Energy-efficient reconfiguration of flash-based FPGAs in heterogeneous wireless sensor nodes
Andreas Engel, Andreas Koch · 2017
Field Programmable Gate Arrays (FPGAs) can be used as hardware-accelerators in Wireless Sensor Networks (WSNs). Their in-field reconfigurability can be utilized for bug fixing and capability enhancements, but the distributed nature of WSNs strongly demands Over-the-air Programming (OTAP) for reconfiguration to avoid manual maintenance at every single network node. In this paper, the implementation of OTAP for Microsemi IGLOO FPGAs utilized in heterogeneous WSN motes is described. As the entire configuration bitstream can not be buffered at the sensor node at once due to memory limitations, a paging mechanism is utilized and improved to minimize the energy-intensive radio network traffic required for the bitstream configuration and verification. By applying lossless bitstream compression, the overall configuration time can be reduced by 11 % to 24 %, depending on the complexity of the configured hardware design. The energy spent during the configuration process is reduced by 11 % to 37 % using this compression. Another approach utilizes the prediction of page requests to overlap the wireless transport of the next page with the processing of the current page. This prediction mechanism reduces the configuration time by 40 %, independently of the actual bitstream content. The required configuration energy is also reduced by 40 % using the page prediction.