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An advanced, high-speed, and universal-coding-rate Viterbi decoder VLSI implementation is presented. Two novel circuit design schemes have been proposed: scarce state transition (SST) decoding and direct high-coding-rate convolutional code generation and variable-rate decoding. SST makes it possible to omit the final decision circuit and to reduce the required path memory length without degrading error probability performance. Moreover, the power consumption of the SST Viterbi decoder is significantly reduced when implemented as a CMOS device. These features overcome the speed limits of high-speed and high-coding-gain Viterbi decoder VLSIs in the rate one-half mode imposed by the thermal limitation. The other Viterbi decoding scheme makes it possible to realize a simple and variable coding-rate forward-error-correction circuit by changing only the branch metric calculation ROM tables. By employing these schemes, high-speed (25-Mb/s) and universal-coding-rate Viterbi decoder VLSIs have been developed