Recent Submissions

Now showing 1 - 5 of 43
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    3D Beamforming for Improving the Security of UAV-Enabled Mobile Relaying System
    (Společnost pro radioelektronické inženýrství, 2019-04) Yuan, Quan-sheng; Hu, Yong-jiang; Wang, Chang-long; Ma, Xiao-lin
    In this paper, we consider an unmanned aerial vehicle (UAV)-enabled mobile relaying system consists of a ground control station (GCS), a high-mobility UAV for relaying, a destination, and an eavesdropper. To improve the security of the three-dimension (3D) mobile relaying system with delayed channel state information (CSI), we propose a destination-specific (DS) 3D beamforming scheme and an eavesdropper-null (EN) 3D beamforming scheme, in both the horizontal angle and the vertical angle of antenna pattern are adapted instantaneously. In particular, we study the secrecy rate maximization problem via trajectory planning. However, this problem with mobility constraint and location constraint is a non-convex optimization problem. To solve it, we propose a successive trajectory planning algorithm by optimizing the incremental in each time-slot. Simulation results verify that the 3D beamforming schemes can greatly improve the security of UAV-enabled mobile relaying system and the proposed trajectory planning algorithm is also proven become effective.
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    Cyclostationary Feature Detection Based Blind Approach for Spectrum Sensing and Classification
    (Společnost pro radioelektronické inženýrství, 2019-04) George, Gemi Rachel; Prema, Samuel Chris
    A Spectrum Sensing (SS) device, regardless of its location, should be able to detect the presence of signal over noise. In certain applications, SS should be able to correctly identify and classify the received signal. These functions are to be performed with little or no prior information about the incoming signal or channel noise. Cyclostationary Feature Detection (CFD) can be used to detect primary users (PU) using periodicity in autocorrelation of the modulated signals. These algorithms attempt to differentiate signal from noise based on the uncorrelated nature of noise. CFD is often considered as a semi-blind approach, since it requires prior information about the PU signal for detection. For identification and classification of PU signal, existing algorithms make use of CFD and neural networks. This paper proposes a novel algorithm to obtain completely blind detection performance based on CFD. Classification of PU signals is based on the basic statistics regarding cyclic spectrum. Further, an algorithm is formulated to identify modulation scheme of the signal and classify it without making use of any training algorithms. The proposed approach is capable of detecting PU reliably for SNR as low as –8 dB with no prior information about PU or noise in the channel.
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    Research on Passive Troposcatter Location System
    (Společnost pro radioelektronické inženýrství, 2019-04) Liu, Zan; Chen, Xihong; Liu, Qiang
    Electromagnetic (EM) wave of enemy radar propagated by troposcatter can be utilized for beyond line-of-sight (b-LoS) location. To provide theoretical basis for passive troposcatter location system, channel characteristics including propagation loss, refraction effect and multipath fading are analyzed. Ray tracing method improved by tropospheric model is employed to describe the refraction effect. Correlation coefficient on the basis of transfer function is deduced to evaluate multipath fading. According to troposcatter characteristics, maximum operating range is estimated, cooperative energy detection is introduced to copy with the received signal without priori knowledge. The principle and accuracy of location algorithm based on azimuth is researched. Spatial smoothing is introduced under the situation that uncorrelated and coherent signals coexist. Through analyzing consequences, future directions for developing are suggested.
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    Harvested Energy and Spectral Efficiency Trade-offs in Multicell MIMO Wireless Networks
    (Společnost pro radioelektronické inženýrství, 2019-04) Tien Ngoc Ha; Ha Hoang Kha
    The paper focuses on designing precoding matrices in multi-cell multiple-input multiple-output (MIMO) simultaneous wireless information and power transfer networks (SWIPT) where the sets of users are selected for data transmission in each time slot and the unselected users are dedicated to energy harvesting. The precoding design for the SWIPT problem is formulated as a general multi-objective maximization problem, in which the sum-rate (SR) and sum harvested energy (SHE) are maximized simultaneously under the transmit power constraints. Since the objective function of the maximization problem is not concave in the design matrix variables, it is difficult to directly obtain the optimal solutions. To tackle this challenge, we recast the SR function into one more amenable by applying the connection between the minimum mean square error and achievable data rate. In addition, to deal with the non-concavity of the harvested energy function, we derive its concave minorant. Then, we develop an efficient iterative algorithm based on alternating optimization (AO) to obtain the optimal precoders. We also analyze the convergence and computational complexity of the proposed algorithm. Finally, by numerical simulation results we investigate the trade-offs between the SR and SHE.
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    Design and Implementation of Synchronization-free TDOA Localization System Based on UWB
    (Společnost pro radioelektronické inženýrství, 2019-04) Wang, Wei; Huang, Junjie; Cai, Shaobin; Yang, Junjie
    At present, indoor localization system based on ultra wideband(UWB) has attracted more and more attention. In UWB system, Time Difference of Arrival (TDOA) and Two-Way Ranging (TWR) are widely used. However, TDOA requires high-accuracy time synchronization between all anchor nodes and even slight noise can cause large localization error. In TWR localization scheme, although two-way communication between anchor nodes and blind nodes can avoid the time synchronization issue effectively, the clock drift and the number of blind nodes will affect the system performance. To overcome these problems, a new synchronizationfree TDOA location algorithm is proposed. Firstly,the clock model is established and the influence of antenna delay is considered. Then, the system signal exchange mechanism and localization model are proposed. In the system, the blind nodes just receive the ranging signals from anchor nodes so that the system has no limit on the number of blind nodes. Finally,the major factor affecting the accuracy of ranging - clock drift, is discussed, and then a clock frequency offset compensation algorithm is proposed. The indoor localization experiment results show that the indoor localization system designed in this paper can achieve 3-D localization.