Proposal of a convolutional coding method for DS/SS systems with M-ary biorthogonal keying

The BER performance of the DS/SS system combined with code shift keying using a non-binary convolutional coding method is investigated. Specifically, the author proposes a non-binary convolutional encoder customized for M-ary orthogonal keying and M-ary biorthogonal keying. The BER performances of the orthogonal and biorthogonal systems are evaluated by means of computer simulations. As a result, a better BER performance is obtained when we use a non-binary convolutional coding method, as opposed to merely increasing the number of codes used, on both M-ary orthogonal keying and M-ary biorthogonal keying. Moreover, a better BER performance is obtained by preparing more codes for the biorthogonal system than in conventional DS/SS systems using binary convolutional coding methods.