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Low-complexity IMP PN code capturing method based on sum-product algorithm

A code capture and algorithm technology, applied in the field of PN code capture, can solve problems such as lack of theoretical basis and high complexity

Inactive Publication Date: 2012-01-25
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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Problems solved by technology

This method of selecting the initial state needs to count the frequency of vector occurrences, which introduces high complexity and lacks corresponding theoretical basis

Method used

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  • Low-complexity IMP PN code capturing method based on sum-product algorithm
  • Low-complexity IMP PN code capturing method based on sum-product algorithm
  • Low-complexity IMP PN code capturing method based on sum-product algorithm

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Embodiment Construction

[0043] Take the polynomial as g(D)=1+D+D 15Take the PN code as an example, the length of received data M=512, and the number of iterations I=100 for sum-product decoding. Then r=15, according to figure 2 The given process can complete the capture of the PN code. The following is an example to analyze the capture performance and complexity of the method proposed in this paper.

[0044] In order to facilitate the comparison of the superiority of this method, the original IMP pseudo-code capture algorithm is first given the method of selecting the initial state and related verification. That is: count the frequency of each column element in A in this column, select the element with the highest frequency in all columns and record its frequency, and then select the element with the highest frequency as the initial state of the m sequence, and record its column Coordinates (representing the position of this initial state in the m-sequence). According to the initial state and ...

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Abstract

The invention provides an iterative massage passing (IMP) PN code capturing method based on a sum-product algorithm on the condition of a low signal to noise ratio. According to the method, an m sequence is modelized into a special linear block code; a sum-product decoding algorithm is executed on a Tanner graph to obtain maximum posteriori estimation of the m sequence; and an initial state is selected by introducing a posteriori log-likelihood ratio to generate a local m sequence; and at last, serial correlation verification is carried out with reception data and capturing is completed. The greatest advantage of the method provided in the invention is as follows: maximum posteriori estimation of an m sequence is directly decoded by utilization of a sum-product decoding algorithm and a posteriori log-likelihood ratio is introduced to select an initial state. Besides, the method has advantages of rapid capturing speed, low complexity and excellent performance under a low signal to noise ratio. According to the invention, a fundamental principle on IMP PN code capturing is mainly introduced and then an IMP PN code capturing method based on a sum-product algorithm is provided; and an analysis on a selection process of an initial state of an m sequence is emphasized and a detailed flow chart is provided; at last, a capturing performance and a complexity of the method are analyzed though examples.

Description

technical field [0001] The present invention relates to the key technology in the spread spectrum communication system, that is, PN code acquisition. Especially under the condition of low signal-to-noise ratio, the design of fast acquisition scheme of PN code with low complexity. Background technique [0002] In many spread-spectrum communication systems, in order to meet the requirements of anti-interference and confidentiality, long PN code sequences are usually used as spread-spectrum codes. Therefore, the acquisition of long PN codes under low SNR is a key issue in system implementation. The traditional PN code capture algorithm includes serial capture and parallel capture. Among them, the complexity of serial capture is low, but the capture time is long; the capture time of parallel capture is short, but the complexity is high. In order to solve this problem, the academic community proposes a pseudo-code capture algorithm based on Iterative Mass Passing (IMP) (herein...

Claims

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Application Information

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IPC IPC(8): H04B1/7075
Inventor 唐发建史治平晏辉张忠培
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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