Reducing Energy Dissipation of Wireless Sensor Processors Using Silent-Store-Filtering MoteCache

Wireless sensor networks (WSNs) gained increasing interests in recent years; since, they allow wide range of applications from environmental monitoring, to military and medical applications. As most of the sensor nodes (a.k.a. motes) are battery operated, they have limited lifetime, and user intervention is not feasible for most of the WSN applications. This study proposes a technique to reduce the energy dissipation of the processor component of the sensor nodes. We utilize a tiny cache-like structure called MoteCache between the CPU and the SRAM to cache the most recently used data values as well as to filter silent-store instructions which write values that exactly match the values that are already stored at the memory address that is being written. A typical WSN application may sense and work on constant data values for long durations, when the environmental conditions are not changing rapidly. This common behavior of WSN applications considerably improves our energy savings. The optimal configuration of MoteCache reduces the total node energy by 24.7% on the average across a variety of simulated sensor benchmarks. The average lifetime of the nodes is also improved by 46% on the average for processor-intensive applications. Using the proposed technique, the lifetime of the nodes that run communication-intensive applications, such as TinyDB and Surge, is also improved as much as 14%.