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Long code DSSS signal blind dispreading method based on semi-definite programming

A technique of semi-definite programming and blind despreading, which is applied in the field of blind despreading and can solve the problem that the symbol cannot be determined.

Inactive Publication Date: 2013-11-27
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Summary
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

The defect of this kind of method is that: the inherent sign ambiguity of the eigendecomposition method makes the symbols of each segment undetermined, and the spread spectrum waveform estimation obtained by splicing these segments together may be different from the Real spread spectrum waveforms are different

Method used

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  • Long code DSSS signal blind dispreading method based on semi-definite programming
  • Long code DSSS signal blind dispreading method based on semi-definite programming
  • Long code DSSS signal blind dispreading method based on semi-definite programming

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Embodiment 1

[0053] The purpose of this embodiment is to simulate the performance of the spread spectrum waveform estimation and the bit error rate of the information code sequence as the SNR (Signal Noise Rate, signal-to-noise ratio) changes. Taking the long-code DSSS signal of L=63, G=30 as an example, y(n) is a discrete signal sample polluted by Gaussian white noise. Fixed signal sample length N=40×L=2520, Signal-to-noise ratio SNR changes from-10dB to-2dB, uses the present invention to estimate spread-spectrum waveform and solves information code sequence, and the method for obtaining information code sequence by despreading in this embodiment adopts where sign( ) represents a sign function. Perform 500 Monte Carlo experiments to obtain the NMSE (Normalized mean square error, normalized mean square error) of spread spectrum waveform estimation, which is obtained from the normalized mean square error of 500 single experiments obtained by calculating the average) and the bit error r...

Embodiment 2

[0057] The purpose of this embodiment is to simulate the estimation performance of the information code sequence and spread spectrum waveform as the sample length changes. Also take the long code DSSS signal of L=63, G=30 as an example, y(n) is a discrete signal sample polluted by Gaussian white noise. The fixed signal-to-noise ratio SNR is -9dB, the signal sample length is N=M×L, and the number of spreading cycles M is taken from 20 to 100. According to the steps in Example 1, the spread spectrum waveform is estimated and despread, and 500 Monte Carlo experiments are carried out to obtain the NMSE estimated by the spread spectrum waveform and the bit error rate variation curve of the information code sequence, and the error rate curve of the cooperative despread information code sequence The bit rate change curves are compared.

[0058] Figure 4 It is a curve diagram of the bit error rate of the information code sequence obtained by despreading the long code DSSS signal wi...

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Abstract

The invention discloses a long code DSSS signal blind dispreading method based on semi-definite programming. A long code DSSS signal spread-spectrum waveform maximum likelihood estimation problem with exponential growth calculation complexity is converted to a semi-definite programming problem with polynomial calculation complexity, the semi-definite programming problem is then solved, the approximate solution of the spread-spectrum waveform maximum likelihood estimation problem is acquired, the spread-spectrum waveform estimation is acquired, and accordingly long code DSSS signal blind dispreading is finally finished. Regarding to long code DSSS signals modulated by BPSK under the multi-path channel condition, the long code DSSS signal blind dispreading method greatly reduces calculation complexity of spread-spectrum waveform maximum likelihood estimation through the adoption of semi-definite programming, can still have good performance even under low signal to noise ratio or short data conditions, and is particularly suitable for blind estimation of long code DSSS signals in the non-cooperative communication field.

Description

technical field [0001] The invention belongs to the technical field of blind despreading, and more specifically relates to a method for blind despreading of long code DSSS signals based on semi-definite programming. Background technique [0002] Direct Sequence Spread Spectrum (DSSS, Direct Sequence Spread Spectrum) communication technology is a common technology in the field of modern communication, which can improve the anti-jamming and anti-interception capabilities of wireless communication. DSSS communication uses a high-rate spread spectrum sequence to multiply the information code sequence at the sending end, so that the spectrum of the original signal is broadened, and the signal energy is dispersed into a wider frequency band, thereby greatly reducing the spectral density of the signal; at the receiving end After despreading with the same spread spectrum sequence, the useful signal spectrum is recovered, and the noise and narrowband interference signals are easily s...

Claims

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Application Information

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IPC IPC(8): H04L25/03H04B1/707H04B1/711
Inventor 李梦冰张花国廖红舒魏平
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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