TABLE OF CONTENTS There has been a paradigm shift in mobile communications systems every decade. The first generation (1G) systems in the 1980s were based on analog technologies, and the second generation (2G) systems in the 1990s, such as Global Systems for Mobile Telecommunications (GSM) [1], Personal Digital Cellular (PDC) [2], and Interim Standard (IS)-95 [3], on digital technologies for voice-oriented traffic. The 3G systems are also based on digital technologies for mixed voice, data, and multimedia traffic and mixed-circuit and packet-switched network [4, 5]. The first 3G system was introduced in October 2001 in Japan [6].
Figure 1.1 shows a rough sketch of present and future mobile communications systems. As an evolutional form of mobile phone systems, International Mobile Telecommunications (IMT)-2000 [4, 5], which corresponds to 3G systems, aims to support a wide range of multimedia services from voice and low-rate to high-rate data with up to at least 144 Kbps in vehicular, 384 Kbps in outdoor-to-indoor, and 2 Mbps in indoor and picocell environments. It provides continuous service coverage in 2-GHz band with code division multiplexing/code division multiple access (CDM/CDMA) scheme and supports both circuit-switched and packet-oriented services. Furthermore, high data rate (HDR), which supports a maximum 2.4-Mbps downlink packet transmission, is proposed [7], and high-speed downlink packet access (HSDPA), which also aims for more than 2-Mbps throughput, is under standardization in the Third Generation Partnership Project (3GPP) [8]. Both HDR and HSDPA are categorized into enhanced IMT-2000 systems, which correspond to 3.5G...
