Performance Evaluation of IEEE 802.15.6 MAC Under Varying Health Emergency Conditions

Wireless Body Area Network (WBAN) consists of health and environmental sensing nodes and a dedicated hub. The hub has more processing power and capabilities than the sensor nodes. It collects sensing data and forwards them to corresponding destinations for further processing and actions. In case of emergencies, the hub delivers the received data to the emergency department to take quick action. The end-to-end link between the sensor node and the emergency department mainly depends on the sensor node's bottleneck link and the hub. WBAN nodes communicate with the hub by accessing the physical communication channel in a randomly distributed fashion. Random channel access may cause retransmission of corrupted frames due to frame collisions. This causes performance degradation of the deployed WBAN. The IEEE 802.15.6 standard specified eight different user priorities for different traffic types. Among these priorities, priority seven is dedicated to reporting emergency and medical implant events. If several nodes report at this priority, this causes lower priority nodes to starve. In this work, we allow nodes to switch from lower priorities to priority seven in emergencies. We conducted several experiments to study the effects of priority seven on other nodes in normal operations and emergencies. The study results showed that the packet delivery rate is severely affected when some nodes switch from normal user priority to priority seven. More studies and investigations need to be conducted to determine the optimum operation of WBAN, especially in the case of an emergency.