Seamless mobility in legacy multi-hop IEEE 802.11 Wi-Fi network is difficult to accomplish due to the lack of handoff mechanism. IEEE 802.11s MAC layer protocol adds the feature of mobile mesh networking to standard Wi-Fi by providing layer-2 routing and handoff mechanisms. With ubiquitous connectivity and seamless handoff, many applications requiring continuous data streaming like video, VOIP, file downloading, etc. become possible in Wi-Fi networks that requires mobility support like highways, railways and underground transportation. In this paper we study the handoff mechanism of IEEE 802.11s protocol extensively in a real mobile testbed. Our testbed comprises three mesh nodes, one of which is installed on a vehicle for finding the impact of vehicle speed on 802.11s handoff mechanism. We found that the vehicle speed does not drastically affect the performance metrics during handoff as previously understood. Moreover the results show frequent handoffs during mobility. This is called the ping pong effect, which indicates the absence of hysteresis mechanism in 802.11s protocol. For improving the performance during handoffs we therefore suggest the use of hysteresis mechanism along with the airtime link metric being used in the default routing protocol of 802.11s.
A Fresh Look into the Handoff Mechanism of IEEE 802.11s under Mobility
2017-09-01
864118 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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