision may not affect the STALs in the secondary channel but will corrupt data destined for the STASs . The STAS receiver can estimates the interference level of the secondary channels based on Rx statistics It is a vendor specific capability. It is up to a vendor to decide how or whether to support it Chao-Chun Wang, MediaTek

Usable Channel Indication by using duplicate ACKs May 2013 Usable Channel Indication by using duplicate ACKs An STAS transmitter starts transmitting using the primary channel and all secondary channels available. A STAS returns duplicate ACKs with reduced bandwidth to the transmitter The transmitter can avoid the secondary channels with the high level of interference in the succeeding transmission The STAss will not interfere STAls sharing a second channel Duplicate ACKs to reduce the channel bandwidth The receiver returns duplicate short ACKs on the primary and usable secondary channels only. Only return duplicate short ACKs on contiguous channels Subsequently, the STAS transmitter data only on the secondary channel indicated as usable by duplicate ACKS. Chao-Chun Wang, MediaTek

May 2013 Straw Poll Do you support the inclusion of the usable channel indication mechanism follows and includes transmitter and receiver capability information When the data is received correctly by a receiver: The receiver returns full bandwidth >= 2MHz short ACK on the primary and usable secondary channels. Only return full bandwidth >= 2MHz short ACKs  on contiguous channels Chao-Chun Wang, MediaTek