携能无线通信系统中多天线全双工中继传输方法研究

The explosive growth of mobile devices brings unprecedented challenges to wireless communications. Nowadays, mobile devices mostly rely on battery system to power wireless communications. However, the battery capacity is limited and cannot support uninterrupted long-lasting standby time. Besides, battery-based energy storage requires periodic recharge or replacement, making it impossible to power billions of mobile devices. The RF-based wireless power transfer is a promising technique to resolve limited power supply for mobile devices. On the other hand, the depleting spectrum resource is also a great challenge for mobile devices with high mobility and density to interconnect. Cooperative relay can improve spectrum efficiency, alleviating the pressure from scarce spectrum resource. However, due to the fading effect of wireless channels, wireless power transfer is subject to low efficiency and high fluctuation, and may even introduce strong interference to information reception. Hence, the transmission control of energy and information becomes more complicated in wireless powered communication systems. This project aims to maximize the energy and spectrum efficiency of the wireless powered communication systems by exploiting multi-antenna full-duplex relay to coordinate the transmission of energy and information. Firstly, we study the effect of the full-duplex relay’s operating modes and parameters on the transmission performance, analyzing the trade-off between energy transfer, information reception and forwarding. Then, we discuss the coupling of energy and information transmissions among multiple full-duplex relays. Moreover, we consider imperfect channel information in real system and study the cooperative relays’ optimal control of energy and information transmission.

随着移动互联网设备爆炸式增长，无线通信技术面临前所未有的挑战。首先，现有电池技术难以满足移动设备持久工作的需求；为海量移动设备频繁更换电池也极不现实。基于射频信号的无线能量传输有望从根本上解决有限储能的问题。其次，日益减少的频谱资源亦是高移动性、高密度移动设备互联互通所面临的难题。协作中继可以提高频谱效率，改善频谱资源稀缺的紧张局面。然而，无线能量传输效率低且波动大，还会干扰有用信号的接收。因此，携能无线系统中的传输控制将变得更加复杂。本项目拟采用多天线全双工中继来协调能量与信息的无线传输，旨在同时提高无线通信的能效和频谱效率。首先研究全双工中继的不同工作模式和工作参数对传输性能的影响, 分析全双工中继在能量传输、信息接收及转发三者之间的权衡关系；并进一步探讨多个中继在信能传输上的耦合关系；此外，考虑不完全信道信息的实际情况，重新审视多中继协作信能传输的最优控制方法。

本项目研究方向集中在动态物联网环境下无线能量传输以及高能效数据通信机制设计，旨在提升新一代无线通信网络中的能量效率及频谱利用率。面向高用户密度、低能量密度的物联网环境，本项目专注于多中继协作式能量与信息协同传输及优化算法研究，提出了信源波束成形、能量传输调度、多中继联合功率优化控制框架，设计了低复杂度的单调最优化方法，为高密度物联网设计与应用提供了理论基础。针对全双工反向散射通信网络，提出了多模混合射频的概念及设计方法，探索反向散射与传统射频通信模式之间的依赖与互补关系，并首次提出了面向多模网络的被动式中继策略，得到国外同行的认可及引用。澳大利亚国立大学的Xiangyun Zhou教授评价本人工作为“第一次探索散射中继策略”（was among the first to explore the relay use case）。..在项目执行阶段（2017/01/01-2019/12/31），项目负责人在相关领域发表30余篇高水平国际论文，其中通讯或一作Trans类论文6篇，通讯或一作IEEE会议论文10篇以上，指导学生获得IEEE WCNC 2019最佳论文奖，获奖比例约为9/500。此外，项目期间关于反向散射通信技术的研究成果合作出版一部英文著作“Ambient Backscatter Communication Networks”，由剑桥大学出版社（Cambridge University Press）发行。