Performance Evaluation of UMTS for Mobile Internet Access

UMTS constitutes the third generation of cellular wireless networks which aims to provide high-speed data access along with real time voice calls (Holma & Toskala, 2001). Wireless data is one of the major boosters of wireless communications and one of the main challenges of next generation standards (Chaudhury & Mohr, 1999). It can provide maximum data-rates ranging from 64kb/s to 2Mb/s in different environmental types. UMTS is designed to provide access to the existing Internet services as well as to UMTS specific services. It will augment the existing capabilities of 2G mobile networks and GPRS, and one often envisaged strategy is to offer a richer set of multimedia services. The most popular and widely used Internet applications are FTP, HTTP, email, etc. These Internet applications rely on two common protocols, namely, Transmission Control Protocol and the Internet Protocol (TCP/IP), to reliably transport data across heterogeneous networks. IP is concerned with routing data from source to destination host through one or more networks connected by routers, while TCP provides a reliable end-to-end data transfer service. Wireless communication use many of the protocols designed for wired links, e.g. TCP. However, TCP could not perform efficiently in wireless environments where the bit error rate is much higher. A general description of the problems of TCP over wireless networks is reported in (Meyer & Sachs, 2003; Barakat, Altman & Dabbous, 2000; Xylomenos, Polyzos, Mahonen & Saaranen, 2001) and some specific solutions are given in (Meyer & Sachs, 2003; Ludwig & Katz, 2000). In this paper we examine the performance of TCP over UMTS Dedicated Channels (DCH). The performance of TCP is evaluated for Constant Bit Rate (CBR) traffic over dedicated channels with different downlink bit rates and TTIs. The remainder of this paper is structured as follows. In section 2 the UMTS architecture is briefly described. Section 3 reviews the main features of the simulation model while section 4 is dedicated to the experiments results. Finally, some concluding remarks and planned next steps are briefly described.