Indoor Carrier Phase Positioning Technology Based on OFDM System

Abstract

Carrier phase measurement is a ranging technique that uses the receiver to determine the phase difference between the received signal and the transmitted signal. Carrier phase ranging has a high resolution; thus, it is an important research direction for high precision positioning. It is widely used in global navigation satellite systems (GNSS) systems but is not yet commonly used inwireless orthogonal frequency division multiplex (OFDM) systems. Applying carrier phase technology to OFDM systems can significantly improve positioning accuracy. Like GNSS carrier phase positioning, using the OFDM carrier phase for positioning has the following two problems. First, multipath and non-line-of-sight (NLOS) propagation have severe effects on carrier phase measurements. Secondly, ambiguity resolution is also a primary issue in the carrier phase positioning. This paper presents a ranging scheme based on the carrier phase in a multipath environment. Moreover, an algorithm based on the extended Kalman filter (EKF) is developed for fast integer ambiguity resolution and NLOS error mitigation. The simulation results show that the EKF algorithm proposed in this paper solves the integer ambiguity quickly. Further, the high-resolution carrier phase measurements combined with the accurately estimated integer ambiguity lead to less than 30-centimeter positioning error for 90% of the terminals. In conclusion, the presented methods gain excellent performance, even when NLOS error occur.

Decimeter-Level Indoor Localization Using WiFi Round-Trip Phase and Factor Graph Optimization

“…Also, the sampling rate for RTP is limited in real-world scenarios and unwrapping the phase over time naively may not work if the fast motions of the robotic vehicle generate Doppler shifts greater than a given threshold. Fortunately, a similar problem has been solved in the GPS system (RTK) for carrier phase tracking and it can be solved by using an integer ambiguity model in phase tracking as [35]. Our proofof-concept prototype is validated in a relatively small area and experiments in a larger area will be done in the future.…”

Advanced Sensors and Systems Technologies for Indoor Positioning

“…In [ 1 ], a carrier phase technology in wireless orthogonal frequency division multiplex (OFDM) systems is applied to improve ranging and positioning accuracy. Carrier phase measurement is a ranging technique that uses the phase difference between the received signal and the transmitted signal.…”