Time Varying Channel Tracking with Spatial and Temporal BEM for Massive MIMO Systems

In this paper, we propose a channel tracking method for massive MIMO systems under both timevarying and spatial-varying circumstance. Exploiting the characteristics of massive antenna array, a spatial-temporal basis expansion model (ST-BEM) is designed to reduce the effective dimensions of uplink/downlink channel, which decomposes channel state information (CSI) into the time-varying spatial information and gain information. We firstly model the users’ movements as a one-order unknown Markov process, which is blindly learned by the expectation and maximization (EM) approach. Then, the uplink time-varying spatial information can be blindly tracked by unscented Kalman filter (UKF) and Taylor series expansion of the steering vector, while the rest uplink channel gain information can be trained by only a few pilot symbols. Due to angle reciprocity (spatial reciprocity), the spatial information of the downlink channel can be immediately obtained from the uplink counterpart, which greatly reduces the complexity of downlink channel tracking. Various numerical results are provided to demonstrate the effectiveness of the proposed method. Index Terms Massive MIMO, channel tracking, spatial and temporal BEM (ST-BEM), DOA, angle reciprocity, unscented Kalman Filter (UKF). This work was presented in part at the 2017 IEEE ICC [1]. J. Zhao, H. Xie and F. Gao are with Tsinghua National Laboratory for Information Science and Technology (TNList) Beijing 100084, P. R. China, (e-mail:[email protected], [email protected], [email protected]). J. Zhao is also with High-Tech Institute of Xian, Xian, Shaanxi 710025, China. W. Jia is with High-Tech Institute of Xian, Xian, Shaanxi 710025, China (e-mail: [email protected]). S. Jin is with the National Communications Research Laboratory, Southeast University, Nanjing 210096, P. R. China (email: [email protected]). H. Lin is with the Department of Electrical and Information Systems, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka, Japan (e-mail: [email protected]).