1,499 research outputs found
Terahertz Wireless Channels: A Holistic Survey on Measurement, Modeling, and Analysis
Terahertz (0.1-10 THz) communications are envisioned as a key technology for
sixth generation (6G) wireless systems. The study of underlying THz wireless
propagation channels provides the foundations for the development of reliable
THz communication systems and their applications. This article provides a
comprehensive overview of the study of THz wireless channels. First, the three
most popular THz channel measurement methodologies, namely, frequency-domain
channel measurement based on a vector network analyzer (VNA), time-domain
channel measurement based on sliding correlation, and time-domain channel
measurement based on THz pulses from time-domain spectroscopy (THz-TDS), are
introduced and compared. Current channel measurement systems and measurement
campaigns are reviewed. Then, existing channel modeling methodologies are
categorized into deterministic, stochastic, and hybrid approaches.
State-of-the-art THz channel models are analyzed, and the channel simulators
that are based on them are introduced. Next, an in-depth review of channel
characteristics in the THz band is presented. Finally, open problems and future
research directions for research studies on THz wireless channels for 6G are
elaborated.Comment: to appear in IEEE Communications Surveys and Tutorial
306-321 GHz Wideband Channel Measurement and Analysis in an Indoor Lobby
The Terahertz (0.1-10 THz) band has been envisioned as one of the promising
spectrum bands to support ultra-broadband sixth-generation (6G) and beyond
communications. In this paper, a wideband channel measurement campaign in an
indoor lobby at 306-321 GHz is presented. The measurement system consists of a
vector network analyzer (VNA)-based channel sounder, and a directional antenna
equipped at the receiver to resolve multi-path components (MPCs) in the angular
domain. In particular, 21 positions and 3780 channel impulse responses (CIRs)
are measured in the lobby, including the line-of-sight (LoS), non-line-of-sight
(NLoS) and obstructed-line-of-sight (OLoS) cases. Multi-path propagation is
elaborated in terms of clustering results, and the effect of typical scatterers
in the indoor lobby scenario in the THz band is explored. Moreover, indoor THz
channel characteristics are analyzed in depth. Specifically, best direction and
omni-directional path losses are analyzed by invoking close-in and alpha-beta
path loss models. The most clusters are observed in the OLoS case, followed by
NLoS and then LoS cases. On average, the power dispersion of MPCs is smaller in
the LoS case in both temporal and angular domains, compared with the NLoS and
OLoS counterparts.Comment: 6 pages, 15 figure
3GPP-Like THz Channel Modeling for Indoor Office and Urban Microcellular Scenarios
Terahertz (THz) communication is envisioned as the possible technology for
the sixth-generation (6G) communication system. THz channel propagation
characteristics are the basis of designing and evaluating for THz communication
system. In this paper, THz channel measurements at 100 GHz and 132 GHz are
conducted in an indoor office scenario and an urban microcellular (UMi)
scenario, respectively. Based on the measurement, the 3GPP-like channel
parameters are extracted and analyzed. Moreover, the parameters models are
available for the simulation of the channel impulse response by the
geometry-based stochastic model (GBSM). Then, the comparisons between
measurement-based parameter models and 3rd Generation Partnership Project
(3GPP) channel models are investigated. It is observed that the case with path
loss approaching free space exists in the NLoS scenario. Besides, the cluster
number are 4 at LoS and 5 at NLoS in the indoor office and 4 at LoS and 3 at
NLoS in the UMi, which are much less than 3GPP. The multipath component (MPC)
in the THz channel distributes more simpler and more sparsely than the 3GPP
millimeter wave (mm-wave) channel models. Furthermore, the ergodic capacity of
mm-wave and THz are evaluated by the proposed THz GBSM implementation
framework. The THz measurement model predicts the smallest capacity, indicating
that high carrier frequency is limited to the single transmission mechanism of
reflection and results in the reduction of cluster numbers and ergodic
capacity. Generally, these results are helpful to understand and model the THz
channel and apply the THz communication technique for 6G.Comment: 13 pages, 12 figures, 3 table
300 GHz Dual-Band Channel Measurement, Analysis and Modeling in an L-shaped Hallway
The Terahertz (THz) band (0.1-10 THz) has been envisioned as one of the
promising spectrum bands for sixth-generation (6G) and beyond communications.
In this paper, a dual-band angular-resolvable wideband channel measurement in
an indoor L-shaped hallway is presented and THz channel characteristics at
306-321 GHz and 356-371 GHz are analyzed. It is found that conventional
close-in and alpha-beta path loss models cannot take good care of large-scale
fading in the non-line-of-sight (NLoS) case, for which a modified alpha-beta
path loss model for the NLoS case is proposed and verified in the NLoS case for
both indoor and outdoor L-shaped scenarios. To describe both large-scale and
small-scale fading, a ray-tracing (RT)-statistical hybrid channel model is
proposed in the THz hallway scenario. Specifically in the hybrid model, the
deterministic part in hybrid channel modeling uses RT modeling of dominant
multi-path components (MPCs), i.e., LoS and multi-bounce reflected paths in the
near-NLoS region, while dominant MPCs at far-NLoS positions can be deduced
based on the developed statistical evolving model. The evolving model describes
the continuous change of arrival angle, power and delay of dominant MPCs in the
NLoS region. On the other hand, non-dominant MPCs are generated statistically.
The proposed hybrid approach reduces the computational cost and solves the
inaccuracy or even missing of dominant MPCs through RT at far-NLoS positions
300 GHz Channel Measurement and Characterization in the Atrium of a Building
With abundant bandwidth resource, the Terahertz band (0.1~THz to 10~THz) is
envisioned as a key technology to realize ultra-high data rates in the 6G and
beyond mobile communication systems. However, moving to the THz band, existing
channel models dedicated for microwave or millimeter-wave bands are
ineffective. To fill this research gap, extensive channel measurement campaigns
and characterizations are necessary. In this paper, using a frequency-domain
Vector Network Analyzer (VNA)-based sounder, a measurement campaign is
conducted in the outdoor atrium of a building in 306-321 GHz band. The measured
data are further processed to obtain the channel transfer functions (CTFs),
parameters of multipath components (MPCs), as well as clustering results. Based
on the MPC parameters, the channel characteristics, such as path loss, shadow
fading, K-factor, etc., are calculated and analyzed. The extracted channel
characteristics and numerology are helpful to study channel modeling and guide
system design for THz communications.Comment: 5 pages, 2 figures. arXiv admin note: text overlap with
arXiv:2203.16745 by other author
Towards 6G with THz Communications: Understanding the Propagation Channels
This article aims at providing insights for a comprehensive understanding of THz propagation channels. Specifically, we discuss essential THz channel characteristics to be well understood for the success of THz communications. The methodology of establishing realistic and 6G-compliant THz channel models based on measurements is then elaborated on, followed by a discussion on existing THz channel measurements in the literature. Finally, future research directions, challenges and measures to enrich the understanding of THz channels are discussed
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