Error rate performance bounds in block coded parallel combinatorial SS systems through a uniform interleaver

Upper bounds on the codeword and bit error probabilities are obtained for maximum-likelihood (ML) decoding of block coded parallel combinatorial spread spectrum (PC/SS) systems in additive white Gaussian noise (AWGN) channels. To make the analysis tractable, we put a uniform interleaver between a block encoder and a PC/SS transmitter. An input-output distance enumerating function (IODEF) is introduced to calculate the number of codewords for an overall coded PC/SS system instead of the input-output weight enumerating function (IOWEF). The average bounds on the bit error rate (BER) of block coded PC/SS systems on AWGN channels are shown. It is demonstrated that the performance advantage between PC/SS systems is determined by the number of information bits per active transmitting PN code. A comparison between the coded PC/SS systems and coded conventional multicode DS/SS systems is also discussed.