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Comparing Radio Propagation Channels Between 28 and 140 GHz Bands in a Shopping Mall
... Regarding indoor scenarios, New York University (NYU) conducted multipath measurements at 140 GHz in an office environment [21][22][23] and factory-like buildings [24][25][26]. At the same band, Aalto University conducted a measurement in a shopping mall [27]. At approximately 100 GHz, the Beijing University of Posts and Telecommunications (BUPT) measured multipath characteristics in an indoor office scenario [28,29]. ...
... ChGen3GPPTHz-InS mainly generates R , R , R , R,< , R,< , and R,< , statistically because this suffices to compose the channel impulse response as in eqs. (26) and (27). The delay and azimuth AoAs are relative to the LoS ray arrival time and its azimuth AoA, respectively, and by following the 3GPP SCM, we consider the first cluster as the LoS cluster, implying that ? ...
... where is the constant value to satisfy (27). Exceptionally, for the cluster where R = 1, R,? and R,? are enforced to 0, and R,? is enforced to R . ...
... In these models, the THz channel has been assumed to consist of a single deterministic LoS coefficient, which has been expressed as the sum of the free space and molecular absorption loss. Various LoS and NLoS indoor measurements are performed for wireless links operating at 28 GHz and 140 GHz 16,17 . Therein, based on the received signal strength of the multipath components of the links, the millimeter wave (mmWave) and THz channels have been deterministically modeled as the logarithmic scale sum of the exponential pathloss and lognormal shadowing. ...
... The indoor THz small-scale fading channel modeling has recently gained a momentum 7,16,17,20,[24][25][26][27][28][29][30][31] . Specifically, for the case of wireless backhaul THz links, the small-scale fading has been theoretically modeled by means of the α−µ distribution 24,26 . ...
... The aforementioned remarks elucidate that, the THz band yields non-rich multipath environments, when compared for example to the mmWave band. However, still there are surfaces that can act as scatterers for propagating wireless THz signals 16,17,20,29,46 . This leads to the existence of reflected NLoS multipath components carrying a significant amount of power, which are capable of being detected by the Rx. ...
Terahertz (THz) band offers a vast amount of bandwidth and is envisioned to become a key enabler for a number of next generation wireless applications. In this direction, appropriate channel models, encapsulating the large and small-scale fading phenomena, need to be developed for both indoor and outdoor communications environments. The THz large-scale fading characteristics have been extensively investigated for both indoor and outdoor scenarios. The study of indoor THz small-scale fading has recently gained the momentum, while the small-scale fading of outdoor THz wireless channels has not yet been investigated. Motivated by this, this contribution introduces Gaussian mixture (GM) distribution as a suitable small-scale fading model for outdoor THz wireless links. In more detail, multiple outdoor THz wireless measurements recorded at different transceiver separation distance are fed to an expectation-maximization (EM) fitting algorithm, which returns the parameters of the GM probability density function. The fitting accuracy of the analytical GMs is evaluated in terms of the Kolmogorov-Smirnov, Kullback-Leibler (KL) and root-mean-square-error (RMSE) tests. The results reveal that as the number of mixtures increases the resulting analytical GMs perform a better fit to the empirical distributions. In addition, the KL and RMSE metrics indicate that the increase of mixtures beyond a particular number result to no significant improvement of the fitting accuracy. Finally, following the same approach as in the case of GM, we examine the suitability of mixture Gamma (MG) to capture the small-scale fading characteristics of the outdoor THz channels.
... In [109] the authors conducted a campaign inside a shopping mall at 28 and 140 GHz to study and compare the difference in their large and small-scale parameters. In addition, the study confirmed that although the strong multipath component (MPCs) structure was similar between the bands, there were a higher number of clusters and paths per cluster in the 28 GHz compared to 140 GHz for the weaker MPCs. ...
... Another study on MPC extraction was carried out in [60] for frequency bands 75 − 110 and 220 − 330 GHz. A similar inference as in [109] was drawn where there was similarity in dominant MPCs but the lower frequency band seemed to present weaker MPCs. In [110], measurement campaigns were conducted for three different frequency bands: 125 − 155, 235 − 265, 270 − 300 GHz in two different laboratories of dimensions 12.9 × 7.15 × 4 m 3 and 9.7 × 4.73 × 4 m 3 respectively for MPC detection, along with clustering of the detected MPCs. ...
... In addition, the inter and intra-cluster models were also reported in this work. In an extension to the study in [109], measurements were conducted in another indoor hotspot (InH), the airport check-in hall [112]. The largescale omnidirectional parameters from the measurement data were found to be in good agreement with those of the Third Generation Partnership Project (3GPP) for New Radio (NR). ...
As the world warms up to the idea of millimeter wave (mmWave) communication and fifth generation (5G) mobile networks, realization slowly dawns that the data rate, latency, throughput, and other performance metrics that are used to assess a new wireless communication technology will not be enough to support the demands of envisioned futuristic applications. Thus there is an eagerness to further climb up the frequency ladder to use the large swathes of available spectrum in the 0.1 - 10 THz band which is expected to act as the key technology enabler to fulfill the requirements of the sixth generation (6G) wireless communication and possibly even beyond. Channel measurement and modeling are crucial to the design and deployment of future wireless communication systems and researchers across the world are putting their best foot forward to accelerate the process. The present article presents comprehensive assimilation of research efforts in the context of THz channel sounding. A detailed overview of the current channel sounding techniques is first introduced followed by their relevance to THz band channel measurement. An in-house novel channel sounder developed for THz band measurement is also briefly introduced in this context. The paper next provides elaborate dissemination of various measurement campaigns in the band of interest followed by the modeling techniques that are available in the literature and are being adopted for the THz band. Post the description of different challenges and future research directions in the context of sounding, measurement, and modeling the article is concluded.
... The average number of clusters µ Nc in NLOS links in the entrance hall environment is 18.0 as listed in Table II. This value is comparable with the indoor NLOS scenario in the 3GPP but noticeably higher than 2.8 in [30] and 5.9 in [31]. This is due to our use of a larger number of dimensions than in [30], which clusters MPCs in temporal and angular domains separately, and in [31], which clusters MPCs only along AOA and path delay. ...
... This value is comparable with the indoor NLOS scenario in the 3GPP but noticeably higher than 2.8 in [30] and 5.9 in [31]. This is due to our use of a larger number of dimensions than in [30], which clusters MPCs in temporal and angular domains separately, and in [31], which clusters MPCs only along AOA and path delay. The number of clusters N c = 3 in our residential NLOS measurements is significantly lower than in 3GPP's UMi-street canyon NLOS case where N c = 19. ...
The 3GPP channel model for new radios, described in 3GPP TR 38.901, is one of the most widely used channel models in the cellular wireless community. Originally established at below-6GHz radio frequencies and gradually expanded to cover new frequencies, its applicability to the new frequencies has always been an interest of the community. Our comparison of the radio channel responses from the measurements and the original 3GPP channel model, along with their variants adapted to sub-Terahertz frequency at 142 GHz in indoor and outdoor environments, sheds light on the possible improvement of the model. The original model defines cluster azimuth angles such that stronger clusters are always concentrated around a reference direction. Meanwhile, the measured azimuth power spectrum indicates that strong clusters randomly come from any direction. An alternative approach to iteratively generate cluster angles is therefore proposed, which provides improved agreement of the angular spread and eigenvalue statistics between measured and generated channels, at the expense of increased computational complexity in generating clusters. Moreover, the number of rays has no significant impact on the eigenvalue statistics. Setting the number of clusters fixed results in inaccurate statistics of the number of eigenmodes in generated sparse multipath channels.
... In [7] the ray-tracing technique in addition to measurements is leveraged to investigate the cluster behavior of the channel. The multipath channel data of a large-sized indoor environment at 28 GHz and 140 GHz is analyzed in [8] to investigate path-loss, delay spread, and angular spread. In [9] a line-of-sight (LoS) measurement is conducted for the ranges up to 5.5 m in 140-220 GHz frequencies to calculate path loss exponent and fading statistics, while in [10] the authors take a further step to model an outdoor channel with a longer range up to 35 m. ...
... Combining (3), (6), (7), (8) and substituting the derived expression for S in i into (14), the received power scattered from tile i after a simple mathematical manipulation is obtained as ...
Terahertz (THz) communications systems have been considered as one of the enabling technologies for beyond 5G mobile networks, with the ability to offer higher capacity and lower latency compared to the current systems. In this paper, we develop a new THz channel model that captures rough surface scattering while considering attenuation due to molecular absorption of the atmosphere. The main advantage of the proposed model is that it conserves the energy of the channel impulse response, regardless of the number of launched rays in the ray-tracing simulator, or the size of the tiles for the scattering surface. Using the proposed model, a simple propagation scenario for the indoor environment has been analyzed, and the improvement over other models discussed in detail.
... In addition to experiencing losses, the signal's polarization may be impacted by the different signal propagation paths within the channel, and the transmitted energy may appear with the Rx-orthogonal antenna orientation [79,80]. When the Tx and Rx antennas are co-polarized, the power received ratio (measured in dB) can identify the propagation feature as cross-polarization discrimination (XPD). ...
Currently, 5G technology is being implemented worldwide to meet the increasing demands of users. However, it is unable to fully achieve the projected growth in data traffic and high-end service quality for emerging applications and intelligent terminal devices. As a result, researchers are exploring other promising technologies and high-frequency bands for the next generation of cellular technology, known as beyond 5G (B5G) or 6G. Millimeter wave (mmWave) communications and Massive Multi-Input-Multi-Output (mMIMO) technology are receiving significant attention from the research community due to the availability of an extremely large frequency spectrum (30–300 GHz) and the ability of mMIMO to reduce propagation and absorption losses. This study provides a comprehensive survey of current achievements in mMIMO-mmWave communication systems, highlighting their benefits, challenges, and proposed solutions. It also describes the channel characterizations, recommended standards, and existing channel models at the 30/60/140 GHz bands, and presents a state-of-the-art comparison in terms of performance measures, parametric specifications, propagation losses, and methodologies for the measurement setup in different propagation environments. Additionally, the paper discusses the importance of beamforming and the challenges in realizing mMIMO communication systems.
... This observation aligns with findings at 28 GHz based on measurements conducted in the same corridor [4]. In contrast, studies in LOS environments at 140 GHz over short distances (1-12 m) showed slope values equal to 2 [1] [5]. ...
... This approach overcomes most of the disadvantages of using stepwise rotating high gain antennas (see e.g. [1]), which are extremely low measurement speed, missing phase coherence between the different paths, as well as a complicated de-embedding of antenna patterns, although the measurement sensitivity is very good. Another known approach is the use of switched directive antennas [2], which have a very fast measurement time and high sensitivity, but still no coherence between different directions, the problem of antenna de-embedding and a poor angular resolution. ...
In this paper a novel frequency-scalable rotary platform design is introduced which allows for flexible directional channel measurements using different types of antennas, and which can also be used with frequency extenders for measurements up to the THz region. The measurement platform has been applied to measure the channel properties including the direction of arrival at the FR3 frequency 14 GHz and in the D-band at 160 GHz in a large hall indoor environment with LOS distances up to 40 m. The results show very good agreement of strong path components for both frequencies as well as interesting dependencies of delay spread, angular spread, and Ricean K- factor on distance and frequency and can be used to parameterize a path loss model.
... The exact measurement setups have been detailed in various previous works, such as in [29] for the Aalto University entrance hall, [30] for the shopping mall, and [31] for the airport and shopping mall. The shopping mall and airport measurements were conducted at 143.1 GHz center frequency, while the remaining ones were conducted in the 142 GHz frequency with 4 GHz bandwidth. ...
Millimeter-Wave (mmWave) (30-300 GHz) and D band (110-170 GHz) frequencies are poised to play a pivotal role in the advancement of sixth-generation (6G) systems and beyond with increased demand for greater bandwidth and capacity. This paper focuses on deriving a generalized channel impulse response for mmWave communications, considering both outdoor and indoor locations for line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. The analysis is based on statistical insights obtained from measurements conducted at distinct locations with a center frequency of 142 GHz, examining parameters such as path gain, delay, number of paths (NoP), and angle distributions. Whereas different distributions serve as candidate models for the gain of LOS communications, only specific distributions accurately describe the NLOS gain, LOS and NLOS delay, LOS and NLOS NoP, and LOS and NLOS angular distributions. The channel is modeled based on geometry-based stochastic channel modeling (GBSM) with parameters derived from the statistical analysis. The maximum excess delay is used as a metric to evaluate the performance of the proposed model against empirical data.
... The 142 GHz propagation channel data used in this work was collected via single-directional channel measurements across several indoor and outdoor environments. The measurement campaigns were conducted at the center frequency of 142 GHz using vector network analyzer (VNA) based channel sounder with the implementation of radio-over-fiber technology as described in [19], [20]. During the measurements, a 0 dBi omnidirectional bicone antenna with 45 • elevation HPBW was fixed on the Tx side and a 19 dBi horn antenna with 10 • azimuth HPBW and 40 • elevation HPBW was used on the Rx side. ...
To provide substantially high capacity, future 6G networks will be able to operate in higher frequency bands than current 5G networks. However, owing to the significant differences in channel characteristics between lower bands (< 100 GHz) and sub-terahertz (sub-THz) band (i.e., 100–300 GHz), novel waveform and air interface design for sub-THz systems need to account for the radio channels observed by practical beam patterns. In this paper, we investigate the beamforming impact on the characterization of angular and time dispersion based on extensive measured channel data at 142 GHz across multiple scenarios. A post-processing method for analysis of beamforming impact on channel dispersion is proposed using measured propagation channel data. Since sub-THz radio links necessitate high antenna gains, we first find the potential beam directions from beamformed channels and then form single- and multi-beam patterns towards desired directions under practical constraints. The angular spread of the beamformed channels observed by steered beams will be widened especially in line-of-sight scenarios. The beam-weighted radio channel is considered as the basis of calculating time dispersion parameters, i.e., beam gains are multiplied by the measured propagation path gains before the analysis. Preliminary results show that the reduction of delay spread and maximum excess delay depends mainly on scenario, link distance, and used beamwidth, and partly on sidelobe level.
... The latter is tied to wave propagation conditions at the sub-THz band, specifically i) attenuation during wireless propagation and ii) angular and frequency selectivity of multipath components (MPCs) observed at link-ends. Studies related to the former are available for various indoor and outdoor scenarios [2]- [7], and channel parameters such as the path loss model and the angular and delay spreads of the same channels considered in this study are briefly reported in Section 6.2.1 of [8]. However, knowledge about the angular and frequency selectivity is less Mar Francis De Guzman and Katsuyuki Haneda are with the Department of Electronics and Nanoengineering, Aalto University, 02150 Espoo, Finland (e-mail: francis.deguzman@aalto.fi; ...
In this paper, an analysis of wave-object interactions is presented for an entrance hall and on a street of a residential area at 142 GHz. Single-directional channel sounding and the resulting spatio-temporal propagation path estimates are fused with the detailed geometry of the environment through a ray-launcher. The improved ray-launcher accounts for higher-order reflections and realizes high correspondence of the measured paths on the geometry, allowing us to analyze wave-object interaction. In channels without line-of-sight, first and second-order reflections contribute about 60% of the total power. Large interior and exterior walls of buildings are found most influential to the multipath channel. About half of the total received power in some links can be attributed to the reflections on small objects such as pillars and staircases in indoor and lampposts in outdoor cases. While large objects produce most of the clusters to the channel, there are links where small objects generate up to four clusters. The obtained knowledge of wave-object interaction at 142 GHz serves as guidelines to set up site-specific and geometry-based channel modeling at the frequency.
... Laboratoire d'électronique des technologies de l'information performed an indoor measurement at 126-156 GHz, where the path loss, angular/delay spreads, and human shadowing effects were extensively studied in a laboratory room, conference room, and personal desktop [10]. Aalto University performed the channel measurement at the 140 GHz band in a shopping mall and analyzed the path loss, angular and delay spreads [11]. Moreover, the measurements at the sub-THz bands conducted by other institutions are listed in [12][13][14]. ...
p>This paper performs a first wideband indoor channel measurement at the 105 GHz sub-terahertz (sub-THz) band and analyzes the multipath characteristics in terms of the omnidirectional path-loss and angular characteristics. The measurement campaigns with the 4 GHz bandwidth are performed focusing on indoor short-range communication scenarios in a conference room, corridor, and office room, which have been considered in the primary 60 GHz communication systems standardized by the IEEE 802.15.3c/11ad. Moreover, to draw full understanding to scale the 60 GHz indoor channel models and 60 GHz system designs for the 105 GHz band, we also conduct 60 GHz channel measurements in the same environment with few modifications in the channel-sounding system and performed the comparison between these two bands. Based on these measurements, we demonstrate the affinity that exists between 105 GHz and 60 GHz bands in terms of path loss exponent and angular characteristics of multipath components, shedding light on the hypothesis that several system designs of the 60 GHz communication systems (e.g., beam switching for non-line-of sight conditions) can be applied to the 105 GHz sub-THz communication systems.
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... Laboratoire d'électronique des technologies de l'information performed an indoor measurement at 126-156 GHz, where the path loss, angular/delay spreads, and human shadowing effects were extensively studied in a laboratory room, conference room, and personal desktop [10]. Aalto University performed the channel measurement at the 140 GHz band in a shopping mall and analyzed the path loss, angular and delay spreads [11]. Moreover, the measurements at the sub-THz bands conducted by other institutions are listed in [12][13][14]. ...
p>This paper performs a first wideband indoor channel measurement at the 105 GHz sub-terahertz (sub-THz) band and analyzes the multipath characteristics in terms of the omnidirectional path-loss and angular characteristics. The measurement campaigns with the 4 GHz bandwidth are performed focusing on indoor short-range communication scenarios in a conference room, corridor, and office room, which have been considered in the primary 60 GHz communication systems standardized by the IEEE 802.15.3c/11ad. Moreover, to draw full understanding to scale the 60 GHz indoor channel models and 60 GHz system designs for the 105 GHz band, we also conduct 60 GHz channel measurements in the same environment with few modifications in the channel-sounding system and performed the comparison between these two bands. Based on these measurements, we demonstrate the affinity that exists between 105 GHz and 60 GHz bands in terms of path loss exponent and angular characteristics of multipath components, shedding light on the hypothesis that several system designs of the 60 GHz communication systems (e.g., beam switching for non-line-of sight conditions) can be applied to the 105 GHz sub-THz communication systems.
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... Laboratoire d'électronique des technologies de l'information performed an indoor measurement at 126-156 GHz, where the path loss, angular/delay spreads, and human shadowing effects were extensively studied in a laboratory room, conference room, and personal desktop [10]. Aalto University performed the channel measurement at the 140 GHz band in a shopping mall and analyzed the path loss, angular and delay spreads [11]. Moreover, the measurements at the sub-THz bands conducted by other institutions are listed in [12][13][14]. ...
p>This paper performs a first wideband indoor channel measurement at the 105 GHz sub-terahertz (sub-THz) band and analyzes the multipath characteristics in terms of the omnidirectional path-loss and angular characteristics. The measurement campaigns with the 4 GHz bandwidth are performed focusing on indoor short-range communication scenarios in a conference room, corridor, and office room, which have been considered in the primary 60 GHz communication systems standardized by the IEEE 802.15.3c/11ad. Moreover, to draw full understanding to scale the 60 GHz indoor channel models and 60 GHz system designs for the 105 GHz band, we also conduct 60 GHz channel measurements in the same environment with few modifications in the channel-sounding system and performed the comparison between these two bands. Based on these measurements, we demonstrate the affinity that exists between 105 GHz and 60 GHz bands in terms of path loss exponent and angular characteristics of multipath components, shedding light on the hypothesis that several system designs of the 60 GHz communication systems (e.g., beam switching for non-line-of sight conditions) can be applied to the 105 GHz sub-THz communication systems.
This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible. </p
... 42. (a) Band-and aperture-limited channel response from a measurement and (b) its band-and aperture-unlimited model as propagation paths. Data are from a shopping mall measurement at 140 GHz[107]. ...
While the 5th Generation (5G) system is being widely deployed across the globe, the information and communication technology (ICT) industry, research, standardization and consensus building for the 6th generation (6G) are already well underway with high expectations towards the merger of digital, physical, and human worlds. The main goal of this book is to introduce the upcoming 6G technologies and outline the foreseen challenges, enablers, and architectural design trends that will be instrumental in realizing a Sustainable and Trustworthy 6G system in the coming years.
The envisioned 6G system promises to offer a more advanced and comprehensive user experience not only by achieving higher speeds, larger capacity, and lower latency, but also much more improved reliability, greater energy efficiency, and an enhanced security and privacy-preserving framework while natively integrating intelligence end-to-end (E2E). Achieving these goals will require innovative technological solutions and a holistic system design that considers the needs of various stakeholders and future 6G use cases.
Capitalizing on the European 5G Public-Private-Partnership (5G PPP) Phase 3 projects working on 5G & Beyond and 6G research in recent years, and the join efforts between the Architecture Working Group (WG) and the 6G flagship Hexa-X project, this book delves into the critical challenges and enablers of the 6G system, including new network architectures and novel enhancements as well as the role of regulators, network operators, industry players, application developers, and end-users. Accordingly, this book provides a comprehensive landscape of the current research activities on 6G in Europe and sets a solid cornerstone on the 6G development towards a more connected, intelligent, and sustainable world.
Furthermore, as 5G PPP Phase 3 consists of the last calls of the Horizon 2020 program, this book is aimed to lay the architectural foundation for the next European program towards 6G, i.e., Smart Networks & Services (SNS) Joint Undertaking (JU).
... Recently, sub-Terahertz-band transmission measurements have been carried out [26]- [29]. According to [27], the total number of observed multipaths at 140 GHz is much smaller than the number at 28 GHz in office environments. ...
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.
... The ever increasing demand for extreme high data rates has already pushed the current sub-6 GHz telecommunication systems to their limits. Sub-THz communications are therefore envisaged to fulfill the requirements for high data-rate communications and successfully complement telecommunication systems operating at lower frequency bands [1], [2]. ...
In this paper, we present new measurement results to model large-scale path loss at the sub-THz (141-145 GHz) band, for both indoor and outdoor scenarios. Extensive measurement campaigns have been carried out, taking into account both lineof- sight (LoS) and non line-of-sight (NLoS) propagation. For all considered propagation scenarios, existing omni-directional and directional path loss model have been developed, based on the so-called close-in (CI) free-space reference distance model. Moreover, path loss modeling is applied for the 2nd and 3rd strongest multipath components (MPCs). Thus, path loss exponent and large-scale shadow fading estimates are provided. Moreover, power angular spread analysis is derived using up to the 3rd strongest MPC.
... Indoor propagation, reflection, and penetration loss measurements at 140 GHz are presented in [18] for a broad set of materials. A comparison between the 28 GHz and 140 GHz channel models for a shopping mall environment confirms the fewer multipath components at 140 GHz, but the strongest paths show a high correlation [19]. Outdoor measurements at 142 GHz, with a distance of 15 m between the antennas, show excess losses ranging from 15 dB to 30 dB for reflected paths in a street canyon [20]. ...
Fixed wireless access networks at millimeter wave frequencies enable an alternative to fiber-optic installations for providing high-throughput internet connectivity. In this letter, we present outdoor channel measurements at D-band frequencies ranging from 120 GHz to 165 GHz, contributing to the design of future fixed wireless access networks. We measure angular path loss (PL) for both Line-of-Sight (LOS) and non-Line-of-Sight (NLOS) scenarios and calculate angular spread. We also measure building reflection loss for different angles and building facades. Directional LOS PL equals free-space PL, whereas omnidirectional PL is slightly lower. The angular spread of the LOS measurements is 19.7∘. The omnidirectional NLOS PL model has a higher PL and the angular spread increases to 54.4∘. Losses up to 11 dB should be taken into account for reflection on a fiber cement or building brick facade. and up to 15.6 dB and 18.5 dB for roughcast and stone bricks. Even though wireless communication via the direct path is preferred, reflected paths can enable high-throughput wireless communication if the direct path is obstructed.
Since the design of wireless MIMO systems requires knowledge of the double-directional (i.e., directionally resolved at both link ends) channel characteristics, and 5G/6G use higher frequency bands, there is the need for double-directional measurements in the mmWave spectrum, along with channel sounders that can accurately perform such measurements. This paper introduces a novel channel sounding approach based on a redirecting rotating mirror arrangement (ReRoMA). The method is low-cost and flexible as it requires only a single radio frequency chain at each link end and performs mechanical beam-steering. However, in contrast to existing rotating-horn systems, it physically separates the signal generation/transmission and the beam steering components, resulting in orders-of-magnitude faster measurements. The paper outlines the fundamental concept, describes details of the implementation, and demonstrates its application and accuracy using a 60GHz prototype for measurements in static reference scenarios, as well as dynamic measurements.We illustrate the detected propagation paths using dynamic angular and delay power spectra and correlate these findings with the surrounding environmental structure. Locations of environmental objects are detected within the Fourier resolution determined by bandwidth and horn width, with no noticeable degradation due to the faster measurements.
As the frequency bands for mobile communication increase, the study of the spatial characteristics of wireless channel for beamforming becomes increasingly important. To overcome high path loss and achieve high angular resolution, a method of measuring channels by rotating a directional antenna is widely used in wireless channel study. However, this method is vulnerable to phase drift. This paper reports the severity of phase drift in a rotating antenna system in the sub-terahertz (THz) band through measurement and analysis results. This paper also introduces a method for estimating multipath components (MPCs) from data affected by phase drift due to antenna rotation, and presents the results of channel characterization in a lecture room at a frequency band of 159 GHz using the proposed method.
Next generation wireless networks will necessitate new and wide spectrum swaths able to accommodate and support Tb/s applications and services. In this regard, frequencies above 100 GHz are anticipated to be allocated, which requires a thorough analysis of the propagation characteristics at those segments. This article presents a detailed analysis of the indoor channel at sub-THz frequencies, modeling its temporal and spatial characteristics for line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, relying on extensive deterministic simulations. According to the results, frequency selective characteristics are revealed. The obtained root-mean-square delay spread is in the range of 4.4–10.3 ns for LOS, and 6.9–18.8 ns for NLOS scenarios, respectively. A high spatial degree of freedom is also observed based on the increased azimuth spreads with a mean value of 57.4for LOS, and 88.1for NLOS locations, which is associated with the environment geometry. All the large-scale features of the channel exhibit a linear variation with distance, whereas according to the Gini Index and K-factor analysis, a channel with limited sparsity is encountered, especially in NLOS scenarios. Furthermore, the spatial coherence of the channels’ attributes is also assessed and modeled using an exponential decaying sinusoid relationship. A faster channel decoherence is observed in NLOS locations. Finally, the temporal and spatial properties of the channel are modeled statistically, delivering its related features that include the ray and cluster decaying rates, the inter-arrival delays, the azimuth and elevation angle-of-arrivals, and the cluster and ray occurrence.
A comprehensive understanding of outdoor urban radio propagation at mmWave and sub-THz frequencies is crucial for enabling novel applications such as wireless cognition, precise position-location, and sensing. This paper summarizes extensive measurements and statistical analysis of outdoor radio propagation data collected in New York City between 2012 and 2021 to formulate a multi-band empirical 3-D statistical channel model (SCM) for outdoor urban open squares and streets. Path loss models and SCMs are derived from over 21000 power delay profiles (PDP) measured in Brooklyn and Manhattan. Analysis of multipath components in PDPs reveal underlying statistical distributions for wireless channel parameters, including number of time-clusters (TC), subpaths in TCs, delays and powers of TCs and subpaths, and spatial-cluster directions. Observations at 142 GHz suggest a sparse channel as subpaths in TCs are exponentially distributed with narrower spread spatial-clusters and higher Ricean K-factor, unlike uniform distributions at 28 and 73 GHz. The proposed SCMs at 142, 73, and 28 GHz extend the open-source NYUSIM channel simulator into sub-THz bands up to 150 GHz. The SCMs can aid in designing modems, antenna arrays, beamforming, and spatial multiplexing approaches, while providing an empirical baseline for propagation simulation and prediction tools, such as ray tracers.
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.
Sub-Terahertz (sub-THz) (i.e., 100-300 GHz) communication is envisioned as one of the key components for future beyond fifth-generation (B5G) communication systems due to its large untapped bandwidth. Sub-THz channel measurements are essential for building accurate and realistic sub-THz channel models. Virtual antenna array (VAA) scheme has been widely employed for radio channel sounding purposes in the literature. However, its application for the W-band (i.e., 75-110 GHz) has been rarely discussed due to system phase instability issues. To tackle this problem, a long-range phase-compensated vector network analyzer (VNA)-based channel sounder at the W-band is proposed. First, the back-to-back measurement of the developed channel sounder is carried out with the presence of cable bending, where the initial phase variation beyond
range due to cable effects can be well corrected to within
range with the proposed phase-compensation scheme, clearly validating its effectiveness. To examine how well it works in practical deployment scenarios, the proposed channel sounder is then employed for channel sounding with two measurement distances, covering both near-field (with a line-of-sight (LoS) distance of 7.3 m) and long-range (with a LoS distance of 84.5 m) cases. Based on the measured data, a high-resolution channel parameter estimator is applied to extract the channel multipath parameters for the large-scale VAA at the W-band, both in the near-field and long-range scenarios, respectively. The high-resolution algorithm was extended to support virtual arrays composed of both omnidirectional antenna and directive antenna in this work. The conventional directional scanning scheme (DSS) measurement is adopted as the reference measurement to validate the effectiveness and robustness of the developed channel sounder. In the end, to demonstrate the state-of-art channel sounding capabilities of the developed channel sounder, ultra-wideband (UWB) channel measurements at 104.5 GHz with 11 GHz bandwidth using the VAA scheme are conducted in a hall scenario with the measurement range up to 58 m with omnidirectional antennas, and the channel parameters are extracted using the validated high-resolution channel parameter estimator for channel modeling purposes.
Technology research and standardization work of sixth generation (6G) has been carried out worldwide. Channel research is the prerequisite of 6G technology evaluation and optimization. This paper presents a survey and tutorial on channel measurement, modeling, and simulation for 6G. We first highlight the challenges of channel for 6G systems, including higher frequency band, extremely large antenna array, new technology combinations, and diverse application scenarios. A review of channel measurement and modeling for four possible 6G enabling technologies is then presented, i.e., terahertz communication, massive multiple-input multiple-output communication, joint communication and sensing, and reconfigurable intelligent surface. Finally, we introduce a 6G channel simulation platform and provide examples of its implementation. The goal of this paper is to help both professionals and non-professionals know the progress of 6G channel research, understand the 6G channel model, and use it for 6G simulation.
6G operators may use millimeter wave (mmWave) and sub-terahertz (sub-THz) bands to meet the ever-increasing demand for wireless access. Sub-THz communication comes with many existing challenges of mmWave communication and adds new challenges associated with the wider bandwidths, more antennas, and harsher propagations. Notably, the frequency- and spatial-wideband (dual-wideband) effects are significant at sub-THz. This paper presents a compressed training framework to estimate the time-varying sub-THz MIMO-OFDM channels. A set of frequency-dependent array response matrices are constructed, enabling channel recovery from multiple observations across subcarriers via multiple measurement vectors (MMV). Using the temporal correlation, MMV least squares (LS) is designed to estimate the channel based on the previous beam support, and MMV compressed sensing (CS) is applied to the residual signal. We refer to this as the MMV-LS-CS framework. Two-stage (TS) and MMV FISTA-based (M-FISTA) algorithms are proposed for the MMV-LS-CS framework. Leveraging the spreading loss structure, a channel refinement algorithm is proposed to estimate the path coefficients and time delays of the dominant paths. To reduce the computational complexity and enhance the beam resolution, a sequential search method using hierarchical code-books is developed. Numerical results demonstrate the improved channel estimation accuracy of MMV-LS-CS over state-of-the-art techniques.
Sub-Terahertz (sub-THz) (i.e., 100-300 GHz) communication is envisaged as one of the key building blocks for future communication systems due to its vast unexploited bandwidth. Knowledge of the radio channel characteristics is key to the design and development of new radio systems and air interfaces. Reliable channel sounding is essential to build accurate and realistic channel models. Virtual antenna array (VAA) has been a popular channel sounding strategy to obtain accurate directional characterization due to its low-cost and simple system implementation. However, this concept has not yet been realized for sub-THz bands in the state-of-the-art works due to difficulty in accurate phase control. The measurement range has been rather limited at sub-THz due to significant signal loss, especially in the radio frequency (RF) cables, compared to microwave or millimeter-wave frequencies. In this paper, we focus on vector network analyzer (VNA)-based channel sounders, highlighting frequency extension with sub-THz frequency extenders, measurement range extension with radio-over-fiber (RoF) schemes, and angular resolution improvement by VAA implementation with phase-compensation scheme. These techniques enable and enhance sub-THz channel characterization. The performance of the proposed long-range phase-compensated sounder is also experimentally demonstrated by the VAA-based channel measurements at 100 GHz in an indoor scenario.
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