The integration of cognitive radios and wireless sensor networks enables a new paradigm of communication in which, sensor nodes can avoid heavily crowded transmission bands by tuning their transmission parameters to less crowded bands thanks to the cognitive radio capabilities. In such setting, sensor nodes act as a secondary user, opportunistically accessing vacant channels within a band originally licensed to a primary user. In this paper, we discuss the problem of how to cluster cognitive radio sensor nodes in a dynamic frequency environment set by the primary users. We introduce Cognitive LEACH (CogLEACH), which is a spectrum-aware extension of the Low Energy Adaptive Clustering Hierarchy (LEACH) protocol. CogLEACH is a fast, decentralized, spectrum-aware, and energy efficient clustering protocol for cognitive radio sensor networks. CogLEACH uses the number of vacant channels as a weight in the probability of each node to become a cluster head. We show that CogLEACH improves the throughput and lifetime of the network compared to the regular LEACH protocol that is operating in the same settings.Index Terms-clustering, cognitive radio, wireless sensor networks.
The control of inverters with output LC filter has a special importance in applications where a high quality voltage is needed. However, the controller design becomes more difficult. A model predictive control (MPC) is used for voltage control of a three-phase inverter with output LC filter. The controller uses a model of the system to predict the behaviour of the variables for a given voltage vector sequence until a certain horizon of time, then a cost function is used as a criterion for selecting the switching state that will be applied during the next sampling interval. This paper presents the effect of considering different number of prediction steps in terms of THD and the number of cycles or the settling time to reach steady state operation. The simulation results for MPC with only one prediction step and the improved MPC with two prediction steps are presented and compared, under linear and nonlinear loads, using MATLAB/Simulink tools. The simulation results show that the improved MPC improves the THD for nonlinear loads and make it constant for different resistive loads. Moreover, the settling time can be considered constant for various linear and nonlinear loads.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.