A cooperator-assisted wireless body area network for real-time vital data collection

Wearable wireless body area network (WBAN) has attracted considerable attention as a means to collect vital data in sports training and urgent life-critical scenarios, which requires high reliability in links from sensor nodes to a central coordinator. Herein, cooperative relaying, which means retransmission not by sensor nodes themselves but through their cooperators, works effectively, since human postures do not suddenly change the states of the links in quite a short duration such as a retransmission interval. In this paper, we propose a cooperator-assisted WBAN for real-time vital data collection. We show that the WBAN is realizable based on two kinds of medium access control (MAC) protocols such as a hybrid-time divison multiple access/carrier sense multiple access (TDMA/CSMA) and a TDMA, both of which are compliant with the IEEE 802.15.4.e standard, and evaluate the packet error rates and power consumptions for a hybrid-TDMA/CSMA-based WBAN and a TDMA-based WBAN. In the evaluation of packet error rates, we use the stored received signal strength indication (RSSI) data, which were obtained from experiments with three subjects in a realistic scenario composed of a series of different actions and postures in a mixed-indoor/outdoor environment.