A Survey on User-centric Networks for 6G
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摘要: 与第5代移动通信网络(5G)相比,第6代移动通信网络(6G)有望引入新的性能指标和应用方案,如全球覆盖、更高的频谱/能源/成本效率、更高的智能和安全水平。用户为中心网络(UCN)将成为实现6G的关键推动者,因为其突破了传统基站为中心网络并与信息产业的新兴技术形成了有效融合。该文将从物理层的信道估计和预测、网络上层的性能分析以及链路层的无线资源管理等方面综述这一新型网络的研究现状。首先,讨论和分析UCN的概念和总体网络架构;其次,总结UCN网络中信道估计预测方法、性能分析策略和无线资源管理(RRM)方案;最后,在广泛的调研基础上,探讨UCN网络中的开放性问题,为今后的研究方向提供思路。此综述旨在使读者快速而全面地了解UCN的当前技术状况,从而吸引更多的研究人员进入这一领域。Abstract: Compared with the Fifth Generation mobile network (5G), the Sixth Generation mobile network (6G) is expected to introduce new performance indicators and application scenarios. Global coverage, high spectrum/energy/cost efficiency, high level of intelligence and security are leading features in 6G era. Different from traditional Base Station (BS)-centric network, the User-Centric Network (UCN) emerges as a key enabler for 6G by combining emerging technologies from information industries. In this novel framework, a comprehensive overview of physical layer, network layer and link layer is provided. As a starting point, the concepts and general architecture of the UCNs are surveied and discussed. Then, the survey is classified as: channel estimation and prediction; performance analysis with diverse performance metrics; different types of RRM (Radio Resource Management). Finally, based on extensive discussions, open issues are provided to guide future scholarly research directions. It is anticipated that this survey will provide a quick and comprehensive understanding of the current state of the arts for UCNs which attracting more researchers into this area.
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图 1 近几年全球移动数据量增长趋势[1]
表 1 已有综述工作对比
表 2 缩略词
缩写 全拼 含义 3GPP the Third-Generation Partnership Project 第3代伙伴计划 5G the Fifth Generation mobile network 第5代移动通信网络 6G the Sixth Generation mobile network 第6代移动通信网络 AP Access Point 接入节点 BCD Block Coordinate Descent 块坐标下降 BINLP Binary Integer Non-Linear Programming 二进制整数非线性优化 CRAN Cloud Radio Access Network 云接入网 CSI Channel State Information 信道状态信息 CVSINR Cluster Virtual Signal-to-Interference-plus-Noise Ratio 群虚拟信干燥比 DeDU Decoupled Downlink and Uplink 上下行解耦 MISO Multiple Input Single Output 多输入单输出 MIMO Multiple Input Multiple Output 多输入多输出 MINLP Mixed-Integer Non-Linear Programming 混合整型非线性优化 SISO Single Input Single Output 单输入单输出 TCN Traditional Cellular Network 传统蜂窝网络 UCN User-Centric Network 用户为中心网络 UDN Ultra-Dense Network 超密集网络 WMMSE Weighted Minimum Mean Square Error 权重最小均方误差 表 3 UCN与TCN之间的对比
对比内容 网络 TCN UCN 部署范围 较大范围 室内/热点区域 AP密度 低 高 用户密度 远高于AP密度 与AP密度相仿 覆盖特点 异构,不规则形状 单层,规则的蜂窝形状 用户移动性 高 低 速率 中低 高 前传链路 理想的有线链路 理想的有线链路/非理想的无线链路 表 4 信道估计与预测研究工作总结
表 5 性能分析研究工作总结
表 6 无线资源管理研究工作总结
类别 资源种类 文献 方法 单维资源管理 功率资源 文献[49-52] 交替迭代、凸优化理论、深度Q学习网络 计算资源 文献[54,55] 深度强化学习、合作博弈理论 训练资源 文献[53] 图论 2维资源管理 子载波&功率 文献[56,57] 分支切割、交替迭代 链路容量&计算 文献[58] 松弛近似、罚函数 比特&计算 文献[58,59] 线性优化理论、循环神经网络 波束方向&功率 文献[60-62] 松弛近似、深度Q学习网络 3维资源管理 子载波、功率&比特 文献[63] 交替迭代 用户调度、子载波&功率 文献[64,65] 交替迭代、粒子群算法、松弛近似 比特、波束方向&功率 文献[66] 深度学习神经网络 AP集群、波束方向&功率 文献[67-72] 粒子群算法、凸优化理论、松弛近似、WMMSE、
深度残差学习网络、深度神经网络导频、波束方向&功率 文献[73] 信号处理理论、松弛近似 4维资源管理 计算、存储、波束方向&功率 文献[74] 松弛近似、交替迭代 AP集群、传输时隙、波束方向&功率 文献[75] 松弛近似、凸优化理论 AP集群、前传链路压缩比、波束方向&功率 文献[76] 范数最小化、凸优化理论 用户调度、AP集群、子载波&功率 文献[77] 交替迭代、协同优化理论 -
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