Research On Energy-Constrained Sensor Scheduling

With the rapid progress of Micro-Electro-Mechanical Systems (MEMS) and wireless communication technologies, small and inexpensive wireless sensors are getting possible. A large number of wireless sensors, which are capable of sensing, collecting and processing, can be deployed extensively to construct a wireless sensor networks and cooperate with each other to monitor a region of interest. Since the sensors will have acoustics, optics, video and wireless communication modes, they can collect useful information on entities of interest and send back the information to base station. Thus wireless sensor networks are widely used recently, especially in surveillance, control system, health care and agriculture etc.Generally, the sensors②are operated on battery power or slow environmental recharge process. Due to expensive manual maintenance, environmental and network size concerns, the sensors are required to work for a long unattended time. This places a hard, stringent energy constraint on the design of the operation, communication times and the deployment of these sensors. Because of this energy constraint, the sensors will be scheduled to turned on and off alternatively for saving energy. However, this alternation will inevitably dis-rupt sensors’ operation, e.g., stop sensing, weaken control of the system. Thus, in order to improve the energy efficiency, a lot of work has been devoted to sensor scheduling inves-tigation. Based on the latest results, this dissertation studies some specific problems for networked sensing and estimation. The main work and contributions are summarized as follows.1. A brief literature review on the development of wireless networked control systems, sensor scheduling and related works are provided.2. Two practical sensor scheduling for stochastic event detection are designed. The first one is for the single-sensor case, where the designed scheme will utilize the event’s information to deicide the sensor’s switching between active and inactive states. And then extend the results to the multiple-sensor case and a sensor schedule which will commands the sensors to detect the events cooperatively is proposed.3. The periodic sensor scheduling for remote state estimation under average transmis-sion energy constraint is considered. The sensor decides whether or not to send its data to a remote estimator due to the imperfect communication. An optimal periodic schedule is found via the tools from Markov chain. Furthermore, a sufficient condi-tion of the system dynamics, energy budget and packet drop rate, under which the remote estimator is guaranteed to be stable, is derived.4. Assume that the sensor has two transmission energy levels, where the high level cor-responds to a high packet reception ratio. By exploiting the feedback information from the remote estimator, a simple and optimal dynamic schedule which minimizes the average estimation error under the energy constraint is developed. The necessary and sufficient condition under which the remote state estimator is stable is also found.5. A schedule problem for a networked control system is considered, where two sen-sors will observe different systems, respectively, and then send the estimation data to a sink node through a network for further processing. Since the sensors and re-lay nodes’ energy are limited and they must work cooperatively, by transferring the estimation problem to an equivalent routing problem, a networked and cooperative sensor scheduling is proposed.In the end, the dissertation is concluded and some future research work are discussed.