i-MAC: In-Body Sensor MAC in Wireless Body Area Networks for Healthcare IoT

The application of Internet-of-Things (IoT) technology in modern healthcare environment has given rise to a new paradigm known as healthcare IoT. The wireless body area network (WBAN) is one of the basic building blocks of IoT-based healthcare system, comprising many wearable (on-body) and implant (in-body) sensors placed in or around patient body connected to a hub for physiological signal monitoring. In in-body sensor-based WBAN, guaranteeing quality-of-service and prolonging network lifetime are major impediments due to the sensor location and limited battery capacity. In this article, we propose a novel energy-efficient medium access control (MAC) protocol for IEEE 802.15.6 standard complaint in-body sensor-based WBAN. Typically, the in-body sensor-based WBAN communication is hub-initiated; however, in case of an emergency event, the in-body sensor node transmits an emergency frame arbitrarily without sensing the channel. This inadvertent in-body sensor-initiated transmission has a very high probability of collision with the ongoing hub-initiated transmission, and/or another in-body sensor-initiated emergency frame transmission. This results in emergency frame retransmission and consequently affects the node's energy consumption and lifetime. To alleviate this issue, we propose a modified superframe structure, in which separate access phases are introduced for the emergency event and regular event. In case of an emergency event, a novel emergency event handling scheme and a ranking and priority assignment protocol is proposed to detect and address the critical event of in-body sensors. To minimize the collision, a scheduled access mechanism is proposed according to the criticality of the node. Performance analysis of the proposed in-body sensor MAC is done in terms of latency and overall power consumption, in case of both emergency and regular events.