查看更多>>摘要：We investigate a wireless-powered co-operative relay network, where an energy constrained relay node accumulates the energy harvested from radio frequency signals, and then assists source signal trans-mission. An adaptive cooperative transmission scheme for cooperative relay network is developed. The relay helps to transmit the source signal only if it has harvested enough energy and the channels between source and relay do not suffer from an outage. Before each transmission block, one out of two transmission modes, i.e., Half-duplex (HD) or Full-duplex (FD), is dynamically adopted based on the maximal instantaneous capacity of the system. A closed-form expression for the exact outage probability of the system with the proposed scheme is derived. Monte Carlo simulations are run to validate the accuracy of the mathematical analysis, and numerical results show that the proposed protocol outperforms the existing fixed cooperative transmission modes.
查看更多>>摘要：This paper analyzed the existing network security situation evaluation methods and discovered that they cannot accurately reflect the features of large-scale, synergetic, multi-stage gradually shown by network attack behaviors. For this purpose, the association between attack intention and network configuration information was deep analyzed. Then a network security situation evaluation method based on attack intention recognition was proposed. Unlike traditional method, the evaluation method was based on intruder. This method firstly made causal analysis of attack event and discovered and simplified intrusion path to recognize every attack phases, then realized situation evaluation based on the attack phases. Lastly attack intention was recognized and next attack phase was forecasted based on achieved attack phases, combined with vulnerability and network connectivity. A simulation experiments for the proposed network security situation evaluation model is performed by network examples. The experimental results show that this method is more accurate on reflecting the truth of attack. And the method does not need training on the historical sequence, so the method is more effective on situation forecasting.
查看更多>>摘要：As an emerging network technology, Software-defined network (SDN), has been rapidly deve-loping for recent years due to its advantage in network management and updating. There are still a lot of open problems while applying this novel technology in reality, especially for meeting security demands. The Address resolution protocol (ARP) spoofing, a representative network attack in traditional networks is investigated. We implement the ARP spoofing in SDN network firstly and find that the threat of ARP attack still exists and has big impact on the network. We propose a novel mechanism as defense solution for ARP spoofing oriented to OpenFlow platform. Theoretical analyzation is given, and the mechanism is implemented as a module of POX controller. Experiment results and performance evaluations show that our solution can reduce the security threat of ARP spoofing remarkably on OpenFlow platform and related SDN platforms.
查看更多>>摘要：Cloud data confidentiality need to be audited for the data owner's concern. Confidentiality auditing is usually based on logging schemes, whereas cloud data dynamics and sharing group dynamics result in massive logs, which makes confidentiality auditing a formidable task for user with limited resources. So we propose a public auditing scheme for data confidentiality, in which user resorts to a Third-party auditor (TPA) for auditing. Our scheme design a special log called attestation in which hash user pseudonym is used to preserve user privacy. Attestation-based data access identifying is presented in our scheme which brings no new vulnerabilities toward data confidentiality and no extra online burden for user. We further support accountability of responsible user for data leakage based on user pseudonym. Extensive security and performance analysis compare our scheme with existing auditing schemes. Results indicate that the proposed scheme is provably secure and highly efficient.
查看更多>>摘要：In social networks, the most studies focus on the trust prediction, but distrust cannot get enough attention. The distinct characteristics of distrust relations present challenges to traditional relation prediction. Distrust relations are very sparse in social network, and negative interaction data is too little. We embark on the problem to investigate the distrust prediction with only network topology. After achieving seven social distrusting-inducing factors, we adopt machine learning and optimization methods to model the prediction process. The framework of Distrust prediction in Signed social network (DP-SSN) is proposed, which can predict distrust relations without any interaction data. Empirically, we perform extensive experiments on real-world data to corroborate the effectiveness of the proposed framework.
查看更多>>摘要：This paper addresses the problem of target localization using Bistatic range (BR) measurements in a distributed multistatic passive radar system. The range-based positioning technique employs multiple transmitter-receiver pairs, which provide separate BR measurements. Based on the Maximum likelihood (ML) function, an efficient algebraic Approximate maximum likelihood (AML) algorithm for single target localization is proposed. The closed-form AML solution has neither initial condition requirements nor convergence difficulty. Simulations are included to compare its performance to that of the Cramer-Rao lower bound (CRLB) and the Two-step Weighted least squares (TS-WLS) algorithm. The proposed method is shown to be able to achieve the CRLB accuracy under Gaussian measurement noise. It is more robust to noise than the TS-WLS method, and presents relative insensitivity to target-sensor geometry.
查看更多>>摘要：To distinguish the dielectric surface break-down from the atmospheric breakdown, one method for atmospheric breakdown experiment by loading dielectric focusing lens is proposed. The focusing characteristics of dielectric focusing lens are investigated for the microwave frequency on the order of 1.3GHz to 9.3GHz, the lens focal length on the order of 0.3m to 0.9m and the dielectric constant on the order of 0.3 to 0.9. Simulations show that higher frequency, shorter focal length, and fitter dielectric constant result in better focus effect that the rising and falling edges of electric field strength change faster near the focus which is closer to the theoretical value. A dielectric focusing lens for the S-band is optimally designed with the polytetrafluoroethylene of 0.32m thickness, 0.6m diameter, and 0.4m focal length. The focus indicator of dielectric lens is measured and the atmospheric breakdown experiment is carried out. The experimental values of atmospheric breakdown are consistent with the theoretical values. The electric field strength with the lens at the focus is 5–6 times greater than that without focusing lens. The image of atmospheric breakdown by the dielectric lens focusing method experiment is clearer than that by the direct radiation method.
查看更多>>摘要：A novel shaped-beam pattern synthesis method of generating an arbitrary footprint pattern under an arbitrary array structure is proposed. The embedded element pattern information is included in the pattern model, and a new cost function composed of three optimization items which are sidelobe levels, mainlobe ripples and mainlobe gains is constructed through the model. During the optimization process, to further enhance the performance of the synthesized pattern, a weight matrix is designed and added to the optimization items, then the generalized Rayleigh quotient approximation method is used to obtain the final array element excitations. To illustrate the good performance of the provided method, several synthesis examples with different arrays and footprints are presented. Compared with other algorithms such as Weighted alternating reverse projection (WARP) method, the proposed method can achieve better results with lower sidelobe levels, smaller mainlobe ripples and less computational load.
查看更多>>摘要：High precision navigation with positioning accuracy of decimeter or even centimeter is becoming more and more important in many fields. Accurate carrier phase observations are the prerequisites for this requirement. Because they have much lower measurement noises than the code observations which are primarily used nowadays. However, the existence of integer ambiguity when counting cycles of carrier phases prohibits the straightforward application of the measurements. Once the integer ambiguity has been resolved, the application of carrier phase measurement is almost equivalent to pseu-dorange however with much higher precision. Therefore ambiguity resolution is key for fast and high precision positioning. The success rate of ambiguity resolution is affected by the ionospheric delay and observation noise. In previous methods, ionospheric errors are simply ignored. To resolve ambiguity reliably and quickly, we propose a modified method for precise point positioning. We analyze the characteristics of the dual-frequency combinations of original observations and the ones with longer wavelengths and lower noises are preferable. The wide-lane and sub-wide-lane combinations with higher success rates are chosen for ambiguity resolution. Extra pseudoranges are included to eliminate the ionospheric delay which hampers ambiguity resolution seriously. After the combined ambiguities have been resolved, the original ambiguities of each frequency can be calculated from the linearly independent equations. Based on real Global positioning system (GPS) navigation data, performances of the modified method are tested and compared with that of the traditional method. The results show that the modified method is less affected by ionospheric delay and can obtain more accurate ambiguity resolution.
NETL
NSTL
万方数据
维普