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Frequency offset estimation method for short burst modulation signal under low signal-to-noise ratio

A technology for frequency offset estimation and signal modulation, which is applied to modulated carrier systems, carrier modulation, phase modulated carrier systems, etc. It can solve the problems of large frequency offset estimation variance, small frequency offset value estimation variance, and low estimation accuracy of CQPSK modulated signals.

Pending Publication Date: 2021-11-05
重庆两江卫星移动通信有限公司
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Problems solved by technology

[0005] The purpose of the present invention is to provide a method for estimating the frequency offset of a short burst modulation signal under a low signal-to-noise ratio, in order to solve the large variance of the frequency offset estimation of the CQPSK modulated signal in the prior art under the condition of a low signal-to-noise ratio As well as the problem of low estimation accuracy, under the premise of low signal-to-noise ratio, for CQPSK modulated signals, the estimated variance of the obtained frequency offset value is small and the estimation accuracy is high

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  • Frequency offset estimation method for short burst modulation signal under low signal-to-noise ratio
  • Frequency offset estimation method for short burst modulation signal under low signal-to-noise ratio
  • Frequency offset estimation method for short burst modulation signal under low signal-to-noise ratio

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Embodiment 1

[0046] According to an embodiment of the present invention, a method for estimating a frequency offset of a short burst modulation signal under low SNR is provided, and the following will introduce a π / 4-CQPSK modulation signal as an example. In this embodiment, considering the phase characteristics of the π / 4-CQPSK modulated signal, two correlation operations are performed on the pilot frequency, and the peak value of the correlation peak is the starting position of the signal, so as to obtain a complete signal. Derotate the signal, calculate its fourth power, perform fast Fourier transform on the result of the fourth power operation, and obtain the estimated value of frequency offset, and measure the estimation of the frequency offset algorithm by calculating the mean square error of the normalized frequency offset precision. Specifically, see figure 1 As shown, this embodiment includes the following steps:

[0047] Step S110, obtaining the position of the frame header accor...

Embodiment 2

[0070] In order to further verify the beneficial effects of the present invention, the second embodiment uses π / 4-CQPSK modulation signals to carry out simulation experiments on the basis of the first embodiment, from burst signal generation to shaping filtering to channel and then to matched filtering. The frequency offset estimation algorithm proposed by the present invention is used to obtain a frequency offset estimation result, and the result is analyzed.

[0071] Burst signal generation process: Randomly generate bit data with a length of 150 bits, using π / 4-CQPSK modulation, that is, first perform QPSK modulation, and then rotate. The rotation angle is related to the serial number in the signal, which is a multiple of π / 4. The resulting constellation diagram is figure 2 As shown, there are 8 phases in total, and each phase jump is a maximum of 3π / 4, which is an improvement on QPSK.

[0072] Such as image 3 As shown, the pilot frequency is modulated by BPSK, and the ...

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Abstract

The invention discloses a frequency offset estimation method for a short burst modulation signal under a low signal-to-noise ratio, relates to the field of wireless communication, and solves the estimation precision problem of a modulation signal under the low signal-to-noise ratio. The technical scheme of the method is characterized by comprising the following steps of: step 1, collecting a frame header position according to a local sequence and a received signal; step 2, intercepting a signal length according to the frame header position, and obtaining a signal symbol stream before frequency offset compensation according to the signal length; step 3, de-rotating the signal symbol stream to obtain a symbol stream before rotation; step 4, performing quartic operation on the symbol stream to obtain a quartic spectrum of the symbol stream; step 5, carrying out L-point fast Fourier transform on the quartic spectrum to obtain a frequency offset estimation value; on the premise of low signal-to-noise ratio and short burst, the estimation variance of the obtained frequency offset value is small, and the estimation precision is high.

Description

technical field [0001] The invention relates to the field of wireless communication, more specifically, it relates to a method for estimating the frequency offset of a short burst modulation signal under low signal-to-noise ratio. Background technique [0002] Synchronization is an important factor affecting the performance of wireless communication. Only when the frequency and phase of the local carrier are synchronized with the received signal, can the correct coherent demodulation of the signal be realized. In a burst communication system, the signal is bursty and short-lived, and synchronization needs to be realized quickly after the burst signal is successfully captured. The shorter the burst signal length, the more important the fast synchronization method becomes. π / 4-CQPSK, which is often used in burst communication, is a linear digital modulation technology developed on the basis of QPSK. It has the characteristics of small peak-to-average ratio, strong anti-multip...

Claims

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Application Information

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IPC IPC(8): H04L27/00H04L27/18
CPCH04L27/0014H04L27/183H04L2027/0026Y02D30/70
Inventor 郑斌李腊程静静高波
Owner 重庆两江卫星移动通信有限公司
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