查看更多>>摘要：The proposed Clock and data recovery system (CDRS) has three improved parts.The second order digital filter with rounding algorithm implements fractional gain and avoids direct current quantization noise which varies between-q/2 and +q/2 while that of traditional filter varies between 0 and +-q (q is quantization step).The hysteresis majority voter can combat high frequency and strong jitter especially in quasi-steady state.The improved Phase interpolator (PI) has much smaller current-switching glitch and phase glitch since the weighting current changes gradually instead of steeply.The optimized CDRS can handle up to ±6000ppm (parts per million) frequency offset and the phase resolution is 1.4Ω/LSB (Least significant bit) according to analysis.The simulations of jitter transfer function and jitter tolerance by Matlab,simulations of phase noise by spectre using Verilog+VeriloA model,and measurements of frequency offset and jitter tolerance all show its good performance.
查看更多>>摘要：Real-time network resource allocation based on virtualization technology is an important method to solve the solidification problem of Fiber-wireless (Fi-Wi) access networks.To increase the resource utilization and meet the specific QoS requirements of smart gird communication services,a Load-balancing and QoS based dynamic resource allocation method (LbQ-DR) is proposed with three sub-mechanisms.A time-window based substrate network resource update mechanism is designed to describe the realtime resource consumption of substrate networks,which can balance the accuracy of resource status and the complexity of the allocation algorithm.A QoS-based Virtual network request (VNR) sorting mechanism is presented to precisely calculate the priority of VNRs and reasonably sort the incoming services.A load-balancing based resource allocation mechanism is designed to avoid unbalanced resource consumption.Especially,the channel interference is considered in the cost of embedding and a collision domain mechanism is introduced to decrease interference.Simulation results demonstrate that the proposed method can provide heterogeneous smart grid businesses with differentiated service,improve the utilization and economic benefits of the network and make the network more balanced.
查看更多>>摘要：Network function virtualization (NFV),has been widely adopted in existing networks since it brings lower capital expenditure and operating expense,as well as flexible and elastic deployment.Based on NFV,dynamic Service function chain (SFC) provides more comprehensive and thorough traffic steering over a series of middleboxes,e.g.,DPI,and IDS.Nevertheless,dynamic SFC involves internal state migration in middleboxes,making it hard to allocate SFC requests.We propose a reconfigurable SFC scheduling approach with consideration on resource constraints and race of the state migration to collaborate the execution of the SFC reconfiguration,in the reasonable fashion based on a heuristic algorithm.The evaluation is conducted through discrete event simulation to validate the efficiency of our reconfigurable SFC scheduling,and the results demonstrate that the proposed method outperforms First Come First Serve scheduling and random scheduling.
查看更多>>摘要：In time-triggered ethernet (TTEthernet),designing and optimizing the static scheduling of TT messages to improve the real-time performance of the whole network control system is important.When there is a high load on TTEthernet network communication,the conventional static scheduling policy introduces certain problems,such as increased packet loss rate,load imbalance,and transmission delay.Meanwhile,basic artificial intelligence algorithms generally features convergence within only a few steps,leading to higher probability to fall into a local optimal solution.To realize these targets,Fuzzy particle swarm optimization (FPSO) based on population diversity is established.By combining Particle swarm optimization (PSO) with a fuzzy algorithm,setting the adjustment of the inertia weight and the regulation of the mutation factor as the controlled variables of the Fuzzy logic controller (FLC),and adjusting the FLC inference rules,a novel static schedule generation for TTEthernet is proposed.Simulation results prove that,compared to the conventional rate-monotonic scheduling algorithm and the PSO algorithm,FPSO has a strong global search capability when the communication of the TTEthernet system is in a high-load state.FPSO improves the load balancing of the network and reduces the transmission delay of TT message packets.FPSO shows excellent ability to optimize scheduling tables and guarantee the real-time performance of the TTEthernet system.
查看更多>>摘要：A Reduced-dimensional spherical harmonics MUSIC (RD-SHMUSIC) is proposed to solve the problem of high computational complexity of Multiple signal classification (MUSIC) algorithm for Two-dimensional (2-D) Direction of arrival (DOA) estimation.The proposed algorithm first expresses the spherical harmonic steering vector as a linear weight of a uniform phase vectors.Via the Lagrange multiplier method,we can get a new search function to estimate elevations.At second step,the algorithm expresses the steering vector in another form,a linear weight of a vector which is constructed by associated Legendre functions.A search function to estimate azimuths can also be obtained.The proposed method only needs One dimensional (1-D) angle search,which means it has a large reduction of computational complexity compared to the traditional Spherical harmonics MUSIC (SHMUSIC).The simulation results show that the accuracy of the proposed method is better than Two-stage decoupled approach (TSDA) algorithm,and has close performance to that of SHMUSIC.
查看更多>>摘要：A coding metasurface is designed based on hybrid Array pattern synthesis (APS) and Particle swarm optimization (PSO) method for ultra-wideband low-detectable application.The metasurface is composed of Electromagnetic band-gap (EBG) structures of two Minkowski fractal elements with reflection phase difference of 180° (±37°) over a wide frequency range.Two different types of EBG unit cell printed on a thin grounded dielectric substrate produce reflection phase difference of about 180 degrees over a wide frequency range.Ultra-wideband Radar cross section (RCS) reduction results from the phase cancellation between two local waves produced by these two unit cells.The diffuse scattering of EM waves is caused by the optimization of phase distribution,leading to a low monostatic and bistatic RCS simultaneously.The proposed metasurface can achieve 10 dB monostatic and bistatic RCS reduction in a wide frequency band from 5.8 to 18.0 GHz with a ratio bandwidth (fH/fL) of 3.10:1 under normal incidence for both polarizations.The theoretical analysis,simulation and experiment results are in good agreement and validate the proposed metasurface can achieve ultra-wideband RCS reduction and diffuse scattering.
查看更多>>摘要：In the problem of aircraft detection for High resolution (HR) Synthetic aperture radar (SAR) images,the background areas commonly contain multiple land cover types,such as runways and grassland.The conventional Constant false alarm rate (CFAR) detection in these non-homogeneous backgrounds with homogeneous assumption leads to unreliable detection results.This paper constructs a one-stage detection method based on the Generalized gamma mixture distribution (GGMD),which is regarded as a competitive and applicable model for combining the advantages of the Generalized gamma distribution (GGD) and the Finite mixture model (FMM).In order to evaluate the availability of the proposed algorithm,HR SAR images for aircraft detection from different product types and with various resolutions are examined.Compared with the CFAR algorithms based on the Gamma distribution,the GGD,and the gamma mixture distribution,the proposed algorithm demonstrates its availability and effectiveness for aircraft detection in HR SAR images in non-homogeneous background.
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