GNSS Timing Receiver Performance in Urban Canyons

Abstract: Time synchronization is critical for the operation of radio base stations (RBS) in telecommunication companies. Global navigation satellite system (GNSS) is an existing technology to provide precise timing information to distributed RBSs. GNSS timing receiver is used for providing higher timing accuracy than normal GNSS receiver in this synchronization domain.In this thesis, an experiment method for GNSS timing receiver performance in urban canyon has been designed and implemented to evaluate information and the quality of the one pulse per second (1PPS) signal generated by two different GNSS timing receivers. Multi-path signals and the gathered satellite geometry caused by poor sky visibility is identified as the main influential factors to the performance of the GNSS timing receivers. A mathematical model has been built for estimating the multi-path effect. GNSS planning tools are used to simulate the number of line-of-sight (LOS) satellites and Dilution of Precision (DOP) value.Sentinel is a 1PPS signal analyzing equipment from Calnex. Sentinel has an embedded rubidium clock, GNSS antenna, and receiver, and it can produce 1PPS signals to be used as a reference. In this report, we installed our GNSS antenna of Sentinel on the roof and test GNSS antenna in two specified positions representing urban canyon and rooftop. Recorded NMEA messages from GNSS receiver can help us to study the number of visible satellites, PDOP value and multi-path signals in realistic situations.The results show how the noise and time phase of 1PPS signals will be influenced in urban canyons. Since, the geometry of used satellites is similar to the rooftop situation, the multi-path effect of signals is identified as the main reason of this difference.This information is useful when telecommunication companies want to install their radio base station in urban canyons. It will help Ericsson to understand how their GNSS timing receiver is working and how the urban canyon will influence its performance.