Improving energy efficiency of embedded and mobile systems is a major design challenge. Such systems involve complex algorithms for audiovisual processing, recognition, and communication that heavily utilize digital signal processing (DSP) architectures. This proposal advances a systematic strategy to reduce energy consumption of DSP sub-systems and thereby make major strides towards a new generation of low-energy embedded applications. The main premise behind the proposal is that signal processing algorithms may accept, in a finely controlled manner, some amount of timing errors in return for significant energy savings. Signal processing algorithms have an intrinsic quality floor, set by quantization and roundoff noise. A traditional design paradigm of worst-case margining is highly suboptimal, and by accepting a small amount of low-probability timing errors, significant energy savings of more than 50% are possible.
Research under this proposal will result in the development of a formal analysis and synthesis framework for integration into a hardware synthesis flow that supports systematic design of ultra low-energy error-permissive DSP systems. A flow for controlled acceptance of timing errors must fundamentally be based on a new formal notion of quality-energy (Q-E) tradeoff, which is unique to error-permissive signal processing, and which will allow treatment of other Q-E techniques, such as approximate signal processing, consistently within the same framework. To this end, the goals of this project are two-fold: (i) to formally develop models and analysis techniques for controlled timing-error acceptance under given input statistics and quality-energy budgets, and (ii) to develop a comprehensive synthesis flow that allows multiple Q-E techniques to be applied to the co-optimization of quality, energy, area and performance objectives for a large class of algorithms that can generally tolerate a small amount of errors. Results of this work will enable automatic exploration of joint algorithm and architecture tradeoffs for implementation of general quality- and energy-tuned error-permissive systems. The new controlled timing error paradigm will facilitate sustained improvement in the energy efficiency of integrated circuits and digital systems, where ultra low-energy operation will enable use of hitherto infeasible portable, implantable, wireless and autonomous systems.
