This paper addresses the issue of deafness and hidden terminal problem in a Mobile Ad Hoc Networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) which employs an enhanced directional network allocation vector (NAV) scheme and, a novel technique of Diametrically Opposite Directions (DOD) transmission of RTS and CTS. We compare MDA with IEEE 802.11 and two recently proposed directional MAC protocols and results show that MDA outperforms these protocols in the majority of scenarios investigated. We also point out that the performance does depend on the network topology and the traffic pattern.
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.
Recently there has been an increasing demand for applications like multiplayer online gaming, where players residing in different parts of the world participate in the same gaming session through the Internet. Multicasting could prove to be an efficient way of providing necessary services for these applications. Furthermore, with increasing popularity of handheld devices and mobile equipment, it is imperative to determine the best way to provide these services in a wireless environment. Due to very diverse requirements, it is necessary to investigate and discern the applicability of existing multicast protocols and qualify which is more suitable for which types of applications. This article provides a detailed description and comparison of IP-based wired and wireless multicast protocols. We hope that the discussion presented here will be helpful to application developers in selecting an appropriate multicast protocol for their specific needs.
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