Performance analysis of CDMA systems by using biorthogonal codes

A new CDMA system is proposed, which is composed of very low rate convolutional codes and biorthogonal codes. Convolutional encoders with rate 1/64 and constraint length 7 and 128 rows/spl times/64 chips biorthogonal codes generated from Walsh codes with 64 rows/spl times/64 chips are used for encoding and spreading. A Viterbi decoder is used for demodulating the newly designed CDMA system. The performance of proposed CDMA system using biorthogonal codes is better than that of the CDMA system using FEC and orthogonal modulation, and from the hardware complexity point of view, the amount of computation for implementing the proposed CDMA system is increased only a little.