Distributed Quality of Service Rouing in 

Mobile Adhoc Networks 

u Balaji A.S   v Balasubramanian. R   w   Jeychandran. J  x Vinod Kumaar A.E

            In an ad hoc network, all communication is done over wireless media, typically by radio through the air, without the help of wired base stations. Since direct communication is allowed only between adjacent nodes, distant nodes communicate over multiple hops. QoS Routing in an ad hoc network is difficult because the network topology may change constantly, and available state information for routing is inherently imprecise.  We use Multi Path routing with diversity coding for distributed QoS routing in mobile adhoc networks(MANETs). 

             To combat the inherent unreliability of ad hoc networks, our scheme uses multiple paths simultaneously by splitting the information among the multitude of paths, so as to increase the probability that the essential portion of the information is received at the destination without incurring excessive delay. The Multiple paths are established using “Token based probing”.

             Our scheme works by adding an overhead to each packet, which is calculated as linear function ( Diversity coding ) of the original packet bits. The resulting packet (information and overhead ) is fragmented into smaller blocks and distributed over the available paths. Our goal is, given the failure probabilities of the paths, to find the optimal way to fragment and then distribute the blocks to the paths, so that the probability of reconstructing the original information at the destination is maximized. Our algorithm has low time-complexity, which is crucial since the path failure characteristics vary with time and the optimal block distribution has to be recalculated in real-time. For a given Probability of success of transmission as the required QoS parameter, our ultimate goal is to find the optimal way to fragment and then distribute the blo cks to the paths.