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 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.
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