55 research outputs found
6G Wireless Communications in 7-24 GHz Band: Opportunities, Techniques, and Challenges
The sixth generation (6G) wireless communication nowadays is seeking a new
spectrum to inherit the pros and discard the cons of sub-6 GHz, millimeter-wave
(mmWave), and sub-terahertz (THz) bands. To this end, an upper mid-band,
Frequency Range (FR) spanning from 7 GHz to 24 GHz, also known as FR3, has
emerged as a focal point in 6G communications. Thus, as an inexorable
prerequisite, a comprehensive investigation encompassing spectrum utilization
and channel modeling is the first step to exploit potential applications and
future prospects of using this FR in the 6G ecosystem. In this article, we
provide FR3 deployment insights into emerging technologies including
non-terrestrial network (NTN), massive multi-input multi-output (mMIMO),
reconfigurable intelligent surface (RIS), and joint communications and sensing
(JCAS). Furthermore, leveraging ray-tracing simulations, our investigation
unveils the channel characteristics in FR3 are close to those in the sub-6 GHz
band. The analysis of RIS-aided communication shows a higher spectral
efficiency achieved in FR3 compared to other FRs when using the same RIS size.
Finally, challenges and promising directions are discussed for FR3-based
communication systems.Comment: 7 pages, 5 figures, 1 tabl
Probability of Line of Sight Evaluation in Urban Environments using 3D Simulator
The integration of Non-Terrestrial Networks (NTNs) into 6G networks is one of
the most promising ways to achieve significant improvements in capacity,
reliability, and global coverage. The design of NTN heavily relies on using
channel models. In this paper, we propose two easy-to-use simulators for
estimating the Line-of-Sight (LoS) probability in a 3D urban
environment. The first simulator is a 3D city simulator that employs simplified
Ray Tracing (RT), while the second one is a lightweight geometry-based
simulator that generates only the relevant buildings between users and Unmanned
Aerial Vehicles (UAVs). Using these simulators, we assess the accuracy of
existing models for estimation and examine
for different UAV heights, user-UAV distances, and
azimuth/elevation angles. We conclude that 1) existing models overestimate
, resulting in overoptimistic NTN performance predictions, 2)
nodes location (including azimuth and elevation angles) is an important factor
influencing , however, this influence is not captured by the
existing models.Comment: 6 pages, submitted to IEEE conferenc
Sensing with OFDM Waveform at mmWave Band based on Micro-Doppler Analysis
Joint communication and sensing (JCAS) technology has been regarded as one of
the innovations in the 6G network. With the channel modeling proposed by the
3rd Generation Partnership Project (3GPP) TR 38.901, this paper investigates
the sensing capability using the millimeter-wave (mmWave) band with an
orthogonal frequency division multiplexing (OFDM) waveform. Based on
micro-Doppler (MD) analysis, we present two case studies, i.e., fan speed
detection and human activity recognition, to demonstrate the target modeling
with micro-motions, backscattering signal construction, and MD signature
extraction using an OFDM waveform at 28 GHz. Simulated signatures demonstrate
distinct fan rotation or human motion, and waveform parameters that affect the
MD signature extraction are analyzed. Simulation results draw the validity of
the proposed modeling and simulation methods, which also aim to facilitate the
generation of data sets for various JCAS applications
Multimodal Fish Feeding Intensity Assessment in Aquaculture
Fish feeding intensity assessment (FFIA) aims to evaluate the intensity
change of fish appetite during the feeding process, which is vital in
industrial aquaculture applications. The main challenges surrounding FFIA are
two-fold. 1) robustness: existing work has mainly leveraged single-modality
(e.g., vision, audio) methods, which have a high sensitivity to input noise. 2)
efficiency: FFIA models are generally expected to be employed on devices. This
presents a challenge in terms of computational efficiency. In this work, we
first introduce an audio-visual dataset, called AV-FFIA. AV-FFIA consists of
27,000 labeled audio and video clips that capture different levels of fish
feeding intensity. To our knowledge, AV-FFIA is the first large-scale
multimodal dataset for FFIA research. Then, we introduce a multi-modal approach
for FFIA by leveraging single-modality pre-trained models and modality-fusion
methods, with benchmark studies on AV-FFIA. Our experimental results indicate
that the multi-modal approach substantially outperforms the single-modality
based approach, especially in noisy environments. While multimodal approaches
provide a performance gain for FFIA, it inherently increase the computational
cost. To overcome this issue, we further present a novel unified model, termed
as U-FFIA. U-FFIA is a single model capable of processing audio, visual, or
audio-visual modalities, by leveraging modality dropout during training and
knowledge distillation from single-modality pre-trained models. We demonstrate
that U-FFIA can achieve performance better than or on par with the
state-of-the-art modality-specific FFIA models, with significantly lower
computational overhead. Our proposed U-FFIA approach enables a more robust and
efficient method for FFIA, with the potential to contribute to improved
management practices and sustainability in aquaculture
Corrosion resistance of a magnesium hydroxide/stearic acid composite coating fabricated by vapor diffusion method on Mg-Li-Ca alloy
A composite coating of magnesium hydroxide/stearic acid on surface of Mg-1Li-1Ca alloy was prepared using vapor diffusion method to improve the corrosion resistance. The surface morphology and chemical composition of the films were characterized by high resolution scanning electron microscopy (HRSEM), Fourier transform infrared spectrometer (FTIR) and X-ray diffraction analysis (XRD). Electrochemical experiments and immersion test were conducted to study corrosion resistance of the obtained composite coating.The formation and degradation mechanisms of the composite coating were proposed.The results show that the magnesium hydroxide coating has a petal-like structure and is well-adhered to the surface of Mg-1Li-1Ca alloy.The stearic acid coating does not change the petal-like structure of the magnesium hydroxide coating. However, the stearic acid can effectively prevent the aggressive medium penetrating into the internal coating due to its low surface energy and good hydrophobicity.The corrosion current density of the magnesium hydroxide/stearic acid (Mg (OH) 2/SA) composite coating (1.45 × 10–7A/cm2) is decreased by two orders of magnitude compared to that of the Mg-1Li-1Ca alloy substrate (2.70 × 10–5 A/cm2), leading to the enhanced corrosion resistance of magnesium alloy
Multi-Frequency Air-to-Ground Channel Measurements and Analysis for UAV Communication Systems
info:eu-repo/semantics/publishe
- …