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Top1. Introduction
Vehicular Ad hoc Network (VANET) is a specific class of Mobile Ad hoc Networks (MANETs) where mobile nodes are represented as vehicles. Nodes’ movement at different speeds creates a dynamic topology with different scenarios (Olariu & Weigle, 2009). In VANET, vehicles are able to exchange data by using either Vehicle-to-Infrastructure (V2I) or Vehicle-to-Vehicle (V2V) communications (Rondinone et al., 2013), as shown in Figure 1. Nevertheless, due to the unstable nature of such networks, packet delivery is a significant challenge, especially in sparse traffic scenarios. Furthermore, in scenarios that are totally disconnected (e.g. in highways during night hours), data can be delivered depending on the available network infrastructure. Many efforts are aimed to enable inter-vehicle communications supplied by existing network infrastructure to provide efficient propagation of data and seamless connectivity (Lupi, Palma, & Vegni, 2012).
A smart new way of using the connectivity of vehicles is defined by Intelligent Vehicular Ad hoc Networking (InVANET). InVANET uses the combination of multiple wireless technologies (e.g. IEEE 802:11p, 3G cellular systems, IEEE 802:16e, etc.) to provide efficient V2I communications (Moustafa & Zhang, 2009). Moreover, V2I and V2V communication technologies are expanded as a portion of the initiative of Vehicle Infrastructure Integration, which always considers the infrastructure of the network as collected Road Side Units (RSUs). The RSUs are supplied with transceivers of 5.9 GHz Dedicated Short Range Communication (DSRC) and a High-Speed Downlink Packet Access (HSDPA) interface to transmit messages to the backbone networks (Bhalla & Bhalla, 2010; Papadimitratos, De La Fortelle, Evenssen, Brignolo, & Cosenza, 2009). Data delivery and dissemination is still considered a challenge in heterogeneous network environments.
In this study, the authors present the fault-tolerance evaluation of VANET under four data dissemination techniques (DSDD, DSSD, SSDD, and SSSD) using three MANETs routing protocols namely: AODV, DSR and DSDV. They use different scenarios that support both V2I and V2V connectivity.
The rest of the paper is organized as follows. First, the authors review the related work. Then they introduce three MANETs routing protocols, VANET characteristics and data dissemination mechanisms in VANETs. Afterward they present four dissemination techniques and introduce the performance evaluation metrics. The authors highlight the simulation tool used and their achieved results. Finally, they provide their conclusions and planned future work.
TopMany research groups, using short range Vehicle-to-Vehicle communication, have explored the idea of data dissemination. Flooding is one of the most popular mechanisms used for broadcasting in MANETs without any explicit information from neighbors. Other studies (Lipman, Liu, & Stojmenovic, 2009) present the problem of broadcast storm that degrades the performance of the network, particularly with a high density. Researchers in (Lou & Wu, 2003) propose how to enhance the flooding mechanism by avoiding the broadcast storm problem. Nevertheless, their proposed model needs knowledge about both the network topology and the nodes’ neighbors.
There are several forwarding-based protocols such as opportunistic forwarding protocol that have been suggested to deal with data dissemination. Researchers in (Chen, Kung, & Vlah, 2001; Niculescu & Nath, 2003) propose an opportunistic forwarding technique and trajectory-based routing scheme. Moreover, the study in (Wu, Fujimoto, Guensler, & Hunter, 2004) suggests using a combination of a trajectory-based scheme and opportunistic routing trying to specifically address vehicle mobility and to enhance the fault-tolerance. The forwarding mechanism is considered more suitable for applications, which have reliable requirements of delivery than for latency-sensitive message dissemination (Nadeem, Shankar, & Iftode, 2006). The latter study shows that broadcast is the preferable message dissemination technique.