Viterbi Decoder for CDMA System with Variable Data Rates

This paper describes an implementation of a variable data rate Viterbi decoder with a modified LOVA (List Output Viterbi Algorithm) algorithm and a fully integrated Rate Determination algorithm. This low power decoder is applicable for decoding variable rate frames for Code Division Multiple Access (CDMA) mobile stations, with code k=9, r=1/2. Reduction in size and power consumption was achieve by truncation of the Survivor Path as well as an update-in-place addressing, and an adaptive rate determination algorithm. The modified L-2 LOVA algorithm improves the decoder performance by 0.1 dB and compared to an optimal decoder, the gain loss is 0.3 dB [1]. The decoder architecture was defined in VHDL, synthesized and implemented in the 3V, 0.5u CMOS process.