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Description
This paper will evaluate the design of an energy-efficient network used for wildlife observation. The network consists of a full mesh topology and contains nodes that communicate via Bluetooth Low Energy (BLE) in advertisement mode. The initial hardware configuration and software algorithm duty cycles the BLE communication to on and off states using a parameter called the BLE active triggering interval. This parameter triggers the BLE communication to be on for 1 s. Turning the BLE communication to off results in lower power consumption. The base case wireless sensor node has a BLE active triggering interval of 10 s and a CPU clock set to 46 MHz. The algorithm is improved by placing the BLE subsystem and CPU to deep sleep when there are no BLE or CPU tasks to process. This alone improves our power performance by 92.16%. However, we extend power performance improvement to 93.41% and 94.48% by changing the CPU clock of the wireless sensor node from 46 MHz to 24 MHz and 14 MHz, respectively. To further optimize the power of our device we used longer lengths of BLE active triggering intervals, however, this implies a drop in the network’s throughput performance. We wanted to track this effect for varying network densities. Therefore, to scale up power optimization and track the trade-off between power and throughput, we created a simulator that modeled our network with dynamic wireless sensor nodes. The simulator verified the base case hardware results. It also showed a median power performance increase of 97.79% in comparison to the base case, yet, throughput decreased by 66.65 %. For this result the wireless sensor node was set with a BLE active triggering interval of 30 s and a CPU clock at 24 MHZ. The highest power performance increased by 98.89% when a wireless sensor node was configured with a BLE active triggering interval of 50 s and its CPU was set at 14 MHz, however, the simulator showed the throughput drop by 79.97%. Depending on the application, a design may tolerate the decline in throughput to achieve higher power performance.
