Fast two-dimensional compressed correlator based acquisition techniques for next-generation GNSS

Abstract

Long spreading code and various modulation techniques are used in the next generation Global Navigation Satellite System (GNSS) to improve positioning performance and to reduce inter-GNSS interference. However, the signal acquisition process of a GNSS receiver can take longer time and require additional hardware resources as compared to legacy Global Positioning System receivers. Moreover, in the next-generation GNSS environment, a large number of satellites are visible due to their increased increased number. Fast acquisition of strong signals is therefore a more important issue than the acquisition of weak signals in outdoor environments for the next-generation GNSS. To deal with this problem, this paper presents a two-dimensional compressed correlator (TDCC) technique for fast, low-computational acquisition of next generation GNSS signals. In the proposed TDCC technique, signal power in neighboring code phase hypotheses and Doppler frequency hypotheses can be coherently combined and reduce the total number of hypotheses to test. TDCC techniques for serial search schemes and parallel search schemes are respectively proposed, and TDCC techniques for binary phase shift keying modulated signal and binary offset carrier modulated signals are also respectively proposed. The performance of the proposed techniques has been analyzed and demonstrated with various simulations. To minimize the mean acquisition time (MAT) and mean acquisition computation (MAC) for the TDCC, optimal detection thresholds are obtained and analyzed via a numerical evaluation for widely used detection strategies, such as threshold crossing (TC), maximum threshold crossing (MTC), and maximum-to-second-maximum-ratio (MTSMR), in the serial and parallel search schemes. It has been shown that the proposed technique has strong advantages over the conventional acquisition techniques in high carrier-to-noise-density ratio ($C/N_0$). Since there are a number of satellite signals arriving at a receiver with high $C/N_0$ (i.e., $C/N_0$ > 44dB-Hz) in most outdoor environments, the proposed technique can be useful for receivers with limited computational resources to quickly acquire the next generation GNSS signals using long Pseudo-random-noise code.