Double chip waveforms in multi-rate CDMA communication systems

Optimum chip waveform selection with arbitrary shape is analyzed and a time domain approach is employed. The problem is posed as an interference minimization problem under energy and time-bandwidth constraints and prolate spheroidal wave functions are used to arrive at a solution. We propose to employ two chip waveforms for two classes of users. A 3 dB gain is possible for one class of users without penalizing another class of users. Various factors affecting the interference are analyzed. The tradeoff between competing factors is quantified. The effect of the interchip interference on the optimum chip waveform design is also quantified under a practical bandwidth constraint