Synchronous processing method based on CMMB signals
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A synchronization processing and signal technology, applied in synchronization devices, baseband system components, digital transmission systems, etc., can solve problems such as reduced effect and poor estimation effect, and achieve the effect of improving synchronization accuracy and improving synchronization performance.
Inactive Publication Date: 2013-01-16
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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However, the estimation of fractional frequency offset is poor in the case o
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[0047] The structure of the CMMB synchronization signal of the present invention is as follows figure 2 As shown, it is composed of a first training sequence and a second training sequence. The first training sequence includes a constant envelope zero autocorrelation CAZAC sequence of length N and a cyclic prefix CP of length GI, and the second training sequence includes A PN sequence of length N and a cyclic prefix CP of length GI. The parts with the same gray scale represent the same value.
[0048] The embodiment process is attached image 3 As shown, the method of the specific embodiment includes the following steps:
[0049] 1. Use the properties of the CAZAC sequence part in the first training sequence to complete rough timing estimation and rough estimation of fractional frequency difference:
[0050] Suppose the received signal sequence of a frame is discretely expressed as r(n), n=1,2...,N.
[0051] Use the autocorrelation of the same repeated part of the CAZAC sequence to ...
specific Embodiment
[0113] The method of the specific embodiment includes the following steps:
[0114] a) From the received signal, use the properties of the CAZAC sequence part in the first training sequence to complete rough timing estimation and rough estimation of fractional frequency difference. The symbol rough timing offset estimation expression is:
[0115] θ opt =mean(U)
[0116] Among them: mean(U) represents the average of all values in U, and U is the peak plateau range.
[0117] U=(d |abs(M(d))≥0.95C 1 ,d∈{1,2…,P}}
[0118] M(d)=|P(d)| 2 / (R(d)) 2 C 1 = arg max d ( M ( d ) )
[0119] P ( d ) = X k = 0 511 r ( d + k ) r * ( d + k + 512 ) R ( d ) = 1 2 X k = 0 1023 | r ( d + k ) | 2
[0120] Rough estimation of fractional frequency deviation Use symbol timing position θ opt P(θ opt ) Is obtained as shown in the following formula. ...
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Abstract
The invention provides a synchronous processing method based on new CMMB (China Mobile Multimedia Broadcasting) synchronous signals. The CMMB synchronous signals comprise first training sequences and second training sequences; the first training sequences comprise CAZAC (Constant Amplitude Zero Auto Correlation) sequences, and the second training sequences comprise PN (Pseudo-Noise) sequences; in the synchronous processing method, the CAZAC sequences are utilized to achieve coarse symbol timing offset estimation and decimal frequency offset coarse estimation; the PN sequences are utilized to achieve the estimation of strongest path time delay in multipath, and the multipath is taken as coarse symbol timing positioning; the CAZAC sequences and the PN sequences are utilized to achieve the integer frequency offset estimation; the fast Fourier transform (FFT) is performed on the PN sequences to achieve the channel response estimation so as to estimate a first path time delay and achieve the fine symbol timing position estimation; and a maximum likelihood (ML) criterion is utilized to process the PN sequences in the second training sequences to obtain the decimal frequency offset fine estimation. The synchronous processing method can effectively improve the synchronous accuracy and can achieve better synchronization performance in the mobile communication environment with low signal-to-noise ratio.
Description
technical field [0001] The invention relates to wireless communication synchronization technology, in particular to an Orthogonal Frequency Division Multiplexing OFDM communication system in wireless communication. technical background [0002] Orthogonal frequency division multiplexing OFDM is a high-speed transmission technology, which is characterized by parallel transmission of a single high-speed data stream on a set of low-speed orthogonal sub-carriers, which has high spectrum utilization, anti-frequency selective fading, and is suitable for high-speed High-speed data transmission and simple implementation. Compared with the single-carrier system, it is very sensitive to time and frequency offset, so in order to eliminate inter-symbol interference and inter-carrier interference, accurate time synchronization and precise frequency synchronization are the prerequisites for OFDM system to work normally. The frequency offset at the receiving end is normalized according to...
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