Low-Complex Fast-Acquisition Algorithm and Analysis for Broadband LEO DSSS System

In recent years, the applications of broadband direct sequence spread spectrum (DSSS) communications based on low earth orbit (LEO) satellites have become increasingly widespread. The high Doppler deviations introduced by LEO and the high throughput requirements of broadband communication pose great challenges to the low-complexity DSSS acquisition algorithm. Firstly, to address the fast acquisition problem of broadband burst DSSS signals, the traditional algorithm combining partial matched filter and fast Fourier transform is improved and a two-stage detection algorithm based on selection is proposed. This algorithm can effectively resist Doppler deviations while achieving fast acquisition with low complexity. Secondly, during the lock verification stage, a peak index verification strategy is employed to verify the detection results and achieve locked state. Finally, for the first time, a general mathematical modeling is established and closed-form expressions are derived for both the traditional and proposed detection algorithms as well as the proposed lock strategy. The quantitative relations between noise, carrier frequency offset, symbol timing offset, and acquisition probability are derived. Theoretical analysis, simulation results and on-board experiment jointly demonstrate that the proposed TSPF algorithm can achieve at least 0.5 dB performance improvement with a slightly cost of 1%-2% of complex multipliers, while can greatly reduce the near 50% lock time with maintaining a 99.99% correct lock probability.