Design of input signal waveshapes for ISI free transmission in bandlimited channels

In this paper, we propose a new technique to eliminate ISI in bandlimited channels, whose characteristics are known a priori, by designing channel-specific input and output waveshapes that can be constrained to the same time-duration. The problem has been worked out for two cases where the channel can be modelled as (i) rational transfer function and (ii) distributed parameter model. For both cases, there is zero ISI at the receiver input and hence only a matched filter is required to maximize the peak signal to noise ratio. For channels as in case (i), the lengths of the associated input and output waveshapes can be made arbitrarily small, thus permitting high signalling rates. For channels as in case (ii), the signalling rate works out to be a function of the line parameters and the line length. Performance analysis, in the presence of channel noise, shows that the SNR, the input power requirements as well as the tolerance to timing offsets, for a defined performance index, is dependent on the signal waveshape.