mobile ad hoc network (MANET) is an autonomous system of mobile hosts (also serving as routers) connected by wireless links, the union of which forms a communication network modeled in the form of an arbitrary communication graph [1] . This is in contrast to the well-known single-hop cellular network model that supports the needs of wireless communication by installing base stations as access points. In cellular networks, communications between two mobile nodes completely rely on the wired backbone and fixed base stations. In a MANET no such infrastructure exists, and the network topology may dynamically change in an unpredictable manner since nodes are free to move. Multicasting is the transmission of datagrams to a group of hosts identified by a single destination address and hence is intended for group-oriented computing. In MANETs, multicasting can efficiently support a variety of applications that are characterized by close collaborative efforts. Think about the scenario where a user is walking with a handheld device or waiting for a flight in an airport terminal. He/she does not know about his/her neighbor, and switches on the handheld device and tries to scan the network to detect if someone would be interested in playing games or start a similar application of interest. This kind of "community-centric" application is envisioned to draw a lot of attention in the data communication world of the near future. This is a typical ad hoc network application, wherein users are mobile and a community of interest is formed on demand using portable devices. There are many applications of MANETs; email and file transfer can be considered easily deployable within an ad hoc network environment. Web services are also possible if any node in the network can serve as a gateway to the rest of the world. We need not emphasize the wide range of military applications possible with ad hoc networks since the technology was initially developed with them in mind, such as a battlefield in unknown territory wherein an infrastructure network is almost impossible to have or maintain. In such situations, MANETs, having self-organizing capability, can be effectively used where other technologies either fail or cannot be deployed effectively. Advanced features of wireless mobile systems, including data rates compatible with multimedia applications, global roaming capability, and coordination with other network structures, are enabling new applications. Therefore, if we can efficiently combine the features of a MANET with the usefulness of multicasting, it will be possible to realize a number of envisioned group-oriented applications. With that in mind, this article provides information about the current state of the art in multicast protocols for MANETs, and compares them with respect to several performance metrics. We also attempt to provide insight into future trends in the area and outline the approaches that are likely to play a major role, as well as point out open problems that need careful attention from the research community. It may be noted that there exists a large amount of literature on multicast in A A Carlos de Morais Cordeiro, Hrishikesh Gossain, and Dharma P. Agrawal University of Cincinnati Recent advances in portable computing and wireless technologies are opening up exciting possibilities for the future of wireless mobile networking. A mobile ad hoc network consists of mobile platforms, which are free to move arbitrarily. In a MANET the nodes are mobile, and internode connectivity may change frequently due to mobility of nodes. Recently, there has been an increasing demand for applications like multiplayer online gaming, where players residing at different locations participate in the same gaming session through their handheld portable devices. Such applications are characterized by a close degree of collaboration, typical of ad hoc network scenarios. Multicasting could prove to be an efficient way of providing necessary services for these kinds of applications; hence, it is imperative to determine what is the best way to provide these services in an ad hoc environment. Due to very diverse requirements of the applications and the unpredictable nature of ad hoc networks, it is necessary to investigate and discern the applicability of existing ad hoc multicast protocols and quantify which is more suitable for which type of applications. In this article we provide a detailed description and comparison of ad hoc multicast protocols. We also hope that the discussion presented here will be helpful to application developers in selecting an appropriate multicast protocol and pave the way for further research. Multicast over Wireless Mobile Ad Hoc Networks: Present and Future Directions
Cordeiro et al. REF present a survey of the multicast routing protocols for ad hoc networks that have been proposed in the literature.
Multicast over Wireless Mobile Ad Hoc Networks: Present and Future Directions
IEEE Network
Computer Science