17-05-2012, 04:39 PM
Improving the Performance of DSR using Cooperative and Asymmetric Caching Technique in a Clustered Environment
mypaper1newversion[1].doc (Size: 288.5 KB / Downloads: 36)
Introduction
Mobile Ad Hoc Network (MANET) is collection of multi-hop wireless mobile nodes that communicate with each other without centralized control or established infrastructure. In MANET [4, 5, 6] each node communicates with other nodes directly or indirectly through intermediate nodes. Thus, all nodes in a MANET basically function as mobile routers participating in some routing protocol required for deciding and maintaining the routes. Routing is one of the key issues in MANETs due to their highly dynamic and distributed nature. The routing protocols of MANETs are divided into two categories as table-driven and on-demand. In table-driven routing protocols, each node attempts to maintain consistent, up-to-date routing information to every other node in the network. Many routing protocols including Destination-Sequenced Distance Vector (DSDV)[9] and Fisheye State Routing (FSR) protocol belong to this category.
Related Works
Caching is an important technique to enhance the performance of both wired and wireless network. A lot of researches have been done to improve the caching performance in mobile ad hoc network environment. The two basic types of cache sharing techniques are push based and pull based. In the push based cache sharing, when a node caches a new data item, it will proactively broadcast the caching updates to its neighbor’s nodes. The neighboring nodes update the caching information for the future use. Push based scheme improves the data availability at the cost of communication overhead. The disadvantage of the scheme is that an advertisement may become useless if no demand for the cached data items occurs in the vicinity.
Cluster Formation
Clustering is a method used to partition the network into several virtual groups based on the some predefined method. For the cluster formation we use least cluster change algorithm [12] which is an improvement of lowest ID algorithm. Each mobile node has a unique id. The node which has least id in the group is elected as a cluster head. Cluster head maintains a list which contains the information of all other nodes in the group. In a cluster, the number of hops between any two nodes is not more than two.
Route Construction
To initiate a new Route Discovery for a node D (the target of the Route Discovery), S (Source) transmits a route request packet, which is received by other nodes located within direct wireless transmission range of S. Each node that receives the route request packet appends its own address to a record in the packet and rebroadcasts it to its neighbors, unless it has recently seen another copy of the route request for this Route Discovery or it finds that its address was already listed in the route record in the packet. The forwarding of the route request terminates when it reaches node D; this node then returns a route reply packet to S, giving a copy of the accumulated route record from the route request, indicating the path that the route request traveled to reach D. The forwarding of the route request also terminates when it reaches a node that has in its cache a route to D;