Return-to-zero Turbo code length and frame synchronization recognition method based on differential likelihood difference

Abstract

The invention discloses a return-to-zero Turbo code length and frame synchronization recognition method based on differential likelihood difference. The method comprises the steps: firstly performingdifferential likelihood difference preprocessing between adjacent code elements of an intercepted soft decision code element sequence; constructing analysis matrix to achieve the code length recognition through the characteristic that the differential likelihood difference of two code elements of a return-to-zero Turbo code frame synchronization header is a positive value '+', and completing the position detection of the differential likelihood difference '+' based on a minimum error decision probability criterion; and completing the frame synchronization by traversing the '+' position and theframe synchronization feature comparison. Compared with a conventional Gaussian elimination method, the method has strong adaptability to a low signal-to-noise ratio and has good real-time parameteridentification performances. The invention can be directly applied to a communication reconnaissance system, and can also be applied to a corresponding software radio system.

Description

technical field [0001] The invention belongs to the non-cooperative communication signal processing technology in the field of signal processing, and specifically refers to a parallel return-to-zero Turbo code code length and a frame synchronization position blind identification method. Background technique [0002] In the field of channel coding identification, to identify the parameters of the zero-returned turbo code, the first thing to solve is the code length of the zero-returned turbo code and the identification of the synchronization position. Some Turbo code component encoders and interleaver identification algorithms will not be applicable, so it is of great significance to complete the identification of the zero-returning Turbo code code length and synchronization parameters under low SNR. [0003] At present, the algorithms for the identification of return-to-zero turbo codes are mainly focused on the identification of component encoders and interleavers. These al...

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Problems solved by technology

[0003] At present, the algorithms for the identification of return-to-zero turbo codes are mainly focused on the identification of component encoders and interleavers. These algorithms are based on the precondition of known code length and frame synchronization, but only for the identification of parameters such as code length and frame synchronization of turbo codes. There are few algorithms, and most of the papers are limited to constructing analysis matrices. The Gaussian elimination method in the binary domain is used to solve the rank of the analysis matrix to complete the code length and frame synchronization recognition. However, these algorithms are only suitable for conditions with few bit errors. When the bit error rate increases or the actual code length is longer, the recognition reliability and timeliness will deteriorate sharply; in order to overcome the shortcomings of the direct Gaussian elimination method, Zrelli et al. In the article "Blind identification of code word length for non-binary error-correcting codes in noisy transmission", a judgment algorithm based on the linear correlation column of the analysis matrix under the minimum judgment error probability under the condition of code error is proposed. This algorithm uses Gaussian elimination The distribution probability of 0 and 1 code elements in the matrix linear correlation column and the independent column is different. By setting the judgment threshold, the identification of the elimination column is completed, so as to obtain the matrix rank under the error condition. Although this method improves the Gaussian elimination The disadvantage of the meta-method is insufficient fault tolerance, but it increases the time consumption of solving the decision threshold. At the same time, with the increase of code length and error code, the recognition performance of the algorithm will drop sharply; similarly, Zhang Min et al. Starting from the article "Blind Recognition Method of Return-to-Zero Turbo Code" in the 6th issue of 2016 in the magazine "System Engineering and Electronic Technology", an analysis matrix column-to-column correlation detection algorithm based on a small-area sliding window is proposed. Although there is a certain improvement in fault tolerance, it is necessary to constantly change the elements in the sliding window and calculate the rank of the sliding window matrix. It is essentially an improvement based on the Gaussian elimination method, and the real-time performance is not good.

For the identification of zero-returning Turbo code length and frame synchronization parameters, the existing methods are all improved based on Gaussian elimination method and use the hard-judgment 0,1 sequence in the channel as the identification object, which is difficult to adapt to the harsh channel environment

[0004] It can be seen from this that the existing methods cannot meet the performance requirements of zero-returning Turbo code length and frame synchronization parameter identification under actual harsh channels, and it is still necessary to study the code length and frame synchronization parameters of zero-returning Turbo codes under low SNR Fast Blind Estimation Method

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