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Joint User Association and Caching Placement for Cache-Enabling UAV Networks

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China Communications 2023年第6期20卷 291-309页

作者： tiankui zhang Chao Chen Dingcheng Yang School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Information Engineering School Nanchang UniversityNanchang 330031China

Cache-enabling unmanned aerial vehicles(UAVs)are considered for storing popular contents and providing downlink data offloading in cellular *** this context,we formulate a joint optimization problem of user association,caching placement,and backhaul bandwidth allocation for minimizing content acquisition delay with consideration of UAVs’energy *** decompose the formulated problem into two subproblems:i)user association and caching placement and ii)backhaul bandwidth *** first obtain the optimal bandwidth allocation with given user association and caching placement by the Lagrangian multiplier *** that,embedding the backhaul bandwidth allocation algorithm,we solve the user association and caching placement problem by a threedimensional(3D)matching *** we decompose it into two two-dimensional(2D)matching problems and develop low-complexity *** proposed scheme converges and exhibits a low computational *** results demonstrate that the proposed cache-enabling UAV framework outperforms the conventional UAV-assisted cellular networks in terms of content acquisition delay and the proposed scheme achieves significantly lower content acquisition delay compared with other two benchmark schemes.

关键词： edge caching unmanned aerial vehicles user association three-dimensional(3D)matching

Deep Reinforcement Learning-Based Resource Allocation for UAV-Enabled Federated Edge Learning

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Journal of Communications and Information Networks 2023年第1期8卷 1-12页

作者： Tianze Liu tiankui zhang Jonathan Loo Yapeng Wang School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China School of Computing and Engineering University of West LondonLondon W55RFUK Faculty of Applied Sciences Macao Polytechnic UniversityMacao 999078China

The resource allocation of the federated learning(FL)for unmanned aerial vehicle(UAV)swarm systems are *** UAV swarms based on FL realize the artificial intelligence(AI)applications by means of distributed training on the basis of ensuring the security of private ***,the direct application of the FL in UAV swarms will incur high ***,in this article,we consider the resource allocation problem in FL for UAV *** avoid the high communication overhead between UAVs and the central server,we proposed an FL framework for UAV swarms based on mobile edge computing(MEC)in which model aggregation is migrated to edge *** the proposed framework,the total cost of the FL is defined as the weighted sum of the total delay of UAV swarms to complete the FL and system energy *** order to minimize the total cost of FL,we propose a resource allocation algorithm for joint optimization of computing resources and multi-UAV association based on deep reinforcement learning(DRL).The simulation result shows that:(1)compared with the benchmark algorithm,the proposed algorithm can effectively reduce the total cost of FL;(2)the proposed algorithm can realize the trade-off between task completion delay and system energy consumption through weight changes.

关键词： DRL FL MEC UAV

Joint Doppler Shift and Channel Estimation for UAV mmWave System with Massive ULA

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China Communications 2022年第4期19卷 67-82页

作者： Yanan Li Yue Zhu tiankui zhang Dian Fan The China Academy of Information and Communications Technology Beijing 100191China School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Beijing key engineering laboratory of testing and validation for smart terminal and hardware

A joint Doppler shift and channel estimation method for the millimeter-wave communication system of an unmanned aerial vehicle(UAV) equipped with a large-scale uniform linear antenna(ULA) array has been proposed. Since Doppler shift induces intercarrier interference, the parameters of the channel paths have been decomposed into the Doppler shift and the channel information. In order to obtain the Doppler shift, a new estimation algorithm based on a combination of discrete Fourier transform and phase rotation has been proposed, which can determine the appropriate number of antennas. In addition to estimating the channel information, a low-complexity joint Doppler shift and channel estimation method has been designed that can quickly obtain accurate estimates. Furthermore, the achievable sum rate, the theoretical bounds of the mean squared errors, and the Cram?er-Rao lower bounds of the estimation method have been derived. The analysis and simulation results prove that the performance of the proposed approach is close to the theoretical inference.

关键词： ULA Doppler shift estimation channel estimation achievable sum rate

Joint task scheduling and multi-UAV deployment for aerial computing in emergency communication networks

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Science China(Information Sciences) 2023年第9期66卷 239-258页

作者： tiankui zhang Chaobin CHEN Yu XU Jonathan LOO Wenjun XU School of Information and Communication Engineering Beijing University of Posts and Telecommunications School of Computing and Engineering University of West London School of Artificial Intelligence Beijing University of Posts and Telecommunications

This article studies mobile edge computing technologies enabled by unmanned aerial vehicles(UAVs) in disasters. First, considering that the ground servers may be damaged in emergency scenarios, we proposed an air-ground cooperation architecture based on ad-hoc UAV networks. We defined the system cost as the weighted sum of task delay and energy consumption because of different delay sensitivity and energy sensitivity tasks in emergency communication networks. Then, we formulated the system cost-minimization problem of task scheduling and multi-UAV deployments. To solve the proposed mixed integer nonlinear programming problem, we decomposed it to two sub-problems that were solved by proposing a swap matchingbased task scheduling sub-algorithm and a successive convex approximation-based multi-UAV deployment sub-algorithm. Accordingly, we propose a joint optimization algorithm by iterating the two sub-algorithms to obtain a low complexity sub-optimal solution. Finally, the simulation results show that(i) the proposed algorithm converges in several iterations, and(ii) compared with the benchmark algorithms, the proposed algorithm has better performance of reducing task delay and energy consumption and achieves a good tradeoff between them for diverse tasks.

关键词： emergency communication mobile edge computing swap matching algorithm unmanned aerial vehicle

Optimal design of coded aperture used for Z-Pinch driven fusion neutron imaging

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Science China(Technological Sciences) 2015年第7期58卷 1289-1293页

作者： JIA QingGang HU HuaSi ZHENG XiangYang zhang FengNa WANG DongMing HU Guang zhang tiankui WU YueLei Institute of Nuclear Science and Technology Xi'an Jiaotong University State Environmental Protection Administration (SEPA) Nuclear and Radiation Safety Centre Research Center of Laser Fusion China Academy of Engineering Physics

Currently,the neutron yield of Z-Pinch is lower than that of laser driven *** the neutron imaging for this facility,the signal to noise ratio(SNR)has a significant influence on the expected spatial resolution of the reconstructed fusion core,especially in the condition of low neutron *** this paper,mathematical model is purposed to describe the dependence of aperture parameters on the imaging *** investigation shows that the imaging SNR is closely related to the size of contrast boundary on the point spread *** to this,a novel non-uniform redundancy penumbra apertures array is *** addition,the imaging performances of this novel coded aperture,penumbra aperture and ring aperture are evaluated and compared by Monte Carlo *** comparison shows that this novel aperture has significant advantage compared to the penumbra aperture which is commonly used for neutron imaging with low *** encouraging results can provide reference for the optimal design of the coded aperture used in the neutron imaging for Z-pinch driven fusion with low neutron yield.

关键词： Z-pinch driven fusion neutron imaging coded aperture signal to noise ratio low neutron yield

Power allocation scheme for multicell interference coordination in OFDMA systems

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Frontiers of Electrical and Electronic Engineering in China 2009年第1期4卷 31-34页

作者： Zhiwei LI Chunyan FENG tiankui zhang Jieying ZHENG Institute of Communication Networks Integrated Technology Beijing University of Posts and TelecommunicationsBeijing 100876China

To coordinate inter-cell interference,a multicell adaptive power allocation scheme is proposed for downlink orthogonal frequency division multiple access(OFDMA)cellular *** scheme uses the difference of the signal to interference plus noise ratio(SINR)between the co-subchannels of adjacent cells to balance SINR for coordinating the transmit power in the *** scheme can improve edge user performance,reduce interference between the co-subchannels of adjacent cells and improve radio resource *** results show that the scheme can balance system performance and ensure system throughput.

关键词： orthogonal frequency division multiple access(OFDMA) power allocation inter-cell interference interference coordination

Limited Feedback Bit Allocation for Cooperative Multi-cell Systems with Multi- user MIMO

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China Communications 2012年第1期9卷 34-39页

作者： Shi Junfeng zhang tiankui Zeng Zhimin Laboratory of Network System Architecture and Convergence Key Laboratory of Beijing CityBeijing University of Posts and TelecommunicationsBeijing 100876P.R.China

For the cooperative multi-cell systems with muki-user MIMO, a new limited feedback bit allocation scheme is proposed to minimize the rate loss caused by quantization error. In the proposed scheme, the Channel State Information （CSI） feedback of cell-edge user for the local service cell and the adjacent interference cell are separately quantized. Based on the upper bound of the rate loss of cell-edge user due to the limited feedback, the number of feedback bits for quantized CSI of the local service cell and the adjacent cell are optimized with the fixed total bits of the limited feedback. The simulation shows that our proposed scheme of feedback bits allocation efficiently decreases the interference and increases the rate of systems compared with that of equal bits allocation and those of other allocations.

关键词： limited feedback Block Diagonalization(BD) precoding multi-cell multi-user MIMO

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用于异构网络的差值门限模糊切换算法

西安电子科技大学学报 2011年第1期38卷 165-170页

作者：张天魁邱禹冯春燕北京邮电大学信息与通信工程学院北京100876 普天信息技术研究院有限公司北京100080

为了提高用户在异构网络中进行垂直切换的准确度,减少"乒乓效应",提出了一种差值门限模糊切换算法(Difference Threshold based Fuzzy Handover,DTFH).DTFH算法考虑异构网络中的切换触发与切换判决两个方面.用户获得当前网络和目标网络... 详细信息

为了提高用户在异构网络中进行垂直切换的准确度,减少"乒乓效应",提出了一种差值门限模糊切换算法(Difference Threshold based Fuzzy Handover,DTFH).DTFH算法考虑异构网络中的切换触发与切换判决两个方面.用户获得当前网络和目标网络的信噪比差值,根据该信噪比差值与设定的切换触发门限的比较结果进行切换触发;然后,采用模糊逻辑方法得到用户当前网络与目标网络的模糊判决值,根据两个网络的模糊判决值之差与设定的切换判决门限的对比结果进行切换判决.以LTE和WiMAX异构网络为仿真场景,仿真结果表明,与传统切换算法相比,DTFH算法能在减少"乒乓效应"的同时,提高用户吞吐量,从而提高垂直切换的性能.

关键词：异构网络垂直切换触发判决模糊逻辑

LTE中适用于MBSFN的自适应资源分配机制

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西安电子科技大学学报 2012年第5期39卷 126-131,191页

作者：张天魁蒋傲雪冯春燕北京邮电大学信息与通信工程学院北京100876 网络体系构建与融合北京市重点实验室北京100876 信元公众信息发展有限责任公司北京100101

提出了一种适用于长期演进(LTE)系统多播广播单频网传输方式的自适应资源分配机制,考虑多播业务的资源需求和信道情况决定每个子帧上传输的业务类型.在每个资源分配周期内,通过估计系统内多播业务所需的子帧比例,选定相应的信干噪比门限... 详细信息

提出了一种适用于长期演进(LTE)系统多播广播单频网传输方式的自适应资源分配机制,考虑多播业务的资源需求和信道情况决定每个子帧上传输的业务类型.在每个资源分配周期内,通过估计系统内多播业务所需的子帧比例,选定相应的信干噪比门限;通过门限判决并考虑多播业务所需资源分配情况,自适应地实现多播业务和单播业务间的子帧分配.仿真结果表明,所提机制在保证多播业务速率的同时,可以提高单播业务吞吐量,优化了系统无线资源的利用率。

关键词：长期演进系统多播广播单频网多播业务资源分配