Criteria affecting the signalling speed of random data transmission

A signalling technique is described in which the sinusoidal spectrum envelope of a random Class 4 partial-response (PR) data signal is truncated at the first spectrum null, or maximum, with subsequent bandwidth expansion at the signal destination enabling data recovery from a reconstituted three-level waveform. The hypothetical case of signalling over a noiseless, ideal low-pass channel is used in order to show that the bandwidth-signalling speed relationship is a function of the digital correlation length; it is shown that a signalling speed indeterminately higher than that obtainable under the Nyquist criterion is conceptually possible as the digital data length approaches infinity. The practical case of using a digital correlation length of two digits in order to achieve a signalling speed twice that obtainable under the Nyquist criterion over a non-ideal low-pass channel is also considered.