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Reconstruction of Feedback Polynomial of Synchronous Scrambler Based on Triple Correlation Characteristics of MSequences
Shu nan HAN Min ZHANG Xin hao LI
Publication
IEICE TRANSACTIONS on Communications
Vol.E101B
No.7
pp.17231732 Publication Date: 2018/07/01 Publicized: 2018/01/16 Online ISSN: 17451345
DOI: 10.1587/transcom.2017EBP3173 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: synchronous scrambler, convolutional code, msequence, triple correlation characteristic, dual word,
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Summary:
For the reconstruction of the feedback polynomial of a synchronous scrambler placed after a convolutional encoder, the existing algorithms require the prior knowledge of a dual word of the convolutional code. To address the case of a dual word being unknown, a new algorithm for the reconstruction of the feedback polynomial based on triple correlation characteristic of an msequence is proposed. First, the scrambled convolutional code sequence is divided into bit blocks; the product of the scrambled bit blocks with a dual word is proven to be an msequence with the same period as the synchronous scrambler. Second, based on the triple correlation characteristic of the generated msequence, a dual word is estimated; the generator polynomial of the generated msequence is computed by two locations of the triple correlation peaks. Finally, the feedback polynomial is reconstructed using the generator polynomial of the generated msequence. As the received sequence may contain bit errors, a method for detecting triple correlation peaks based on the constant falsealarm criterion is elaborated. Experimental results show that the proposed algorithm is effective. Ulike the existing algorithms available, there is no need to know a dual word a priori and the reconstruction result is more accurate. Moreover, the proposed algorithm is robust to bit errors.

