Studies And Analysis Of Topological, Geographical, And Network Coding-Aware Ad Hoc Routing Protocols With Realistic Vehicular Mobility

A Vehicular Ad hoc NETwork (VANET) is a special subset of multi-hop Mobile Adhoc NETworks (MANETs) in which vehicles equipped with wireless interfaces are able tocommunicate with each other as well as with fixed equipments alongside highways andcity roads. To support path discovery and path maintenance for efficient data transmissionwithin VANETs, effective routing is one of the main research issues with the primaryobjective of information transfer in terms of high reliability, throughput, and lowestpossible delay. Unique characteristics of vehicular mobility dynamics (including highspeed, predictable, restricted mobility patterns) and underlying PHY/MAC layerimplementation significantly affect the performance of routing protocols in real VANETsas obtained results may vary to a great extent. Therefore, contrary to earlier work in thisarea, the first part of this study (with proposed modified Freeway, Stop Sign, and TrafficSign mobility models) considers realistic vehicular mobility patterns with modified802.11a for the evaluation of topological and geographical routing protocols. Obtainedsimulation results demonstrate the suitability of geographical routing protocols overreactive protocols in VANETs and this comprehensive evaluation with specific macro-/micro-mobility parameters will assist to address challenges associated with futuredeployment of routing protocols integrated upon devices with IEEE802.11p.With the primary objective of throughput improvements, the second part of this treatisedeals with the study of two emerging approaches i.e., Network Coding (NC) andOpportunistic Routing (OR) as well as their implications within VANETs. NC schemerefines the precise flow of data in a network by transmitting encoded packets from certainsource(s) to respective receiver(s) and extends the job of intermediate nodes from simplestore-and-forward to store-process-and-forward. On the other hand, mainly composed oftwo components i.e. forwarder set selection and the prioritization among nodes offorwarder set, OR by taking advantage of the broadcast nature of wireless medium,suppresses duplicate data transmissions in ad hoc networks and significantly improves theperformance of wireless ad hoc networks in terms of transmission reliability and networkthroughput. Following the opportunistic packet forwarding paradigm of OR, the NC-aware routing paradigm considers coding opportunities at intermediate nodes to support efficientpacket delivery in wireless ad hoc networks. Concerning data delivery, coding-awarerouting protocols either deal with route selection issues or focus on packet forwardingissues within wireless networks. Therefore, the fundamental issues with NC-aware routingin wireless networks are related to identify routes with the highest coding opportunitiesand the finding of exact coding capabilities at each coding node. While exploring theimplications of NC-aware routing in wireless ad hoc networks, this preliminarycomprehensive study provides the taxonomy of NC-aware routing protocols. Followingdifferent criteria, NC-aware routing protocols have been classified into distinct categoriesi.e., Active, Passive, Centralized, Distributed, Source, and Hop-by-hop.In addition, finding out a class of NC-aware routing protocols, which is suitable tohighly dynamic VANETs is also the part of this study. From the synthesis of availableliterature, it has been concluded that hop-by-hop and active NC-aware routing techniquesare more suitable for VANETs in comparison with centralized and source NC-awarerouting techniques. Moreover, in a specific freeway mobility scenario, obtained simulationresults in terms of coding gain and percentage of encoded transmissions also strengthenthe use of hop-by-hop NC-aware schemes in VANETs. In the last, while identifyingchallenges and specific design issues with the implementation of the NC-aware routing inVANETs, an adaptive topology-based flow-oriented hop-by-hop NC-aware routingscheme has been proposed. In the proposed approach, a coding node takes into account thecomposition of multiple unicast data flows and encodes data packets while estimating thetopology of the network at any instant of time. Obtained simulation results indicate thesignificance of proposed scheme over non-coding aware routing in VANETs. It is hopedthat this work will open up new research directions with reference to the use of NC-awarerouting within the context of VANETs.