Capacity of the overlapped carriers scheme in FD/DS-CDMA

This paper investigates the performance of coherent direct-sequence CDMA in terms of the SNR as the decision parameter of the correlation receiver when adjacent carriers are permitted to overlap. The variance of the decision parameter due to multi-user interference from adjacent carriers is derived in terms of the power spectral densities. Numerical results illustrate how the integrator in the correlation receiver suppresses interference from co-carrier and adjacent carriers. Adjacent carrier interference and system capacity increase by overlapping of carriers are also presented. In all the numerical results, various spectral shapes of the transmitted signal are investigated and compared in order to show the degree of dependency of the capacity on the shapes of the power spectral densities of the transmitted signals. It is also shown that by this scheme a capacity increase of up to 56% is easily achievable at no extra complexity.