Routing protocols for mobile ad-hoc networks

We continue our series on mobile ad-hoc networks with a discussion of routing protocols, or how the information is going to move throughout the network.
Mobile ad-hoc networks, also known as short-lived networks, are autonomous systems of mobile nodes forming network in the absence of any centralized support. This is a new form of network and might be able to provide services at places where it is not possible otherwise. Absence of fixed infrastructure poses several types of challenges for this type of networking. Among these challenges is routing.
By routing, we mean process of exchanging information from one station to the other stations of the network. Routing protocols of mobile ad-hoc network tend to need different approaches from existing Internet protocols, since most of the existing Internet protocols were designed to support routing in a network with fixed structure. In the academic and industrial world, those who think about such things have written quite a few papers proposing various routing solutions for mobile ad-hoc networks. Proposed solutions could be classified into six types: table-driven, on-demand, hierarchical, power-aware, geographical, and multicast protocols.
Table-driven protocolsTable-driven protocols are one of the old ways of acquiring routing in mobile ad-hoc networks. These protocols maintain consistent overview of the network. Each node uses routing tables to store the location information of other nodes in the network. This information is used to transfer data among various nodes of the network.
To ensure the freshness of the routing tables, these protocols adopts different sorts of mechanisms. One of the adopted methods is broadcasting "hello," a special message containing address information, at fixed intervals of time. On receiving this message, each node updates its routing tables with fresh locations information of other participating nodes. Destination Sequence Distance Vector routing protocol (DSDV), Wireless Routing Protocol (WRP) and Cluster-head Gateway Switch Routing (CGSR) are some of the popular table-driven protocols for mobile ad-hoc networks.
Table-driven protocols might not be considered an effective routing solution for mobile ad-hoc network. Nodes in mobile ad-hoc networks operate with low battery power and with limited bandwidth. Presence of high mobility, large routing tables and low scalability result in consumption of bandwidth and battery life of the nodes. Moreover continuous updates could create unnecessary network overhead.

source:http://www.computingunplugged.com/issues/issue200407/00001326001.html