An integrated RF and ambient magnetic field approach for indoor positioning

Background: A new technology for indoor positioning is proposed in this paper by applying combined RFID (Radio Frequency ID) / IRID (Infrared ID) and spatial fluctuations of the ambient magnetic field. Due to the presence of interior reinforced concrete construction, furniture, electronics and other indoor subjects, the distribution of the magnetic field intensity is fluctuated. Methods: Based on the spatial fluctuations, a particle filter algorithm can be employed to locate the indoor target. However, the computation power required for positioning in a large area could be very high because of the complexity of the application of the particle filter. Results: Similar patterns of magnetic field in large area could also result in wrong location. Because of the short and tunable radiating range of the RF signal and the short response time of identification signal, the target may be positioned within a certain range by using RFID. Therefore, RFID/IRID positioning technique is introduced to approximate the position of the target and then particle filter is applied for precise positioning in the range of RFID/IRID signals. Conclusion: This can effectively reduce the number of required particles to carry out the particle filter algorithm, thereby reducing the amount of computation power, reducing the response time of the positioning and improving the accuracy of the estimated target position.