Performance assessment of tandem connection of enhanced cellular coders

The growth and increased competition in the secondgeneration (digital) cellular communication market has led service providers to improve the speech quality in their systems by introducing enhanced speech coders. Advancements in speech coding allowed designers to aim at toll-quality for these enhanced coders, and investigation of the impact of speech coders on the end-to-end quality of the public switched telephone network (PSTN) is necessary. This paper presents the continuation of a series of studies on the impact of tandem connection of cellular systems, where the quality of the enhanced cellular coders for major systems in use today is studied in the context of PSTN interconnection. A major conclusion of this study is that deployment of enhanced coders in second-generation cellular systems makes possible a substantial increase in quality of the cellular connections when in tandem with other speech coders in long haul international networks.