Exploiting faster-than-Nyquist signaling

Faster-than-Nyquist signaling introduces inter-symbol interference, but increases the bit rate while preserving the signaling bandwidth. For sinc pulses, it has been established that with a small increase in the signaling rate beyond the Nyquist rate, there is no reduction in the minimum Euclidean distance for binary signaling. In this paper, we generalize these observations to the family of raised-cosine pulses. The structure of the error events that reduce the minimum distance is examined, and constrained coding ideas are suggested that theoretically allow even faster signaling. Then we propose ways of practically achieving these gains by designing appropriate constrained codes and through equalization and iterative joint equalization and decoding (turbo equalization).