Joint Charging, Routing, and Power Allocations in Rechargeable Wireless Sensor Networks

Prolonging the battery lifetime of sensors has been one of the most important issues in wireless sensor networks (WSNs). With the development of Wireless Power Transfer (WPT) technology, sensors can be recharged and possibly have infinite lifetime. One common approach to achieving this is having a wireless charging vehicle (WCV) move in the system coverage area and charge sensors nearby when it stops. The duration that the WCV stays at each charging location, the amount of traffic that each sensor carries, and the transmission power of individual sensors are closely related, and their joint optimization affects not only the data transmissions in the WSN but also energy consumption of the system. This problem is formulated as a mixed integer and non-convex optimization problem, which is transformed and solved optimally. Numerical results demonstrate that the average power consumption of the system can be significantly reduced by optimizing the charging time of individual sensors instead of that of a cluster of sensors.

I. Introduction

Wireless Sensor Networks (WSNs) have been used for many applications, such as environmental monitoring, military surveillance, and industry automation [1]. Sensors are usually battery powered and the batteries have low capacity due to the limited size required by many applications. The lifetime of the sensors limits that of a WSN [2] [3], while the cost of replacing these “dead” sensors can be very high, especially in harsh environments or areas that human cannot easily reach [4]. With the increasing applications of WSNs, managing the energy consumption of the networks has become one of the most important issues.