Joint Code Acquisition and Doppler Frequency Shift Estimation for GPS Signals

Abstract

The unavoidable Doppler frequency shift reduces the correlation peak for code acquisition in global positioning system (GPS). In contrast to conventional methods where the code phase and Doppler frequency shift are separately treated, this paper proposes a novel three-step scheme for joint code acquisition and Doppler estimation, whereby not only the Doppler effect on the correlation peak is removed, but also the reduced detection probability due to noise enhancement in low signal-to-noise ratio (SNR) environments is avoided. The theoretical analysis shows that the proposed method has low complexity and fast acquisition speed. Computer simulations demonstrate that code acquisition with high detection probability and Doppler frequency shift estimation with high accuracy can be simultaneously achieved.

Reduced-complexity FFT-based method for Doppler estimation in GNSS receivers

“…It shows that the Doppler shift affects the CF's peak in two ways: First, it introduces an exponential term of e jπ f l (N−1) which is a constant phase rotation. Second, the term sin(π f l N)/ sin(π f l ), attenuates the magnitude of the CF and may jeopardize the correlation process [13,15]. Thus, before checking whether the signal is present, it is necessary to estimate the Doppler frequency shift with sufficient resolution.…”

Reduced-complexity binary search for Doppler estimation in GNSS receivers

“…Second, sin(πδf i N )/sin(πδf i ) which attenuates the power of CF and may degrades the peak value of the CF [6]. Thus, in order to check whether the signal is present it is necessary to estimate the Doppler frequency shift with a reasonable error.…”

Statistical characterisation and analysis of differential correlation‐based frame detector

“…In these methods, a windowing technique is adopted for frame acquisition, where coherent integration is performed over a sub‐section of the transmitted synchronisation sequence and the residual integration is then performed after detection. Another efficient coarse frame acquisition scheme based on differential correlation is proposed in the literature [14–19]. In this method, the received signal as well as the reference preamble are modified by multiplying them with a delayed conjugate copy before the correlation process.…”

“…In this method, the received signal as well as the reference preamble are modified by multiplying them with a delayed conjugate copy before the correlation process. The differential correlation method can be generalised to multi‐span differential correlation where the correlation outputs at different delays can be combined to improve the overall detection performance [14–16].…”