In urban areas, due to the obstruction/reflection of GNSS signals by roadside buildings, position accuracy is greatly degraded, or even outage occurs when no enough satellites are available. To address this problem, vehicles and roadside units have been used as positioning anchors to estimate pedestrian position. Although previous methods exploited channel state information, which is superior to received signal strength for distance estimation, they rely on signal attenuation characteristics, and the accuracy is limited by temporal resolution and multipath propagation. This work focuses on using the phase information of V2X OFDM signals to estimate distance differences more robustly. We investigated the impact of the sampling rate, a crucial parameter, and conducted simulation evaluations using 3D maps and ray-tracing. Additionally, we built a testbed and performed evaluations with real-world OFDM signal data, which demonstrates that phase information can significantly improve the accuracy of distance measurements.

Monitoring the displacements of structures caused by slight or big seismic shakings and landslides the irrespective of observation points by simply taking the data using a single equipment is useful. GNSS antennas and receivers on the roof of a steel tower to monitor the displacement of the structure caused by the wind etc. has already been reported, but ours is the first study on a low-cost GNSS system attached to the wall of a building to monitor structure deformations. More specifically, this research focuses on real time monitoring for structure deformations using hand-held RTK-GNSS (Real-Time Kinematic Global Navigation Satellite System) receivers installed on building wall. RTK positioning is normally carried out using expensive receivers and antennas compatible with dual frequencies. However, aside from its high cost, this type of equipment is also not easy to procure. This study addresses this problem by using a single-frequency low-cost receiver, with comparable results in centimeter level. The methods presented make use of horizontal spread and statistical values to come up with the positioning results. Our work on the proposed revolutionary monitoring system with a robust RTK improvement method will serve as basic research for monitoring the fluctuations and deformations of structures in the fields of architecture and construction.

Critical government and industry sectors (such as law enforcement, transportation, communication, and finance) are growing increasingly dependent on Global Navigation Satellite Systems (GNSS) for positioning, navigation, and timing. At the same time, the availability of low-cost GNSS jamming devices are presenting a serious threat to GNSS and increasing the likelihood of outages to infrastructures relying on GNSS. The attacks range from malicious parties intentionally jamming GNSS signals within a targeted geographical region to uninformed users causing accidental interference. This paper is an overview of different approaches adopted to date to mitigate GNSS disruption caused by intentional and unintentional jamming. The first approach outlined in this paper is the use of inertial systems to aid GNSS. The second and third approaches are the filtering of jamming/interference in the spatial and time-frequency domains, respectively. The fourth approach is vector tracking of GNSS signals in the receiver.

This paper describes outdoor localization for a mobile robot using precise point positioning (PPP) based on the Quasi-Zenith Satellite System (QZSS) L-band Experiment (LEX) signal. For autonomous navigation applications, a real-time kinematic (RTK) global positioning system (GPS) technique is widely used to estimate user position with high-precision accuracy in real time. However, RTK-GPS requires a reference station, and there are data acquisition costs involved in estimating the position. Our approach corrects position error by applying PPP using the QZSS LEX message. PPP can estimate a single receiver position without any reference station or baseline, through use of satellite position fixing and clocks. We developed a method for extracting the QZSS LEX message in real time using a software GNSS receiver. We then constructed the PPP framework based on an LEX message containing the satellite ephemeris and clock errors. Finally, we conducted field experiments to evaluate the accuracy and precision of our proposed method. The experimental results confirmed that our method made a localization precision of 1.29 m possible without using a GNSS reference station.