Capacity and signal design for L-out-of-K CDMA Gaussian channels

We consider the symbol-synchronous Gaussian L-out-of-K CDMA channel, and obtain the capacity region and an upper and a lower bound to the symmetric capacity. The capacity region is found to be the same with or without frame synchronism. The lower bound depends on the signature waveforms through the eigenvalues of the product of the crosscorrelation matrix and the diagonal power matrix. We find a sufficient condition for the signature waveform set to maximize this lower bound. We also compare the performance of CDMA with that of FDMA