| A Vehicular Ad hoc NETwork (VANET) is a special subset of multi-hop Mobile Ad hoc NET works (MANETs) in which vehicles equipped with wireless interfaces are able to communicate with each other as well as with fixed equipments alongside highways and city roads. To support path discovery and path maintenance for efficient data transmission within VANETs, effective routing is one of the main research issues with the primary objective of information transfer in terms of high reliability, throughput, and lowest possible delay. Unique characteristics of vehicular mobility dynamics (including high speed, predictable, restricted mobility patterns) and underlying PHY/MAC layer implementation significantly affect the performance of routing protocols in real VANETs as obtained results may vary to a great extent. Therefore, contrary to earlier work in this area, the first part of this study (with proposed modified Freeway, Stop Sign, and Traffic Sign mobility models) considers realistic vehicular mobility patterns with modified 802.11a for the evaluation of topological and geographical routing protocols. Obtained simulation results demonstrate the suitability of geographical routing protocols over reactive protocols in VANETs and this comprehensive evaluation with specific macro-/micro-mobility parameters will assist to address challenges associated with future deployment of routing protocols integrated upon devices with IEEE 802.11 p.With the primary objective of throughput improvements, the second part of this treatise deals with the study of two emerging approaches i.e., Network Coding (NC) and Opportunistic Routing (OR) as well as their implications within VANETs. NC scheme refines the precise flow of data in a network by transmitting encoded packets from certain source(s) to respective receiver(s) and extends the job of intermediate nodes from simple store-and-forward to store-process-and-forward. On the other hand, mainly composed of two components i.e. forwarder set selection and the prioritization among nodes of forwarder set, OR by taking advantage of the broadcast nature of wireless medium, suppresses duplicate data transmissions in ad hoc networks and significantly improves the performance of wireless ad hoc networks in terms of transmission reliability and network throughput. Following the opportunistic packet forwarding paradigm of OR, the NC-aware routing paradigm considers coding opportunities at intermediate nodes to support efficient packet delivery in wireless ad hoc networks. Concerning data delivery, coding-aware routing protocols either deal with route selection issues or focus on packet forwarding issues within wireless networks. Therefore, the fundamental issues with NC-aware routing in wireless networks are related to identify routes with the highest coding opportunities and the finding of exact coding capabilities at each coding node. While exploring the implications of NC-aware routing in wireless ad hoc networks, this preliminary comprehensive study provides the taxonomy of NC-aware routing protocols. Following different criteria, NC-aware routing protocols have been classified into distinct categories i.e., Active, Passive, Centralized, Distributed, Source, and Hop-by-hop.In addition, finding out a class of NC-aware routing protocols, which is suitable to highly dynamic VANETs is also the part of this study. From the synthesis of available literature, it has been concluded that hop-by-hop and active NC-aware routing techniques are more suitable for VANETs in comparison with centralized and source NC-aware routing techniques. Moreover, in a specific freeway mobility scenario, obtained simulation results in terms of coding gain and percentage of encoded transmissions also strengthen the use of hop-by-hop NC-aware schemes in VANETs. In the last, while identifying challenges and specific design issues with the implementation of the NC-aware routing in VANETs, an adaptive topology-based flow-oriented hop-by-hop NC-aware routing scheme has been proposed. In the proposed approach, a coding node takes into account the composition of multiple unicast data flows and encodes data packets while estimating the topology of the network at any instant of time. Obtained simulation results indicate the significance of proposed scheme over non-coding aware routing in VANETs. It is hoped that this work will open up new research directions with reference to the use of NC-aware routing within the context of VANETs.
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