Approximate differential encoding for energy-efficient serial communication

Embedded computing systems include several off-chip serial links, that are typically used to interface processing elements with peripherals, such as sensors, actuators and I/O controllers. Because of the long physical lines of these connections, they can contribute significantly to the total energy consumption. On the other hand, many embedded applications are error resilient, i.e. they can tolerate intermediate approximations without a significant impact on the final quality of results. This feature can be exploited in serial buses to explore the trade-off between data approximations and energy consumption. We propose a simple yet very effective approximate encoding for reducing dynamic energy in serial buses. Our approach uses differential encoding as a baseline scheme, and extends it with bounded approximations to overcome the intrinsic limitations of differential encoding for data with low temporal correlation. We show that encoder and decoder for this algorithm can be implemented in hardware with no throughput loss and truly marginal power overheads. Nonetheless, our approach is superior to state-of-the-art approximate encodings, and for realistic inputs it reaches up to 95% power reduction with <;1% average error on decoded data.