Impacts of sub hub on connectivity of IEEE 802.15.4 in healthcare environments

In this paper, we consider IEEE 802.15.4 based wireless body area sensor networks(WBASN) in the healthcare environment. Connectivity is a critical constraint in the healthcare environment. In particular, disconnection from a sensor hub is a significant problem that leads to sensor node orphaning. To address this, we propose to use a sub hub designed to enhance WBASN connectivity. The sub hub understudies the original (main) sensor hub and acts to resolve the problems associated with disconnection. We also propose two protocols for use in operating the sub hub. Each protocol prevents the sensor nodes from being orphaned, and forwards data from the sensor nodes to the original sensor hub. In addition, we evaluate the connectivity performance of our proposed protocols and analyze the disconnection tolerance and the number of packet drops. To demonstrate the performances of the proposed protocols, we developed an IEEE 802.15.4 compliant system level simulator with an OPNET Modeler. Simulation results show the individual merits and the demerits of each of the protocols in terms of connectivity. In addition, the energy efficiency of our proposed protocol is evaluated.