Downlink time frequency synchronization method jointly using synchronization sequence and OFDM cyclic prefixes

Abstract

The invention discloses a downlink time frequency synchronization method jointly using a synchronization sequence and OFDM cyclic prefixes. The method achieves downlink time frequency synchronizationof a communication system by jointly using the synchronization sequence and multiple OFDM cyclic prefixes and can solve the problem that in a communication scene, due to factors such as large frequency offset and low signal to noise ratio, time frequency synchronization of an OFDM system is difficult. According to the method, one-dimensional time offset searching is conducted according to a time offset likelihood function, and after a time offset estimation value is obtained, a frequency offset estimation value is obtained by conducting one-dimensional frequency offset searching on a frequencyoffset likelihood function or directly using a low-complexity frequency offset estimation method. In the method, in a timing synchronization stage, time offset likelihood function values of multiplesynchronization cycles can be selected to be subjected to incoherent combination to improve the estimation accuracy degree. Compared with a synchronization method that two-dimensional time offset searching is directly conducted according to the time frequency joint likelihood function to obtain time offset and frequency offset, the method has the advantage that the searching complexity is greatlyreduced. The method is not only suitable for an initial synchronization stage of a communication system, but also suitable for a tracking synchronization stage of the communication system.

Description

technical field [0001] The invention relates to a downlink time-frequency synchronization method using synchronous sequence and OFDM cyclic prefix jointly. Background technique [0002] In recent years, research on the fifth-generation mobile communication technology (5G) is in full swing. In 5G research, the integration of terrestrial cellular mobile communication systems and other communication networks has become a research hotspot. Typical examples include terrestrial cellular mobile communication systems and Convergence of satellite mobile communication systems. The downlink of the terrestrial cellular mobile communication system adopts Orthogonal Frequency Division Multiplexing (OFDM technology), and OFDM technology is very sensitive to frequency offset, and a small frequency offset will affect the orthogonality between OFDM subcarriers , thus affecting the performance of the communication system. For communication scenarios such as low-orbit satellite mobile communi...

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Problems solved by technology

[0004] Purpose of the invention: The purpose of the present invention is to provide a downlink time-frequency synchronization method that jointly uses a synchronization sequence and an OFDM cyclic prefix, which can solve OFDM system problems caused by factors such as large frequency offset and low signal-to-noise ratio in some communication scenarios. Difficulty in time-frequency synchronization

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