Increased information rate by oversampling

A noiseless ideal low-pass filter, followed by a limiter, is normally used as a binary data channel by sampling the output once per Nyquist interval. Detectors that sample more often encounter intersymbol interference, but can be used in ways that increase the information rate. A signaling system that achieves an information rate of 1.072 b/Nyquist interval by allowing the detector to sample at times a half Nyquist interval apart is presented. This rate increase is small, but it shows that, in principle, oversampling does permit faster rates. Another signaling system that more closely resembles a digital data system is also presented; it has rate 1.050. By allowing a more irregular pattern of sampling times, the rate is increased to 1.090 (or 1.062 for the 'digital' system).< >