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Zhang H.,University of Electronic Science and Technology of China | Zhang H.,Science and Technology on Communication Information Security Control Laboratory | Wei P.,University of Electronic Science and Technology of China
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2013

In this paper, a spreading sequence estimation algorithm based on constant modulus property is proposed for the QPSK-DSSS signals in low signal to noise ratio and non-cooperative scenarios. First, the single-user QPSK-DSSS signal can be equivalently represented as a two-user BPSK-DSSS signal, and then the two-dimensional signal subspace spanned by the in-phase and quadrature binary spreading sequences is estimated by the eigen-decomposition of the covariance matrix. Finally, to estimate the spreading sequences accurately, its constant modulus property is exploited to cope with the unitary matrix ambiguity resulting from eigen-decomposition. The proposed algorithm is simple and easy to implement, and has a lower computational complexity compared to existing methods. And simulation results demonstrate the significant performance gains of the proposed algorithm in low signal to noise ratio situations. Source


Zhang W.,Science and Technology on Communication Information Security Control Laboratory
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

Automatic classification of the modulation format of a detected signal plays an important role in cognitive radio system and several military and civilian applications. Without previous knowledge of the received data, automatic modulation classification (AMC) becomes a difficult task. This paper discusses AMC of digital schemes which are commonly used in today's communication systems. Several statistical features are extracted to represent signals and Support Vector Machines (SVMs) are then applied to classify the unknown modulation schemes. Experiment results demonstrate that the proposed AMC algorithm is a practical algorithm and it has high robustness in a wide range of SNR. © 2014 IEEE. Source


Feng R.,Beihang University | Che S.,Beihang University | Wang X.,Beihang University | Wang X.,Science and Technology on Communication Information Security Control Laboratory | Yu N.,Beihang University
International Journal of Distributed Sensor Networks | Year: 2013

Trust management scheme has been regarded as a powerful tool to defend against the wide set of security attacks and identify malicious nodes. In this paper, we propose a trust management scheme based on revised Dempster-Shafer (D-S) evidence theory. D-S theory is preponderant in tackling both random and subjective uncertainty in the trust mechanism. A trust propagation mechanism including conditional trust transitivity and dynamic recommendation aggregation is developed for obtaining the recommended trust values from third part nodes. We adopt a flexible synthesis method that uses recommended trust only when no direct trust exists to keep a good trust-energy consumption balance. We also consider on-off attack and bad mouthing attack in our simulation. The simulation results and analysis show that the proposed method has excellent ability to deal with typical network attacks, better security, and longer network lifetime. © 2013 Renjian Feng et al. Source


Zhang Y.,Science and Technology on Communication Information Security Control Laboratory | Zhang Y.,China Electronics Technology Group Corporation
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2011

In order to solve the problem of the blind recognition of Turbo codes, some methods for blind recognition of the Turbo coding parameter with trellis termination are proposed for the first time. Based on the analysis of the sub-encoder structure of Turbo codes, some analytical models of convolutional codes at a rate of 1/2 are proposed, and by recoverying the interleaver sequence of Turbo codes, interleaver mapping is decided by exhaust comparison, and blind recognition of Turbo codes with trellis termination is realized. Simulation results illustrate that given the unknown Turbo encoded data sequence, the recognized coding parameters are correct by comparing prior conditions which validates the accuracy of the proposed methods. Source


Wang W.,Science and Technology on Communication Information Security Control Laboratory | Wang W.,China Electronics Technology Group Corporation
Journal of Digital Information Management | Year: 2012

Focusing on the protection of privacy and non- publicity of special networks, the CPN model is extended to PCPN by the protocol factor and the formal model. The FPCPN (Formal Protocol Colored Petri Net) is presented to analyze the operation mechanism of protocols. It is introduced by four steps, such as the whole structure, the network element conversion, the conditions of transition triggers/executions and sub-system partitions. Finally, the feasibility and efficiency of FPCPN is validated by an example. Source

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