A Coexistence Discovery Mechanism

1. A Coexistence Discovery Mechanism Authors: Date: 2016-05-18 Hyunduk Kang et al, ETRI

2. Interference vs. Coexistence 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) • Coexistence discovery let you know • Who is your neighbor that can cause co-channel or adjacent channel interference • What is further information regarding your neighbors such as network type, operating parameters, and so on. Hyunduk Kang et al, ETRI

3. Hidden neighbors • AP1 and AP2 directly can NOT hear each other • Hidden neighbors cause more severe interference each other since they are blinded each other Hyunduk Kang et al, ETRI

4. Hidden neighbor discovery with geo-location information • Geo-location information not always provide hidden neighbor information because of the followings; • Only in some conditions (e.g., outdoors with clear line of site to GPS), accurate geo-location information is achievable • Other conditions, particularly indoors, it may be more challenging • To increase the accuracy of hidden neighbor discovery, we can make good use of results of spectrum sensing (or radio measurement) by each wireless systems Hyunduk Kang et al, ETRI

5. Example of hidden node situation • AP1 has hidden neighbors, AP2 and AP3 • AP2 has a hidden neighbor, AP1 • AP3 has a hidden neighbor, AP1 Hyunduk Kang, et al, ETRI

6. How to discover hidden neighbors (1/3) • After channel scanning and association • Each AP and STA discovers • AP1: no AP • AP2: AP3 • AP3: AP2 • STA11: AP1 • STA21: AP2 • STA31: AP1, AP2, AP3 • STA32: AP2, AP3 • STA33: AP3 Hyunduk Kang, et al, ETRI

7. How to discover hidden neighbors (2/3) • STA31 located in overlapped area of three APs’ coverage can sense all APs • AP3 knows the existence of hidden AP1 based on the result of channel scanning of the associated STA31 • There exist two blinded APs • AP1 should know the existence of hidden AP2 and AP3 • AP2 should know the existence of hidden AP1 • AP3 can spread hidden neighbor information to the neighbors still blinded Hyunduk Kang, et al, ETRI

8. How to discover hidden neighbors (3/3) • Spreading hidden neighbor information to the neighbors Hyunduk Kang, et al, ETRI

9. A proposed hidden neighbor discovery mechanism (1/3) • Discovery mechanism includes the following steps; • EachAP andSTAperform channel scanning • EachSTA associates its selected AP • Each STA sends channel scanning information to the associated AP • Each AP discover hidden APs and updates neighbor AP lists by comparing the followings; • Channel scanning by itself • Channel scanning information to the associated STAs • If hidden APs are exist, the AP selects one or more STA among its associated STAs Hyunduk Kang, et al, ETRI

10. A proposed hidden neighbor discovery mechanism (2/3) • Discovery mechanism includes the following steps (cont.); • The AP sends APDiscovery_indication message to the selected STA(s) • APDiscovery_indication message may include channel scanning information of the selected STA(s) and neighbor information regarding the associated AP of the selected STA(s) • The selected STA(s) received APDiscovery_indication message from its associated AP, send APDiscovery_indication message to neighbor APs discovered by the selected STA(s) based on channel scanning • Neighbor AP(s) received APDiscovery_indication message, recognize existence of hidden AP(s) and update neighbor AP lists Hyunduk Kang, et al, ETRI

11. A proposed hidden neighbor discovery mechanism (3/3) • Message exchange among APs and STAs Hyunduk Kang, et al, ETRI