TCP-ADA: TCP with adaptive delayed acknowledgement for mobile ad hoc networks

Earlier studies have shown that TCP suffers from performance degradation over mobile ad hoc networks due to poor wireless channel characteristics and host mobility. This paper shows that generating acknowledgement for each data packet also deteriorates TCP throughput over these networks more significantly than in wired networks. In these networks, acknowledgement packets share the path with data packets. This creates the contention and collision between ACK and DATA packets, resulting in reduced TCP throughput. Decreasing the number of ACKs enhances the performance of TCP as it reduces the contention and collision with DATA packets. We analyse this enhancement mathematically and derive the relationship between throughput and number of DATA packets covered in one ACK. The study shows that maximum throughput is achieved when one ACK acknowledges full congestion window of packets. Based on this analysis, we devise and propose TCP with adaptive delayed acknowledgement (TCP-ADA), which tries to decrease the number of ACKs to one per congestion window, adapting the ACK generation time. Simulation analysis is performed to investigate the enhancement achievable in practical scenario and these results corroborate our mathematical study.