.FLYINGHEAD WIRELESS INFRASTRUCTURE
.TITLE Routing protocols for mobile ad-hoc networks
.AUTHOR Humayun Bakht
.SUMMARY 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. This interesting article discusses some of the routing issues.
.OTHER
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.
.H1 Table-driven protocols
Table-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.
.H1 On-demand routing protocols
Another in the family of routing protocols for mobile ad-hoc network is on-demand routing protocols. With on-demand protocols, if a source node requires a route to the destination for which it does not have route information, it initiates a route discovery process which goes from one node to the other until it reaches to the destination or an intermediate node has a route to the destination.
It is the responsibility of the route request receiver node to reply back to the source node about the possible route to the destination. The source node uses this route for data transmission to the destination node. Some of the better known on-demand protocols are Ad-hoc On-demand Distance Vector routing (AODV), Dynamic Source Routing (DSR) and Temporary Ordered Routing Algorithm (TORA).
These protocols differ on storing the previously known route information and on how they use the established route data. Again, in a network with many participating nodes we may suffer with same sort of problems what we have seen in table-driven protocols.
.H1 Conclusion
In conclusion, routing is one of the core issues in mobile ad-hoc network. An effective routing mechanism will be helpful to extend the successful deployment of mobile ad-hoc networks. Current routing protocols provide routing solutions up to a certain level, but are lacking the ability to handle other related issues.
Moreover most of these protocols have designed and implemented on small scale. If these protocols could be extended further by taking into accounts other routing related factors we may come out with a standard routing solution for mobile ad-hoc network.
.BIO
