The Design and Implementation of a RSSI-Based Localization System

Existing localization algorithms in Wireless Sensor Network (WSN) can be divided into two categories: range-based and range-free. Most of the range-based localization algorithms proposed made use of the Received Signal Strength Indication (RSSI) to make an estimation of the distance between transmitter and receiver. Based on our experiments, there is no relationship between RSSI and distance in indoor situations. But the outdoor experiments show that RSSI is closely related with distance, direction of antenna, the height of nodes above the ground and obstructions. The Gaussian model by curve fitting the average RSSI value with distance resulted the formulation that can be used to compute the distance between unknown node and its neighboring nodes. Then, by applying Trilateration method, a localization system was implemented. This system are specially designed for outdoor without obstructions, tiny variance of physical conditions and all sensor nodes should be placed 2 meters higher than playground. Finally, some errors were analyzed in detail and corresponding proposals were given.