OFDM (Orthogonal Frequency Division Multiplexing) frequency synchronizing method based on Zadoff-Chu sequence

Abstract

The invention discloses an OFDM (Orthogonal Frequency Division Multiplexing) frequency synchronizing method based on a Zadoff-Chu sequence, belongs to the technical field of wireless communication, and aims at overcoming the shortcoming that the precision of the traditional frequency synchronizing algorithm is limited by the timed synchronizing accuracy and complicated to reach. The method is characterized in that the fractional frequency offset can be estimated through two repetitive sequences, the integer frequency offset can be estimated according to the influence of the frequency deviation on the self-correlated influence of the Zadoff-Chu sequence, wherein the estimation can cover the whole OFDM bandwidth, all operations are finished at the time domain, and any time-frequency transform is saved. Compared with the traditional frequency offset estimation algorithm, the method has the advantages that the operation complexity is small, and the robustness is high; the verification shows that the method has high performances under a high-speed moving and multi-path environment.

Description

technical field [0001] The invention relates to OFDM system frequency synchronization technology, in particular to a Zadoff-Chu sequence-based OFDM frequency synchronization method, which belongs to the field of communication technology. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) system can provide higher data transmission rate and spectrum utilization rate, and has strong anti-multipath fading ability. It is the core technology of the new generation of broadband mobile communication system. Carrier synchronization is the key technology of OFDM. In general, the frequency offset error is less than 4% of the subcarrier spacing in Gaussian channels, and less than 2% of the subcarrier spacing in multipath channel environments. Therefore, the research of frequency offset estimation algorithm has important practical significance. [0003] The existing OFDM frequency synchronization methods include: Literature [1] proposed a S&C algorithm, whic...

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Problems solved by technology

[0003] The existing OFDM frequency synchronization methods include: Literature [1] proposed a S&C algorithm, which can estimate integer and fractional frequency offsets, but when the number of subcarriers is less than the number of system IFFT points, the carrier synchronization performance will decline rapidly; Literature [1] [2] proposed the Best Linear Unbiased Estimation (BLUE) algorithm using L repeated sequences, the estimation range can reach L / 2 subcarrier spacing, but in order to ensure the performance of the algorithm, the length of each repeated sequence It must be greater than the maximum channel delay extension, which reduces the transmission efficiency. Under the same conditions, its estimation is more accurate than the S&C algorithm, but the complexity is greatly increased; although the literature [3] obtained the closed expression of the carrier frequency offset, the exponential factor in the algorithm The setting of p is limited by the estimation accuracy, integer times frequency offset estimation range and system tolerable peak-to-average ratio (Peak-Average Power Ratio, PAPR). The Constant Envelope Zero Auto-Correlation (CAZAC) sequence performs frequency synchronization, and the algorithm has high estimation accuracy, but its feedback time from frequency offset estimation to frequency offset compensation is long, which is not suitable for burst communication; literature [5 ] proposed a Ren algorithm, which has a large range of frequency offset estimation by weighting the CAZAC sequence for frequency synchronization, but the algorithm has poor performance in independent Rayleigh fading channels

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