Search-Range-Correction-Based Doppler Shift Acquisition for Space Communications

Abstract

For space communication circumstances, long-distance transmission significantly deteriorates the received signal-to-noise ratio (SNR) at the receiver. Moreover, the high-speed relative movement between the transmitter and the receiver causes a very large Doppler shift, thus imposing a new challenge for the acquisition. To address the Doppler shift acquisition problem under not only the very low SNR but under the very high relative movement scenarios as well, in this paper, we develop one search range correction (SRC)-based acquisition scheme, which includes three algorithms called single SRC, overlapping SRC, and iterative SRC, respectively, to significantly increase the acquisition probability for space communications. First, the single SRC algorithm, which has a simple closed-form expression for the net increment of acquisition probability, uses multiple combination periods to correct the search range for the succeeding period. Moreover, the special case using two combination periods for the single SRC algorithm is already verified to increase the acquisition probability. Second, the overlapping SRC algorithm, which is based on the period overlapping of the single SRC algorithm, enjoys much implementation feasibility and saves many received signals. Third, the iterative SRC algorithm, which builds on the iteration of the overlapping SRC algorithm, can further increase the acquisition probability as compared with that of the overlapping SRC algorithm. Simulations results show that our proposed scheme can obtain much higher acquisition probability of Doppler shift, compared with existing acquisition schemes, including the fast Fourier transform (FFT), time–frequency, and single SRC using two combination periods.