Benefits of sparse signaling in asynchronous multi-access channel communication

This paper considers transmission over a fully asynchronous multi-access waveform channel. Sparse signaling turns out to maximize achievable transmission rates on this channel, as for the derived capacity-optimal signaling, number of transmitted O's greatly exceeds number of transmitted I's. Simulation results are also presented for a turbo coded communication system that utilizes the derived sparse signaling and achieves promising transmission rates. In addition, the sparse-signaling approach turns out to be beneficial also in case of frequency-hopping CDMA.