Impact of transmission power on TCP performance in vehicular ad hoc networks

Vehicular ad hoc networks (VANET) are characterized by high velocities and relatively uniform mobility of vehicles. As a result, the dynamics of VANET are different from generic mobile ad hoc networks. The behavior of vehicles and their effect on the protocol performance has not been comprehensively investigated in the context of VANET. In this work, we analyze the performance of multi-hop TCP in a multi-lane highway environment where vehicles are configured as clients or routers trying to reach a fixed access point. In particular, we look at the effect of tuning transmission power in dense and sparse road scenarios on the TCP throughput and latency. To conduct our study, we have developed an integrated simulation tool that accurately models both the vehicular mobility and the networking protocol stack. Using our simulation tool we obtain detailed TCP statistics and correlate them with the location, velocity, and other properties of VANET nodes. We study scenarios with a single sender as well as multiple senders. In each case, results show that throughput significantly deteriorates as the number of hops from the sender to the access point increases. A higher number of hops results in higher losses due to interference and loss of connectivity, which causes TCP to throttle back the sending rate unnecessarily