An Adaptive Beaconing MAC Protocol Providing Energy-Efficient Healthcare Service

Abstract

We present an Adaptive Beaconing Medium Access Control (AB-MAC) protocol based on time division multiple access (TDMA) in order to provide healthcare services. The purpose of our protocol is to gain not only energy-efficiency but also provide low delivery latency when both periodic data and event-driven data are present. In order to satisfy these requirements, we propose standby slots that are deployed during each beacon interval. The standby slots are able to identify unscheduled data with low delivery latency. An adaptive beacon is then provided that quickly reschedules the time slots. Furthermore, the AB-MAC asymmetrically assigns energy consumption to a coordinator instead of the sensor nodes when possible in order to reduce sensor node energy waste. In this paper, we analyze the IEEE 802.15.4 and the AB-MAC, and evaluate their energy consumption and delivery latency. NS-2 simulations are used to validate the numerical analysis. The evaluation results indicate that the AB-MAC is a more suitable protocol than the IEEE 802.15.4 when used in WBANs.

Appendix

The number of events in any interval $t$ is the Poisson distributed with the mean $\lambda \,t$. Therefore, the probability that exactly $k$ events occur is equal to:

$$\begin{aligned} P\left( {k,t} \right) =\frac{\left( {\lambda \cdot t} \right) ^{k}}{k!}\cdot e^{-\lambda \cdot t}, \end{aligned}$$

(22)

where $\lambda$ is the expected number of occurrences of an event during the given interval.

Thus, the probability that any event does not occur in a standby slot interval is given by:

$$\begin{aligned} P\left( {0, SI } \right) =e^{-n\cdot \lambda \cdot SI }, \end{aligned}$$

(23)

and the probability that at least one event occurs in a standby slot interval is:

$$\begin{aligned} P(k\ge 1, SI )=1-P\left( {0, SI } \right) =1-e^{-n\cdot \lambda \cdot SI }. \end{aligned}$$

(24)

From (24), we can derive P(Event) by substituting $\lambda$ as $1/R_{ Event }$.