Energy-Aware Data Compression for Multi-Level Cell (MLC) Flash Memory

We discover significant value-dependent programming energy variations in multi-level cell (MLC) flash memories, and introduce an energy-aware data compression method that minimizes the flash programming energy rather than the size of the compressed data. We express energy-aware data compression as an entropy coding with unequal bit-pattern costs. Deploying a probabilistic approach, we derive the energy-optimal bit-pattern probabilities and the expected values of the bit-pattern costs for the large amounts of compressed data which are typical in multimedia applications. Then we develop an energy-optimal prefix coding that uses integer linear programming, and construct a prefix code table. From a consideration of Pareto-optimal energy consumption, we make tradeoffs between data size and programming energy, such as a 35% energy saving for a 50% area overhead.