LNS and Power Dissipation

LNS is applicable for low-power design at logic level because it reduces the bit activity. A design parameter that is often neglected despite playing a key role in an LNS-based processor performance is the base of the logarithm b [4], [5], as demonstrated in Fig. 1. The choice of base has a substantial impact on the average bit activity. Figure 1 shows activity per bit position; i.e., the probability of a transition from “low” to “high” in a particular bit position, for a two’s-complement word and several LNS words, each of a different base b. It can be seen that departing from the traditional choice b = 2 can substantially reduce the signal activity in comparison to the two’s-complement representation. The input data are sampled from a zero-mean Gaussian process with a correlation factor ρ = -.099.