基于仿射预编码的虚拟全双工中继干扰抑制技术研究

Virtual full-duplex (VFD) relaying achieves the full-duplex communications by exploiting two alternative half-duplex (HD) relay nodes, which can recover the loss in the spectral efficiency of HD relays and alleviate the strong self-interference in full-duplex relaying. The main performance bottleneck of the VFD relay networks is the so-called inter-relay interference (IRI) due to alternate transmission relaying. To combat the IRI, the interference suppression model is strived to establish by extending the affine precoding superimposed signals to the VFD relay networks. By projecting the transmitted signal onto the null space of the inter-relay interference signal using row-space mapping that is independent of the channel state information (CSI), the perfect IRI suppression can be achieved without any CSIs at the relays, which breaks through the traditional idea of the precoding-based interference suppression and the differential interference suppression in VFD relay networks. Consequently, the impact on the interference suppression algorithms due to the imperfect channel estimation is eliminated, which can improve the flexibility and robustness of the interference suppression schemes. Furthermore, the joint transceiver beamforming design for multiple nodes is decoupled from the IRI suppression, which can reduce the complexity of the joint optimization design, and may be regarded as a potential novel solution to the MIMO relay networks. The objective of the researches is to construct a novel theoretical framework for interference suppression in VFD relay networks and provide a key technical support for effective transmission in the typical applications over future ultra-dense heterogeneous cellular networks, wireless sensor networks and multihop Ad hoc networks.

虚拟全双工中继网络借助两个半双工中继节点交替转发信息来实现全双工通信，在弥补半双工速率损失的同时可以有效缓解全双工中继带来的严重同频自干扰问题。然而，两节点交替收发会引入中继间干扰（IRI）信号，成为制约网络性能和容量提升的瓶颈。本项目以IRI抑制作为切入点，通过拓展仿射预编码叠加信号分离理论，构建基于仿射预编码的虚拟全双工中继干扰抑制模型。借助行空间预编码，将发送信号映射到不依赖信道的干扰零空间，实现未知信道条件下完美IRI抑制，突破传统预编码干扰抑制和差分干扰抑制的局限，消除非理想信道估计对干扰抑制算法的影响，提高干扰抑制的灵活性和鲁棒性；进一步将干扰抑制与波束成形联合设计解耦，有效降低多节点联合优化设计的复杂度，为MIMO中继干扰抑制提供新的解决思路。研究旨在建立新的虚拟全双工中继干扰抑制理论框架，为高密度异构蜂窝网、无线传感器网及多跳Ad hoc网等高效传输提供关键技术支撑。

本项目以高密度异构蜂窝网、无线传感器网、战场无人机协作网等潜在虚拟全双工中继应用领域为研究背景，通过拓展仿射预编码叠加信号分离理论，构建基于仿射预编码的虚拟全双工中继干扰抑制模型。重点针对AF协议下的两路虚拟全双工中继网络，以高效、低复杂度的中继间干扰抑制为目标，从消除信道估计误差引入的剩余IRI入手，对未知信道状态信息条件下的预编码干扰抑制机理、行空间映射理论、预编码矩阵设计等展开研究；借助矩阵变换和映射理论，分析行空间映射与列空间映射两种方式下收发信号所在子空间的差异，阐明信道矩阵特性对预编码信号所在子空间的影响；针对不同衰落信道环境，结合单载波和多载波传输体制，建立发送信号的行空间预编码模型，完成正交域空间构造方法；并构建相应的预编码发射信号模型，设计与两路中继交替转发机制相一致的编解码策略，推导预编码矩阵与解码矩阵满足的正交约束条件，给出满足约束条件的预编码矩阵设计和构造方法，分析了预编码矩阵参数变化对噪声方差的影响，提出基于行空间映射的OFDM和MIMO虚拟全双工中继干扰抑制模型。本研究成果初步建立了新的虚拟全双工中继干扰抑制理论框架，设计了不依赖信道状态的干扰零空间，实现未知信道条件下干扰抑制和信号分离，突破传统基于CSI的干扰抑制的局限，并初步将其拓展到MIMO和OFDM的虚拟全双工中继网络。在本项目研究阶段内，共资助发表论文10篇，其中SCI期刊论文6篇，EI论文4篇，申请国家发明专利2项，培养毕业博士生2名，毕业硕士生1名。