Chip shaping and channel coding for CDMA

This work considers asynchronous DS‐CDMA systems with single‐user receivers. The focus is on chip pulse shaping and combined error control/PN sequence spreading. It is shown that pulse shaping can significantly reduce the effects of cross‐talk interference. A criterion which measures the ability of a chip waveform to reduce cross‐talk interference is derived, taking into account, the signal bandwidth. This work also shows that the best performance is achieved when all the bandwidth expansion is accomplished by error control coding. instead of PN sequences. Comparisons of CDMA systems using different pulse shapes are presented, taking into account the bandwidth of each pulse. Finally CDMA is compared to orthogonal multiple access (TDMA/FDMA) in an interference free environment. It is shown that for the same bandwidth (99% energy containment bandwidth), CDMA with suitable chip waveforms and coding yields the same performance as binary orthogonal multiple access with raised cosine shaping of 70% excess bandwidth.