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A new technique is proposed that enables TCP to distinguish wireless packet losses and spurious timeouts from congestion-related packet losses and timeouts. This is achieved by introducing a wireless enhancement proxy (WENP) that provides radio network feedback to the TCP sender with the aid of two of the TCP header reserved bits. The standard TCP congestion control mechanism is modified to accommodate these effects. WENP measures the wireless round trip time and detects sudden increase in delay across the wireless link with the use of a timer. This timer is similar to the standard TCP retransmission timer, which times out when acknowledgements are not received in time across the wireless link. The scheme is modeled using the OPNET tool, and the simulation results are presented and explained. The performance of the proposed scheme is compared with that of TCP Reno over UMTS and the simulation results show that WENP significantly improves the TCP performance in a UMTS environment by minimizing the spurious TCP timeouts.
Date of Conference: 2-5 Dec. 2007