Bandwidth-constrained signature waveforms for maximizing the network capacity of synchronous CDMA systems

Synchronous code-division multiple-access systems where each receiver is a minimum mean-squared-error receiver and each user has the same received power, signaling rate, and required signal-to-interference ratio are considered. Based on the results Viswanath, Anantharam and Tse (see IEEE Trans. Inform. Theory, vol.45, p.1968-83, 1999), the optimal signature waveforms under both fractional out-of-band energy and root-mean-square bandwidth constraints that maximize the network capacity are determined. Comparison to various suboptimal signature waveforms, including the ones constructed from rectangular pulses, is also made to quantify the gain achieved by the optimal signature waveforms.