J. Li, D.Y. Montuno, J. Wang, and Y.Q. Zhao (Canada)
3G wireless networks, UMTS, RLC, performance evaluation, error correction
With the rapid advances in wireless communications and in ternetworking, Universal Mobile Telecommunications Systems (UMTS), playing a main role in the emerging third-generation (3G) wireless networks, have aimed to provision high-speed data integrated with voice services. UMTS employs the Radio Link Control (RLC) protocol to support reliable upper layer protocols such as Transmission Control Protocol (TCP), which is the most widely used upper layer protocol for data traffic. RLC uses so phisticated retransmission schemes to perform partial error recov ery at the link layer, thus hiding transmission errors from upper layers and reducing the chances of upper layer protocols perfor mance degradation. Therefore, it is critical to optimize the RLC protocol to achieve the best performance. In this paper, UMTS and RLC protocol is briefly reviewed, and the three important operations of the protocol, polling mechanism, status transmis sion mechanism and Service Data Unit (SDU) discard mecha nism, are discussed. Then the RLC performance, measured by the SDU average delay, the RLC throughput, and the RLC good put in a scenario of bulk data transfer from a Radio Network Con troller (RNC) to a User Equipment (UE), is evaluated using sim ulation. Two important retransmission triggers, Poll timer and status period timer , are considered under various Block Er ror Rates (BLERs). The performance trends poll timer and status period timer settings are analysed and summarized, re spectively, for use in the design of optimized 3G UMTS systems for data services.
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