Design and evaluation of a custom ZigBee platform
Wireless sensor networks o er signi cant advantages over wired solutions, including savings in installation and maintenance costs. The ZigBee stack speci es additional application and networking layers to be used with the IEEE 802.15.4 low-rate wireless personal area network standard. A custom hardware and software platform is detailed, and measurements are performed to characterise the platform. Packet Error Rate (PER) measurements for both a star network and a multi-hop network show that the PER increases as the number of devices simultaneously transmitting increases. The maximum goodput (data payload bits transmitted over time) attained is 37 kb/s. Latency measurements show an increase in microcontroller clock speed will reduce message generation and deconstruction processing time. Device lifetime estimations show the signi cant e ect of the chosen regulator's quiescent current, reducing device lifetime when using a 9 V, 500 mAh battery from 49 days to 8 days when excluding regulator current. Valid sensor results require monitoring the device power supply, as a failing power supply in uences sensor measurements whilst successful radio transmission is still possible. Devices lasted up to 71 % of the predicted lifetime.