Electronic health monitoring is one of the major applications of wireless body area networks (WBANs) that helps with early detection of any abnormal physiological symptoms. In this paper, we propose and solve an optimization problem that maximizes the energy efficiency (EE) of WBAN consisting of sensor nodes (SNs) equipped with energy harvesting capabilities communicating with an aggregator. We exploit the structure of the optimization problem to provide a suboptimal solution at a lower computational complexity and derive the mathematical expressions of upper and lower bounds of the source rates of the SN. The simulation results reveal that the optimal allocation of the source rate to energy critical SNs improves the system performance of WBAN in terms of energy efficiency during different everyday activities.Index Terms electronic health monitoring, energy harvesting, energy efficiency optimization, wireless body area network.
I. INTRODUCTIONElectronic Health (eHealth) monitoring systems with wireless body area networks (WBANs) help integrate the patient's data processing and communications technologies into traditional medical facilities and serves as a promising approach to boost the health-care efficiency. In WBAN, the sensor nodes (SNs) monitor the patient's vital signs and send the data wirelessly to the aggregator [1]. These SNs are conventionally powered by batteries, which are needed to be replaced once the energy is consumed. Therefore, wireless energy harvesting serves as an alternative approach that enables self-sustained SNs operations by scavenging energy from biomechanical, biochemical, and ambient sources (e.g., thermal, electromagnetic radiations) [2].Due to limited battery life, saving energy of the SNs is of significant importance. Therefore, WBAN has to provide sustainable battery lifetime, high energy efficiency (EE), and quality-of-service (QoS) of the data stream. In [3], an efficient power QoS control scheme for energy harvesting WBAN is proposed that ensures the best possible QoS by efficiently transmitting the data packets. Stochastic modeling of wirelessly powered wearables proposed in [4] provides an analytical framework for the SNs ability to notify the medical staff about the patient's condition promptly. In [5], a medium access control (MAC) layer protocol for WBAN is proposed that utilizes the CSMA/CA-TDMA hybrid schemes to extend the lifetime and EE of SNs by saving energy. In [6], a MAC protocol for WBAN is proposed that ensures QoS and EE in the power constrained network by dynamically optimizing the transmission slot such as the energy consumption of the SNs is minimized. Cooperative energy harvesting-adaptive MAC protocol proposed in [7] improves the WBAN performance in terms of delay, EE, and throughput by changing its operation based on the energy harvesting conditions.Compared to the existing work, this paper aims to maximize the overall EE of the energy harvesting WBAN. In particular, we formulate and solve a novel optimization problem that optimally allocates each SN sour...