Multipath-Assisted Indoor Localization Using a Single Receiver

Target localization using a single receiver is highly needed due to the mobility of the target. In indoor environment, multipath signals are rich and usually relate the target location and structure of indoor environment through geometry parameters such as Angle of Arrival (AOA) and Time of Flight (TOF). Based on this, in this article we propose a multipath-assisted indoor localization system using commodity WiFi signals which contain phase errors caused by imperfect hardware and non-synchronized clocks. The proposed system is different from conventional localization algorithms which treat multipath signals as enemies, and only uses a single receiver. To realize accurate localization without interferences of phase errors, we firstly construct a geometry model for jointly estimating the locations of the target and scatterers which can be regarded as objects such as furniture, by using TOF differences between reflection paths and direct path. Considering more constrains on target location, we select the direct path as the reference. Then, with the help of AOAs, we develop a location searching algorithm of the target and scatterers based on Particle Swarm Optimization (PSO). We have implemented the proposed system on the commodity WiFi devices, and the experiment results in actual indoor environment show that the median location error is around 1.5m by using only one receiver. What’s more, the intensive simulation results show that the proposed system is promising in the emerging networks such as 5G, where higher bandwidth of signal and more antennas can be used for providing accurate AOA and TOF.

I. Introduction

Location plays an important role in many intelligent applications such as smart homes [1] and Augmented Reality (AR) [2], and thus the demand for accurate localization has been rapidly increasing. Recent years, indoor localization using WiFi signals has been advanced greatly due to Channel State Information (CSI), which contains phase and amplitude information, is available in the commodity WiFi networks. Compared with Received Signal Strength (RSS) [3], CSI is a more fine-grained measurement, which captures the information of multipath signals. Thus, geometry parameters such as Angle of Arrival (AOA) [4], [5] and Time of Flight (TOF) [6], [7] of multipath signals can be obtained, which contribute to a more accurate localization. Localization of the target can be realized by means of different methods such as trilateration with multiple TOFs and AOAs.