Multiaccess Dispersive Channels: Maximizing Sum Capacity and Interference Avoidance

By both lengthening the transmission interval so that ISI is almost inconsequential and by using combinations of channel eigenfunctions to convey the bits, communications over dispersive channels can be cast as a multiuser detection problem where each bit is assigned its own waveform. For a single dispersive channel – through interference avoidance or some other numerical method – a uniform maximum signal-to-interference plus noiseratio (SINR) can be achieved for each bit. These codeword ensembles also maximize the mutual information between the channel input and channel output assuming Gaussian signaling (sum capacity). For the multiple access case where different signals are received at a common base over different dispersive channels, we show that application of interference avoidance again yields an information theoretically optimal ensemble of codewords. Popescu and Rose: Multiaccess Dispersive Channels and IA 2