A ML rate detection algorithm for IS-95 CDMA

A variable rate source code is often employed for coding of voice frames in CDMA communication systems followed by forward error correction coding. This paper derives a maximum likelihood detection algorithm for determination of the source rate prior to decoding of the forward error correction code. When the source rate is not known to the receiver a-priori, a rate detection algorithm can reduce the computational complexity with respect to decoding once for every possible source rate. The maximum likelihood rate detection algorithm is developed for rate set 1 and rate set 2 of the IS-95 standard, and the performance of the rate set 1 algorithm is characterized via simulation for AWGN and Rayleigh fading channels.