GPS L2C Signal Quality Analysis

Liliana Sukeova, Marcelo C. Santos, Richard B. Langley, Rodrigo F. Leandro, Okwuchi Nnani, and Felipe Nievinski

Abstract:	A new generation of Global Positioning System (GPS) satellites, called Block IIR-M, has been launched since December of 2005. These satellites are part of the modernization effort that the GPS is undergoing. The signals transmitted by these satellites contain a new civilian code superimposed on the L2 carrier, called the L2C code. Research into the characteristics of the L2C code is based on an International GNSS Service (IGS) L2C dedicated Test Network. This network is composed of both existing stations as well as newly established ones with receivers capable of tracking the L2C signal. The IGS L2C Test Network is composed only of Trimble receivers. The University of New Brunswick (UNB), Fredericton Campus, Department of Geodesy and Geomatics Engineering (GGE), obtained a Trimble R7 and a Trimble NerR5 receiver on loan from Cansel, a Canadian distributor of Trimble products. Both receivers are capable of tracking the L2C code. The Trimble R7 receiver was collocated with IGS station UNB1 (now station UNBJ), sharing the same antenna, and has become a part of the L2C signal tracking network since January 2006. From November 2006 we have replaced the R7 receiver by the NetR5. This paper presents results of our analysis on the L2C data collected by the L2C Test Network. Our investigation starts with an examination of the signal-tonoise ratio (SNR) on the L1 and L2 frequencies. The range of the SRN values on the L1 frequency is similar for all satellites, whilst the range of the SRN on the L2 frequency for the three modernized satellites is higher than those for all other satellites. This indicates an improvement in the SNR of the L2C signal over the P(Y) code. It follows with a study on the multipath and noise levels of C/A and L2C code pseudorange for PRN 17 in the Trimble R7 receiver. These values were calculated and compared. A typical standard deviation of the C/A and L2C code noise and multipath is 0.27 m and 0.61 m, respectively. The difference between the standard deviations is caused by issues in the firmware versions 2.26 and 2.28, which were used in the Trimble R7 receiver during the observation period. Further, we have analyzed the C/A and L2C code multipath and noise levels based on the L2C global Test Network. We chose four stations (FAIC, UNAC, UNB3 and GANP) to be used in this analysis The first two stations use a Trimble NetRS receiver; while the last two stations use a Trimble NetR5 receiver Standard deviations of multipath and noise values were computed over the entire 24-day period and each day separately for each elevation angle bin, each modernized satellite, each four stations and code (C/A and L2C). After examining the results from the stations using Trimble NetR5 receiver we realized that the standard deviations of the C/A and L2C codes were similar in the case of all modernized satellites. However, stations using Trimble NetRS receiver had higher standard deviations for the L2C code then for the C/A code. This can be also explained by the firmware versions used in the receivers.
Published in:	Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007) April 23 - 25, 2007 Royal Sonesta Hotel Cambridge, MA
Pages:	232 - 241
Cite this article:	Sukeova, Liliana, Santos, Marcelo C., Langley, Richard B., Leandro, Rodrigo F., Nnani, Okwuchi, Nievinski, Felipe, "GPS L2C Signal Quality Analysis," Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007), Cambridge, MA, April 2007, pp. 232-241.
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