A TCP-physical cross-layer congestion control mechanism for the multirate WCDMA system using explicit rate change notification

In this paper, the authors proposed an explicit rate change notification (ERCN) mechanism to improve the transmission control protocol (TCP) performance in the wideband code-division multiple-access (WCDMA) system. The base station in the WCDMA system dynamically adapts transmission data rates according to the wireless channel condition. Therefore, if the TCP sender can not be notified about the rate change in the wireless channel, congestion in the radio link between the base station and mobile terminal occurs quite often. In this work, the relation between the bandwidth in the physical layer and the maximum queue size in the TCP layer was first derived, and then obtain a closed-form expression for the average throughput in terms of average queue size, queue delay and channel capacity. The results by simulations were validated. The analytical formula could facilitate the design of a cross-layer TCP-physical congestion control mechanism for the rate adaptive wireless system.