摘要
在物联网(Internet of Things,IoT)系统中,信道具有高度时变性,直接链路有概率被阻塞。为了确保状态更新信息的及时传递,设计了一种智能反射面(Intelligent Reflecting Surface,IRS)辅助无人机(Unmanned Aerial Vehicle,UAV)服务地面多用户的无线下行链路系统。UAV在下行链路中作为一个移动基站,沿着优化的轨迹飞行并在靠近地面用户的合适位置悬停,再与地面上的用户进行数据传输。通过时间离散化、数学建模等手段构建联合优化的模型,建立一个多约束优化问题。目标是通过对无人机轨迹和流调度、IRS相移设计等变量的联合优化以最小化系统的信息年龄。研究了IRS反射传输信号辅助改善无线环境的过程,即通过改变信道增益来改变最大数据传输速率。采用IRS相移调整的方式来提高时变的信道增益,以改善通信质量。由于目标函数和约束公式中含有的非凸公式以及多个优化变量之间的耦合关系,采用连续凸逼近(Successive Convex Approximation,SCA)和块坐标下降(Block Coordinate Descent,BCD)等技术设计优化算法,将非凸优化问题简化后求得总优化问题的解。仿真结果表明,算法能得到平滑曲线,系统信息年龄随发射功率和数据传输速率阈值升高显著降低,体现了所提算法的可行性。
In Internet of Things(IoT)systems,channels are highly time-varying,and direct links have a probability of being blocked.A wireless downlink system for an intelligent reflecting surface(IRS)assisted unmanned aerial vehicle(UAV)serving multiple users on the ground is designed to ensure the timely delivery of status update information.The UAV acts as a mobile base station in the downlink,flying along an optimized trajectory and hovering at a suitable location close to the user on the ground before transmitting data to users on the ground.A multi-constraint optimization problem is modeled by constructing a joint optimization through time discretization and mathematical modeling.The goal is to minimize the information age of the system through the joint optimization of variables such as the UAV trajectory,flow scheduling,and IRS phase shift design.The process of IRS assisting in improving the wireless environment by transmitting signals through reflection,that is,varying the maximum data rate by changing the channel gain,is investigated.IRS phase shift adjustment is used to increase the time-varying channel gain to improve the communication quality.Due to the non-convex formulation contained in the objective function and constraint formulation as well as the coupling between multiple optimization variables,optimization algorithms are designed using techniques such as successive convex approximation(SCA)and block coordinate descent(BCD)to simplify the non-convex optimization problem to find the solution of the total optimization problem.Simulation results demonstrate that the algorithm can obtain smooth curves,and the age of information in the system decreases significantly with increasing transmit power and data transmission rate thresholds,which imply the feasibility of the proposed algorithm.
作者
陈宫紫钰
贾向东
张鑫
CHEN Gongziyu;JIA Xiangdong;ZHANG Xin(College of Computer Science and Engineering,Northwest Normal University,Lanzhou,Gansu 730070,China;Wireless Communication Key Lab of Jiangsu Province,Nanjing University of Posts and Telecommunications,Nanjing,Jiangsu 210003,China)
出处
《信号处理》
CSCD
北大核心
2024年第8期1480-1488,共9页
Journal of Signal Processing
基金
国家自然科学基金(61861039,62261048)。
关键词
信息年龄
智能反射面
用户调度
轨迹优化
块坐标下降
age of information
intelligent reflecting surface
users scheduling
trajectory optimization
block coordinate descent
