Consideration on Neighbor Discovery January 2015 Consideration on Neighbor Discovery Date: 2015-01-15 Authors: Hyunduk Kang et al, ETRI Steve Shellhammer, Qualcomm

Interference vs. Neighbor discovery January 2015 Interference vs. Neighbor discovery Interference among wireless systems is caused by wireless systems located nearby each other A first step on interference mitigation might be which wireless systems are interfering me on which channel Interference on the same operating channel Interference on the adjacent channel (due to partial channel overlap) Hyunduk Kang et al, ETRI

Case Study: Interference vs. Neighbor Discovery among WLANs January 2015 Case Study: Interference vs. Neighbor Discovery among WLANs Inter-BSS Interference (IBI) is interference among multiple basic service sets (BSSs), located nearby each other There are three types of inter-BSS interference AP-AP IBI AP-STA IBI STA-STA IBI Hyunduk Kang et al, ETRI

Inter-BSS Interference: AP-AP January 2015 Inter-BSS Interference: AP-AP It occurs when a AP receiving data from its associated STA is interfered by a neighbor AP transmitting data to its associated STA, and vice versa. Hyunduk Kang et al, ETRI

Inter-BSS Interference: AP-STA January 2015 Inter-BSS Interference: AP-STA It occurs when a AP receiving data from its associated STA is interfered by a neighbor AP transmitting data to its associated STA, and vice versa. Hyunduk Kang et al, ETRI

Inter-BSS Interference: STA-STA January 2015 Inter-BSS Interference: STA-STA It occurs when a STA receiving data from its associated AP is interfered by a neighbor STA transmitting data to its associated AP, and vice versa. Hyunduk Kang et al, ETRI

Overlapping Geography January 2015 Overlapping Geography It is possible to categorize overlapping geography based on IBI classification Types of overlapping AP-AP overlapping BSS-BSS overlapping STA-STA overlapping Hyunduk Kang et al, ETRI

AP-AP Overlapping AP1 and AP2 directly can hear each other January 2015 AP-AP Overlapping AP1 and AP2 directly can hear each other APs and STAs might suffer from AP-AP IBI AP-STA IBI STA-STA IBI Hyunduk Kang et al, ETRI

BSS-BSS Overlapping AP1 and AP2 directly can NOT hear each other January 2015 BSS-BSS Overlapping AP1 and AP2 directly can NOT hear each other APs and STAs might suffer from AP-STA IBI STA-STA IBI Hyunduk Kang et al, ETRI

STA-STA Overlapping AP1 and AP2 directly can NOT hear each other January 2015 STA-STA Overlapping AP1 and AP2 directly can NOT hear each other STAs might suffer from STA-STA IBI Hyunduk Kang et al, ETRI

No Overlapping: BSS-BSS Separation January 2015 No Overlapping: BSS-BSS Separation There is no interference between BSSs Ideal spatial reuse is possible Hyunduk Kang et al, ETRI

Comparison among Types of Overlap January 2015 Comparison among Types of Overlap AP-AP could get lot of co-channel interference. However, it might be favorable to mitigate interference since AP can hear each other directly BSS-BSS seems to difficult to mitigate co-channel interference since APs are blinded each other Type of overlapping Inter-BSS interference: AP-AP Inter-BSS interference: AP-STA Inter-BSS interference: STA-STA Amount of Inter-BSS interference Hidden neighbor AP AP-AP YES Heavy - BSS-BSS Medium STA-STA Light No Hyunduk Kang et al, ETRI

Existing Mechanisms for Neighbor Discovery on WLANs January 2015 Existing Mechanisms for Neighbor Discovery on WLANs Spectrum sensing CCA-ED (for other wireless system) CCA-SD (for WLANs, preamble detection is possible) Passive scanning Beacon listening Active scanning Probe request/response Virtual carrier sensing RTS/CTS BSS color: 802.11ah-D2.0 Neighbor report Reduced neighbor report: 802.11af-2012 Radio measurement Hyunduk Kang et al, ETRI

Possible Mechanisms for Neighbor Discovery among Wireless Systems January 2015 Possible Mechanisms for Neighbor Discovery among Wireless Systems Spectrum sensing (or radio measurement) Each wireless systems perform it by itself In general, two methods are Energy detection (to reveal existence of wireless systems) Feature detection (to identity type of wireless systems) Message exchanging (directly or indirectly) Neighbor information could be exchanged Via wireless channel Via wired channel Neighbor information could be obtained by combinations of Results of spectrum sensing (or radio measurement) by each wireless systems Geo-location information if available Hyunduk Kang et al, ETRI

Intuition on Interference Mitigation for Coexistence January 2015 Intuition on Interference Mitigation for Coexistence Which system is interfering on which channel? (Seen/Hidden) How to identify neighbor systems which interfere my system “Stay on the channel” or “Switch to new channel” Determination based on what grounds? What is useful information for decision? Stay on the channel with which channel sharing method? Existing methods, e.g., LBT, are enough or we need a new one? Select to new channel with which channel allocation method? Existing methods, e.g., DFS, are enough or we need a new one? Hyunduk Kang et al, ETRI

January 2015 Concluding Remarks Neighbor discovery is the very first step for interference mitigation for better coexistence among wireless systems Neighbor discovery among dissimilar wireless systems might be more difficult than that among similar wireless systems Just to reveal existence of neighbor is not enough for interference mitigation. The more information on neighbor, the better coexistence among neighbor Neighbor discovery without geo-location information would be a challenging issue on unlicensed frequency bands Hyunduk Kang et al, ETRI