A new method for non-cooperative signal parameter estimation

Navigation signals are one of the most crucial components of the Global Navigation Satellite System (GNSS), acting as a hub among satellites, users, and ground control systems. Conducting space signal quality assessments and monitoring the navigation system are essential means to ensure the normal functioning of navigation system capabilities such as positioning, speed measurement, and timing. These assessments not only provide high-quality services to users but also offer theoretical support for navigation system design and technical validation. In scenarios lacking prior information, it is necessary to estimate parameters such as the initial value of the carrier phase and carrier frequency to achieve signal demodulation and recover the pseudocode for subsequent capture and tracking, thus enabling signal assessment in non-cooperative settings. Existing methods for parameter estimation, particularly under conditions of low signal-to-noise ratios and the presence of interference, do not provide satisfactory accuracy and fail to meet the requirements for capture and tracking. This paper introduces a method for estimating the parameters of QPSK signals, utilizing image information combined with unsupervised clustering algorithms. Simulations show significantly improved estimation accuracy under low signal-to-noise ratio conditions. This method can also be applied to the estimation of signal modulation characteristic parameters and eye diagram parameters, providing important technical support for signal quality assessment.