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Measurement of Multipath Waves at 160 GHz and 300 GHz in an Indoor Conference Room
... For DOA measurement, methods using array antennas with super-resolution algorithms [4,5] and methods using physically rotating large aperture antennas [6,7] are employed. For frequencies beyond 100 GHz, the first method is not easy to prepare array antennas. ...
... For frequencies beyond 100 GHz, the first method is not easy to prepare array antennas. On the other hand, the second method requires only one antenna, and a large-aperture antenna can be realized in a realistic size, and several measurement results using this method have been reported [3,6,7]. However, the method using a large-aperture antenna is characterized by a longer measurement time than the method using an array antenna because of the physical rotation involved. ...
In next-generation mobile communications, the proactive use of millimeter-wave and terahertz-wave frequencies, which can secure a wide frequency bandwidth, is anticipated. The authors reported a measurement method using a rotating reflector antenna to realize high-speed direction-of-arrival (DOA) measurement by rotating a large-aperture antenna at these frequencies. The conventional proposal method adopted a circularly polarized antenna as the primary radiator to accommodate the polarization rotation of the antenna. However, this method had the issue of angle dependency in the angular profile. To solve this problem, this paper proposes a measurement method that uses an orthogonally polarized antenna as the primary radiator of a rotating reflector antenna for rotational measurements, and processes the acquired data offline. To confirm the effectiveness of the proposed method, a demonstration experiment is conducted in an anechoic chamber, and it is shown that an angular profile with less angular dependence can be obtained than using a circularly polarized antenna as the primary radiator. We also show that the proposed method is capable of fast DOA measurement.
... Characteristics in Indoor Conference Room DOCOMO has measured radio propagation characteristics at 160 GHz and 300 GHz in indoor environments [39], and the measurement results have been submitted to ITU Radiocommunication (ITU-R) Working Party 5D (WP5D) through Beyond 5G Promotion Consortium's Beyond 5G white paper (version 1.51) [40]. Due to larger blocking loss of obstacles in the sub-Terahertz band, it is necessary to investigate methods to relax the severe blocking effect, such as utilizing reflected waves from walls and ceilings or artificially generated by IRSs. ...
... Thus, it is important to clarify both path loss and angle of arrival (AOA) of direct and reflected waves in the sub-Terahertz-band indoor environments. In this subsection, an example of 160 GHz-band measurement results of the path loss and AOA in an indoor conference room is introduced briefly [39]. As shown in Figs. ...
Technology for sixth-generation (6G) mobile communication system is now being widely studied. A sub-Terahertz band is expected to play a great role in 6G to enable extremely high data-rate transmission. This paper has two goals. (1) Introduction of 6G concept and propagation characteristics of sub-Terahertz-band radio waves. (2) Performance evaluation of intelligent reflecting surfaces (IRSs) based on beamforming in a sub-Terahertz band for smart radio environments (SREs). We briefly review research on SREs with reconfigurable intelligent surfaces (RISs), and describe requirements and key features of 6G with a sub-Terahertz band. After that, we explain propagation characteristics of sub-Terahertz band radio waves. Important feature is that the number of multipath components is small in a sub-Terahertz band in indoor office environments. This leads to an IRS control method based on beamforming because the number of radio waves out of the optimum beam is very small and power that is not used for transmission from the IRS to user equipment (UE) is little in the environments. We use beams generated by a Butler matrix or a DFT matrix. In simulations, we compare the received power at a UE with that of the upper bound value. Simulation results show that the proposed method reveals good performance in the sense that the received power is not so lower than the upper bound value.
Millimeter-wave (mmWave) and sub-Terahertz (THz) frequencies are expected to play a vital role in 6G wireless systems and beyond due to the vast available bandwidth of many tens of GHz. This paper presents an indoor 3-D spatial statistical channel model for mmWave and sub-THz frequencies based on extensive radio propagation measurements at 28 and 140 GHz conducted in an indoor office environment from 2014 to 2020. Omnidirectional and directional path loss models and channel statistics such as the number of time clusters, cluster delays, and cluster powers were derived from over 15,000 measured power delay profiles. The resulting channel statistics show that the number of time clusters follows a Poisson distribution and the number of subpaths within each cluster follows a composite exponential distribution for both LOS and NLOS environments at 28 and 140 GHz. This paper proposes a unified indoor statistical channel model for mmWave and sub-Terahertz frequencies following the mathematical framework of the previous outdoor NYUSIM channel models. A corresponding indoor channel simulator is developed, which can recreate 3-D omnidirectional, directional, and multiple input multiple output (MIMO) channels for arbitrary mmWave and sub-THz carrier frequency up to 150 GHz, signal bandwidth, and antenna beamwidth. The presented statistical channel model and simulator will guide future air-interface, beamforming, and transceiver designs for 6G and beyond.
Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. These frequencies also offer the potential for revolutionary applications that will be made possible by new thinking, and advances in devices, circuits, software, signal processing, and systems. This paper describes many of the technical challenges and opportunities for wireless communication and sensing applications above 100 GHz, and presents a number of promising discoveries, novel approaches, and recent results that will aid in the development and implementation of the sixth generation (6G) of wireless networks, and beyond. This paper shows recent regulatory and standard body rulings that are anticipating wireless products and services above 100 GHz and illustrates the viability of wireless cognition, hyper-accurate position location, sensing, and imaging. This paper also presents approaches and results that show how long distance mobile communications will be supported to above 800 GHz since the antenna gains are able to overcome air-induced attenuation, and present methods that reduce the computational complexity and simplify the signal processing used in adaptive antenna arrays, by exploiting the Special Theory of Relativity to create a cone of silence in over-sampled antenna arrays that improve performance for digital phased array antennas. Also, new results that give insights into power efficient beam steering algorithms, and new propagation and partition loss models above 100 GHz are given, and promising imaging, array processing, and position location results are presented. The implementation of spatial consistency at THz frequencies, an important component of channel modeling that considers minute changes and correlations over space, is also discussed. This paper offers the first in-depth look at the vast applications of THz wireless products and applications and provides approaches for how to reduce power and increase performance across several problem domains, giving early evidence that THz techniques are compelling and available for future wireless communications.
The use of massive Multiple-Input Multiple-Output (MIMO) systems is becoming progressively feasible, as well as progressively important, as the carrier frequency increases. Terahertz (THz) frequencies lead to smaller-sized RF components including antennas, so that even antenna arrays with a large number of antennas have a reasonable form factor while providing large beamforming gain and multi-user MIMO (MUMIMO) capability. However, the THz propagation mechanisms differ in various ways from previously explored channels. In fact, reflections by a rough surface and diffuse scattering mechanisms are the most critical features contributing to spatial and temporal dispersion at THz frequencies. For this study, first, we develop a hybrid modeling approach of 3D ray-tracing simulations in a realistic office room at 300 GHz and 350 GHz to obtain estimates of the impact of surface roughness on the channel capacity which depends on generic channel characteristics. Then, the indoor multipath propagation and its impact on massive MIMO channels considering smooth and rough surfaces are investigated by employing the Beckmann-Kirchhoff (B-K) model. Finally, channel capacities of indoor THz massive MIMO channels with different surface roughnesses for both line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios are calculated. Though based on modeling results, the scattering properties of materials can favorably be exploited to maximize spatial multiplexing gains, especially in LoS scenarios.
For seamless communication in millimeter-wave (mm-wave) transmission systems, the robustness against link blockage and user mobility should be guaranteed. Cooperative joint network design over conventional microwave bands and mm-wave bands is essential in future mm-wave WLANs (e.g., IEEE 802.11ay) and 5G cellular networks, and hence understanding the discrepancy between the propagation properties at those frequency bands is crucial. In this letter, the angle-of-arrival characteristics at mm-wave band (60 GHz) and microwave band (2.4 GHz) in indoor environments are presented. From the measurement results, it was seen that the line-of-sight and first-order reflected paths agree well each other, but diffraction and scattering are observed only at microwave band. It was also shown that the angular spreads at mm-wave band was about 25 degrees smaller than those at microwave band.
The increasing requirement for the mobile data traffic accelerates the research of millimeter-wave (mm-wave) for future wireless systems. Accurate characterization of the mmwave propagation channel is fundamental and essential for the system design and performance evaluation. In this paper, we conducted measurement campaigns in various indoor scenarios, including classroom, office and hall scenarios at the frequency bands of 27-29 GHz. The spatial channel characteristics were recorded by using a large-scale uniform circular array (UCA). A high resolution parameter estimation (HRPE) algorithm was applied to estimate the mm-wave spherical propagation parameters i.e., the azimuth angle, elevation angle, delay, source distance and complex amplitude of multipath components (MPCs). With the same measurement system, the channel parameters including decay factor, delay spread, angular spread and line of sight (LOS) power ratio are investigated thoroughly in individual indoor scenarios and compared in different indoor scenarios. Furthermore, the impact of the furniture richness level and indoor geometry on the propagation parameters are also investigated.
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.
In order to realize the vision of “smart rail mobility”, a seamless high-data rate wireless connectivity with up to dozens of GHz bandwidth will be required. This forms a strong motivation for exploring the underutilized millimeter wave (mmWave) and sub-mmWave bands. In this paper, the wireless channel in one “smart rail mobility” scenario – the Intra-wagon scenario – is characterized through ultra-wideband (UWB) channel sounding and ray tracing at mmWave and submmWave bands. To begin with, a series of horizontal-directionalscan- sounding measurements are performed inside a real highspeed train wagon at 60 GHz and 300 GHz frequency bands with 8 GHz bandwidth. Correspondingly, the channel characteristics such as Rician K-factor, root-mean-square (RMS) delay spread (DS), azimuth spread of arrival, and azimuth spread of departure are extracted and analyzed. Based on the measurements, a selfdeveloped ray-tracing (RT) simulator is validated through the reconstruction of the three-dimensional wagon model and the calibration of the electromagnetic (EM) properties of the main materials. This gives the chance to physically interpret the measurement results and characterize the intra-wagon mmWave and sub-mmWave channels more comprehensively through extensive RT simulations.
Communication at terahertz carrier frequencies is a promising way to satisfy the ever-growing demands for high-speed wireless networks. The studies of terahertz wireless channels have so far been limited to the atmospheric transmission bands below 350 GHz. Availability of high-power transmitters and high-sensitivity receivers at higher frequencies necessitates extending the wireless channel studies to enable higher data-rate communication systems. With a view to assessing communication system design requirements at higher frequencies, we present the channel measurement results for 650 GHz carrier frequencies in comparison with 350 GHz carrier frequencies in a typical indoor environment. To obtain the spatial and temporal characteristics of the channel, the power angle profile (PAP) and the power delay profile (PDP) are measured based on new measurement methods. Multiple spatially resolvable paths are observed at both 350 GHz and 650 GHz carrier frequencies. Signal-to-noise ratio (SNR) of the received signal through the non-line-of-sight (NLoS) paths is sufficiently high to enable robust communication when the direct line-of-sight (LoS) path is blocked due to a moving object. The measurement results are used to calculate the reduction in the 650 GHz channel capacity in comparison with that of the 350 GHz channel for both LoS and NLoS paths. Channel dispersion characterization over a 10 GHz bandwidth shows that the delay spreads for the resolved LoS and NLoS paths are less than 80 ps for both 350 GHz and 650 GHz bands. Therefore, no complicated equalizer is required to compensate for channel dispersion at both 350 GHz and 650 GHz, which greatly simplifies the terahertz transceiver design.
This paper presents details and results of doubledirectional propagation measurements carried out in two indoor office environments: a semi-open, cubicle-type office space and a more traditional work environment with closed offices. The measurements cover seven frequency bands from 2.4 to 61 GHz, permitting propagation characteristics to be compared over a wide range of candidate radio frequencies for next-generation mobile wireless systems, including ultra-high frequency and millimeterwave bands. A novel processing algorithm is introduced for the expansion of multiband measurement data into sets of discrete multipath components. Based on resulting multipath parameter estimates, models are presented for frequency-dependent path loss, shadow fading, co-polarization ratio, delay spread, and angular spreads, along with their inter-frequency correlations. Our results indicate a remarkably strong consistency in multipath structure over the entire frequency range considered.
Most millimeter wave (mmWave) channel measurements are conducted with different configurations, which may have large impacts on propagation channel characteristics. Also, the comparison of different mmWave bands is scarce. Moreover, mmWave massive multiple-input multiple-output (MIMO) channel measurements are absent, and new propagation properties caused by large antenna arrays have rarely been studied yet. In this paper, we carry out mmWave massive MIMO channel measurements at 11, 16, 28, and 38 GHz bands in indoor environments. The space- alternating generalized expectation-maximization (SAGE) algorithm is applied to process the measurement data. Important statistical properties like average power delay profile (ADPD), power azimuth profile (PAP), power elevation profile (PEP), root mean square (RMS) delay spread (DS), azimuth angular spread (AAS), elevation angular spread (EAS), and their cumulative distribution functions (CDFs) and correlation properties are obtained and compared for different bands. New massive MIMO propagation properties like spherical wavefront, cluster birth-death, and non-stationarity over the antenna array are validated for the four mmWave bands by investigating the variations of channel parameters. Two channel models are used to verify the measurements. The results indicate that massive MIMO effects should be fully characterized for mmWave massive MIMO systems.
This paper presents the results of an experimental investigation of 60 GHz wireless local area network (WLAN) systems in an office environment. The measurement setup with highly directional mechanically steerable antennas and 800 MHz bandwidth was developed and experiments were performed for conference room and cubicle environments. Measurement results demonstrate that the 60 GHz propagation channel is quasioptical in nature and received signal power is obtained through line of sight (LOS) and reflected signal paths of the first and second orders. The 60 GHz WLAN system prototype using steerable directional antennas with 18 dB gain was able to achieve about 30 dB baseband SNR for LOS transmission, about 15-20 dB for communications through the first-order reflected path, and 2-6 dB SNR when using second-order reflection for the office environments. The intra cluster statistical parameters of the propagation channel were evaluated and a statistical model for reflected clusters is proposed. Experimental results demonstrating strong polarization impact on the characteristics of the propagation channel are presented. Cross-polarization discrimination (XPD) of the propagation channel was estimated as approximately 20 dB for LOS transmission and 10-20 dB for NLOS reflected paths.
White paper: 5G Evolution and 6G
- Ntt
- Inc Docomo
The Effect of Reflection Wave at 300 GHz-Band in Indoor Environment Simulations
- M Nakamura
- S Satoshi
- K Kitao
- T Tomie
- Y Oda
The Effect of Reflection Wave at 300 GHz-Band in Indoor Environment Simulations
- nakamura