Utilization of multi-rate signal processing for GNSS-SDR receivers

Abstract

In this article, we propose a low-complexity solution for the decimation chain in the digital front-end (DFE) of global navigation satellite system (GNSS) receivers. The received signals are typically highly oversampled in the DFE of GNSS receivers to reduce the ranging error and therefore to improve the positioning accuracy in the tracking stage of the GNSS receivers. However, this oversampling imposes unnecessary complexity on the acquisition stage of the GNSS receivers where an approximate estimate of the code phase and Doppler frequency shift is produced. Therefore, reducing the sampling frequency for the acquisition stage reduces the overall receiver complexity without any significant effect on the performance of such receivers. The proposed solution for the decimation chain involves the use of infinite impulse response (IIR) filters as the decimation filter as they can be implemented more efficiently in comparison to finite impulse response (FIR). In addition, a hybrid time-frequency domain filtering scheme is proposed here to alleviate the effects of non-linear phase in the decimation IIR filter as well as the analog front-end receivers. The advantages of this proposed method is explored and stated, both from performance and complexity perspectives, through rigorous comparison with alternative available solutions. © 2014 Soltanian et al.; licensee Springer.