Routing and data diffusion in VANETs -- Routing protocols
Editor's Note: Wireless sensor networks lie at the heart of emerging applications in nearly every industry segment. In building these networks, designers contend with issues that encompass real-time communications, efficient high-bandwidth data exchange, multiple network topologies, selection of optimal routing strategies, and more. The book, Building Wireless Sensor Networks, offers detailed treatments on critical requirements and promising solutions in each of these areas and more.
This excerpt focuses on design challenges and methods associated with creating a vehicular ad hoc network (VANET). To share data as vehicles pass on roads or rest in parking areas, a VANET must contend with issues as varied as the physics of signal propagation, the fluid nature of data routing, and the security vulnerabilities associated with participation in an ad hoc network. Because of the changing nature of a VANET, designers need a broad understanding of these issues.
In this excerpt from the book, the authors offer an in-depth discussion that defines the nature of VANET challenges and discusses alternatives for their solution. Continuing the description of VANETs in part 1, part 2 and part 3, this installment of this series provides an in-depth discussion of routing protocols for VANETs.
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Adapted from Building Wireless Sensor Networks, by Smain Femmam, Editor.
Chapter 3. Routing and data diffusion in vehicular ad hoc networks (Cont.)
By Frédéric Drouhin and Sébastien Bindel
3.3.2. Routing protocols
Routing protocols dedicated to MANET have been widely investigated in the past. Considered as a subset of MANET, some routing protocols from MANET can also be used in VANET. However, the high velocity of vehicles and their specific motion have been taken into account in the design of specific routing protocols for VANET. A first survey made by [LI 07] introduced a classification based on the following criteria: ad hoc, position-based, cluster-based, broadcast and geocast-based. Even if an author has the merit of giving a classification and introducing concepts, they have become out of date due to recent research advances. [LEE 10] and [SHA 14] investigate in depth routing solutions. The most recent classification is given by [SHA 14] and is based on the VANET architecture, V2V and V2I. Routing protocols dedicated to the V2V architecture can be classified into six categories: (i) topology-based, (ii) position-based, (iii) cluster-based, (iv) geocast-based, (v) multicast-based and (vi) broadcast-based. Figure 3.9 depicts the different delivery scheme used by unicast, broadcast, multicast and geocast protocols. Concerning routing protocols for V2I, two groups are considered: (i) for static infrastructure and (ii) for mobile infrastructure.
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Figure 3.9. Type of delivery scheme
126.96.36.199. V2V routing protocols
Routing protocols designed for a V2V architecture exploit the distributed feature of such a network. The most beneficial aspects are the loss of tolerance and its scalability; moreover, it is often hard to maintain stability, which therefore requires several approaches that have been investigated and detailed in the following paragraphs.
188.8.131.52.1. Topology based
Topology-based protocols have been inherited from MANET and rely on topology information to construct a routing path. These protocols are classified into three categories: proactive, reactive and hybrid. Proactive protocols, also called table-driven, maintain a periodic routing path discovery. This strategy has the benefit of providing nodes with a fresh vision of the topology, but it requires a significant bandwidth, not available for data. The most popular protocol is certainly the optimized link state routing (OLSR) protocol, but there are others such as: destination-sequenced distance vector (DSDV), fisheye state routing (FSR), global state routing protocol (GSRP), wireless routing protocol (WRP) and topology dissemination based on reverse-path forwarding routing (TBRPF). Reactive protocols, also called on-demand routing protocols, start the routing discovery process when data need to be transmitted to a desired destination. These protocols have the benefit of having a reduced bandwidth consumption, unlike proactive protocols; however, since the routing process is triggered only by data needed to be transmitted, the delay related to the routing path discovery is then added. The most popular protocol is ad hoc on-demand distance vector (AODV) but there are others: temporally ordered routing algorithm (TORA), prediction-based AODV (PRAODV) and dynamic source routing (DSR). The last category includes protocols that combine both a proactive and a reactive routing scheme. Most protocols define a zone wherein a proactive scheme is used and a reactive scheme to route data inter-zone. The main idea of this approach is to profit from the benefits of proactive and reactive schemes and avoid drawbacks. The best known protocols are zone routing protocol (ZRP) and hybrid ad hoc routing protocol (HARP).