Uplink-Aided High Mobility Downlink Channel Estimation Over Massive MIMO-OTFS System
Uplink-Aided High Mobility Downlink Channel Estimation Over Massive MIMO-OTFS System
复制标题
大规模 MIMO-OTFS 系统上行链路辅助的高移动性下行链路信道估计
DOI：
10.1109/jsac.2020.3000884
复制
发表时间：
2020-09-01
影响因子：
16.4
通讯作者：
Wang, Xianbin
中科院分区：
文献类型：
--
作者：
Liu, Yushan;Zhang, Shun;Wang, Xianbin
虽然它经常被用于正交频分复用（OFDM）系统中，但是在高移动性场景中，在正交时频空间（OTFS）调制上的大规模多输入多输出（MIMO）的应用可能遭受巨大的训练开销。本文针对大规模MIMO-OTFS网络，提出了一种上行辅助的高移动性下行信道估计方案。具体地说，首先建立上行链路沿着的时域大规模MIMO-OTFS信号模型，并采用基于期望最大化的变分贝叶斯（EM-VB）框架来恢复每个物理散射路径的上行信道参数，包括角度、延迟、多普勒频率和信道增益，相应地，借助于快速贝叶斯推理，构造了一种低复杂度的方法来克服EM-VB的瓶颈。然后，我们充分利用角度，延迟和多普勒之间的相互作用的上行链路和下行链路和重建的角度，延迟和多普勒频率的下行链路的大规模信道在基站。此外，我们研究了下行链路大规模MIMO信道估计的延迟多普勒角域。仔细分析OTFS在延迟-多普勒域上的信道色散，并且如果任何用户的不同路径具有可区分的延迟-多普勒签名，则利用OTFS将一个给定路径与一个特定延迟-多普勒网格相关联。此外，当任意用户的所有路径在角度域上完全分离时，设计了有效的路径调度算法，将不同用户的数据映射到正交的时延-多普勒-角度域资源上，实现了并行、低复杂度的下行3D信道估计。对于一般情况，我们采用降维的最小二乘估计器来捕获下行延迟多普勒角信道。各种数值例子来证实所提出的计划的有效性和鲁棒性。
Although it is often used in the orthogonal frequency division multiplexing (OFDM) systems, application of massive multiple-input multiple-output (MIMO) over the orthogonal time frequency space (OTFS) modulation could suffer from enormous training overhead in high mobility scenarios. In this paper, we propose one uplink-aided high mobility downlink channel estimation scheme for the massive MIMO-OTFS networks. Specifically, we firstly formulate the time domain massive MIMO-OTFS signal model along the uplink and adopt the expectation maximization based variational Bayesian (EM-VB) framework to recover the uplink channel parameters including the angle, the delay, the Doppler frequency, and the channel gain for each physical scattering path. Correspondingly, with the help of the fast Bayesian inference, one low complex approach is constructed to overcome the bottleneck of the EM-VB. Then, we fully exploit the angle, delay and Doppler reciprocity between the uplink and the downlink and reconstruct the angles, the delays, and the Doppler frequencies for the downlink massive channels at the base station. Furthermore, we examine the downlink massive MIMO channel estimation over the delay-Doppler-angle domain. The channel dispersion of the OTFS over the delay-Doppler domain is carefully analyzed and is utilized to associate one given path with one specific delay-Doppler grid if different paths of any user have distinguished delay-Doppler signatures. Moreover, when all the paths of any user could be perfectly separated over the angle domain, we design the effective path scheduling algorithm to map different users' data into the orthogonal delay-Doppler-angle domain resource and achieve the parallel and low complex downlink 3D channel estimation. For the general case, we adopt the least square estimator with reduced dimension to capture the downlink delay-Doppler-angle channels. Various numerical examples are presented to confirm the validity and robustness of the proposed scheme.