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

Synchronous CDMA systems where each receiver is a minimum mean-squared-error (MMSE) receiver and each user has the same received power, signaling rate and required signal-to-interference ratio (SIR) are considered. Given a SIR requirement and under different bandwidth constraints and a fixed-dimension signature space, the optimal signature waveforms to maximize the network capacity, i.e., the maximum number of users that can be accommodated in the systems are determined. Both fractional out-of-band energy (FOBE) and root-mean-square (RMS) bandwidth constraints are examined. Comparison to various suboptimal signature waveforms, including the commonly used rectangular pulses, is also made to quantify the gain achieved by the optimal signature waveforms.