Implantable body sensor network MAC protocols using wake-up radio — Evaluation in animal tissue

Applications of implantable sensor networks in the health-care industry have increased tremendously over the last decade. There are different types of medium access control (MAC) protocols that are designed for implantable body sensor networks, using different physical layer technologies such as narrow band, ultra wide-band, human body communication, and ultrasound with an innovative low power access technology called wake-up radio (WuR). The WuR operates alongside the main radio either in the same frequency or different frequency, with much lower power and reduced hardware components than main radio. In this article we analyze the impact of WuR on commonly used MAC protocols and evaluate three MAC protocols with WuR using real hardware implanted in animal tissue and compare them with three other MAC protocols without WuR. The hardware implantable board is embedded with a micro-processor, wireless communication unit and is subcutaneously implanted under the skin of the animal tissue. Five nodes with one of them being the central controller connected in star topology are used for evaluation. Energy efficiency, reliability in terms of packet loss ratio, and end-to-end delay for each node are considered as the evaluation criteria.