Carrier synchronization method based on rotation average period map 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 field of wireless communication technology, and relates to a method for acquiring synchronization information by using pilot frequency and demodulation soft information in digital communication, and can be used in satellite and high-speed mobile short-frame burst communication systems. Background technique [0003] Short-frame burst communication systems are widely used in high-speed mobile communications, satellite communications, military communications and other fields. Due to the Doppler effect produced by the relative movement of the two communication parties, the received signal produces a large frequency deviation. Under the conditions of low signal-to-noise ratio and Doppler frequency offset, it is of great significance to use pilot sequences with small overhead to achieve effective and reliable carrier synchronization in burst communication mode. In order to ensure communication quality, short-frame burst commun...

AI Technical Summary

Problems solved by technology

DA algorithms such as Kay, Fitz, FFT (Fast Fourier Transform) 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] Calvo P M, Sevillano J F, Velez I and Irizar A proposed R&A 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) Frequency offset estimation algorithm, which divides the pilot into several blocks, rotates the corresponding frequency offset for each block, and then makes an average periodogram. However, when the pilot overhead is constant, the segmentation of the pilot leads to a decrease in the spectral resolution, and the estimation accuracy is not high. , can never approach MCRB (Modified Cramer-Rao Bound)

[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 (Maximum Likelihood) pilot combined with SOQPSK (Shaped-Offset Quadrature Phase-Shift Keying) to demodulate soft information. Although this method can achieve ± 50% of the symbol rate frequency offset estimation range, and can obtain close to the ideal bit error performance, but the complexity of this method is high, the fine estimation part uses a one-step search, and the amount of calculation is large, so it is not suitable for the application of the actual system

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