I. Introduction
With the worldwide development of the fifth generation (5G) wireless communication networks, research on the new/sixth-generation (6G) wireless communication systems has been embarked. The upcoming 6G wireless network is expected to satisfy the extreme communication requirements, such as seamless holographic projection for smart working [1], real-time digital twins for smart manufacturing [2], and wireless brain-computer interactions for smart living [3]. To achieve the goals, various advanced wireless communication techniques, such as Terahertz communication, network densification, integrated air-ground networking, and ultra-massive massive multiple-input multiple-output (MIMO) have been paid attention to industry and academia [4], [5]. Despite that the emerging technologies have the great potential to improve the wireless communication performance, the required large-scale antenna arrays will be costly in terms of energy consumption, hardware implementation, signal processing complexity, especially for the Terahertz (THz) frequency. Therefore, developing high-capacity but cost-effective communication technique is important for the future wireless communication systems.