Analysis and Measurement of TCP/IP Performance over GPRS Networks

The paper presents an experimental analysis of some link layer characteristics of GPRS (General Packet Radio Service) mobile networks and discusses their relationship to TCP/IP performances. Mobile networks implement sophisticated mechanisms in order to provide mobility and capacity in a wide area. Unfortunately, large delays along the radio path may be introduced, thus reducing throughput in data transfers. The paper focuses its attention on a set of phenomena (excess queuing, delay spikes, redundant retransmissions and bandwidth oscillations) that were observed in real mobile GPRS systems. Analyses are carried out on a set of TCP traffic traces captured by passive monitoring at the main protocol interfaces. Several aspects related to TCP performances and throughput are then discussed and results obtained are compared with simulation studies and characterisations already available in the literature. Optimal network configurations and tuning of various parameters are also discussed.