Program

MBStar : A Real-time Communication Protocol for Wireless Body Area Networks

Abstract

In this paper, we report on the design and implementation of MBStar, a higher-frequency, real-time, reliable, secure protocol for wireless body area networks(WBAN). MBStar adopts the star topology as most proposals for body sensor networks and the message rate can be as high as 400 Hz, which, to the best of our knowledge, is the highest among low-power wireless communication protocols implemented at the present time. The physical layer of MBStar utilizes 802.15.4 DSSS compatible radio for which a higher-frequency, reliable, TDMA MAC layer is built. There is also a simple application layer designed for security on top. MBStar utilizes public/private key encryption for provisioning devices and does not involve any human configuration before device join. Considering the resource limit of most embedded systems, the TDMA requirement of computing a shared global communication schedule presents a practical problem since it may not be feasible for all the devices to communicate in a long hyper-period while the communication schedule between devices is being created or modified. We solve this problem by keeping only the global hyper-period on the gateway side, with each device being configured with a shorter period. Then, retransmission is employed to resolve any conflicts between the devices. This strategy has the property that the minimal average number of retransmissions is independent of any scheduling algorithm for the same task set and the EDF (Earliest deadline First) is an optimal communication scheduling policy. Finally, we present experimental results that demonstrate that MBStar is an effective protocol for wireless body area networks.