面向6G的MIMO⁃OTFS系统低复杂度预编码方案  

6G-Oriented Low-complexity Precoding Scheme in MIMO-OTFS Systems

作　　者：邹婷婷 许文俊[1] 胡靖宇 高晖 张治[2] ZOU Tingting;XU Wenjun;HU Jingyu;GAO Hui;ZHANG Zhi(School of Artificial Intelligence,Beijing University of Posts and Telecommunications,Beijing 100876,China;School of Information and Communication Engineering,Beijing University of Posts and Telecommunications,Beijing 100876,China)

机构地区：[1]北京邮电大学人工智能学院,北京100876 [2]北京邮电大学信息与通信工程学院,北京100876

出　　处：《无线电通信技术》2021年第6期789-798,共10页Radio Communications Technology

基　　金：国家自然科学基金项目(61871057)。

摘　　要：6G致力于打造“空天地海”一体化网络,构成泛在通信基础设施,对高移动等场景下传输能力提出了更高要求,正交时频空(Orthogonal Time Frequency Space,OTFS)调制是克服高速移动场景下通信挑战的重要技术途径。聚焦于下行多用户MIMO⁃OTFS系统,为了克服该系统的符号间干扰及用户间干扰,同时获得多天线增益,在时延-多普勒域提出一种低复杂度预编码方案———利用迭代方法逼近最小均方误差准则(Approximate Iteration⁃MMSE,AI⁃MMSE)的预编码方案。所提方案充分利用MIMO⁃OTFS系统中信道矩阵在时延-多普勒域及空域的稀疏结构特征,降低矩阵相乘的计算复杂度;同时,利用高斯-赛德尔(Gauss⁃Seidel,GS)迭代近似方法,降低矩阵求逆的计算复杂度。仿真结果表明:由于符号间干扰及用户间干扰的消除,所提预编码方案相比于匹配滤波、基于零空间块对角化等典型方案,系统误码率性能得到明显提升;而且,针对MIMO⁃OTFS系统常见参数配置,所提方案的计算复杂度能够降低2~3个数量级。6G is committed to building Space-Air-Ground Integrated Networks,which will constitute ubiquitous communication infrastructures,and imposes higher performance requirement for high-mobility communication scenarios.Orthogonal Time Frequency Space(OTFS)modulation is considered as a promising technique for addressing the communication challenges in high-mobility scenarios.In this paper,aiming at eliminating inter-symbol interference and inter-user interference,and harvesting multi-antenna diversity,we propose a delay-Doppler-domain low-complexity precoding scheme for downlink multi-user MIMO-OTFS systems,which leverages an approximate and iterative equation-solving method to approach the minimum mean square error precoding,referred to as AI-MMSE.Therein,the sparse structure of delay-Doppler-space domain is exploited to reduce the computational complexity of matrix multiplication,and the Gauss-Seidel iteration approximation is adopted to reduce the computational complexity of matrix inversion.Simulation results validate that compared with classical precoding schemes,e.g.,match filter and null-space based block-diagonalization,the proposed scheme significantly enhances the bit-error-rate performance,due to the elimination of inter-symbol interference and inter-user interference.Moreover,for commonly-adopted MIMO-OTFS parameter setting,the proposed scheme reduces the computational complexity by 2~3 orders of magnitude.

关 键 词：高速移动通信场景 正交时频空 MIMO⁃OTFS 

分 类 号：TN929[电子电信—通信与信息系统]