Interference avoidance applied to multiaccess dispersive channels

We consider the application of interference avoidance to multiaccess dispersive channels corresponding to the uplink of a CDMA system in which the channel between each user and the base station is assumed to be known. By using a symbol transmission interval long enough a common set of signal space basis functions (sinusoids) is shared by all users at the base. Each user sends frames containing multiple symbols (as many as there are signal space dimensions) and each symbol is assigned a signature waveform. Optimal signature waveforms which achieve sum capacity are obtained through iterative application of interference avoidance. Such optimal signature waveforms provide to each user a uniform signal-to-interference plus noise-ratio (SINR) for all its symbols, and the optimal linear detector for each symbol is a matched filter.