Sampling frequency difference correction method and device of orthogonal frequency division multiplexing (OFDM) system

Abstract

Disclosed are a method and an apparatus for correcting sample frequency difference in Orthogonal Frequency Division Multiplexing (OFDM) system. The correction method includes: firstly, performing interpolation filtering or decimation filtering to the over-sampled data of the receiving terminal by a Farrow structure filter; then, performing down sample to the over-sampled data which is performed the sample frequency difference correction, to obtain the baseband OFDM time symbols; secondly, eliminating the guard interval for the OFDM time symbols, then performing Fourier transform, to obtain the OFDM frequency symbols; thirdly, extracting the continuous pilot information from the OFDM frequency symbols and estimating the sample frequency difference to obtain the sample relative frequency difference estimate value, lastly, performing Proportional Integration to it to obtain the integral value. Correspondingly, the correction apparatus includes a Farrow structure filter, a down-sample unit, a Fast Fourier Transform (FFT) unit, a sample frequency difference estimation unit, a proportional integration unit, etc. The method and apparatus enable to estimate and correct the sample frequency difference effectively and instantly, and have the advantages of high accuracy, good stability, etc.

Description

technical field [0001] The present invention relates to the communication field, in particular to a sampling frequency difference correction method and device for an OFDM system. Background technique [0002] OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) system is a multi-carrier communication system, which uses multiple subcarriers within the channel bandwidth to send data, and is resistant to multipath delay spread and frequency selective fading It has the characteristics of high acceptance, high effectiveness of spectrum use, and good anti-interference performance. It can be used for data with a large transmission rate and has broad application prospects. For example, it is currently used in the CMMB (China Mobile Multimedia Broadcasting, China Mobile Multimedia Broadcasting) system. Among them, OFDM technology is used as the modulation transmission technology. [0003] In an OFDM system, factors such as symbol synchronizat...

AI Technical Summary

Problems solved by technology

However, since the subcarrier spacing of OFDM symbols is relatively small, the system is very sensitive to frequency deviation. The existence of sampling frequency difference will cause the window position of OFDM symbols at the receiving end to drift, resulting in phase rotation of each subcarrier of OFDM symbols, resulting in ICI The generation and increase of , so the frequency difference estimation and correction is the primary task of the receiver to synchronize OFDM symbols

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