Performance evaluation of retransmission mechanisms in GPRS networks

This paper studies the performance of the three retransmission mechanisms (i.e., RLC/MAC, LLC and TCP) in a General Packet Radio Service (GPRS) network accessing the Internet. This assessment is done through the end-to-end performance evaluation of Internet applications such as HTTP and FTP over GPRS. A simulation platform including client mobile stations, base station subsystems, GPRS support nodes, servers and an Internet backbone was implemented in OPNET. The low transmission rate and high radio link error rate over the air interface of a GPRS network affect the overall system performance greatly. Simulation results show that whereas the RLC/MAC block retransmission mechanism is crucial to increase the link utilization efficiency, LLC layer user-data retransmission is not necessary for TCP traffic over GPRS.