查看更多>>摘要：A leaky-wave antenna with horizontal scanning beams and broadside radiation is presented on the peri-odically modulated microstrip.The horizontal radiation is realized by periodically etching a set of resonant open-ended slots on the ground plane.Dispersion diagrams and Bloch impedance are first analyzed to investigate the propagation and radiation characteristics of the periodic structure.Subsequently,shunt matching stubs are installed aiming to obtain seamless beam scanning property through the broadside.Finally,a prototype is implemented as verification of the presented antenna.Results of the simulations and measurements agree well with each other,indicating the elimination of the open-stop band effect and the horizontal radiation beams.The fabricated antenna exhibits a beam range from-62° to+34°,and provides a maximum measured gain about 14.6 dBi at 10 GHz.
查看更多>>摘要：By using a novel meta-resonator structure,a miniaturized,surface mountable,shared aperture,and hybrid electric/magnetic dipole pattern diversity antenna is proposed for Internet of things(IoT)applications.By exploring the shared electric(E-dipole)and magnetic dipole(M-dipole)structures,a novel T-shaped split-ring res-onator(SRR)with even and odd modes is presented and studied by current distributions and equivalent circuits.Broadside and omnidirectional(monopole-like)patterns are achieved by exciting the M-dipole and E-dipole modes of the T-shaped SRR,respectively.To validate the proposed design,this shared aperture metamaterial-inspired pattern diversity antenna with a small size of 0.295λ0× 0.0065λ0× 0.115λ0 is fabricated and measured.The measured over-lapped-10 dB bandwidth is from 3.40 GHz to 3.63 GHz(7.0％,covering the LTE B42 band)and the port isolation is greater than 23 dB.Both two modes achieve a good radiation efficiency better than-0.79 dB(＞83.0％).
查看更多>>摘要：This paper proposes a wideband cavity-backed slotted patch antenna,loaded with a magneto-electric(ME)-dipole and fed by a microstrip line,for millimeter wave(mm-Wave)applications.The coupled-feed cavity-backed slotted patch antenna is loaded with the ME-dipole.The slotted patch antenna serves as both a radiator and a ground for the ME-dipole.The combination of the ME-dipole antenna and the slotted patch antenna realizes a-10 dB impedance bandwidth covering over 22.86-44.35 GHz(63.9％).The pattern of the antenna element remains stable throughout this bandwidth.The proposed broadband antenna unit not only realizes single linearly polarized(LP)radiation but also can be designed for dual-LP radiation.The dual-polarized radiation can be achieved by changing the slot of the patch antenna to a crossed slot and altering the ME-dipole antenna to a dual-polarization form.A 2 × 2 dual-polarized array has been designed,fabricated,and tested.A novel dual-polarized feeding network is proposed.To achieve higher isolation,broadband in-phase feed and differential feed are adopted,respectively.A low-loss single to the differential structure is proposed for differential feeding.The simulated isolation of the array is higher than 40 dB.Measured results show that the dual-polarized 2x2 array has an overlapping bandwidth of 52.3％(|S11|＜-10 dB and|S21|＜-30 dB)with a peak gain of 14 dBi.The proposed antenna,featuring a wide overall bandwidth,low cost,and good radiation performance,is well suited for mm-Wave applications.
查看更多>>摘要：Dual-polarized antennas are required in the current mobile communication to increase the channel capacity and reducing multi-path effects.Utilizing characteristic mode(CM)analysis,this paper presents a five-patch substrate integrated suspended line(SISL)antenna with suppressed unwanted higher-order modes,and achieves an enhanced bandwidth by using differential multi-point feeding(MPF)systems.Compared to single-point feeding systems,the proposed dual-polarized SISL antenna with the MPF system demonstrates a bandwidth 1.87 times wider.The novel SISL feeding system incorporates two pairs of differentially-fed branch line feed structures.A prototype of the proposed differential-fed antenna is fabricated and measured,showing good agreement between simulated and measured results.The dual-polarization SISL antenna can achieve realized gain from 8.1 dBi to 10.8 dBi within a working frequency from 3.17 GHz to 3.61 GHz(12.98％).Moreover,utilizing low-cost substrates,the proposed SISL antenna has the potential for 5G applications.
查看更多>>摘要：To describe and control the polarization state of electromagnetic waves,a polarization control operator of the complex vector form is proposed.Distinct from traditional descriptors,the proposed operator employs an angle parameter to configure the polarization state of the polarized wave.By setting the parameter in the proposed operator,the amplitude of the field components can be modified,resulting in changes in the magnitude and direction of the field vector,and thus realizing control of the polarization state of the electromagnetic wave.The physical meaning,orthogonal decomposition,and discrete property of the proposed operator are demonstrated through mathematical derivation.In the simulation examples,the polarization control operator with fixed and time-varying parameters is applied to the circularly polarized wave.The propagation waveform,the trajectory projection and the waveform cross section in different reception directions of the new electromagnetic waves are observed.The simulation results indi-cate that complex electromagnetic waves with more flexible polarization states can be obtained with the aid of the polarization operator.
查看更多>>摘要：Cross-chain technology,which enables different blockchains to intercommunicate with one another,is challenging.Many existing cross-chain platforms,such as Polkadot and Cosmos,generally adopt a relay-based scheme:A relaychain(relay blockchain)receives and records the state information from every parachain(parallel blockchain),and publish the information on the platform,by which parachains are able to efficiently acquire the state information from one another.In the condition when parachain is consortium blockchain,the cross-chain plat-form cannot work properly.On the one hand,whether state information is submitted to relaychain is completely decided by the internal decision of parachain.The timeliness of state information cannot be guaranteed.On the other hand,the transfer of state information will be interrupted due to the failure of parachain or relaychain-parachain connection.In this paper,we propose a relay-based blockchain intercommunication framework,called XPull(cross-pulling).Specifically,to ensure the timeliness of state information,we propose a cross-chain state pulling scheme based on cosigned state pulling agreement.To solve the interruption of state transfer,we propose a random schedul-ing scheme to resume the transfer,or confirm the failure of parachain.The security analysis and experimental results demonstrate that XPull is secure and efficient.
查看更多>>摘要：This paper first investigates and compares the uplink spectral efficiency(SE)of distributed cell-free massive multiple-input multiple-output(mMIMO)and cellular mMIMO networks,both with user equipment(UE)hardware impairments.We derive a lower bound on the uplink ergodic channel capacity of the cellular mMIMO with UE hardware impairments,based on which we determine the optimal receive combining that maximizes the instanta-neous effective signal-to-interference-and-noise ratio.Then,a lower bound on the uplink capacity of a distributed cell-free mMIMO with UE hardware impairments is derived using the use-and-then-forget technique.On this basis,the optimum large-scale fading decoding vector is found using generalized Rayleigh entropy.By using three combining schemes of minimum mean-square error(MMSE),regularized zero-forcing(RZF),and maximum ratio,the uplink SEs of distributed cell-free mMIMO and cellular mMIMO networks are analyzed and compared.The results show that the two-layer decoding distributed cell-free mMIMO network with MMSE combining outperforms the cellular mMIMO network,and the advantage is more evident as the hardware impairment factor increases.Finally,the uplink energy efficiency(EE)of the distributed cell-free mMIMO networks is analyzed and evaluated through the established realis-tic power consumption model with hardware impairments.Simulation results show that two-layer decoding provides higher SE and EE than single-layer decoding.In addition,RZF achieves almost the same SE and EE as MMSE in a two-layer decoding architecture.
查看更多>>摘要：Optimization-based radio resource management(RRM)has shown significant performance gains on high-throughput satellites(HTSs).However,as the number of allocable on-board resources increases,traditional RRM is difficult to apply in real satellite systems due to its intense computational complexity.Deep reinforcement learning(DRL)is a promising solution for the resource allocation problem due to its model-free advantages.Never-theless,the action space faced by DRL increases exponentially with the increase of communication scale,which leads to an excessive exploration cost of the algorithm.In this paper,we propose a recursive frequency resource allocation al-gorithm based on long-short term memory(LSTM)and proximal policy optimization(PPO),called PPO-RA-LOOP,where RA means resource allocation and LOOP means the algorithm outputs actions in a recursive manner.Specifi-cally,the PPO algorithm uses LSTM network to recursively generate sub-actions about frequency resource allocation for each beam,which significantly cuts down the action space.In addition,the LSTM-based recursive architecture allows PPO to better allocate the next frequency resource by using the generated sub-actions information as a prior knowledge,which reduces the complexity of the neural network.The simulation results show that PPO-RA-LOOP achieved higher spectral efficiency and system satisfaction compared with other frequency allocation algorithms.
查看更多>>摘要：With the advent of the 5G era and the accelerated development of edge computing and Internet of Things technologies,the number of tasks to be processed by mobile devices continues to increase.Edge nodes be-come incapable of facing massive tasks due to their own limited computing capabilities,and thus the cloud and edge collaborative environment is produced.In order to complete as many tasks as possible while meeting the deadline constraints,we consider the task scheduling problem in the cloud-edge and edge-edge collaboration scenarios.As the number of tasks on edge nodes increases,the solution space becomes larger.Considering that each edge node has its own communication range,we design an edge node based clustering algorithm(ENCA),which can reduce the feasi-ble region while dividing the edge node set.We transform the edge nodes inside the cluster into a bipartite graph,and then propose a task scheduling algorithm based on maximum matching(SAMM).Our ENCA and SAMM are used to solve the task scheduling problem.Compared with the other benchmark algorithms,experimental results show that our algorithms increase the number of the tasks which can be completed and meet the latest deadline con-straints by 32％-47.2％under high load conditions.
查看更多>>摘要：Nonnegative CANDECOMP/PARAFAC(NCP)tensor decomposition is a powerful tool for multiway signal processing.The alternating direction method of multipliers(ADMM)optimization algorithm has become in-creasingly popular for solving tensor decomposition problems in the block coordinate descent framework.However,the ADMM-based NCP algorithm suffers from rank deficiency and slow convergence for some large-scale and highly sparse tensor data.The proximal algorithm is preferred to enhance optimization algorithms and improve convergence properties.In this study,we propose a novel NCP algorithm using the alternating direction proximal method of mul-tipliers(ADPMM)that consists of the proximal algorithm.The proposed NCP algorithm can guarantee convergence and overcome the rank deficiency.Moreover,we implement the proposed NCP using an inexact scheme that alterna-tively optimizes the subproblems.Each subproblem is optimized by a finite number of inner iterations yielding fast computation speed.Our NCP algorithm is a hybrid of alternating optimization and ADPMM and is named A2DPMM.The experimental results on synthetic and real-world tensors demonstrate the effectiveness and efficiency of our pro-posed algorithm.
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