Downlink Time-Frequency Synchronization Method Using Synchronization Sequence and OFDM Cyclic Prefix

Abstract

The invention discloses a downlink time-frequency synchronization method using synchronous sequence and OFDM cyclic prefix jointly. The method jointly uses the synchronization sequence and the multi-segment OFDM cyclic prefix to realize the downlink time-frequency synchronization of the communication system, which can solve the difficult problem of OFDM system time-frequency synchronization caused by factors such as large frequency offset and low signal-to-noise ratio in the communication scene. In this method, the one-dimensional time offset search is firstly performed according to the time offset likelihood function, and the frequency offset is obtained by performing a one-dimensional frequency offset search on the frequency offset likelihood function or directly using a low-complexity frequency offset estimation method after obtaining the estimated value of the time offset estimated value. In this method, the timing synchronization stage can also choose to non-coherently combine the time offset likelihood function values ​​of multiple synchronization periods to improve the estimation accuracy. Compared with the synchronization method of directly performing time-frequency two-dimensional search according to the time-frequency joint likelihood function to obtain time offset and frequency offset, this method greatly reduces the search complexity. At the same time, the method is not only applicable to the initial synchronization stage of the communication system, but also applicable to the 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 are 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 communicati...

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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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