Validation of novel navigation signal structures for future GNSS systems

Abstract

Prior to the design and development phase of the European Galileo programme, the European Space Agency (ESA) undertook several pre-development projects to reduce the overall programme risk. Navigation signal bandwidth was determined to be one key risk area. This paper describes the development and use of a highly flexible signal validation facility designed to generate and receive novel, band-limited GNSS signals. The GNSS signal validation facility consists of a fully functioned real-time GNSS constellation simulator and signal generator; a dedicated receiver, a navigation processing unit and a performance analysis software suite. The constellation simulator, receiver and navigation processing unit are capable of operating in real-time with 12 satellites in view and three frequencies per satellite. The GNSS signal validation facility itself is extremely flexible to allow performance comparisons of different satellite constellations, signal designs, code lengths, data rates and frequencies. The GNSS signal validation facility has been used in an extensive test campaign to evaluate the performance of the novel band-limited GNSS signals under realistic user conditions with a representative Galileo satellite constellation. A strong focus of the signal validation test campaign was the performance of three-carrier differential navigation algorithms. This paper briefly describes the operation of the GNSS signal validation facility and provides an overview of the main test campaign performance results. This paper contains the first published results from the GNSS signal validation facility. A major result from the test campaign is that the novel band-limited GNSS signals provide robust and accurate positioning capability with navigation data rates of up to 3000 s/s. The receiver was shown to receive 24 MHz band-limited signals with a loss of less than 1 dB for a spreading code of 15.345 Mc/s and a sampling frequency of 56 MHz.