Improving GPS L1 C/A Code Correlation Properties Using a Novel Multi-correlator Differential Detection Technique

Cross-correlation interference introduced by stronger GPS signals constitutes a major problem in acquisition and tracking. For instance, the presence of a single strong GPS signal can mask other weak signals in indoor positioning. Furthermore, the use of GPS pseudolite can also cause near-far problem due to its proximity to the GPS receiver. The weak signal acquisition and tracking should also suppress considerable background noise besides the crosscorrelation interference. Cross-correlation mitigation schemes, such as interference cancellation methods and subspace projection techniques have been proposed for GPS acquisition and tracking. While these schemes are attractive in terms of their mitigation performance, they are limited by their complexity and also by stability. Most importantly, the legacy GPS system is being modernized to include new signal structures with better auto and crosscorrelation properties. However, availability of these signals in near future is still an issue. The main objective of this paper is to demonstrate that the auto and cross-correlation properties of the contemporary C/A code could be significantly improved using a novel multi-correlator differential detection (MCDD) technique. The proposed MCDD method utilizes the shift-and-add property of the underlying C/A code and parallel correlators to improve the correlation properties. The proposed MCDD method simultaneously suppresses both the auto-correlation side-peak as well as cross-correlation interference. Simulations and hardware simulated GPS data analysis substantiate the advantages and the uniqueness of the proposed MCDD method over traditional correlation detection.