Cooperative Scheduling for Adaptive Duty Cycling in Asynchronous Sensor Networks

Abstract

To support the sustainable operation of wireless sensor networks using limited energy, duty cycling is a promising solution. However, it is a challenge to guarantee each node communicating with its neighbors under duty cycle when the network is asynchronous. The challenge becomes bigger when nodes' duty cycles are required to be adjusted separately according to their demands to save energy and achieve high channel utilization. Existing low power listening-and contention-based protocols are not energy-efficient and cannot ensure high channel utility. Additionally, synchronizationbased media access control (MAC) protocols suffer from extra energy consumption and low synchronization precision. This paper proposes a localized and on-demand (LOD) duty cycling scheme based on a specifically designed semi-quorum system. LOD can adjust duty cycle of each node adaptively according to its demand so as to avoid channel contention, consequently achieving high channel utilization. This allows the fairness for channel access within asynchronous sensor networks. Extensive experiments are conducted on a real test-bed of 100 TelosB nodes to evaluate the performance of LOD. As compared with B-MAC, LOD substantially reduces contention for channel access and the energy consumption, thus improving the network throughput significantly.

Discrete-Time Dynamical Maximum Power Tracking Control for a Vertical Axis Water Turbine with Retractable Blades

“…This paper's contribution lies in its employment of an effective MPPT control and optimal LQT control for varying operating conditions. Optimal LQT control is one of the most successful control algorithms and is widely used in handling multivariables and constraints [13][14][15][16][17]. The designed control discipline is based on a mathematic model of a controlled object with the prescribed limit to acquire the optimal performance index [18][19][20].…”