On spectral efficiency of CDMA mobile radio systems

A new technique for increasing the capacity of cellular mobile radio CDMA systems is proposed and its potentials are numerically evaluated. Under this scheme adjacent CDMA channels are permitted to overlap in frequency. Such a practice results in adjacent channel interference; however, the larger bandwidth realized for each channel increases the processing gain, and hence, reduces the interference. This scheme has been tested using various degrees of channel overlap, square and raised cosine pulse shapes, and for different choices of preemphasis-deemphasis filters. A major result shows that for the optimum degree of overlap, capacity increases up to 50% are feasible, with the introduction of minimal additional system complexity