Position and ephemeris-based synchronization method and system for low-earth-orbit satellite communication system

Abstract

The invention belongs to the technical field of low-earth-orbit satellite communication, and particularly discloses a position and ephemeris-based synchronization method and system for a low-earth-orbit satellite communication system. The system comprises a low-earth-orbit satellite and a terminal, a computer program is stored in the terminal, and when the computer program is executed by the terminal, the terminal realizes the method. By adopting the technical scheme, the Doppler frequency offset and the frequency offset change rate are calculated according to the ephemeris broadcasted to the user by the satellite and the terminal position, and the terminal estimates the Doppler frequency offset caused by the movement of the low-earth-orbit satellite according to the downlink frame number, the time slot number and the frequency point, so that the Doppler frequency offset and the frequency offset change rate can be effectively compensated during uplink transmission, the frequency offset caused by terminal movement and crystal oscillator is compensated, the complexity of load demodulation is reduced, and the reliability and stability of the satellite communication system are improved.

Description

technical field [0001] The invention belongs to the technical field of low-orbit satellite communication, and relates to a position- and ephemeris-based synchronization method and system for a low-orbit satellite communication system. Background technique [0002] Satellite communication network, as the hub of the combination of sea, land and air information platforms, makes the information platforms change from relatively scattered to integrated into an organic whole. The low-orbit satellite system has become an important supplement to the ground mobile communication system, making up for the disadvantages of the natural geographical obstacles and limited coverage of the ground mobile communication system. At the same time, low-orbit satellites have unique advantages such as low orbits, short transmission delays, flexible networking, and wide coverage, which can meet users' access needs at any time and anywhere. [0003] However, low-orbit satellites move fast and have l...

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Problems solved by technology

[0003] However, low-orbit satellites move fast and have low orbital altitudes. When low-orbit satellites communicate with ground mobile terminals, they will produce large frequency deviations, frequency deviation change rates, and even higher-order change rates, which increase the impact of satellite loads on Difficulty in acquiring and tracking terminal signals, which can seriously affect demodulation and reduce the quality of satellite communications

[0004] For the Doppler frequency deviation, the satellite load can use a high sampling rate to sample the received signal to estimate the frequency deviation, but the high sampling rate increases the power consumption, and the satellite load power is limited, which reduces the capacity and life of the system; and the frequency deviation The rate of change estimation algorithm is more complicated, which increases power consumption and delay, and also reduces system performance

[0005] At present, some foreign low-orbit satellite systems mainly use ephemeris for pre-compensation. However, due to the error of time synchronization of the entire network and various perturbations, there is still a large deviation after pre-compensation of ephemeris, which has a great impact on narrowband communication. In addition, the instability of the satellite-ground clock and the frequency deviation will also affect the demodulation performance

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