Stepwise Noncoherent Accumulation Acquisition for High-Dynamic DSSS Communications

Abstract

For direct sequence spread spectrum (DSSS) communication circumstances, the high-speed relative movement with large acceleration between the transmitter-receiver pair causes a large variation rate in Doppler shift. Moreover, the long transmission distance significantly deteriorates the received signal-to-noise ratio (SNR) at receiver. To address the acquisition problem under not only the very weak received signal but under the high dynamic scenarios as well, in this paper, we propose a stepwise noncoherent accumulation (SNCA) acquisition scheme with dynamic noncoherent accumulation length (DNCAL) capping for various signal strength, which is based on the traditional fast Fourier transform based partial matched filter (PMF-FFT) acquisition architecture. First, we compensate Doppler shift variation rate in parallel so that it is small enough to be ignored in one Doppler shift variation rate bin. Second, we adopt noncoherent accumulation to overcome the problem caused by the weak received signal. And, the minimum noncoherent accumulation length (MNCAL) for a specific acquisition probability under constant false alarm rate (CFAR) is analyzed quantitatively. Third, the SNCA acquisition scheme with DNCAL capping defined by the MNCAL for a specific acquisition probability under CFAR is developed to further reduce the average NCAL. Simulations results show that the analysis of MNCAL is effective, and our proposed scheme can obtain almost the same acquisition probability with less NCAL, compared with the PMF-FFT acquisition scheme with fixed NCAL.