Nonlinear equalisers using modulo arithmetic

The recent published literature contains a description of a data-transmission system in which the data signal at the transmitter is fed through a channel equaliser that includes a device for holding the transmitted signal within a given range of values. The paper presents a theoretical analysis of the system, together with the results of computer simulation tests, and proposes a simple modification to the equaliser that maximises the tolerance of the data-transmission system to additive white Gaussian noise. It is shown that the original and modified equalisers are equivalent, both in their basic methods of operation and in their tolerances to noise, to the corresponding conventional nonlinear equalisers, used at the receiver. Finally, a simple error detector is described which operates on the received signal, with no need for any redundant data, and which gives extremely powerful protection against errors when used with the original nonlinear equaliser at the transmitter.