Interconnection channel capacity under crosstalk noise

The channel capacity of a parallel bus structure was examined in relation to the ever increasing demand for signal input and output. The limitations on signal integrity caused by both far-end and near-end crosstalk noise were considered. Expressions for the signal waveforms were developed using a rudimentary model. The expressions were then used to evaluate the channel capacity for perfectly matched lines in the high-frequency regime where skin effect and dielectric loss dominate the loss due to the static resistance. The analysis showed that binary logic yields the maximum channel capacity. For the parameters assumed as an illustrative example, the input rise time needed to achieve the maximum channel capacity cannot be achieved with today's technology. For source rise times longer than this threshold or optimum rise time, the maximum channel capacity is achieved by using multilevel logic. In the case of short lines, insufficient coupling exists between lines to meet the channel capacity condition for two levels. Therefore, for short lines multiple logic also is necessary to achieve maximum channel capacity.