Avariety of applications is provided by the VANETs (Bali et al., 2009). There can be three major sections for theseapplications: commercial, non-safety, and safety applications.
The main objective of the Vehicle SafetyCommunication Consortium (VSCC) is the safety applications. An effective and new class ofcommunication applications is enabled by the DSRC. The safety of the road is improved by theseapplications. Traffic information distribution is a unique problem inVANET. In most of the applications inVANET and safety applications in particular, there are no specific destinationfor the exchanged messages. In fact, theRegion of Interest (RoI) for these messages is all of the surrounding vehiclesand these vehicles are the targeted destinations. In other words, the public interest is theaim of these applications and instead of a particular individual; a group ofusers are the beneficiaries of them.
Asa result, instead of using a unicast routing scheme to distribute the trafficinformation, the application of a broadcasting scheme is more appropriate. However, the blind broadcasting of thepackets can initiate and cause conflict in the transmissions that take placebetween the neighboring vehicles. Thisis a problem that has been referred to as the broadcast storm problem (Williamsand Camp, 2002). During the rush hour traffic, it is more likely for VANETsto be formed a highly dense network in urban areas or freeways.Until now, the focus of the most of the broadcastingresearch in VANET has been on the analyzing the protocols in order to deal withthe problem of the broadcast storm in a network with high density under an oversimplified assumption, a typical VANET is a connected network in nature (Tonguzet al.
, 2007). However frequent network fragmentation is expected to beexperienced by the VANETs during the late night hours or in the rural freewaysof sparsely populated areas. In addition to research carried out ondense networks, there is an increasing demand for investigation on thefragmentation problem in sparse VANETs, in which the nodes are positionedsparsely, and in these conditions, generally there cannot be found paths fromsource to destinations (Rodrigues et al., 2011).
Various routing protocols have been proposedspecifically to solve the routing problem within the fragmented networks, forexample store carry forward (Sahin and Chindapol, 2007), Mobyspace (Santa etal., 2009), Spray and Wait (Huang et al., 2011).