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Joint Inter-and-intra-multiplexing and Hybrid Beamforming for Terahertz Widely-spaced Multi-subarray Systems
arXiv - CS - Information Theory Pub Date : 2021-01-20 , DOI: arxiv-2101.07936
Longfei Yan, Chong Han, Jinhong Yuan

Terahertz (THz) communications with multi-GHz bandwidth are envisioned as a key technology for 6G wireless systems. While suffering from huge propagation loss, large arrays of sub-millimeter wavelength antennas can be realized in ultra-massive (UM) MIMO systems to overcome the distance limitation. However, channel sparsity and low spatial degree-of-freedom of the THz channel limit the spatial multiplexing gain and hence the achievable rate. In this paper, a widely-spaced multi-subarray (WSMS) hybrid beamforming architecture is proposed for THz UM-MIMO systems to improve the multiplexing gain. In each subarray, the antennas are critically-spaced to utilize the inter-path multiplexing and beamforming gains, while the subarrays are widely-spaced to harvest the novel intra-path multiplexing gain through exploiting the phase differences over the subarrays. By exploring the THz channel peculiarity, a dominant-LoS-relaxation (DLR) method is proposed to balance the multiplexing and beamforming, and a block-diagonal vectorization-based (BD-VEC) algorithm is developed to solve the hybrid beamforming problem. Extensive simulation results demonstrate that the multiplexing gain is improved by a factor of the number of subarrays in the THz WSMS system. The low-complexity DLR method maximizes the achievable rate near-optimally. Compared to existing hybrid beamforming algorithms, the BD-VEC algorithm achieves higher spectral efficiency with substantially lower computational complexity.

中文翻译:

太赫兹宽间隔多子阵列系统的联合内部和内部复用以及混合波束成形

设想将具有数GHz带宽的太赫兹(THz)通信作为6G无线系统的一项关键技术。在遭受巨大的传播损耗的同时,可以在超质量(UM)MIMO系统中实现亚毫米波长天线的大型阵列,以克服距离限制。但是,信道稀疏性和太赫兹信道的低空间自由度限制了空间复用增益,从而限制了可达到的速率。本文提出了一种用于THz UM-MIMO系统的宽间隔多子阵列(WSMS)混合波束成形架构,以提高复用增益。在每个子阵列中,天线间隔都非常关键,以利用路径间复用和波束成形增益,通过利用子阵列上的相位差,将子阵列间隔开,以获取新颖的路径内多路复用增益。通过探究太赫兹信道的特殊性,提出了一种主要的LoS松弛(DLR)方法来平衡复用和波束成形,并提出了一种基于块对角矢量化的(BD-VEC)算法来解决混合波束成形问题。大量的仿真结果表明,在THz WSMS系统中,多路复用增益提高了子阵列数量。低复杂度DLR方法将近乎最佳的可实现速率最大化。与现有的混合波束成形算法相比,BD-VEC算法以较低的计算复杂度实现了更高的频谱效率。提出了一种主要的LoS松弛控制(DLR)方法来平衡复用和波束形成,并提出了一种基于块对角矢量化的(BD-VEC)算法来解决混合波束形成问题。大量的仿真结果表明,在THz WSMS系统中,多路复用增益提高了子阵列数量。低复杂度DLR方法将近乎最佳的可实现速率最大化。与现有的混合波束成形算法相比,BD-VEC算法以较低的计算复杂度实现了更高的频谱效率。提出了一种主要的LoS松弛控制(DLR)方法来平衡复用和波束形成,并提出了一种基于块对角矢量化的(BD-VEC)算法来解决混合波束形成问题。大量的仿真结果表明,在THz WSMS系统中,多路复用增益提高了子阵列数量。低复杂度DLR方法将近乎最佳的可实现速率最大化。与现有的混合波束成形算法相比,BD-VEC算法以较低的计算复杂度实现了更高的频谱效率。大量的仿真结果表明,在THz WSMS系统中,多路复用增益提高了子阵列数量。低复杂度DLR方法将近乎最佳的可实现速率最大化。与现有的混合波束成形算法相比,BD-VEC算法以较低的计算复杂度实现了更高的频谱效率。大量的仿真结果表明,在THz WSMS系统中,多路复用增益提高了子阵列数量。低复杂度DLR方法将近乎最佳的可实现速率最大化。与现有的混合波束成形算法相比,BD-VEC算法以较低的计算复杂度实现了更高的频谱效率。
更新日期:2021-01-21
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