用于同时同频全双工MIMO无线通信系统的同频自干扰抵消技术的研究

Owing to recent developments of the co-channel self-interference cancellation technologies, in-band full duplex wireless communication technology has been considered a hot topic in the research area of the fifth generation mobile communication system, though it was once regarded as a mission impossible. However, this technology is far from practical applications and its development is still limited in the laboratory。It can’t support MIMO technology properly due to the complexity to implement, and its ability to suppress the self-interference is limited due to the lack of solutions to handle the RF impairments in transceivers, therefore it only support low power wireless applications for now. Based on the master of the transfer characteristics of the self-interference channel, effective frequency domain adaptive filter technology will be utilize in this project to reduce the complexity of the analog self-interference cancellation circuit and related algorithms. Second, the correlation components among the self-interference channel and cross-interference channels will be extracted in the MIMO operation mode and utilized to reuse the analog self-interference cancellation circuits sufficiently, therefore the complexity of the in-band full duplex MIMO system will be reduced. Then the system characteristics of nonlinearity and I/Q imbalance will be modeled and compensated, thus the performance of the self-interference cancellation will be improved. Last, low complexity co-channel self-interference cancellation circuits and related algorithms which support MIMO technology will be realized based on the achievements mentioned above, and their performance and reliability will be tested experimentally.

同时同频全双工无线通信曾被认为是不可能完成的任务，如今却成为第五代移动通信技术研究的热点，其关键原因在于近年来同频自干扰抵消技术的进步。然而目前该技术的发展仍处于实验室阶段，实用性较差，并且由于复杂度较高，无法有效支持MIMO技术。另外由于缺乏对收发信机射频缺陷的处理，限制了其自干扰抵消性能，目前仅适用于低功率无线应用。本项目将在充分掌握同频自干扰信道传输特性的基础上，采用有效的频域自适应滤波技术，降低模拟自干扰抵消电路与算法的复杂度；其次，在MIMO传输模式下，提取同频自干扰信道和互干扰信道之间的相关性分量，并利用该相关性对模拟自干扰抵消电路充分复用，降低同时同频全双工MIMO系统的复杂度；然后对系统非线性失真和I/Q不平衡的特性进行提取与补偿，提高自干扰抵消性能。集成上述研究成果，本项目将实现支持MIMO技术且复杂度较低的同频自干扰抵消链路硬件和相应算法，并对其抵消性能进行实验验证。

本课题围绕同频全双工通信系统的实现，在同频自干扰抵消技术上进行了持续的研究，取得的成果主要包括以下几个方面。一、采用收发天线分离的方案，实现了单通道的自干扰射频抵消电路，自干扰抵消带宽达到50MHz以上，自干扰抵消性能达到50dB以上。同时实现了自干扰抵消电路参数的实时优化算法。二、改进了传统的基于功率检测的残留自干扰信号检测方法，采用相关检测的方案，实现了较低复杂度的模拟自干扰抵消电路和自适应抵消算法，显著提高了自干扰抵消算法的速度和健壮性，使射频自干扰抵消电路可以较好的应对自干扰信道特性的快速变化。三、采用创新的电路结构，以及相关检测电路，实现了支持2X2 MIMO工作模式的射频自干扰抵消电路，以及相关算法。自干扰抵消带宽达到50MHz以上，同时自干扰抵消性能达到50dB以上。四、采用FDTD算法对室内自干扰信道的特性进行了计算与特性提取。同时开发了自动测量软件对矢量网络分析仪进行自动控制，实地测量了实验室环境下自干扰信道的特性并对其进行了分析，为多支路自干扰抵消电路的设计提供了参考。五、针对非线性失真的数字抵消技术，研究了在实际通信信号（单载波和OFDM模式）的作用下非线性系统产生的弱非线性分量的特性，给出了相关的计算公式，简化了非线性分量的计算，为非线性失真的数字抵消技术打下了基础。六、为了实现4x4 MIMO工作模式的自干扰抵消设备，研制了符合IEEE 802.11ac 标准的高性能4通道射频收发信机。