The mobile and personal communication systems (PCS) revolution is well underway [l]. Spectral efficiency, a major requirement of these systems, means the use of low bit rate (LBR) speech and channel coders with low frequency reuse factors. Rampant frequency reuse however, leads to high levels of co-channel interference which result in bursty errors in the base-band, thus degrading speech quality. This situation is worsened by the constraint on the redundancy for channel coding. In this paper, we propose the use of multi-rate speech and channel codecs for future PCS. In the base-band of such systems, a balance between the source and channel coding bit rate is struck based on a quantitative estimate of the prevailing channel conditions. This idea can either be used to increase the capacity of interference limited CDMA systems (with lower speech quality) or maintain an average speech quality over a wider range of channel degradations.
Keywords: speech and channel coding, spread spectrum, mobile communications.
Bibliographic reference. Atungsiri, S. A. / Kondoz, A. M. / Evans, B. G. (1993): "Multi-rate source and channel coding for mobile communication systems", In EUROSPEECH'93, 1151-1154.