C/N0 Estimation: Design Criteria and Reliability Analysis under GNSS Weak Signal Scenarios

C/N0 Estimation: Design Criteria and Reliability Analysis under GNSS Weak Signal Scenarios Shashank Satyanarayana, Daniele Borio and Gérard Lachapelle [email protected], [email protected], [email protected] Position Location And Navigation (PLAN) Group, Department of Geomatics Engineering, University of Calgary, 2500 University Dr NW Calgary, Alberta T2N 1N4 Canada. Abstract This paper provides a comprehensive theoretical analysis of a modified Maximum Likelihood Signal-to-Noise Ratio (SNR) estimator and quantifies the minimum coherent integration time required to achieve a predefined level of accuracy. The SNR estimator is derived under the assumptions of perfect frequency synchronization, data bit aiding and constant signal phase during the observation window. The probability density function (pdf) of the SNR estimator in logarithmic units is derived and used to quantify the bias and error bounds associated with the considered SNR estimator. The minimum coherent integration time is determined by requiring a desired level of accuracy with a given probability level, i.e. the integration time is chosen in order to make the SNR estimate lie in a predefined confidence interval. Theoretical results have been validated using GNSS software and hardware simulations. The agreement between theoretical and experimental results supports the validity of the developed theory. Index Terms —Coherent integration, SNR Estimation, GNSS Weak Signal Characterization