Table of Content

20 August 2017 Volume 44 Issue 4

  

MAC layer approaches to mitigating the spectrum underutilization due to the overlapping BSS problem in WLAN

LIU Gang;GUO Qiujin;GUO Yi;YANG Shiyong

Journal of Xidian University. 2017, 44(4):  1-6+143.  doi:10.3969/j.issn.1001-2400.2017.04.001

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Considering the OBSS-induced spectrum underutilization problem in Wireless Local Area Networks(WLAN), two complementary contention-based Media Access Control(MAC) layer schemes are proposed by setting up a virtual-primary channel for contention. The proposed transmission opportunity(TXOP) scheme is designed for transmitting long data packets, which is suitable for applications requiring high throughputs. In contrast, the multi-contention(MC) scheme is designed for transmitting short data packets, which is suitable for applications requiring short delays. By efficiently exploiting the OBSS-induced underutilized spectrum, simulation results verify the fact that the proposed TXOP scheme can increase the throughput greatly and the proposed MC scheme can reduce the delay for short data packets significantly.

Optimal power allocation and optimal relay selection for D2D communication

GUO Yi;LV Yuxuan;LIU Gang;YANG Shiyong

Journal of Xidian University. 2017, 44(4):  7-11+180.  doi:10.3969/j.issn.1001-2400.2017.04.002

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Cellular users can be regarded as relay nodes in cooperation with the Device-to-Device (D2D)communication so as to lower the cost, improve spectrum efficiency and solve the problems of network coverage, as well as improving service quality. In this paper an optimal power allocation and optimal relay selection algorithm based on network coding is proposed for using cellular users in the bidirectional relay nodes system. By fixing the total power of the D2D link to be transmitted, this algorithm optimizes the transmission power of each node, and selects the relay node which can maximize the channel capacity of the D2D link as the best relay node. Simulation results show that compared with other protocols, the proposed protocol can significantly improve the channel capacity of the D2D link.

Frequency increment optimization method for frequency diverse radar

XIANG Zhe;CHEN Baixiao;YANG Minglei

Journal of Xidian University. 2017, 44(4):  12-17.  doi:10.3969/j.issn.1001-2400.2017.04.003

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The conventional Frequency diverse array (FDA) employs the fixed frequency increment，which restricts its applications in various environments. With the above findings，we propose an optimal frequency increment selection method based on oblique projection filtering for mainlobe interference suppression. We can obtain the optimal frequency increment by maximizing the output SINR of the oblique projection filter in each coherent processing interval (CPI). Inspired by the cognitive radar，the optimal frequency increment will be used in the next CPI. Simulation results demonstrate that jamming can be effectively suppressed with the radar configuration，and that better performance is achieved with an optimal frequency increment.

Efficient verifiable multi-keyword search over encrypted data

MIAO Yinbin;MA Jianfeng;ZHANG Junwei;LIU Zhiquan

Journal of Xidian University. 2017, 44(4):  18-23+68.  doi:10.3969/j.issn.1001-2400.2017.04.004

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Most of existing searchable encryption (SE) schemes cannot support fine-grained access control and accurately verify the correctness of search results. Moreover, single keyword search will return many irrelevant search results and definitely bring down user search experience. Along this direction, we propose an efficient verifiable multi-keyword search scheme by exploiting CP-ABE (Ciphertext-Policy Attribute-Based Encryption) and the private audit server. Rigorous security analysis proves that our scheme is secure against the chosen-keyword attack in the random oracle model, and an empirical study of the real-world dataset justifies that this scheme is feasible and efficient in practice.

Analysis of satellite reflector antenna radiation characteristics perturbed by plume

YIN Weike;WEI Bing

Journal of Xidian University. 2017, 44(4):  24-28+61.  doi:10.3969/j.issn.1001-2400.2017.04.005

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The electric thruster has the advantage of high specific impulses and requiring much less fuel compared with the chemical thruster, and it will improve the mobility and life span of a satellite. Electromagnetic waves will be attenuated in the plasma plume because of absorption and refraction effects. In this paper, Ray tracing, aperture integral and the superposition principle of the electric field are used to analyze the effects of the plasma plume on antenna performance. The attenuation of the plume between 2GHz and 5GHz frequencies are calculated. For a 20cm electric thruster plume, simulation results vary from 0.3dB to 2.5dB compared with the experimental data, and the angle of the main lobe bending away from the thruster is less than 0.5 degree for the E-plane pattern.

RF build-in self-test and key measurement processing for the low-cost system-on-chip

ZHU Jia;LIU Hongxia

Journal of Xidian University. 2017, 44(4):  29-33.  doi:10.3969/j.issn.1001-2400.2017.04.006

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The major occupation in testing cost for the RF blocks of a system-on-chip (SOC) makes it a critical issue in the current complex integrated system. In this paper, a low cost RF Build-In Self-Test structure and methods for processing test data are proposed. The RF front-end has been tested with the help of on-chip DSP, CORDIC and ADC converters. The Digital Fourier Transform (DFT) and SNR results of the generated digital signature are presented in detail with the innovated logarithm calculation method. With the specified loopback structure design, the internal test tone can be used to avoid external noise influence. The RF BIST is applied and verified in mass production, which is effective for low-cost production. Compared to the traditional RF testing, this method can reduce the hardware overhead and decrease the cost with high testing quality.

Augmented Lagrangian bonding block model for contact problems

SUN Yue;FENG Xiangchu;LI Xiaoping;ZHANG Rui

Journal of Xidian University. 2017, 44(4):  34-39.  doi:10.3969/j.issn.1001-2400.2017.04.007

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A novel bonding block model is proposed for elastic contact simulations. The original model problem is expressed as the minimization problem with the penalty item of gluing spring strain energies, and Lagrangian multipliers are introduced to represent gluing spring forces. In this way, the total potential energy as the objective function becomes an augmented Lagrangian function. To solve this model, a new algorithm is presented by implementing augmented Lagrangian iterations to obtain the optimal solution in every time step. A numerical example is conducted to verify the accuracy and effectiveness of the presented model and algorithm.

Energy consumption estimation for 3D graphics rendering

XING Lidong;LI Tao;HUANG Hucai;HAN Jungang

Journal of Xidian University. 2017, 44(4):  40-46+74.  doi:10.3969/j.issn.1001-2400.2017.04.008

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From the perspective of hardware design and graphics programming, a new energy consumption estimation model of 3D graphics rendering is proposed. Aiming at the energy consumption of the vertex shader and pixel shader in the 3D rendering pipeline, the loads of the vertex shader and the pixel shader which affect the rendering quality are analyzed, and the model of the ratio the number of pixels to the number of vertexes is obtained. At the same time, the energy consumption of vertex shading stages and pixel shading stages are modeled. The model is used to estimate the energy consumption of the benchmark programs, and simulations are performed using the Synopsys VCS simulator and the Power Compiler to obtain the actual energy consumption of these programs. The results show that the geometric mean of the model's prediction error is less than 3％, which can be used to guide the power consumption analysis and management of graphics hardware and software.

Design of a novel miniaturized broadband microstrip antenna

ZHENG Gengqi;SUN Baohua

Journal of Xidian University. 2017, 44(4):  47-50+137.  doi:10.3969/j.issn.1001-2400.2017.04.009

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The method of broadening the bandwidth of the low-profile single patch antenna is studied. A novel rectangle-shape broadband signal patch antenna using the dumbbell-shape Defect Ground Structure (DGS) is proposed in this paper. The antenna consists mainly of the rectangle patch and two surrounding parasitic patches with a C-shaped slot. The resonance characteristics of the parasitic patches are analyzed to determine the dimension of the parasitic patches, and then taking advantage of the gap in etching and DGS, the bandwidth of the antenna is widened. This patch antenna is calculated by Ansoft HFSS. The results validate the proposed approach, which helps the improvement of the bandwidth of the antenna from 500MHz to 1000MHz. Compared with the typical microstrip antenna, the proposed antenna is compact in size, light in weight, and low in longitudinal dimension. The designed antenna is suitable for the design of an array to reduce the coupling among array elements. The substrate of the antenna is the signal layer RF4, and it can be applied in industrial production expediently.

Novel 3-DOF micro translational parallel manipulator

ZHAO Ze;QIU Yuanying;DUAN Xuechao

Journal of Xidian University. 2017, 44(4):  51-55+131.  doi:10.3969/j.issn.1001-2400.2017.04.010

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Aiming at the active vibration control for a CPU crystal oscillator in electronic equipments, a novel 3-DOF (degree of freedom) micro translational parallel manipulator with linear driving and six passive joints is presented. It possesses the dimension of 75mm×67mm×25mm, and performs 3-DOF translational motions at 50Hz within a space of (±2mm)×(±2mm)×(±2mm). Finally a computational simulation validates the novel design. Its configuration is chiefly characterized by a constant Jacobian matrix between input and output, which facilitates the implementation of real-time control. It can be used not only for active vibration control, but also for industrial robots, precision machineries, optical testing platforms and the design of parallel machine tools.

Design method of an identity-based fully homomorphic encryption library

HAN Kun;ZHANG Hailin;XIN Dan;WU Bo;KANG Yuanji

Journal of Xidian University. 2017, 44(4):  56-61.  doi:10.3969/j.issn.1001-2400.2017.04.011

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To avoid the weaknesses of the present fully homomorphic encryption algorithms which have a large public key and low calculation efficiency, the identity-based homomorphic encryption scheme is studied and the corresponding function library is designed. First, the IHEL(Identity-based Homomorphic Encryption Library) is constructed based on the basic definitions and operations of the SEAL (Simple Encrypted Arithmetic Library). Then, the encoding method for the integer and string into the plaintext polynomial is given and the parameters selection is analyzed. Last, an automatic parameter generation tool for the users is designed to meet the needs of safety and efficiency. The identity-based homomorphic encryption scheme has high calculation efficiency and does not need a public key certificate. The corresponding function library IHEL lays a foundation for the practical application of the identity-based homomorphic encryption scheme.

Two-layered game-theoretic based resource allocation in femtocell networks

ZHOU Yanguo;ZHANG Hailin;CHEN Ruirui

Journal of Xidian University. 2017, 44(4):  62-68.  doi:10.3969/j.issn.1001-2400.2017.04.012

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In orthogonal frequency division multiple access(OFDMA) based femtocell networks, to improve the spectrum efficiency and avoid the interference from the femtocell user equipment(FUE) to macrocell user equipment(MUE) and other femtocell users equipments(FUEs), the joint power control and subcarrier selection distributed algorithm is proposed. In the framework of the two-layered game, the proposed distributed algorithm, which is based on the pricing mechanism and the dynamic replication scheme, can effectively suppress the interference from the FUE to other users and select the optimal subcarrier by the alternate iterations of the non-cooperative game and evolutionary game. Simulation results show that the proposed algorithm can converge to the Nash equilibrium(NE) of the two-layered game.

High-speed serial interface for converter using the JESD204B protocol

TIAN Rui;LIU Maliang

Journal of Xidian University. 2017, 44(4):  69-74.  doi:10.3969/j.issn.1001-2400.2017.04.013

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In order to reduce the pin count, the cost and size of packaging, and complexity of system design, a high speed serial interface protocol named JESD204B has been proposed by the JEDEC committee. This paper presents a specific implementation scheme of the transceiver controller based on this protocol. The implemented controller of the transceiver with 4 lanes has been verified with the high speed serial transceiver Xilinx FPGA GTH under a data rate of 6.25Gbit/s.

High precision frequency measurement based on the characteristic of the fuzzy area

JIA Zhaomin;LI Zhiqi;ZHOU Wei;YANG Xuhai;SUN Baoqi;MIAO Miao;DONG Shaofeng

Journal of Xidian University. 2017, 44(4):  75-79.  doi:10.3969/j.issn.1001-2400.2017.04.014

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The phase difference change is random in the discrete fuzzy area by considering the limit of device resolution, which the device can not stably capture, and the precision of the measured value only reaches the level of ns, but the phase difference change in the concentrated fuzzy area is step by step, and the device can stably capture the change of ps. By using the fuzzy area conversion technology, a high precision frequency measurement is designed. Through computer control and frequency synthesis,the discrete fuzzy area is converted to the concentrated fuzzy area, the ps stability properties of phase difference change on the border of the concentrated fuzzy area is used, the precision can be improved two or three orders of magnitude, and the high precision measurement in a wide range is achieved.

Quantization noise shaping of the sigma-delta modulator based on the all phase FFT in OFDM systems

GE Lijun;ZHAO Lan;LI Yue;GUO Hui;LI Mingyang;ZHAO Ruijun

Journal of Xidian University. 2017, 44(4):  80-85+117.  doi:10.3969/j.issn.1001-2400.2017.04.015

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To solve the problem of quantization noise in OFDM systems, a study of sigma-delta quantization noise shaping based on the all phase FFT is presented. This paper first gives single zero and multiple zeros sigma-delta modulators used for the theoretical analysis of quantization noise shaping for the OFDM system, and points out that the non-cyclic quantization noise structure results in inter-carrier interference (ICI) and inter-symbol interference (ISI) of quantization noise at the frequency points of OFDM sub-carriers; then it gives the scheme and performance analysis based on the all phase FFT to further reduce the quantization noise at the frequency points. Simulations show that the multi-zero sigma delta modulator performs better in noise shaping compared to the conventional single-zero modulator in OFDM systems, and can further reduce the quantization noise, and that under the conditions of 2bit quantization and 5dB SNR, the bit error rate of the system deceases by 1 order of magnitude.

Object tracking algorithm using objectness detection

HU Xiuhua;GUO Lei;LI Huihui

Journal of Xidian University. 2017, 44(4):  86-94+111.  doi:10.3969/j.issn.1001-2400.2017.04.016

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To solve the tracking drift problem caused by the low discrimination of object appearance information in complex environment, the paper proposes an object tracking algorithm using objectness detection. First, the algorithm obtains the preliminary object prediction state with kernelized correlation filters. Then, according to the objectness detection principle of the proposal bounding box, it generates the original proposal bounding box set with the consideration of the scale and aspect ratio, and further gets optimized sets with the refined selection criterion. By introducing motion continuity, the prediction location and scale based on the proposal bounding box are calculated, and then the final optimum object state estimation is acquired comprehensively. Finally, taking into account the occlusion influence judge of target appearance at the current frame, the corresponding template updating scheme is given. Experimental results demonstrate that the novel algorithm achieves robust tracking performance in various typical testing scenarios.

Perturbation sensitivity analysis of azimuth estimation of the acoustic source for the planar microphone array

XU Zhiyong;ZHAO Zhao

Journal of Xidian University. 2017, 44(4):  95-99+150.  doi:10.3969/j.issn.1001-2400.2017.04.017

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Aiming at the requirements of quantitative analysis of the array scheme and positioning performance of a practical compact acoustic detection node system, the upper bound of the far-field azimuth estimation error for an arbitrary small-size planar array is derived and the four elements of the corresponding perturbation sensitivity factor with explicit physical significance are determined. It is proved that the perturbation sensitivity of the source direction-finding algorithm to the time difference of arrival (TDOA) estimates between microphones can be lowered obviously by means of increasing the number of distinct microphone pairs as well as employing spatially uniform distribution of array elements. Simulation results demonstrate that this study provides a quantitative approach to evaluating and comparing the azimuth estimation performance of different planar arrays.

Low false alarm probability howling detection method

ZHANG Tao;LI Kangkang;JIAO Haiquan

Journal of Xidian University. 2017, 44(4):  100-105.  doi:10.3969/j.issn.1001-2400.2017.04.018

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Howling detection is the key of the notch-filter-based howling suppression algorithm. However, the traditional howling detection method with a problem of high probability of false alarm will lead to speech distortion easily. So a novel howling detection method based on long-term signal variability at the specific frequency band is proposed in this paper. First, we pick the candidate howling competent by means of extracting the power spectrum peak; then, we select several bins on both sides of the candidate howling competent as the target specific frequency band; lastly, whether howling occurs or not depends on the value of long-term signal variability at the target spectral frequency band. Simulation results show that compared with the traditional howling detection method, the probability of false alarm can be controlled more effectively while keeping a high probability of detection by the proposed method.

TDOA localization with linear-correction in the presence of sensor position errors

DENG Bing;SUN Zhengbo;YANG Le;HE Qing

Journal of Xidian University. 2017, 44(4):  106-111.  doi:10.3969/j.issn.1001-2400.2017.04.019

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This paper considers the problem of locating a source using time difference of arrival(TDOA) measurements obtained at spatially distributed sensors in the presence of sensor position errors. A linear-correction TDOA localization algorithm that involves closed-form weighted least squares(WLS) optimization only is developed. The proposed method first converts nonlinear TDOA equations into pseudo-linear ones by introducing an intermediate variable and obtains the initial source position estimate using the WLS technique. Then a linear-correction method is applied to improve the initial localization result by estimating and subtracting its positioning error. Simulation results demonstrate the good performance of the proposed method.

Generalized extended approximation algorithm for vehicle satellite communication on the move

ZHANG Zhifu;PEI Jun;HU Chao;JI Yuanfa

Journal of Xidian University. 2017, 44(4):  112-117.  doi:10.3969/j.issn.1001-2400.2017.04.020

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In order to improve the tracking precision of the satellite beacon signal in the Vehicle Satellite Communication on the Move(SOTM) system, an improved frequency tracking algorithm based on generalized interpolation fitting is proposed. The algorithm establishes a joint generalized extended model based on the peak of the signal's initial power spectrum. The boundary points of the extension region satisfy the interpolation conditions, and the best fitting is achieved in the element region. A one-dimensional discrete solution space of the model solution and the initial peak value is established, and the occurrence of the error in the direction of the valuation is effectively avoided, and the accuracy of the whole domain is improved. The results of the static and dynamic tracking of the satellite signal show that, in 40s integration time, the frequency tracking error can be limited to within plus or minus 2Hz. The algorithm achieves a certain dynamic performance, and can effectively improve the tracking accuracy of the carrier frequency tracking loop. The mathematical model of the generalized extended approximation frequency tracking algorithm is robust and of low complexity, and it can be realized in the premise of ensuring the dynamic performance and high tracking accuracy.

Linear frequency diversity array synthetic aperture radar imaging based on enhanced back-projection algorithm

RAN Da;YIN Canbin;JIA Xin

Journal of Xidian University. 2017, 44(4):  118-124.  doi:10.3969/j.issn.1001-2400.2017.04.021

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Based on the signal model of multiple carrier frequency (MCF) for linear frequency diversity array synthetic aperture radar (LFDA-SAR), we propose an enhanced back-projection (EBP) algorithm. Compensation for the quadratic phase error in echoes is executed and the spatial-variant range drifting amount and phase of the target are amended during the process of back-projection. The proposed algorithm can effectively rectify the image blurring and geometric distortion problem in classical back-projection imaging results, realize a high precision imaging of targets with an arbitrary imaging geometry and distinguish adjacent strong and weak targets. All results verify the effectiveness of the proposed algorithm.

MIMO radar waveform design in the presence of clutter and colored noise

WANG Yuxi;HUANG Guoce;LI Wei;WANG Yequn

Journal of Xidian University. 2017, 44(4):  125-131.  doi:10.3969/j.issn.1001-2400.2017.04.022

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The existing MIMO radar waveform design methods only deal with the optimization of radar waveform with the presence of clutter or colored noise, and unfortunately can not get the optimal waveform with the scenario when the clutter and colored noise coexist, which is more realistic in practical applications. To address this problem, a novel MIMO radar waveform design method based on mutual information in the presence of clutter and colored noise is proposed. The proposed scheme considers the influence of the target's response, clutter and colored noise on the optimization of the radar waveform. The mathematical expression for the transmit waveform matrix is achieved by theoretical derivation. What is more important, an optimal pairing of the eigenvectors of the target, clutter and colored noise is given and the power allocation for each antenna is optimized by the water-filling method. Simulation results show that when the total transmit power is 10dB, the proposed method's MI is 8bit and 4bit more than that of the general water-filling method and the method which only considers the pairing of the target's response and noise, respectively.

Radio frequency interference suppression algorithm in the spatial domian for high-frequency radars

WEN Biyang;HAN Jinzhu;ZHOU Qihao;LI Yan

Journal of Xidian University. 2017, 44(4):  132-137.  doi:10.3969/j.issn.1001-2400.2017.04.023

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Radio frequency interference suppression is a very important issue in applications of high-frequency surface wave radar. This paper proposes a new interference suppression algorithm which makes use of RF interference azimuth information on the basis of learning common RF interference suppression algorithms and spatial spectrum estimation. First, we apply the MUSIC algorithm to estimate the interference azimuth and obtains the interference's signal space after the first Fourier transform; next, we use space decomposition to decompose the radar echo and obtain interference components; last, we subtract radio frequency interference components from the original signals. This algorithm can do great amount of RF interference suppression in actual data and get good results.

Hardware efficient 2-D DWT architecture without off-chip RAM

JIA Qi;LIANG Yu;ZHANG Wei

Journal of Xidian University. 2017, 44(4):  138-143.  doi:10.3969/j.issn.1001-2400.2017.04.024

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Two-dimensional(2-D) Discrete Wavelet Transform(DWT) is a commonly used image processing method. Due to its large amount of computation, it is often implemented in the hardware circuit to meet the need of high throughput. The existing hardware architectures have a large storage requirement for the input data. Therefore, a hardware efficient 2-D DWT architecture using the line-based and dual-scan method without multipliers is proposed. The total ram requirement of the proposed architecture is reduced to 10N bytes, while the off-chip RAM is not required. Besides, a Critical Path Delay(CPD) of one full-adder delay is achieved by using Canonic Sign Digit(CSD) multipliers. The estimated hardware requirement shows that the proposed architecture involves at least a 4％ smaller number of transistors and 33％ less transistor count-delay-product(TDP) than the existing architectures.

Fast direct position determination method based on the sharpening function genetic algorithm

REN Yanqing;LU Zhiyu;BA Bin;WANG Daming

Journal of Xidian University. 2017, 44(4):  144-150.  doi:10.3969/j.issn.1001-2400.2017.04.025

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The traditional DPD algorithm has a slowly-varying cost function near the peak, which makes it ineffective to get the optimization location result. To solve the problem, a fast direct position determination method based on the sharpening genetic algorithm is proposed in this paper. First, the algorithm constructs a sharpening function to sharpen the target function of DPD and enhances the algorithm selection ability. Then the algorithm combines with the initialization in the convergence process to increase the diversity of the population and preventes the algorithm into a local optimum. Finally, the algorithm realizes the fast estimation of the target's position. Simulation results show that the algorithm proposed can obtain a higher positioning accuracy than a fast DPD method based on the traditional genetic algorithm in the high SNR condition. Compared with ML-DPD, the computation  can be reduced 3 orders of magnitude at 95％ probability and the computational efficiency is greatly improved.

Proton irradiation damage mechanism of the InAlAs／InGaAs／InAlAs quantum well

WANG Haili;JI Huifang;SUN Shuxiang;DING Peng;JIN Zhi;WEI Zhichao;ZHONG Yinghui;LI Yuxiao

Journal of Xidian University. 2017, 44(4):  151-155+161.  doi:10.3969/j.issn.1001-2400.2017.04.026

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InP-based high electron mobility transistors (HEMT) have shown a great potential for national defense and satellite radar in space radiation environment applications. This paper studies the proton radiation damage mechanism of its critical structure InAlAs／InGaAs／InAlAs quantum well. The proton projection range and vacancy defect information are obtained at different incident proton energies of 50keV, 75keV and 200keV by SRIM software. With the increase of proton energy, the proton injection depth is increasing and eventually protons pass through the material layers. Besides, the proton radiation induced vacancy defects numbers around hetero-junction increase first and decrease subsequently, and As vacancies are the main proton radiation induced defects. In addition, non-ionizing energy loss (NIEL) of In_0.52Al_0.48As and In_0.53Ga_0.47As material is computed under different incident proton energies by the analytical model. The change trend of NIEL is identical to the induced vacancy numbers, namely, NIEL first increases and then decreases as the incident proton energy increases. Finally the degrading effect of the radiation-induced As defect is detected in the two-dimensional electron gas in the quantum well, which confirms that the major proton radiation damage mechanism of the quantum well is the induced vacancy defects by NIEL.

Visible light localization algorithm based on multi-measurements constraints

LU Hang;CUI Weijia;BA Bin;LU Zhiyu

Journal of Xidian University. 2017, 44(4):  156-161.  doi:10.3969/j.issn.1001-2400.2017.04.027

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In the indoor visible light transmission environment with complex noise, traditional received signal strength indication(RSSI)localization algorithm and imaging localization algorithm are unable to accurately determine the reason of the inaccurate localization model and inadequate constraints of position coordinates. In order to solve the problems, a visible light localization algorithm based on multi-measurements constraints is presented in the paper. The algorithm first constructs a joint localization state space model based on RSSI localization and the imaging localization algorithm. Then, states, measurements and their equations are constructed based on the space model. Finally, the equations are resolved using the unscented Kalman filter(UKF). Compared with RSSI localization and imaging localization, simulation results show that the RMSE of the proposed algorithm could be closer to the Cramer Rao bound. Besides, the localization probability of the proposed algorithm is higher than that of RSSI localization and imaging localization algorithm.

Ultra-low latency and omit-iteration CORDIC algorithm

YAO Yafeng;FENG Zhongxiu;CHEN Zhao

Journal of Xidian University. 2017, 44(4):  162-166.  doi:10.3969/j.issn.1001-2400.2017.04.028

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The pipeline structure Coordinate Rotation Digital Computer (CORDIC) algorithm improves its precision by increasing the stages of iterations, which leads to a large delay, excessive consumption of hardware and limits its applications.The omit-iteration CORDIC algorithm is proposed to solve this problem by using the methods of binary to bipolar recoding, folding angle domain, merging iteration and optimizing the lookup table. Simulation results show that this method needs only two clock cycles to get the output and also makes improvement on the hardware consumption and its precision, especially having privilege to the application on high speed and real-time occasions compared with other realization of the CORDIC algorithm.

3D indoor floor localization based on WiFi and PDR

HE Leinan;LU Hu;JI Zhengzhou

Journal of Xidian University. 2017, 44(4):  167-173+166.  doi:10.3969/j.issn.1001-2400.2017.04.029

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A layered indoor 3D positioning technology based on WiFi positioning and Pedestrian Dead Reckoning (PDR) is proposed to solve the problem that the pedestrian can only get coordinates in the 2D plane and low accuracy of current indoor localization from intelligent terminal. In the PDR location, the pedestrian's horizontal walking or taking up-down stairs can be distinguished by detecting the pitch-rate mutation. Height change of the pedestrian is obtained by using the effective steps and stairs information. The equations of the two different behavior patterns are constructed and three-dimensional PDR is realized. In the part of the filter, a particle filter algorithm combining WiFi, PDR, building information and behavior patterns is proposed. By fusing the building information and behavior models into the weight calculation and the sampling of the particle, the localization precision is effectively improved. The results show that the average error of the horizontal location is 2.6m and the average error of the height estimation is 1.1m, which satisfies the demand of the individual intelligent terminal for the location service, with the elevation parameter enabling the user to recognize floor information.

Multispectral imagery denoising using hierarchical dictionary learning with spatial-spectral information

LIU Shuai;MA Wenping;YANG Shuyuan;CHEN Puhua

Journal of Xidian University. 2017, 44(4):  174-180.  doi:10.3969/j.issn.1001-2400.2017.04.030

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A novel denoising method is proposed for the multispectral imagery by combining the hierarchical dictionary learning and the spatial-spectral information. First, the band-subset segmentation is developed by exploiting the highly structural correlations between adjacent bands. Second, the hierarchical dictionary learning model with spatial information is applied to sequentially denoise each band-subset. The noise characteristics of the multispectral images is well depicted by decomposing the noise term into the Gaussian noise term and the sparse noise term, and Gibbs sampling is utilized to solve the model. The effectiveness of the proposed method is compared with that of the state-of-the-art approaches and validated on two multispectral images.