A Non-data-aided Frequency Offset Estimation Method Suitable for Amplitude Phase Shift Keying

Abstract

The invention discloses a non-data auxiliary frequency offset estimation method applicable to amplitude phase shift keying and relates to the technology of digital communication system receiving end processing. Frequency offset estimation and compensation are carried out on APSK signals by a receiving end. According to the method, the precision of carrying out the frequency offset estimation and compensation on the APSK signals by the receiving end is improved. The method comprises the steps of processing receiving signals by a rooted raised cosine filter and carrying out synchronization processing on the signals, wherein the synchronization processing comprises timing synchronization, frequency synchronization and phase synchronization processing. According to the method, for the frequency synchronization processing, frequency offset coarse estimation is carried out through utilization of an M&M algorithm according to a frequency range of the APSK signals, a frequency offset range is reduced, n times of frequency offset fine estimation is carried out through selective utilization of a Fitz algorithm according to a precision demand, and finally a precise frequency offset value is obtained. After the synchronization processing is carried out, judgment, constellation graph demapping and output are carried out. The invention provides an effective solution scheme for the APSK signal frequency offset estimation and compensation.

Description

technical field [0001] The invention relates to the technical field of digital communication, in particular to a non-data-aided frequency offset estimation method suitable for APSK signals at a receiver. Background technique [0002] In the satellite mobile communication system, the local carrier is generally generated by its own oscillator when the receiving end performs down-conversion, and then multiplied by the received signal. However, because the oscillator at the receiving end has limited precision and is affected by various factors in the actual system, it is impossible to achieve complete synchronization with the carrier frequency at the sending end, resulting in a certain frequency deviation. In the communication process, the reason why the actual frequency of the signal received by the receiver deviates from the frequency of the signal sent by the transmitter is also the relative motion between the receiver and the transmitter, that is, the Doppler effect. Theref...

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Problems solved by technology

[0004] Usually, in the synchronization process of the APSK signal at the receiving end, if the carrier frequency offset is relatively large, it is difficult to obtain a high-precision frequency offset estimation value when the receiving end simply uses a frequency offset estimation algorithm when designing carrier synchronization.

However, the characteristics of Fitz, L&R and M&M algorithms are obtained through simulation verification and comparison. Among them, the advantages of Fitz and L&R algorithms are that the frequency offset estimation accuracy is high, and the frequency offset estimation variance approaches CRB (Cramer-raoBound, Kramero boundary), but the approximate range of the normalized frequency offset of the L&R frequency offset estimation algorithm is just twice the approximate range of the normalized frequency offset estimation of the Fitz frequency offset estimation algorithm, so the normalization of the Fitz frequency offset estimation algorithm The frequency offset estimation range is the smallest

However, these two algorithms have disadvantages: compared with the M&M algorithm, the frequency offset estimation range is small, and it is easily affected by the observation data. The larger the observation data, the smaller the estimation range. The M&M algorithm has a larger estimation range and can estimate large frequency offsets.

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