TCP performance in WCDMA-based cellular wireless IP networks

The performance of TCP (Transmission Control Protocol) is evaluated for downlink data transmission in a cellular WCDMA (Wideband Code Division Multiple Access) network where variable rate transmission is supported at the RLC (Radio Link Control)/MAC (Medium Access Control) level. A simple rate search procedure (based on the number of simultaneous TCP connections and the channel condition) is proposed for the RLC/MAC level transmission rate selection for downlink data transmission. The dynamic rate variation is assumed to be achieved by using single-code transmission with variable spreading factor, where the spreading factor varies inversely with the transmission rate. A novel 'mean-sense' approach to calculate inter-cell interference in such an environment is developed assuming homogeneous traffic load (in terms of active TCP connections) in different cells. The impact of the different physical layer, RLC/MAC layer and TCP parameters on the end-to-end throughput performance are investigated by simulating the system dynamics under multiple concurrent TCP connections.