RSSI ranging model and 3D indoor positioning with ZigBee network

Received signal strength indicator (RSSI) has become a standard feature in most wireless devices, therefore RSS based localization techniques require no additional hardware. It has attracted researchers´ interest for their advantages of simplicity and low-cost, and so on. But it has some disadvantages of signal disturbance and lower accuracy. According to the previous experiments, we will pay more attention to develop more accurate signal strength-distance models and three dimension positioning methods.The path loss exponent (PLE) is a key parameter in the distance estimation based localization algorithms, where distance is estimated from the RSS. The PLE measures the rate at which the RSS decreases with distance, and its value depends on the special propagation environment. It consists of lots of separate parts of the environment, the distance from the transmitter to the receiver. And each parts of the environment have a PLE which is different from the others. According to this idea, it can construct a novel model (N-Model) which is dynamics of the path loss exponent. Currently, researchers are mostly two-dimensional positioning system research, but in some occasions, three-dimensional positioning is extremely important. By analyzing some common algorithms, the paper presented a new three-dimensional weighted centroid localization algorithm. The positioning system is to implement the algorithm in a ZigBee hardware platform. The experiment results show that positioning error of less than 4m the probability of reaching 70% and same error the probability of reaching 85% indoors.