For Full-Text PDF, please login, if you are a member of IEICE,|
or go to Pay Per View on menu list, if you are a nonmember of IEICE.
Sub-Terahertz MIMO Spatial Multiplexing in Indoor Propagation Environments
IEICE TRANSACTIONS on Communications
Publication Date: 2022/10/01
Online ISSN: 1745-1345
Type of Manuscript: Special Section INVITED PAPER (Special Section on Multidisciplinary and Innovative Key technologies in Advanced communication systems (MIKA))
6G, sub-Terahertz band, hybrid MIMO system, spatial multiplexing, channel capacity, beam steering,
Full Text: FreePDF(5.4MB)
A sub-Terahertz band is envisioned to play a great role in 6G to achieve extreme high data-rate communication. In addition to very wide band transmission, we need spatial multiplexing using a hybrid MIMO system. A recently presented paper, however, reveals that the number of observed multipath components in a sub-Terahertz band is very few in indoor environments. A channel with few multipath components is called sparse. The number of layers (streams), i.e. multiplexing gain in a MIMO system does not exceed the number of multipaths. The sparsity may restrict the spatial multiplexing gain of sub-Terahertz systems, and the poor multiplexing gain may limit the data rate of communication systems. This paper describes fundamental considerations on sub-Terahertz MIMO spatial multiplexing in indoor environments. We examined how we should steer analog beams to multipath components to achieve higher channel capacity. Furthermore, for different beam allocation schemes, we investigated eigenvalue distributions of a channel Gram matrix, power allocation to each layer, and correlations between analog beams. Through simulation results, we have revealed that the analog beams should be steered to all the multipath components to lower correlations and to achieve higher channel capacity.