Evolution of Distributed Detection Performance over Balanced Binary Relay Tree Networks with Bit Errors

Target detection based on wireless sensor networks can be considered as a distributed binary hypothesis testing problem. In this paper, the evolution of detection error probability with the increase of network scale is studied for the balanced binary relay tree network with channel noise. Firstly, the iterative expressions of false-alarm probability and missed-detection probability depending on the number of tree network layers are given. Then, the iterative process of two types of error probabilities in the network space is described as a discrete nonlinear switched dynamic system, and the dynamic properties of two types of error probabilities are analyzed in a plane rectangular coordinate system. A globally attractive invariant set of the state of the dynamic system, which is not related to the channel noise, is derived. The switching mode of the system and the total error probability in the invariant set are further analyzed, and a necessary and sufficient convergence condition of the total error probability is provided. Based on this condition the following detection properties of the network are revealed: (1) as long as the channel bit error probability is not zero, the total error probability does not tend to zero with the increasing network size; (2) when the channel bit error probability is greater than 2-/3/ 2 the total error probability will continue to increase with the increase of network size.

Application of a wireless sensor system for object protection using infrared sensors

In this work, an algorithm that makes decisions on whether or not an object under protection has been penetrated based on data from infrared (IR) sensors included in a wireless sensor system is considered. Based on theoretical considerations, methods for calculating the attenuation of infrared radiation by the medium, including attenuation due to molecular gases and aerosol attenuation, are presented. Peculiarities of the external environment impact on the functioning of local heat sensors are shown. Also, peculiarities of the noise immunity characteristics of a radio communication channel are considered with due regard for signal fading. With the purpose of analyzing the environment impact on the efficiency of the entire system, we present dependencies of the total error probability on the energy parameter, taking into account the attenuation of infrared radiation in both the environment at the level of local sensors and the radio communication channel. In addition, a dependence of the total error probability on the communication distance under the influence of fading is presented. The results arrived at are analyzed and the degree of influence of the environment on the quality of functioning of the wireless sensor system of thermal type is evaluated. It is shown that adverse weather conditions can have a significant impact on the efficiency of local sensors, and, hence the entire system. However, despite the possible significant deterioration in efficiency due to the IR signal attenuation in the medium and in the radio channel, the efficiency can be increased by increasing the number of sensors used.