Time-Domain Channel Estimation for Extremely Large MIMO THz
Communications with Beam Squint
Abstract
In this paper, we study the problem of extremely large (XL)
multiple-input multiple-output (MIMO) channel estimation in the
Terahertz (THz) frequency band, considering the presence of propagation
delays across the entire array apertures, which leads to frequency
selectivity, a problem known as beam squint. Multi-carrier transmission
schemes which are usually deployed to address this problem, suffer from
high peak-to-average power ratio, which is specifically dominant in THz
communications where low transmit power is realized. Diverging from the
usual approach, we devise a novel channel estimation problem formulation
in the time domain for single-carrier (SC) modulation, which favors
transmissions in THz, and incorporate the beam-squint effect in a sparse
vector recovery problem that is solved via sparse optimization tools. In
particular, the beam squint and the sparse MIMO channel are jointly
tracked by using an alternating minimization approach that decomposes
the two estimation problems. The presented performance evaluation
results validate that the proposed SC technique exhibits superior
performance than the conventional one as well as than state-of-the-art
multi-carrier approaches.