1,162 research outputs found
Analytical characterisation of the terahertz in-vivo nano-network in the presence of interference based on TS-OOK communication scheme
The envisioned dense nano-network inside the human body at terahertz (THz) frequency suffers a communication performance degradation among nano-devices. The reason for this performance limitation is not only the path loss and molecular absorption noise, but also the presence of multi-user interference and the interference caused by utilising any communication scheme, such as time spread ON—OFF keying (TS-OOK). In this paper, an interference model utilising TS-OOK as a communication scheme of the THz communication channel inside the human body has been developed and the probability distribution of signal-to-interference-plus-noise ratio (SINR) for THz communication within different human tissues, such as blood, skin, and fat, has been analyzed and presented. In addition, this paper evaluates the performance degradation by investigating the mean values of SINR under different node densities in the area and the probabilities of transmitting pulses. It results in the conclusion that the interference restrains the achievable communication distance to approximate 1 mm, and more specific range depends on the particular transmission circumstance. Results presented in this paper also show that by controlling the pulse transmission probability and node density, the system performance can be ameliorated. In particular, SINR of in vivo THz communication between the deterministic targeted transmitter and the receiver with random interfering nodes in the medium improves about 10 dB, when the node density decreases one order. The SINR increases approximate 5 and 2 dB, when the pulse transmitting probability drops from 0.5 to 0.1 and 0.9 to 0.5
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
ISAC-Enabled Beam Alignment for Terahertz Networks: Scheme Design and Coverage Analysis
As a key pillar technology for the future 6G networks, terahertz (THz)
communication can provide high-capacity transmissions, but suffers from severe
propagation loss and line-of-sight (LoS) blockage that limits the network
coverage. Narrow beams are required to compensate for the loss, but they in
turn bring in beam misalignment challenge that degrades the THz network
performance. The high sensing accuracy of THz signals enables integrated
sensing and communication (ISAC) technology to assist the LoS blockage and user
mobility-induced beam misalignment, enhancing THz network coverage. In line
with the 5G beam management, we propose a joint synchronization signal block
(SSB) and reference signal (RS)-based sensing (JSRS) scheme to predict the need
for beam switches, and thus prevent beam misalignment. We further design an
optimal sensing signal pattern that minimizes beam misalignment with fixed
sensing resources, which reveals design insights into the time-to-frequency
allocation. We derive expressions for the coverage probability and spatial
throughput, which provide instructions on the ISAC-THz network deployment and
further enable evaluations for the sensing benefit in THz networks. Numerical
results show that the JSRS scheme is effective and highly compatible with the
5G air interface. Averaged in tested urban use cases, JSRS achieves near-ideal
performance and reduces around 80% of beam misalignment, and enhances the
coverage probability by about 75%, compared to the network with 5G-required
positioning ability
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