A unified table based trellis subset decoder for high speed voice-band modems

An unified table based trellis subset decoder for the Viterbi algorithm is designed which is capable of decoding any constellation size for any data rate scheme of the CCITT V.32, V32bis, and IBM "V.32ter" full duplex high speed voice-band modem standards with constant number of computations. In addition, no error is introduced as the result of this subset decoding. The data rates include the trellis coded 7200, 9600, 12000, 14400, 16800, and 19200 bps. The number of computations necessary to perform such a task is the same for any given data rate. This results in reductions in the computational complexity up to a factor of 32 times over the existing direct methods. The memory consumption of this algorithm is small and increases proportionally with the data rate.