One Viterbi decoder with data rate estimation for IS-95 CDMA wireless communications

The information data rate transmitted from a base station (BT) to a mobile station (MT) changes for every frame of 20 ms in the Interim Standard (IS)-95 code division multiple access (CDMA) wireless communication system. The possible data rates are 1200, 2400, 4800, and 9600 bits per second (bps). The data rate information is not transmitted in order to reduce the overhead in a frame. The existing mobile station receiver employs four Viterbi decoders for all possible data rates, and uses the output of a decoder with minimum errors. The Viterbi decoding process for each data rate takes significant complexity in the MT receiver design. This paper improves the complexity of the IS-95 CDMA MT receiver. In this paper an efficient data rate estimation scheme is presented before Viterbi decoding, and one Viterbi decoder instead of four is proposed to be employed with the estimated data rate