Journal of Astronautics

Journal of Astronautics ›› 2019, Vol. 40 ›› Issue (7): 818-823.doi: 10.3873/j.issn.1000-1328.2019.07.011

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An ILSP-Based Fast Blind Despreading Algorithm for Synchronous DS-CDMA Signals

ZHANG Hua guo, ZENG Hui,YOU Shao qin   

  1. 1. School of Information and Communication Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China;2. Meteorological Information and Signal Processing Key Laboratory of Sichuan Higher Education Institutes, Chengdu 610225, China;3.Center for Cyber Security，University of Electronic Science and Technology of China, Chengdu 611731, China
  • Received:2018-05-03 Revised:2018-08-08 Online:2019-07-15 Published:2019-07-25

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Abstract:

In order to solve the blind despreading problem of the synchronous DS-CDMA signals, a fast blind despreading based on iterative least squares with projection (ILSP) is proposed. Firstly, the signal subspace spanned by the spreading sequences of all users is estimated via the eigen-decomposition of the intercepted signal covariance matrix. Then with the finite alphabet property of the spreading sequences, the ILSP algorithm is exploited to cope with the unitary matrix ambiguity resulting from the eigen-decomposition operation and estimate the spreading sequences accurately. Finally, the symbol sequences are obtained by despreading the intercepted signal using the estimated spreading sequences. The simulation results demonstrate that the proposed algorithm has good performance under the low SNR (Signal to noise ratio) environment and much lower computational complexity compared with the traditional algorithms.

Key words:  Synchronous DS-CDMA signal, Spreading sequence, Signal subspace, ILSP algorithm, Unitary matrix ambiguity, Blind despreading

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