Optimal resource allocation for transmission diversity in multi-radio access networks： a coevolutionary genetic algorithm approach

The next generation wireless communication systems aim at supporting enhanced diversified network access and data transmission abilities via the cooperative integration and unified management of various radio access technologies(RATs).The resource allocation is the core component leading the network system and mobile terminals to the service robustness and performance maximization.In this paper,a numeric optimization model for optimizing terminals’transmission power and allocated RAT bandwidth for maximizing system capacity is proposed with the focal consideration of the multi-radio transmission diversity for parallel transmission through multiple links from diferent RATs,and diferent terminal characteristics on RAT supports.Also,we design a centralized and periodic scheduling algorithm including an improved coevolutionary genetic algorithm for efciently solving the optimization problem.Simulation results demonstrate that our propose algorithm can distinctly enhance the system performance and improve the computational efciency.     

基于发布订阅结构的计算机视觉跟踪研究

文中报道了使用发布订阅中间件搭建的一个跟踪系统,通过单摄像头采集图像,经过分析处理,计算出运动物体的相对位置,同时控制摄像头转动,对运动物体进行实时追踪.整个系统主要包括4个方面,以发布/订阅为中心结构连接3个子系统、目标获取、目标跟踪、采集摄像头控制.文中为卡尔曼滤波定义了新的向量,预测目标运动趋势;根据物体的运动信息自行设计了摄像头控制程序.算法有充分的理论依据和实验验证.     

Blind velocities mitigation for MIMO GMTI radar with Doppler division multiple access waveforms

Multiple-input multiple-output (MIMO) radar with multiple transmitters and multiple receivers can achieve a larger virtual antenna array and more system degrees of freedom; thus applying it to ground moving target indication (GMTI) radar can improve the performance of GMTI. Doppler division multiple access (DDMA) waveforms are approximately orthogonal providing good minimum detectable velocity (MDV) performance. However, in such DDMA systems, a sufficient pulse repetition frequency (PRF) design freedom is required. Furthermore, these waveforms suffer from blind velocities which are serious problems, especially in radar systems with high carrier frequency or low PRF. This paper analyses the blind velocities problem and show that blind velocities are relative to variation of the PRF and/or the carrier frequency. Variable PRF techniques are widely used in conventional GMTI radar including multiple PRFs and variable pulse repetition intervals (PRI). Combined with the characteristics of the DDMA MIMO GMTI radar, this paper proposed two methods to mitigate blind velocities: “multi-PRF DDMA” which employs multiple PRFs over successive coherent processing intervals, and “PRI-dithered DDMA” which employs nonuniform sampling by dithered PRI in slow time. Simulation results demonstrate that both the methods are effective ways to mitigate blind velocities in DDMA MIMO GMTI radar systems.     

A 5000 h RF life test on 330 W RF-LDMOS transistors for radars applications

A reliability test bench dedicated to RF power devices is used to improve 330 W LDMOS in a radar conditions. The monitoring of RF power, drain, gate voltages and currents under various pulses and temperatures conditions are investigated. Numerous duty cycles are applied in order to stress LDMOS. It shows with tracking all this parameters that only few hot carrier injection phenomenon appear with no incidence on RF figures of merit (P_out or PAE). Robustness and ruggedness are shown for LDMOS with this bench for radar applications in L-band.     

Dynamic modeling and fuzzy logic control of vibrations of a railway vehicle for different track irregularities

Safe and comfortable transportation of passengers and goods on railways can be achieved by solving the vibration problem. In this study, the dynamic modeling of the full railway vehicle is used to perform vibration analysis in order to observe displacements and accelerations. The full railway vehicle model consists of 54 degrees of freedom which are defined by differential equations. Additionally, wheel–rail contact problem (i.e. creepage factors and hertzian spring stiffness of rails) is analyzed by finite element method. Dynamic modeling and vibration analysis are carried out using Matlab–Simulink software. Using the developed model, the car body vibrations, caused by a lateral and two vertical sinusoidal track irregularities, are controlled by fuzzy logic controllers placed between the car body and bogies. The fuzzy logic algorithm herein is used for realizing the active control of car body vibrations. The simulations of vibration analysis are obtained in time and frequency domains and compared with passive controlled status. The robustness of the designed controller is verified by simulations, carried out for the cases of car body mass variations. The results show the effectiveness of the proposed algorithm.     

Design and implementation of a high-efficiency concurrent dual-band power amplifier

This paper studies the behaviors of power amplifier (PA) driven by a single-carrier continuous wave (CW) signal and a two-carrier CW signal both in theory and simulation, and explains why the traditional dual-band PA failed to perform satisfactory results when a two-carrier CW signal is applied to, called concurrently. Besides that, an evaluation standard of concurrent dual-band PA was presented to value its performance. Solution was given with design and fabrication of a concurrent 1.85 GHz/2.65 GHz class F PA, employing a 10W GaN HEMT device from Cree, CGH40010, whose measurement shows the saturated output power is 40.6 dBm and 40.8dBm with drain efficiencies (DE) of 77.4% and 75.3% at 1.85 GHz and 2.65 GHz, respectively. On the other hand, we see that the peak DE achieves 59.7% with an output power of 39.9 dBm in concurrent mode, which follows up with the standard.     

Design and analysis of a structure-based microstrip bandpass filter

A structure-based microstrip passband filter with the center frequency of 2.6 GHz was put forward by using double-mode resonator based on defected ground structure （DGS） technology. A double-mode coupling resonator combined with DGS structure was used to achieve the resonance frequency and the filter size. CST microwave studio was used to optimize the attenuation performance to get the filter parameters. A structure-based passband filter was fabricated. Simulation is consistent with the measurement. Performance shows that the proposed filter could be suitable for the time division-long term devolution （TD-LTE） microwave systems at 2.6 GHz.     

Fairness-oriented routing algorithm joint with power control and channel assignment for multi-radio multi-channel wireless mesh networks

The multi-radio multi-channel wireless mesh network （MRMC-WMN） draws general attention because of its excellent throughput performance, robustness and relative low cost. The closed interactions among power control （PC）, channel assignment （CA） and routing is contributed to the performance of multi-radio multi-channel wireless mesh networks （MRMC-WMNs）. However, the joint PC, CA and routing （JPCR） design, desired to achieve a global optimization, was poor addressed. The authors present a routing algorithm joint with PC and CA （JPCRA） to seek the routing, power and channel scheme for each flow, which can improve the fairness performance. Firstly, considering available channels and power levels, the routing metric, called minimum flow rate, is designed based on the physical interference and Shannon channel models. The JPCRA is presented based on the genetic algorithm （GA） with simulated annealing to maximize the minimum flow rate, an non-deterministic polynomial-time hard （NP-Hard） problem. Simulations show the JPCRA obtains better fairness among different flows and higher network throughput.     

Efficient scalable spatiotemporal visual tracking based on recurrent neural networks

Robust and accurate visual tracking is challenging as targets undergo significant changes in appearance by scale variance, occlusion and fast motion. We propose a novel tracking framework, called scalable spatiotemporal visual tracking algorithm (SSVT). First, we construct the Direction Prediction Model (DPM) to predict the spatiotemporal correlation of the target in the next frame. That will efficiently narrow down the search area and improve the accuracy of spatial location. Then, Occlusion Detection algorithm (ODA) is presented to overcome the wrong updates stemming from the region of interest (ROI) based on the estimated direction and Kalman filter. Finally, the multi-scale pyramid kernelized correlation filter (MSPKCF) is presented in tracking to realize the adaptive adjustment of the varying scales of the targets and the ROI size. Extensive experiments on OTB100 and VOT2016 datasets demonstrate that our tracker performs favorably against state-of-the-art trackers, which can effectively reduce computation redundancy and improve tracking accuracy.

     

Mutual coupling reduction in an antenna array by using two parasitic microstrips

This paper presents a new method of reduction mutual coupling. The proposed antenna array operating at 2.4 GHz is comprised of two rectangular patches and two parasitic microstrips, the parasitic microstrips are printed on substrate top layer over two rectangular patches. The measured results indicate that the mutual coupling is greatly suppressed, which becomes to −32 dB from −13.4 dB, and the radiation patterns are practically unaffected, as demonstrated by the comparison of identical antenna arrays with and without parasitic microstrips.