doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 1 Spatial Reuse and Interference Mitigation in 60 GHz Date: Authors: NameAffiliationsAddressPhone Carlos CordeiroIntel Corp.OR, Sai ShankarBroadcomCA, Gal Liwen ChuST MicroCA, James Yong LiuMarvellCA, Yongho SeokLGES. Minyoung ParkIntel Corp.OR, Solomon TraininIntel Jason TrachewskyBroadcomCA, Chao-Chun Christopher HansenBroadcomCA,

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 2 Introduction and Goals As described in [2], channel access in 60GHz will use directional communication As a result, there is a big potential to exploit spatial reuse in 60GHz and increase the spectrum efficiency –This becomes even more important in those regulatory domains with a single 60GHz channel (e.g., Australia) On the flip side spatial reuse may also increase interference, since a higher number of links will operate simultaneously and may interference with each other Therefore, in this presentation we: –Introduce spatial reuse and the potential it holds in 60GHz –Propose that TGad provides means for spatial reuse and interference mitigation in 60GHz

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 3 What is spatial reuse? Spatial (Frequency) Reuse = Two or more links sharing the same frequency channel in the same spatial vicinity at the same time STA 3 STA 4 STA 2 STA 1 PCP Spatial reuse within one BSS/PBSS [1] Example in the home Spatial reuse across neighboring BSS/PBSS [1] Example in the office

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 4 Example usage models [3][4] which can take advantage of spatial reuse Wireless networking for small office (usage 2d in [3]) Multi-media mesh backhaul (usage 4a in [3]) –Hotspot, enterprise, small Office or home, campus- wide deployments, municipal deployments Enterprise cubicle [4] The Enterprise Cubicle [4]

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 5 Recap of [1]: the Personal BSS and high-density environments To support several key TGad usages [3] and cope with directional communication in 60GHz, the Personal BSS (PBSS) was introduced in [1] –PBSS is an extension of the IBSS PBSSs are logical and “unmanaged” networks –Not defined by physical proximity (e.g., as it is typical in a BSS), and hence there can be multiple PBSSs in the same vicinity –Typically not managed by an authority with global information (e.g., IT department) –Thus, PBSSs can lead to a highly dense environment Number of interfering links >> the number of available 60GHz channels (e.g., enterprise cubicle [4]) Important TGad usages require a high spectrum efficiency and interference mitigation mechanisms

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 6 Assessing the spatial reuse gain (1) Goal: compare the potential of spatial reuse with omni and directional communication Topology –Enterprise cubicle [4] –9 cubicle office space, each office has one randomly placed link Simulation parameters –Transmit power = 10 dBm –Square ant. array (random orientation) –No. of ant. elements = 1 (omni) and 16 (directional) –NF=8 dB, implementation loss = 2dB –5 reflectors/cube (2 dB reflection loss) –Penetration loss of partition wall = 3 dB * Methodology –Links are added to the office as long as the SINR of active links do not drop below a prescribed SINR Threshold * This is based on internal channel measurements, which revealed that the penetration loss of a cubicle wall ranges from -3~-1 dB

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 7 Assessing the spatial reuse gain (2) Spatial reuse through directional only communication can provide up to 5 times performance gain over omni communication Spatial reuse gain SINR Threshold = 20dBSINR Threshold = 10dB Spatial reuse gain

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 8 The Impact of Spatial Reuse on Interference Spatial reuse provides large gain, but may also lead to increased interference To evaluate this, we have setup a simple MAC simulator in OPNET –No “multiple access” (only 2 STAs per link and per PBSS) The Antenna/RF model of this simulator is the same as in [5] –The simulator implements the partition-based path loss model [6]

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 9 Simulation parameters PHY: –Antennas: PCP [1]: 36 antenna elements STA: 16 antenna elements –TX_Power: 10dBm output power –PHY_Rate (fixed, no real time link-adaptation) PHY rate of 3.8 Gbps used for directed data transmission PHY rate of 0.9Gbps used for directed control transmissions Beacon is transmitted with an effective rate of 2.5Mbps MAC: 16msec beacon interval Traffic: each PBSS has one flow which sends data at 751 Mbps CBR traffic rate

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 10 Example: Spatial Reuse (1) PBSS 2 PBSS 1 PBSS 2 CBR Traffic Load 751 Mbps Packet Drop0% Application Throughput 751 Mbps The two PBSSs can achieve spatial reuse with good throughput and no packet drop Transmissions on top of each other: allowing spatial reuse CBR=Constant Bit Rate time PBSS 1 “on” times PBSS 2 “on” times 1m

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 11 PBSS 2 PBSS 1 STA in PBSS 2 moved to a different location PBSS 1 suffers significant throughput degradation due to interference from PBSS 2 Also leads to higher power consumption and latency Example: Interference impact (2) Transmissions on top of each other: causing interference PBSS 1PBSS 2 CBR Traffic Load751 Mbps Packet Drop before re- transmission 59%0% Packet Drop after re- transmission 33%0% Application Throughput 504 Mbps751 Mbps time PBSS 1 “on” times PBSS 2 “on” times 1m

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 12 How to mitigate the interference impact? Some options Several mechanisms are possible to mitigate interference such as channel switching and power control In addition, there are options which are access scheme dependent. For example: –Random access inherently adapts to the available bandwidth (there are challenges to this in 60GHz though [2]) –For scheduled access, re-scheduling on the basis of interference may be used Or a combination of an access scheme dependent option with power control and/or channel switching

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 13 PBSS 2 PBSS 1 STAs in PBSS 1 detect the interference and re-schedule their links This helps the performance of PBSS 1 to recover If security is not a concern, PBSS 1 and PBSS 2 could also be merged Example: Interference mitigation in scheduled access Time-sharing the channel PBSS 1PBSS 2 CBR Traffic Load751 Mbps Packet Drop Before re-transmission 4%0% Packet Drop After re-transmission 3%0% Application Throughput 730 Mbps751 Mbps time PBSS 1 “on” times (after re-scheduling) PBSS 2 “on” times (after re-scheduling) 1m

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 14 Conclusions Directionality makes spatial reuse a natural characteristic in the 60GHz band TGad should define means to enable interference mitigation and exploit spatial reuse in order to: –Take advantage of directionality in 60GHz –Satisfy the needs of important usage models (e.g., high- density scenarios such as enterprise cubicle) –Better utilize the limited number of channels available in the 60GHz spectrum –Substantially increase network capacity

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 15 References [1] C. Cordeiro et al., /0391r0 [2] S. Shankar et al., /0572r0 [3] A. Myles and R. de Vegt, /2988r3 [4] E. Perahia, /296r6 [5] M. Park et al., /559r0 [6] C. R. Anderson and T. S. Rappaport, “In- Building Wideband Partition Loss Measurements at 2.5 and 60 GHz,” IEEE Trans. on Wireless Comm., Vol. 3, No. 3, May 2004, pp

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 16 Backup

doc.: IEEE /0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 17 Assessing the spatial reuse gain in terms of aggregate throughput PHY rate=4Gbps for SINR ≥ 20 dB PHY rate=2Gbps for 10 dB ≤ SINR < 20dB PHY rate=6Gbps for SINR ≥ 20 dB PHY rate=2Gbps for 10 dB ≤ SINR < 20dB