Consideration on Neighbor Discovery

1. Consideration on Neighbor Discovery Authors: Date: 2015-01-15 Hyunduk Kang et al, ETRI

2. 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) Interference vs. Neighbor discovery Hyunduk Kang et al, ETRI

3. 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 Case Study: Interference vs. Neighbor Discovery among WLANs Hyunduk Kang et al, ETRI

4. 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. Inter-BSS Interference: AP-AP Hyunduk Kang et al, ETRI

5. 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. Inter-BSS Interference: AP-STA Hyunduk Kang et al, ETRI

6. 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. Inter-BSS Interference: STA-STA Hyunduk Kang et al, ETRI

7. Itis possible to categorize overlapping geography based on IBI classification • Types of overlapping • AP-AP overlapping • BSS-BSS overlapping • STA-STA overlapping Overlapping Geography Hyunduk Kang et al, ETRI

8. AP-AP Overlapping • AP1 and AP2 directly can hear each other • APs and STAs might sufferfrom • AP-AP IBI • AP-STA IBI • STA-STA IBI Hyunduk Kang et al, ETRI

9. BSS-BSS Overlapping • AP1 and AP2 directly can NOT hear each other • APs and STAs might sufferfrom • AP-STA IBI • STA-STA IBI Hyunduk Kang et al, ETRI

10. STA-STA Overlapping • AP1 and AP2 directly can NOT hear each other • STAs might sufferfrom • STA-STA IBI Hyunduk Kang et al, ETRI

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

12. 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 Hyunduk Kang et al, ETRI

13. 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 Existing Mechanisms for Neighbor Discovery on WLANs Hyunduk Kang et al, ETRI

14. 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 Possible Mechanisms for Neighbor Discovery among Wireless Systems Hyunduk Kang et al, ETRI

15. 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? Intuition on Interference Mitigation for Coexistence Hyunduk Kang et al, ETRI

16. 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 informationwould be a challenging issue on unlicensed frequency bands Concluding Remarks Hyunduk Kang et al, ETRI