The Research Of Device-Free Indoor Perception Based On Wireless Sensor Networks

Nowadays, wireless sensor network(WSN) plays an important role in information gathering and propagation, improving the capacity of perception. WSN combines wireless communication technology, embedded computer technology, MEMS technology, distributed computing theory and other advanced technologies, and it is a interdisciplinary research field and a new direction of information science. Especially, as the concept of Internet Of Thing(IOT) rises, WSN which is an underlying key part of IOT will get great development and application.WSN is typically used in passive perception by measuring directly the physical properties of the object itself or the environment, such as pressure, temperature, light intensity, sound, but some traditional sensors have many limits. For example, camera, widely used in security system, is sensitive to changes in light intensity. As the light dims, the recognition rate decreases, and it is not allowed that an obstacle exists between the camera and the measured target. Fortunately,the radio frequency(RF) signal transmitted by wireless sensor node itself can overcome the above disadvantages. It has a strong resistance to environmental change, and travels through non-metallic obstacles, which greatly improves the space and suitability of perception. Perception by RF signal has potential applications in security, emergency rescue, intelligent monitoring and other fields.When a person enters a grid composed of many radio links, he will destroy the original pattern of the grid. A obvious result is that the received signal strength indication(RSSI) of some links decrease significantly. This paper will analyze the RSSI changes to monitor the intrusion into a critical area.In this paper, we firstly inspected the indoor wireless environment, including understanding the indoor wireless channel characteristics and analyzing power consumption for indoor radio propagation. Subsequently, we theoretically explained signal power attenuation and fluctuation phenomena caused by person’s existence on radio LOS links and NLOS links respectively. With theory support, we designed a passive perception model based on WSN, proposed a RSSI gathering protocol, and a perception algorithm was given. The WSN node hardware was implemented using CC2530radio frequency SoC, and we completed the software design. In the end, we tested the RF indoor passive perception system, and analyzed the results.