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An Adaptive TCP Delayed Acknowledgment Strategy in Interaction with MAC Layer over Multi-hop Ad Hoc Networks

The acknowledgment strategy has great potential to increase the TCP throughput when it runs over 802.11 MAC protocol. In particular, TCP acknowledgments carry out an extensive number of medium accesses as they compete in the same route as data packets for media. As the load increases, the well-known hidden terminal effects caused by interference between ACK and data packets in MAC layer can degrade TCP performance dramatically if TCP acknowledges every incoming data packets. In this paper a dynamic TCP-MAC interaction strategy has been proposed which tries to reduce the number of induced ACKs by monitoring the channel condition. To this end, the total collision probability collected along the path from sender to receiver in MAC layer has been used to properly set the number of delayed ACKs (DA) in TCP. Based on the measured collision probability, TCP sender dynamically adjusts itself to the channel condition by delaying less ACKs in high traffics and more in low traffic conditions. The simulation results show a throughput improvement up to 15% over the existing method called dynamic adaptive acknowledgment (TCP-DAA) and much more over the regular TCP in the scenarios dealing with a dynamic loss rate.