Carrier synchronization method and system in helicopter satellite communication

Abstract

The invention relates to a carrier synchronization method and system in helicopter satellite communication. The method comprises the steps of 101, evenly inserting reference symbols in a data physical layer waveform sent by a sending end; and step 102, carrying out primary carrier synchronization by employing a phase-lock loop, and on the basis of discretized phase information, repeatedly iterating messages between a detector and a decoder through a message passing algorithm based on a factor graph, thereby restoring a carrier phase and realizing final carrier synchronization. The invention provides the carrier synchronization method based on the phase-lock loop and the message passing algorithm. According to the method, the carrier synchronization is carried out by employing the phase-lock loop, the phase is fuzzified and discretized, and the messages are repeatedly iterated between the detector and the decoder, thereby restoring the carrier phase. The simulation result indicates that according to the method provided by the invention, the carrier synchronization problem under the periodic interruption channel in the helicopter satellite communication can be effectively solved, and the high bit error rate BER performance can be acquired through relatively few overheads of the reference symbols.

Description

technical field [0001] The invention belongs to the field of satellite communication, in particular to a carrier synchronization method based on a phase-locked loop and a message transfer algorithm in helicopter satellite communication. Background technique [0002] Satellite communication has the advantages of wide coverage, wide frequency band, and strong adaptability. Helicopters are widely used in search and rescue, command and dispatch and other fields due to their flexible maneuverability, ultra-low altitude, and hoverability. Therefore, the installation of a satellite communication system on a helicopter is an effective guarantee for exerting the application capability of the helicopter. [0003] Because in the field of wireless communication, the synchronization problem of the signal should be considered first. Due to the consideration of helicopter aerodynamic layout and other factors in the helicopter satellite communication system, the installation position of t...

AI Technical Summary

Problems solved by technology

The occlusion of the rotor will cause periodic fading of the signal, and even the signal is completely occluded

In such an occluded channel, when only the traditional phase-locked loop is used for carrier synchronization, cycle skipping or "lost-lock-recapture" phenomenon will occur frequently, resulting in failure to demodulate

Since the occlusion position of the rotor to the signal may occur at any position in the physical frame, the method of inserting reference symbols at a fixed position in the physical frame to correct the phase ambiguity adopted in the prior art will fail due to the occlusion of the reference symbols and cannot correct the phase ambiguity , so that it cannot be correctly demodulated

[0004] In the prior art, in order to deal with the difficulty of carrier synchronization caused by rotor occlusion, some technical solutions use differential encoding of symbols to solve the phase ambiguity, but it will bring about 3dB demodulation threshold performance loss

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