Qcelp: The North American Cdma Digital Cellular Variable Rate Speech Coding Standard

Digital cellular telephone systems require efficient encoding of speech to achieve capacity improvements required of the next generation of cellular systems. The use of a variable rate speech coder can reduce the average data rate required to transmit conversational speech by a factor of two or more, while providing many other advantages. This reduction in average data rate leads to a factor of two increase in the capacity of a Code Division Multiple Access, or CDMA, based digital cellular telephone system by decreasing the mutual interference among users. This chapter describes the “QCELP” algorithm, which has recently been selected as the North American CDMA digital cellular variable rate speech coding standard [l, 21.