Towards ubiquitous e-health: modeling of SmartBAN hybrid MAC under periodic and emergency traffic

The Smart Body Area Network (SmartBAN) is a recently proposed system for wireless body area networks (WBANs). Unlike widely-used WBANs that employ contention-based medium access control (MAC) protocols, the SmartBAN MAC specifies a joint time division multiple access (TDMA) and slotted ALOHA access framework. To date, a criterion for determining the time duration of different channel access phases remains unaddressed in current WBAN MAC designs. There is also a lack of understanding of how the duration of these timing periods impacts the SmartBAN's performance. In this paper, we derive closed-form analytical models for the uplink transmission delay, which is defined as the duration a data packet generated by a sensor has to wait prior to its uplink transmission. We adopt a flexible channel access mechanism considering the characteristics of two major traffic patterns in medical applications: periodic monitoring traffic and Poisson-distributed emergency traffic. Then, based on both analytical models and simulation of the MAC timing parameters, and in conjunction with the behavior of a typical SmartBAN in terms of delay and energy consumption with aggregated traffic load, we present our solution to determine different access periods of the SmartBAN MAC. With extensive simulations, the accuracy of the delay model is validated and a blocking state of the SmartBAN is discussed, where the delay and energy performance is degraded significantly due to the queuing at each sensor. The results obtained in this paper provide a first in understanding how timing parameters and the traffic features impact SmartBANs' delay and energy performance.