Variable transmission bit rate discrimination method and apparatus

Claim 2

A variable bit rate discrimination apparatus for a mobile communication system wherein a variable bit rate including four different transmission bit rates is used as a transmission rate of a traffic channel from a base station to a mobile station and transmission data are encoded using convolutional encoder for error correction and transmitted, said variable bit rate discrimination apparatus being provided in the mobile station, characterized in that it comprises: means (201) for demodulating received data from the base station and despreading a spectrum of the received data; means (202) for descrambling the received data based on information passed on thereto from the base station on a synchronization channel; means (203) for block interleaving the descrambled received data to restore an original order of the received data; received symbol adders (303, 306, 309) for adding the block interleaved received data of the individual transmission bit rates by repetition symbol rates corresponding to the transmission bit rates; calculators (301, 304, 307, 3010) for calculating branch metrics for use for Viterbi decoding based on the thus added received data; Viterbi decoders (302, 305, 508, 3011) for performing Viterbi decoding based on values of the thus calculated branch metrics and outputting results of the decoding and path metric values for the individual transmission bit rates; a comparator (3012) for comparing the path metric values outputted from said Viterbi decoders with each other in magnitude and selecting and outputting a lowest one of the path metric values; and a switch (3013) for selecting, in response to an output of said comparator, one of output terminals of said Viterbi decoders from which the received data of the transmission bit rate having the lowest path metric value are outputted and connecting the selected output terminal to an information source decoder for information bits of the received data.