Carrier Synchronization Method Based on Rotating Average Periodogram and Demodulation Soft Information

Abstract

The invention discloses a carrier synchronization method based on a rotation average period map and demodulation soft information and mainly aims at solving problems in the prior art, such as low carrier rough estimate accuracy, large pilot frequency expense and large carrier fine synchronization search operation amount. The method is realized by the following steps of carrying out demultiplexing on digitally sampled base band complex signals to obtain received pilot frequency signals; utilizing the pilot frequency signals to obtain the rough estimate values of a carrier frequency offset and a carrier phase offset by a carrier rough synchronization method; utilizing the carrier rough estimate values to correct the received signals; and respectively carrying out one-dimensional progressive search on the frequency offset and the phase offset by the corrected signals to obtain accurate frequency offset and phase offset values and realize carrier fine synchronization. With carrier rough synchronization disclosed by the invention, not only is the frequency spectrum resolution rate increased, but also higher estimate accuracy can be obtained at a low cost of the pilot frequency. Through carrier fine synchronization disclosed by the invention, search points are effectively reduced, the search efficiency is improved, and the operation amount is reduced. The method can be used for satellites and short-frame burst communication in high-speed movement.

Description

[0001] background field [0002] The invention belongs to the technical field of wireless communication, and relates to a method for obtaining synchronous information by using pilot frequency and demodulation soft information in digital communication, which can be used in satellite and short-frame burst communication systems in high-speed movement. Background technique [0003] The short-frame burst communication system is widely used in high-speed mobile communication, satellite communication, military communication and other fields. Due to the Doppler effect caused by the relative movement of the communication parties, the received signal has a large frequency deviation. Under the condition of low signal-to-noise ratio and large Doppler frequency deviation, it is of great significance to use the pilot sequence with small overhead to achieve effective and reliable carrier synchronization in burst communication mode. In order to ensure the quality of communication, it is requi...

AI Technical Summary

Problems solved by technology

DA algorithms such as Kay, Fitz, FFT (FastFourierTransform) and other algorithms cannot take into account the working signal-to-noise ratio threshold and estimation range, and need to increase the estimation accuracy by increasing the number of pilot symbols, which is not suitable for short burst systems

NDA generally uses demodulated soft information or decoded soft information to blindly search parameters in a large range, which is highly complex, especially at low signal-to-noise ratios. Only when the data length is long can the reliability of soft information be guaranteed, while increasing information data The length will further increase the complexity of the algorithm, which is not suitable for application in actual systems

[0005] CalvoPM, SevillanoJF, VelezI and IrizarA proposed an R&A frequency offset estimation algorithm in "Enhanced Implementation of Blind Carrier Frequency Estimators for QPSK Satellite Receivers at Low SNR" (IEEE Transaction on Consumer Electronics, 2005, 51(7): 442-448). This algorithm divides the pilot frequency into several blocks, and each block rotates the corresponding frequency , and then make an average periodogram, but when the pilot overhead is constant, the pilot segmentation leads to a decrease in spectral resolution, and the estimation accuracy is not high, and it is still unable to approach MCRB (Modified Cramer-RaoBound)

[0006] The above traditional carrier synchronization algorithms cannot take into account the pilot overhead and estimation accuracy at the same time, so a joint pilot and soft information estimation algorithm is needed

Yan Hui, Tang Fajian, Zhang Zhongpei etc. in "A Coding and Pilot Combined Assisted Carrier Synchronization Algorithm Based on Low Bit Rate LDPC Code" (Journal of Electronics and Information Technology, 2011, 33(2): 470-474) adopted the combination of pilot and pilot The joint estimation algorithm of LDPC decoding soft information is to estimate the frequency offset by using the pilot and soft information. Although this method can take into account the pilot overhead and estimation accuracy, it cannot correct the frequency deviation of the symbol rate in the range of ±50%. Offset, not suitable for large frequency offset carrier synchronization system

[0007] In order to meet the requirements of large frequency offset carrier synchronization system, Sun Jinhua, Zhu Jili and others filed a patent application "SOQPSK carrier synchronization method based on joint assistance of pilot frequency and soft information" (application number 20120073562.X, application date: March 20, 2012 ) discloses a carrier synchronization method based on ML (MaximumLikelihood) pilot combined with SOQPSK (Shaped-OffsetQuadraturePhase-ShiftKeying) demodulation of soft information. Although this method can achieve ±50% symbol The frequency offset estimation range of the rate can be obtained, and the bit error performance close to the ideal can be obtained, but the complexity of the method is high, and the fine estimation part adopts one-step search, and the calculation amount is large, so it is not suitable for the application of the actual system

Images