# A Novel UWB Positioning Method Based on a Maximum-Correntropy Unscented Kalman Filter
## 1 Introduction  
In recent years, with the advent of the Internet of Things era, all aspects of human life have basically been related to location-based services. For example, in large supermarkets, people can quickly and conveniently find particular goods. In large office buildings, people can find particular locations accurately and quickly. Parents can discern their children's location in real time to avoid losing them. Vehicles in a parking lot can automatically find parking spaces and park. These services are inseparable from accurate location information. Positioning and navigation technology has become the key to smart city construction, which directly affects people's safety and economic development. Therefore, research and implementation of location technology based on wireless technology has an extremely high engineering-application value [1]. The global navigation satellite system (GNSS) is a positioning system based on satellites; it uses satellites as basic reference objects. Because of its high positioning accuracy and its high strategic value, GNSS has now become a focus of all countries and has independently developed its own navigation systems. Compared with other positioning systems, it has unique advantages. Satellite signals can be sent to the global scope, enabling people to obtain positioning information anytime and anywhere. In addition, the satellite system has other characteristics, such as high positioning accuracy, high robustness and all-weather free-space optical communication technology. However, because transmission of satellite signals over a long distance is very weak by the time the signals reach the ground, those signals could rapidly decline or even be unable to be used under the influence of buildings on the ground [2]. Generally, satellite navigation system is suitable for open outdoor environments, while in indoor environments, people urgently need a high-precision, highly reliable indoor positioning system to meet their growing needs. Ultra wideband (UWB) technology is a new type of wireless communication technology. At this stage, it is mainly used to obtain point-to-point distance based on time andachieve final positioning with the distances between the label to be tested and multiple reference base stations. Because UWB technology uses narrow nanosecond nonsinusoidal pulses for data transmission and its spectrum range is very wide, in theory, UWB technology can achieve centimeter-level positioning accuracy [3]. In addition, UWB technology also has the advantages of low transmission power, strong multipath anti-interference capability and high security, so it is very suitable for indoor and other closed-area positioning applications. Non line of sight (NLOS) environments affect the positioning accuracy of UWB technology, and many scholars have put forward their own opinions on reducing NLOS error. A study in the Reference [4], proposed a tight combination of UWB/inertial navigation system (INS) indoor positioning and an attitude-determination method. The difference between the round trip time (RTT) ranging information corrected with a standard time deviation and the distance information calculated with an INS was used as measurement information. NLOS errors were eliminated according to the set threshold, and indoor position and attitude determination were conducted through an extended Kalman filter. Reference [5] proposes an adaptive robust Kalman filtering method that uses the threshold to construct a robust factor that identifies and weakens NLOS ranging errors. Meanwhile, the same study used a Sage Husa filter to estimate and correct system noise in real time in order to improve the accuracy of the UWB positioning. Another study in the Reference [6], analyzed the characteristics of the clock that is offset of the UWB antenna in the actual environment, the relative speed between the nodes and the ranging errors caused by the non line of sight environment.