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Reliable data transmission over wireless multi-hop networks, called ad hoc networks, has proven to be non-trivial. TCP (Transmission Control Protocol), a widely used end-to-end reliable transport protocol designed for wired networks, is not entirely suitable for wireless ad hoc networks due to the inappropriateness of TCP congestion control schemes. Specifically, the TCP sender concludes that there is network congestion upon detecting packet losses or at time-outs. However, in wireless ad hoc networks, links are broken as a result of node mobility and hence some time is needed to perform route reconfiguration. During this time, packets could be lost or held back. Hence, the TCP sender could mistake this event as congestion, which is untrue. A route disconnection should be handled differently from network congestion. In this paper, we propose a new mechanism that improves TCP performance in a wireless ad hoc network where each node can buffer ongoing packets during a route disconnection and re-establishment. In addition to distinguishing network congestion from route disconnection due to node mobility, we also incorporate new measures to deal with reliable transmission of important control messages and exploitation of TCP fast recovery procedures. Our simulation compares the proposed TCP-BuS approach with general TCP and TCP-Feedback. Results reveal that TCP-BuS outperforms other approaches in terms of communication throughput under the presence of mobility.
Kim et al. (Fri,) studied this question.