This paper presents an exhaustive comparison of channel measurements and appropriate channel statistics at 28 GHz, 38 GHz, and 130 GHz in the light of massive measurements conducted in an aircraft cabin environment. A total of 84 transmitter-receiver (Tx-Rx) positions are measured, covering both line-of-sight (LoS) and non-line-of-sight (NLoS) cases, with Tx-Rx distances ranging from 1 m to 10 m. The close-in and floating-intercept path loss models are presented for the cabin environment, and root-mean-square (RMS) delay spread (DS) and angular spread (AS) are compared and analyzed. The results indicate that the path loss exponent (PLE) is smaller than the free space PLE in the LoS aisle case over all measured frequencies. Moreover, the RMS DS and AS decrease as frequency increases in LoS and NLoS cases. This work can be applied to the design and optimization of the wireless communication system within the aircraft cabin.

This paper presents a comparative investigation of channel measurements and corresponding channel characteristics at 28 GHz, 38 GHz and 132 GHz in two different industrial environments, including a micro drilling-milling area and a large milling area. To depict the channel characteristics in industrial environments accurately, the close-in free space path-loss model and the alpha-beta-gamma model are used to examine path loss. Additionally, we analyze and compare the root mean square (RMS) delay spread (DS) and angular spread (AS) in different areas. The findings indicate the path loss exponent (PLE) has a dependency on the frequency, and all PLEs are less than the free space value 2.0 for the LoS case. Furthermore, RMS DS and AS exhibit distinct characteristics across various environments. This research provides valuable insights for design and optimization of industrial environmental systems.

The Terahertz (THz) band, which spans the frequency range from 0.1 to 10 THz, is widely regarded as a promising candidate for next-generation mobile communication. It has the potential to meet the demand for terabit-per-second data rates and facilitate network densification, making it a highly attractive field of research. In particular, the sub- THz band (100–300 GHz) is currently receiving significant attention in scientific research. This paper presents the characterization of Spatiotemporal channel measurements based on vector network analyzer in typical indoor scenarios at frequencies ranging from 215 to 225 GHz. The effects of both line-of-sight and non-line-of-sight conditions, caused by walls and pillars, are taken into consideration. Based on the directional measurements, the omnidirectional power angular delay profile is extracted. Char-acterization and analysis for multi path component parameters and cluster studies are also presented. The characterization of sub- THz channels extracted in this paper is instrumental in the development of channel modeling, system design, and performance assessment for sub- THz communication systems.

Terahertz (THz) communication technology holds significant potential for applications in the industrial internet of things (IIoT). Accurately characterizing the THz channel is critical for designing and optimizing communication systems in IIoT scenarios. However, the significantly higher frequencies in the THz band impede the effective utilization of channel models designed for microwave or millimeter-wave frequency bands. To overcome this challenge, extensive measurement campaigns are necessary to thoroughly investigate the characteristics of THz channels in indoor IIoT scenarios. This paper presents a measurement-based channel characterization in indoor IIoT scenarios at a frequency range of 215–225 GHz. We first present VNA-based channel measurement campaigns in micro drilling-milling and large milling areas. The measured data are further processed to obtain the channel impulse response. The key prop-agation channel parameters, e.g., path loss, power delay angle profile, delay spread, and angular spread, are calculated and analyzed in the line-of-sight case. Results demonstrate a favorable spatio-temporal consistency in multipath signal propagation and the physical spatial environment. Furthermore, significant correlations are observed between the channel characteristics and scatterer distribution within IIoT scenarios. The findings of this paper will make substantial contributions to the design and development of THz communication systems in IIoT scenarios.

Terahertz (THz) communications are envisioned as a promising technology for sixth-generation (6G) and beyond systems, owing to its unprecedented multi-gigahertz (GHz) bandwidth. In this paper, channel measurement campaigns in indoor scenarios at low-THz frequencies, i.e., 201-209 GHz, are reported. Four different communication scenarios including 90 transmitter-receiver pairs are measured in two channel measurement campaigns of a meeting room and an office room, respectively. The two measurement campaigns contains four scenarios, namely, a meeting room, cubicle area, hallway and non-line-of-sight (NLoS) case. The propagation of multi-path components (MPCs) in the four scenarios is characterized by the power-delay-angular profiles. Based on them, the temporal and spatial consistency for varying receiver locations in the complex hallway and NLoS scenarios are verified. To characterize, the large-scale best-direction and omni-directional path losses in indoor scenarios are separately analyzed and modeled by the close-in (CI) model. Furthermore, the small-scale channel parameters, e.g., the number of clusters, delay spread, angular spread, and cluster time-of-arrival are analyzed and modeled by proper distributions. As a general framework, a ray-tracing-statistical hybrid model is proposed for wireless propagation at 201-209 GHz, although, admittedly, the measurement results and analysis reveal that the channel characteristics in various indoor scenarios exhibit noticeable differences that need tailored parameter settings.

This paper presents the large-scale fading characteristics of Terahertz (THz) channel in indoor hotspot scenarios. A series of channel measurements at 219–224 GHz are conducted in a classroom and a hallway. In order to investigate the large-scale fading characteristics, the omnidirectional and best directional path loss are separately analyzed by close-in and floating-intercept models, and the Rician$K$-factor, root mean square delay spread and angular spread are analyzed to estimate the multi-path component richness, time and angle dispersion in various indoor scenarios. Further, these values are compared with what has been given in the Third Generation Partnership Project 38.901 in frequency bands lower than 100 GHz. In light of the results, the office area in hallway scenario shows the most severe path loss, and derives the highest time and angle dispersion. Besides, the measurement results enrich the datasets of THz channel propagation, which is helpful for the design and optimization of THz communication systems for sixth-generation.

Integrated sensing and communication (ISAC) is believed to play a vital role for connected intelligence in 6G. Radio waves can be used to sense surrounding and obtain the environment information. Furthermore, the environmental knowledge provided by sensing improves the accuracy of channel estimation, resulting in better communication throughput. This paper provides a study of sensing assisted environment reconstruction and communication in ISAC scenario. We propose a multi transmission reception points (TRP) sensing architecture based on scatter polygon assumption to improve environment sensing accuracy. Then a polygon trace scheme is introduced to reconstruct communication channel hinging on sensing reconstructed environment. Cm-level sensing accuracy and ns-level communication channel reconstruction can be achieved by 140 GHz indoor measurement campaign validation.

In this paper, we propose a scatterer-based hybrid channel model framework for integrated sensing and communication (ISAC). The basic idea of the scatterer-based ISAC channel model is to first generate scatterers in the propagation environment and then use simplified ray-tracing to generate both communication and sensing channels. The proposed model is hybrid in the aspect of scatterers i.e., the scatterers consists deterministic part and stochastic part. The deterministic part of the scatterers is from the input environment geometry while the stochastic part is constructed from the stochastic MPCs generated by 3GPP channel standardization framework. A method to couple the stochastic scatterers with the input environment geometry is proposed to avoid unrealistic ray propagation. To support the proposed ISAC channel model in the application of THz communications, we conduct RCS measurement campaigns with common building materials for developing deterministic propagation models at 140 GHz. Also, we conduct communication and sensing channel measurement campaigns in both indoor and outdoor scenarios for extracting fast-fading parameters for 3GPP channel standardization framework. The simulation results show that the proposed model has the capability of characterizing ISAC channel properties and validate with the measurement results.

This paper presents the latest design, development, and field trial results of a comprehensive ultra-broadband terahertz (THz) prototype platform, for the next-generation integrated sensing and communication (ISAC) applications. Particularly, the hardware architecture, link budget, and the baseband are firstly introduced. Then, representative scenarios are carefully selected, and the corresponding field trials are conducted extensively to verify a number of the most concerning parameters. According to the analysis of the results, it can be observed that this work has realised a co-hardware and co-waveform ISAC prototype, which supports high data rate communication and millimetre-level high resolution sensing functionalities. The prototype has also adopted THz compound semiconductor device, digital-to-analogue and analogue-to-digital converter boards, and low complexity signal processing techniques to simultaneously provide up to 3.5 km long-distance, up to 240 Gbps high data rate, and 17+ bit/s/Hz high spectrum efficiency ISAC service.

Spectrum sensing is an indispensable technique in new radio (NR) and future envisioned 6G communications. Particularly, perception results are foundations of several higher (sub-)layer functionalities such as beam management (BM). Motivated by the objective of enhancing sensing performance given limited sensing resources in an integrated sensing and communication (ISAC) system, novel sensing techniques which can provide accurate results in shorter perception time are of great significance. This paper investigates both half duplex (HD) and full duplex (FD) adaptive probability-based weighted energy detection (ED) techniques, which assign different weights according to the probability distribution of the perceived samples, to enhance sensing accuracy in millimetre-wave (mmWave) and terahertz (THz) beam-based networks. The proposed technique is evaluated in terms of the commonly used probabilities of detection, false alarm, and mis-detection. Results firstly show that the conventional ED technique can meet the sensing demand in the NR standard settings for mmWave, but it does not satisfy the foreseen enhanced mmWave transmissions, and especially THz systems in 6G. They also show that the proposed method fits better in mmWave, and THz systems in particular, in terms of sensing time duration as well as detection performance.

For better integrated sensing and communication (ISAC) performance, high-resolution range and velocity estimation is a crucial metric. On the premise of the E-Band platform, the feasibility of root multi-signal classification (RMUSIC) algorithm in millimeter wave frequency band is verified in this paper via the orthogonal frequency division multiplexing (OFDM) waveform. Compared with other super-resolution algorithms, the RMUSIC algorithm has not only higher estimation accuracy but lower complexity. Simulation experiments and laboratory measurements at 72 GHz show that the algorithm is superior in performance while ensuring the communication function. While maintaining a capacity of about 10 GHz, the sensing ranging measurement accuracy can reach the centimeter level, and the velocity measurement accuracy can reach the several centimeters per second level.

To mitigate the overlapping of the radar and communication frequency bands caused by large-scale devices access, we propose a novel integrated sensing and communication (ISAC) system, where a micro base station (MiBS) simultaneously carries out both target sensing and cooperative communication. Concretely, the MiBS, acting as the sensing equipment, can also serve as a full-duplex decode-and-forward relay to assist end-to-end communication. Moreover, nonorthogonal downlink transmission (NO-DLT) is adopted between the macro base station and the Internet of Things devices, so that the spectrum utilization can be further improved. To facilitate the performance evaluation, both the exact and asymptotic outage probabilities, the ergodic rates associated communication, and the probability of successful sensing detection are characterized. Subsequently, a pair of problems of maximizing the receive signal-to-interference-plus-noise ratio of the sensing signal and maximizing the sum rate of communication are formulated that are solved by the classic Lagrangian method while exploiting the associated function monotonicity. Our simulation results demonstrate that: 1) The proposed ISAC NO-DLT system improves both the communication and sensing performance under the same power consumption as noncooperative NO-DLT and 2) the proposed power allocation (PA) schemes are superior to the random PA scheme.

The electromagnetic information theory (EIT) is a general methodology framework, which should be able to achieve the wireless network design and performance analysis. Its one of the main objective is exploring how to increase spectral efficiency of the multiple input multiple output (MIMO) communication. The array arrangements, mutual-coupling effects between antennas, and antenna radiation characteristics may play important roles. Therefore, the electromagnetic (EM) theory will be a non-negligible analysis tool in the EIT. In this paper, we present an electromagnetic information methodology (EIM) combining the EM theory with information theory for the fast and accurate MIMO channel analysis. This methodology decouples MIMO antenna arrays with propagation environments, of which advantages are as follows: 1) for channel analysis of variable MIMO array arrangements, it avoids inefficient recalculation of complex and large-scale propagation environments; 2) It can determine the antenna radiation characteristics that achieves capacity maximization for the given propagation scenario; 3) The EM computation techniques can be applied in this framework, which makes the methodology more practical.

TeraHertz (THz) communications are envisioned as a promising technology, owing to its unprecedented multi-GHz bandwidth. One fundamental challenge when moving to new spectrum is to understand the science of radio propagation and develop an accurate channel model. In this paper, a wideband channel measurement campaign between 130 GHz and 143 GHz is conducted in an office room. The channel measurement campaign in the office room scenario consists of three cases: 1) LoS case in the office area 2) Line-of-Sight (LoS) case in the hallway and 3) NLoS case. Directional antennas are utilized and rotated for resolving the multi-path components (MPCs) in the angular domain. With careful system calibration that eliminates system errors and antenna effects, realistic power delay angular profiles (PDAP) are developed. In light of the measurement results, channel parameters and insights in the THz indoor channel are comprehensively analyzed, including the path loss, delay spread, angular, and correlations among the channel parameters. Furthermore, the propagation of NLoS multipath components (MPCs) in the office room scenario and its impact on the THz channel are discussed and compared with the channel measurement in the meeting at 140 GHz. Our analysis shows that the MPCs that reflect from the partitions dominate in NLoS propagation in office room.

In this paper, the channel modeling for integrated sensing and communication for 6G systems are studied. The channel modeling approaches, requirements, and challenges for communication cases and sensing cases are summarized and discussed. In particular, a 3-D metallic test chart is designed as a reference for studying electromagnetic imaging quality. The deterministic channel modeling approaches, i.e., geometrical optics method, physical optics method, and integral equation method, are introduced to simulate the imaging channel of the designed 3-D test chart. And the electromagnetic inverse scattering method is adopted as an imaging tool. The test is experimentally measured by 140 GHz signal with horn antennas in a chamber. The modulation transfer function (MTF) is applied to assess the imaging quality numerically, and the simulated and measured images are compared, which suggests that the imaging by integral equation is in agreement very well with that of measurement for 3-D test chart, and the geometric optics and physical optics methods can only show the characteristics of 2-D optical imaging.

TeraHertz (THz) communications are envisioned as a promising technology, owing to its unprecedented multi-GHz bandwidth. One fundamental challenge when moving to new spectrum is to understand the science of radio propagation and develop an accurate channel model. In this paper, a wideband channel measurement campaign between 130 GHz and 143 GHz is investigated in a typical meeting room. Directional antennas are utilized and rotated for resolving the multi-path components (MPCs) in the angular domain. With careful system calibration that eliminates system errors and antenna effects, a realistic power delay profile is developed. Furthermore, a combined MPC clustering and matching procedure with ray-tracing techniques is proposed to investigate the cluster behavior and wave propagation of THz signals. In light of the measurement results, physical parameters and insights in the THz indoor channel are comprehensively analyzed, including the line-of-sight path loss, power distributions, temporal and spatial features, and correlations among THz multi-path characteristics. Finally, a hybrid channel model that combines ray-tracing and statistical methods is developed for THz indoor communications. Numerical results demonstrate that the proposed hybrid channel model shows good agreement with the measurement and outperforms the conventional statistical and geometric-based stochastic channel model in terms of the temporal-spatial characteristics.

We consider multi-antenna systems carrying OAM waveforms, which are limited by the transmit power and receive antenna aperture. Under the line-of-sight (LOS) channel condition, we propose the multi-mode-multi-spatial (MOMS) solution as a low complex and flexible engineering implementation without any loss of degrees of freedom. The basic idea of MOMS is that the transmitter uses multiple OAM waveforms to carry multiple independent data streams, and the receiver uses a multiple antenna channel equalization algorithm to de-multiplex the multiple eigenchannels. Link-level and Monte Carlo simulation show that our MOMS solution has higher capacity than common uniform linear array LOS-MIMO within the Rayleigh distance of antenna array. However, it has a lower capacity at longer distances due to the faster power intensity decrease of OAM waveforms in comparison with plane waveforms.

In this paper, we propose a joint channel estimation and beamforming (BF) scheme for the wide band millimeter wave (mmWave) cellular system. Specifically, low complexity compressive sensing (CS) based estimation algorithm is used to estimate the sparse mmWave channels. Based on the estimated channel, low complexity BF scheme is proposed to adapt to the channel for data communications. The algorithm is designed by considering the practical hardware and channel constraints. Furthermore, the complexity is very low without matrix inverse and singular value decomposition (SVD) compared with traditional algorithms, which is well suitable to practical realization. Finally, we show by simulations that the performance of proposed scheme is close to the optimal scheme with extremely less overhead.

Urban outdoor millimeter wave communication systems will comprise of dense cell deployment and large-sized array antennas. In this paper, a millimeter wave downlink system-level simulator operating at 73 GHz, which emulates multiple base stations (BSs) and user equipments (UEs) in an outdoor street geometry, is developed. Each BS and UE are surrounded by moving obstacles (e.g., moving cars and walking pedestrians). Two-dimensional (2D) array antennas are employed at both UE and BS to form the 3-dimensional (3D) beams to combat the severe pathloss found in the spectrum. The 3D ray tracer customized to the 3D beam patterns is implemented in the simulator using the OpenGL platform. The 3D ray tracer, in our simulator, carries out the beam alignment task and produces physical channels between UE and BS. The physical channel representation characterizes useful link statistics, e.g., link blockage and co-channel interference statistics. It is shown through the simulation study that high density BS deployment with the directional 3D beamforming enhances the link quality and decreases outage probability compared to the lower density BS deployment. However, the performance degradation caused by the co-channel interference compared to the zero-interference case is still significant. Furthermore, it is observed that high density moving obstacles deteriorate both the throughput and outage performances compared to the low density case because of the increased link blockage.

Millimeter wave multiple-input multiple-output (MIMO) systems equipped with large-sized array antennas have a great potential to boost the achievable data rates by leveraging large bandwidth available at the spectrum. In this paper, we focus on the angle of departure (AoD) and angle of arrival (AoA) tracking problem for temporally correlated sparse millimeter wave MIMO channels. With the beam space MIMO channel modeling, a low complexity two-sided channel sounding scheme for the AoD and AoA tracking is investigated. The adoption of the sparse beam space MIMO channel representation eventually converts the AoD and AoA estimation problem to the support recovery problem. For the support recovery, we employ an iterative soft thresholding algorithm which is broadly referred to as the approximate message passing (AMP) algorithm. The support recovery performance of the AMP, however, suffers from serious deterioration especially at the low SNR regime. To remedy, several directional sounding beam design schemes are proposed to ameliorate the performance of the channel tracking at the low SNR. Simulation results demonstrate that the proposed AoD and AoA tracking outperforms other benchmark schemes when compared in a low SNR setting.

Double-directional, ultra wideband dual-polarized channel measurements at 70 GHz have been carried out in a small-office environment. The aim of these measurements is to study the temporal, directional, and polarization properties of the channel for modelling purposes of the future wireless communication systems at mm-waves. A highly deterministic behaviour of the channel and the environment has been identified, as well as the limitations of only parameterizing channel models as WINNER for the new mm-wave channel models.