Computer Science Thesis Oral

Friday, August 7, 2015 - 11:00am


Traffic 21 Classroom 6501 Gates & Hillman Centers



Vehicular Ad-Hoc Networks (VANETs) aim to increase traffic safety and efficiency through wireless communication. Due to the vehicles’ limited radio range, multi-hop communication is useful to extend coverage. However, the dynamic topology and spatial heterogeneity that characterize VANETs make this challenging, requiring a fundamental change from traditional topology-based routing protocols. In this thesis we focus on the development of specialized vehicular geographic multi-hop communication protocols that address these challenges. First we tackle topology instability with the Density-Aware Zone-based Limited (DAZL) forwarding protocol. Instead of choosing a single relay as is traditional, DAZL specifies a geographic forwarding zone and has multiple vehicles inside it cooperate in forwarding. We show experimentally that forwarders can cover each other’s losses, increasing reliability through node diversity. Moreover, zone nodes coordinate to prioritize the best forwarders and avoid replication. Second, we propose the Look-Ahead Spatial Protocol (LASP). LASP addresses the issue of spatial heterogeneity by using measured spatial connectivity information describing the probability of delivery between different geographic areas. Observed vehicular connectivity data exhibited a strong correlation between location and packet delivery ratio, justifying the use of spatial connectivity as an heuristic. LASP combines global historical spatial connectivity information with real-time local neighborhood information to select a next hop that maximizes end-to-end delivery probability. Finally we join both ideas in the LASP-MF (Multi-Forwarder) protocol, which combines LASP’s spatial connectivity-based routing with DAZL’s zone-based forwarding approach in a single protocol. Instead of picking a specific next-hop node, LASP-MF uses spatial connectivity to select a forwarding zone where nodes cooperate in forwarding in a manner similar to DAZL. Throughout the thesis we leverage two vehicular testbeds currently deployed in the city of Porto, Portugal, to both validate the concepts underlying our protocols and evaluate their performance. Thesis Committee:Peter Steenkiste (Co-Chair)João Barros (Co-Chair, University of Porto)Srinivasan SeshanRagunathan (Raj) RajkumarMario Gerla (University of California, Los Angeles)Paulo Ferreira (University of Aveiro)

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Thesis Oral