Interaction between UMTS MAC scheduling and TCP flow control mechanisms

The goal of the Universal Mobile Telecommunication System (UMTS) is the delivery of multimedia services to the mobile user. Each different service requires its specific quality of service (QoS) to satisfy the mobile user. The QoS requirements will be supported by several protocol layers. In this paper, the interaction between the medium access control (MAC) scheduling and the transmission control protocol (TCP) flow control mechanisms at the UMTS radio interface is presented. Whereas the MAC is responsible to guarantee delay and throughput requirements at the radio interface, TCP realizes an end-to-end flow control. Nevertheless both protocols show dependencies on each other that might reduce the data transmission efficiency. In this paper, the overall performance of Internet applications running over TCP by using different MAC scheduling strategies is discussed. A UMTS radio interface simulator (URIS) is used to emulate the standardized UMTS protocol stack and the TCP/IP protocol suite. Simulation results of QoS parameters depict the performance of the mobile applications over UMTS.