Requirements on speech coders imposed by speech service solutions in cellular systems

Many digital cellular systems have been put into operation during the last few years in North America, Europe and Asia. The growth rate is high and the penetration is steadily increasing. New forecasts talk about 480 million subscribers in the world at the end of year 2000. The number of services and key features are increasing and will do so as the market is expanding. The trend is to build this on existing platforms, but beyond this an evolution into a third generation for wireless wideband, called Universal Mobile Telecommunication Services (UMTS), has already started. In this paper we will point out different aspects of the requirements on speech coding algorithms that are seen in the cellular systems. It will be shown that to meet the diverse needs and applications no single speech and channel coding scheme is sufficient. We will see a need of flexibility and multiple speech coders that can meet the different requirements on quality, capacity and functionality.