Enhancing Wireless TCP: A Serialized-Timer Approach

In wireless networks, TCP performs unsatisfactorily since packet reordering and random losses may be falsely interpreted as congestive losses. This causes TCP to trigger fast retransmission and fast recovery spuriously, leading to under-utilization of available network resources. In this paper, we propose a novel TCP variant, known as TCP for non-congestive loss (TCP-NCL), to adapt TCP to wireless networks by using more reliable signals of packet loss and network overload for activating packet retransmission and congestion response, separately. TCP-NCL can thus serve as a unified solution for effective congestion control, sequencing control, and loss recovery. Different from the existing unified solutions, the modifications involved in the proposed variant are limited to sender-side TCP only, thereby facilitating possible future wide deployment. The two signals employed are the expirations of two serialized timers. A smart TCP sender model has been developed for optimizing the timer expiration periods. Our simulation studies reveal that TCP-NCL is robust against packet reordering as well as random packet loss while maintaining responsiveness against situations with purely congestive loss.