Signal coding for low power: Fundamental limits and practical realizations

Transitions on high-capacitance buses result in considerable system power dissipation. Therefore, various coding schemes have been proposed in the literature to encode the input signal in order to reduce the number of transitions. In this paper, we present: 1) fundamental bounds on the activity-reduction capability of any encoding scheme for a given source and 2) practical novel encoding schemes that approach these bounds. The fundamental bounds in 1) are obtained via an information-theoretic approach, where a signal x(n) with entropy rate H is coded with R bits per sample on average. The encoding schemes in 2) are developed via a communication-theoretic approach, whereby a data source is passed through a decorrelating function followed by a variant of entropy coding function which reduces the transition activity. Simulation results with an encoding scheme for data busses indicate an average reduction in transition activity of 36%.