The Evolution of Third-Generation Cellular Standards

This paper provides an overview of the evolutionary path of mobile/terrestrial cellular standards, leading up to the now defined third-generation cellular standards. Commercial mobile cellular systems first became available in the early 1980’s. These first systems were deployed, utilizing analog technology over circuitswitched networks. They had very limited features, poor voice quality, and limited radio coverage, although they have vastly improved over the last two decades and are still widely deployed around the world. In addition, data transfer was limited to 9600 baud. In the early 1990’s, the second generation of mobile cellular systems was introduced. Based upon digital technology and still utilizing the circuit-switched network, new features and services were introduced. Speech quality, although not equivalent to that of analog, was digitized through a low 8kbps bitrate vocoder that used Code Excited Linear Projection (CELP) technology. This has also been enhanced, over the past five years, to the extent that speech quality now exceeds that of the FM analog systems. The immediate motivating factor for the third-generation communications systems is to increase system capacity. The overall number of users is exceeding the radio spectrum allocated to the second-generation; however, receiving and sending data are the essential building blocks to widespread mobile Internet access and to mobile data transfer, capabilities enabled with the thirdgeneration. The third-generation is a generic term used for the next generation of mobile communications systems, often referred to simply as “3G.” 3G mobile systems will provide enhanced services such as voice, text, and high-speed data, with 144kbps as an overall goal. The technology involved in the deployment of 3G systems and services is currently under development throughout the industry. Attaining the goals of 3G will be an evolutionary migration from the installed 2G systems. Operators are phasing in new enhanced 2G capabilities, preparing for 3G services, and attempting to provide a seamless transition from existing digital systems, including full backwards compatibility. From a consumer perspective, this integration of system and service profiles, along with multi-mode terminals will mean worldwide roaming possibilities. 3G systems offer up to fifteen times the network capacity of analog networks. With the initial third-generation networks due to be launched in Japan in early 2001, and with European countries following in early 2002, 3G is already in sight. To enable thirdgeneration capabilities, especially worldwide roaming, the radio interface specifications need to be defined and adopted, and complete interoperability needs to be finalized.