Analysis of switching activity in DSP signals in the presence of noise

Input switching activity is one of the deciding factors for power consumption in digital signal processing components. For accurate power estimation, it is essential to have knowledge about the switching activity in the input signal, including how this activity changes in different environments, e.g., in the presence of noise. The dual bit type (DBT) method aims at characterizing the bit-level switching activity in a signal, using signal statistics. However, the DBT method requires that the correlation coefficient and switching activity for the most significant bit of the signal are available. In this paper we give an expression for direct calculation of the correlation coefficient for the most significant bit in a signal, using the word-level correlation coefficient. Using simulation results we examine the accuracy of the given method to calculate the switching activity and correlation coefficient for the most significant bit. Furthermore, we derive expressions for accurately calculating the variance and word-level correlation coefficient for a correlated signal, when an additional noise of a given variance is added to the signal. This can be used to estimate the bit-level switching activity in a signal in the presence of noise. Finally, based on this we study the impact the additional noise has on the switching activity of the resulting signal.