Experimental Study on TCP Enhancement Interest in Ad Hoc Networks

As TCP performance over ad hoc networks is degraded, many enhancements have been proposed in the literature. We classify them as: intra layer, under layer and cross layer enhancements. We examine by simulation the interest to optimize the flow control mechanism and analyze that, compare to the routing protocol impact, the flow control one over the performance is marginal. Simulation results of a cross layer method, which is representative of enhancements recently proposed, are then examined. The cross layer mechanism is based on a freezing process triggered by a route failure event. With this type of optimization, the performance gain can be important but it is strongly dependent on the network mobility and in some cases it can work worst than TCP. From the TCP optimization analysis it appears that a mobile oriented self adaptive mechanism would be profitable.