A novel carrier tracking method for frequency-hopping system

The frequency-hopping (FH) method is widely applied in broadband satellite communication systems because of its low interception rate and good anti-jamming performance. In order to design an FH system, the core issue to be considered is synchronization. For a frequency-hopping time-division multiple access (FH-TDMA) system set in satellite optical communication or satellite wireless communication with large orbital angular momentum (OAM), imperceptible changes in carrier frequencies due to the network properties of large bandwidth, low signal-to-noise ratio (SNR), and high-frequency will cause large equivalent doppler frequency shift of the baseband signal, manifesting 'linear inconsistence' in the FH pattern of the network. Furthermore, the receiver of such a system needs to be robust to adapt to complex and harsh environments of noise interference for the purpose of fast synchronization and tracking progress. This paper proposes an open-loop carrier synchronization and tracking method based on dichotomous iterations by establishing a maximum likelihood (ML) doppler frequency shift estimation model. This method realizes the multidimensional search for frequencies and phases at low SNR. Compared with traditional open-loop carrier synchronization methods, this method can be functional based on mere complex multiplications and additions, and can realize high-accuracy frequency offset estimation of data at normalized frequency offset within 4.8e-4.