No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
On the Frequency Dependency of Radio Channel's Delay Spread: Analyses and Findings From mmMAGIC Multi-frequency Channel Sounding
... Frequency dependence of the mmWave propagation channels is a question of continued interest. Recently, an extensive study of channels measured at 6-100 GHz as a part of the mmMAGIC project [48] concluded that a relationship between the carrier frequency and the fast fading parameters is hard to define. In our measurement campaign performed in Ilmenau, we followed the same guidelines used in [48] for the inter-band comparison. ...
... Recently, an extensive study of channels measured at 6-100 GHz as a part of the mmMAGIC project [48] concluded that a relationship between the carrier frequency and the fast fading parameters is hard to define. In our measurement campaign performed in Ilmenau, we followed the same guidelines used in [48] for the inter-band comparison. The results in Fig. 5 show linear fits of the measured fast fading parameters compared to the 3GPP model [49]: ...
Vehicle-to-Vehicle (V2V) channels exhibit unique properties, due to the highly dynamic environment and low elevation of the antennas at both ends of the link. Of particular importance for the behavior of V2V channels, and consequent reliability of the communication link, is the severity and dynamics of blockage of both line-of-sight (LOS) and other multipath components (MPCs). The characteristics of blockage become more important as the carrier frequency increases and the ability of the signal to penetrate through objects diminishes. To characterize the effects of vehicle blockage, we performed V2V channel measurements in four different frequency bands (6.75, 30, 60, and 73 GHz) in urban and highway scenarios. We analyzed the impact of the blocker size and position on the received power and fast fading parameters, as well as the frequency dependency of these parameters under blockage. Our results show there is a strong influence of the size of the blocking vehicle on the blockage loss and the angular/delay spread. The position of the blocker relative to the transmitter and receiver also plays an important role. On the other hand, the frequency dependency is quite limited, with the blockage loss increasing slightly and the number of scattered MPCs reducing slightly as frequency increases. The main conclusion of this study is that V2V communication will be possible in high (millimeter wave) frequencies, even in the case of blockage by other vehicles.
... It is commonly accepted that the new mm-wave systems will have to coexist with the legacy networks (4G, LTE, WiFi etc.) operating mostly below 6 GHz. Consequently, a host of other papers [105][106][107][108][109] compared the characteristics of below-6 GHz channels with mm-wave propagation and discuss the frequency dependency of the channel parameters. However, all of these work measure disjoint sub-bands rather than a continuous frequency band. ...
... In [108], similar models for the frequency dependency of the RMS-DS in several indoor environments were proposed. The most relevant campaign to our work is the EAB Office measurements performed at 2.4 GHz, 5.8 GHz, 14.8 GHz and 58.7 GHz center frequencies. ...
... A method proposed in [15] performs rough and quick angle estimation at a lower frequency and reuses the estimated spatial profiles for precious beam operation at high frequency, considering the high similarity of spatial profiles between low and high frequency bands. In [20], channel sounding results reported in mmMAGIC project, covering different propagation scenarios and different frequency bands in 2 to 86 GHz [21], were summarized with the focus on the statistical analysis of delay dispersion parameters. Though multi-band channel similarity can be directly observed, there is a lack of metrics to characterize the degree of it. ...
Prolonged beam alignment is the main source of overhead in mobile wireless communications at millimeter-wave (mm-wave) frequencies due to narrow beams following the requirement of high antenna gains. Out-of-band spatial information may be used in initial beam search when lower frequency band radios are operating in conjunction with mm-wave radios. The feasibility of using low-band channel information for coarse estimation of high-band beam directions strongly depends on the spatial congruence between the two frequency bands. In this work, we try to answer two related questions. First, how similar is the power angular spectrum (PAS) of propagation channels between two widely separated frequency bands? Then, what is the impact of practical antenna configurations on spatial channel similarity? We propose a beam directions based metric to assess the power loss and number of false directions if out-of-band spatial information is used instead of in-band information. This metric is more practical and useful than comparing the PASs directly. Point cloud ray tracing and propagation measurement results across multiple frequency bands and environments are used to show that the degree of spatial similarity of beamformed channels is related to antenna beam widths, frequency gap, and radio link conditions.
... In addition, path loss and delay dispersion parameters at 28, 73, and 140 GHz in an indoor scenario have been presented, where good similarity in path loss yet reduced time dispersion were observed in higher frequency bands [15]. In [16], channel sounding results reported in mmMAGIC project (covering different propagation scenarios and different frequency bands in 2 to 86 GHz [17]) were summarized with a focus on root mean square (rms) delay spread (DS), showing that any frequency trend of the DS is small considering its confidence intervals and largely dependent on the specific scenario. ...
The rollout of millimeter-wave (mmWave) cellular network enables us to realize the full potential of 5G/6G with vastly improved throughput and ultra-low latency. MmWave communication relies on highly directional transmission, which significantly increase the training overhead for fine beam alignment. The concept of using out-of-band spatial information to aid mmWave beam search is developed when multi-band systems operating in parallel. The feasibility of leveraging low-band channel information for coarse estimation of high-band beam directions strongly depends on the spatial congruence between two frequency bands. In this paper, we try to provide insights into the answers of two important questions. First, how similar is the power angular spectra (PAS) of radio channels between two well-separated frequency bands? Then, what is the impact of practical system configurations on spatial channel similarity? Specifically, the beam direction-based metric is proposed to measure the power loss and number of false directions if out-of-band spatial information is used instead of in-band information. This metric is more practical and useful than comparing normalized PAS directly. Point cloud ray-tracing and measurement results across multiple frequency bands and environments show that the degree of spatial similarity of beamformed channels is related to antenna beamwidth, frequency gap, and radio link conditions.
... This frequency-dependence of the channel DS is an issue that has also been subject of intense discussions within the mmMAGIC project to which studies conducted herein have contributed. In a landmark paper [100], the frequency-dependence of the channel DS was P. 55 ...
The advent of bandwidth–demanding mobile applications and services has led to a massive explosion of the network data traffic. In order to alleviate this issue, millimeter–Wave communications systems are a promising technology for future 5G systems thanks to the large amount of bandwidth available in this frequency range. However, in order to take full advantage of this technology, knowledge of the radio propagation channel characteristics in these frequency bands is paramount. Therefore, in this thesis, the objective is to study the frequency–dependence of the propagation channel large scale parameters (LSPs), which describe the main channel characteristics. These LSPs include the building penetration losses, the channel delay spread, the channel azimuth spread and the propagation path–loss. The studies are performed thanks to measurement campaigns conducted in Belfort, in typical 5G deployment scenarios such as outdoor–to–indoor and urban outdoor environments, between 3 and 60 GHz.
... There are several works reporting on multi-band measurements and comparisons of large-scale parameters as DS and azimuth spread (AS) at different bands [8]. However, a general scaling relation between the parameters and frequency has not yet been observed as shown in [9], [10], and [11]. Furthermore, most of the comparisons between mm-wave and sub-6 GHz bands have been done by contrasting different campaigns in the same idealized concept of scenario, or by measurements in the same environment but at different times, using different bandwidths, dynamic range (DR), etc., which introduces a large bias on comparisons. ...
We introduce simultaneous multi-band ultra wide-band directional measurements at 6.75 GHz, 30 GHz, and 60 GHz in an indoor environment with different visibility conditions. Large scale parameters and path-loss has been analysed for the different bands considering the propagation channel, and later the influence of the system aspects in the radio channel. We have observed that the major differences between bands are introduced by the characteristics of the targeted system.
To realize the sixth-generation (6G) vision may require additional spectrum to support the framework and objectives. The sub-6 GHz of fifth-generation (5G) can be used for spectrum refarming, but we also need to find more spectrum with larger bandwidth. This article focuses on the new mid-band (6-24 GHz) that 6G is concerned with, and gives several considerations from the channel perspective. First, we review the global efforts in recent years to study the candidate frequency bands for 6G, as well as spectrum-related works and views of the different organizations. Second, from large/small-scale fading and new characteristics, the recent research findings and considerations are investigated for the channel of the different bands. The channel characteristics of the new mid-band and the influence on the system performance are discussed in depth. Some views and suggestions on the reasonable utilization of the new mid-band for 6G communication systems are put forward. Finally, open issues and future research directions for the 6G spectrum are pointed out. This article sheds light on the more reasonable use of the new mid-band for 6G.
In the 5G-Advanced and beyond systems, multi-frequency cooperative networking will become an inevitable development trend. However, the channels have not been fully investigated at multi-frequency bands and in multi-scenarios by using the same channel sounder, especially for the sub-6 GHz to millimeter-wave (mmWave) bands. In this paper, we carry out channel measurements at four frequency bands (3.3, 6.5, 15, and 28 GHz) in two scenarios including Urban Micro (UMi) and Outdoor-to-Indoor (O2I) with the same channel sounder. The channel characteristics are extracted and modeled, including path loss (PL), shadow fading, frequency dependence of cluster features, root mean square (RMS) delay spread (DS), Ricean K-factor, and the correlation properties. We mainly focus on the analysis of large-scale parameters and more consideration of the link budget coverage problem. We present the frequency dependence model of the channel characteristics. Among them, in the non-line-of-sight (NLoS) condition, it is found that except for theoretical value brought by higher frequency, additional path loss increment will be generated. Based on these channel characteristics, the impact on performance of the wireless system is analyzed including cell coverage radius, data rate and bit error rate (BER). The results can give an insight into the spectrum selection and optimization in 5G-Advanced and beyond multi-frequency communication systems.
This paper presents a novel and cost-effective vector network analyzer (VNA)-based phase-compensated channel sounder operating in the frequency range of 10-50 GHz using radio-over-fiber (RoF) techniques, which can support multi-link/channel long-range phase-coherent measurements. The optical cable enables long-range channel measurements with a dynamic range of 115.7 dB at 30 GHz (for the back-to-back connection). The phase compensation scheme is utilized for stabilizing the inherent phase variations introduced by the optical fiber of the channel sounder to enable its application in multi-channel/antenna measurements. A novel optical delay line and combiner scheme is proposed and implemented to separate the signals, thereby saving the port resource on the VNA for multi-link/channel measurements. The proposed channel sounder is validated in back-to-back measurements under two optical cable conditions, i.e., with the presence of thermal changes and mechanical stress. The phase change could be maintained within 3 • at 10-30 GHz and 7 • in 30-50 GHz, respectively, compared to the over 80 • phase variation introduced by the cable effects at 10-50 GHz, demonstrating the robustness and effectiveness of the developed channel sounder in practice. With the proposed optical delay line and combiner scheme, multiple channels can be measured simultaneously with minimal VNA ports, significantly reducing the measurement cost and time for multi-link channel measurements. Two multi-link indoor channel measurements are conducted and analyzed using a virtual uniform rectangular array (URA) at 28 GHz bands. The results demonstrate the capability of the proposed channel sounder to perform high-fidelity long-range ultrawideband multi-link channel measurements.
This article provides an overview of measurements and models of millimeter-wave (mmWave) propagation channels. After a review of the frequency dependence of propagation phenomena and the definition of parameters of interest, we then discuss the different methods for measuring mmWave channels both indoors and outdoors. Then follows an overview of the key measurement results, surveying again the literature of indoor channels, outdoor channels, and the impact of moving people. A survey of different types of channel models, including 3GPP type, geometry-based stochastic channel models, and map-based models elucidates the aspects of those models that are particularly relevant for mmWave frequencies. A discussion of the interaction of channels and mmWave systems and an outlook and discussion of future research topics round off this article.
Due to the need for larger bandwidth, future mobile networks may primarily operate over millimeter-wave (mmWave) bands. In this regard, one of the central research topics today is mmWave channel modeling. However, highly mobile vehicle-to-vehicle (V2V) mmWave channels pose an open question because conducting measurements may be challenging in this environment. The existing publications on mmWave V2V channel modeling consider line-of-sight (LoS) or single-blocker scenarios. Accordingly, the impact of interference from adjacent vehicles is not taken into account. Conventional analytical models suggest that path loss (PL) strikes equally in all directions whereas measurements are inherently directional, especially in the case of mmWave propagation. Recently, it was proposed to synthesize the omnidirectional PL from directional measurements. However, with this method, the resulting PL is underestimated. Moreover, theoretical models assume that vehicular transceivers follow a certain predetermined distribution, which may not be accurate in real-world scenarios. Several works take into account the directionality of an antenna pattern when the antenna orientation is known. However, the effects of reflection, diffraction, and transmission through obstacles are not considered. One way to avoid these limitations is to use ray-based simulations. However, the ray-launching (RL) approach does not specify any criteria for the directionality of the antenna patterns. Assuming omnidirectional PL appears impractical for mmWave transmission where directional communication is crucial to combat high PL. In this paper, we propose an approach for synthesizing directional PL based on extensive RL modeling. For the obtained directional and omnidirectional PL, we parametrize the close-in (CI) and float-intercept (FI) channel models. As a result of our modeling, from 0.1 to 2.7 for the LoS and from 0.1 to 2.6 for the non-LoS (NLoS) higher PL exponent is observed as compared to the omnidirectional case.
Concerning the design and planning of new radio interfaces for the fifth-generation (5G) systems, this paper presents a useful contribution to the characterization of the wideband indoor radio channel in the 3 to 4 GHz frequency band. A measurement campaign has been carried out in two different indoor scenarios to analyze some of the most important wideband parameters of the propagation channel, including a thorough analysis of its behavior to meet the new radio technology challenges. The channel measurement setup consists of a virtual vertical uniform array at the receiver side of the link that remains at a fixed position, whereas the transmitter side, which is equipped with a single antenna, is placed at different positions in the environment under analysis. The measurement setup emulates the up-link of a multi-user multiple-input multiple-output (MIMO) system, and allows obtaining the broadband parameters of the multiple channels that are established between the transmitter and each one of the antennas of the receiver array. Results and conclusions about the path loss, temporal dispersion and coherence bandwidth are included, along with an analysis of the spatial correlation between wideband channels when one of the antennas is an array.
This paper presents system design, calibration and example measurements of a novel ultra-wideband, low-cost, realtime channel sounder. The channel sounder operates in the frequency range from 3 GHz to 18 GHz with a 15 GHz bandwidth thus providing a Fourier delay resolution of 66.7 ps. It sequentially measures overlapping sub-bands of 1 GHz bandwidth to cover the whole frequency range. By using a waveform generator and a digitizer with relatively lower sample rates, the design significantly lowers the cost compared to sampling the whole band simultaneously. With the transmitting power of 40 dBm, the maximum measurable path loss is 132 dB without accounting for possible antenna gains. In this work, we also describe the calibration procedure along with the method to stitch sub-bands into a combined channel response across 15 GHz of bandwidth. The channel sounder performance is compared with vector network analyzer (VNA) measurements acquired in the same static channels. In contrast to VNAs, however, our channel sounder can measure the whole band in 6 ms and can thus operate in dynamic environments with coherence time more than 6 ms. Additionally, we present sample results from a measurement campaign performed in an indoor corridor investigating the delay spreads statistics over the range of 3- 18 GHz.
This paper presents a benchmarking analysis of wideband channel characteristics in two indoor environments in the 59-65 GHz and 80.5-86.5 GHz bands. Measurements were carried out by performing mechanical steering of directive antennas at both the transmitter and receiver sides. Omnidirectional power delay profiles were obtained from directional measurements and multipath components are subsequently estimated. Comparison of large-scale parameters such as the path loss, the delay and angular spread is provided. Multipath clustering was investigated for both bands and environments, and wide band channel model parameters are provided. Based on measurement results, commonness between paths in different bands was analyzed, highlighting the presence of some well-identified paths plus frequency dependent ones. IEEE
Fifth generation cellular systems will operate in a wide range of frequencies, covering both the traditional cellular bands, and mm-wave frequency bands, either selecting a specific band or operating in multiple bands simultaneously. For the design of such systems, a detailed understanding of the frequency dependence of the propagation channel is essential. While many channel measurements exist in either microwave bands (< 6 GHz) or near mm-wave bands (> 20 GHz), the results are not easily comparable, and furthermore the transition between these bands is not well studied. This paper aims to bridge the gap by providing the results from a channel measurement campaign conducted in urban macro and micro-cellular environments, over the continuous frequency band of 3–18 GHz. We characterize the pathloss, shadow fading, Root-Mean- Square (RMS) delay spreads, Ricean factor and coherence bandwidth in urban macro-cellular (UMa) and urban microcellular (UMi) environments. Measurements were taken in both line-of-sight (LOS) and non-line-of-sight (NLOS) environments. The pathloss exponents and the RMS delay spreads increase with the Base Station (BS) height in NLOS environment; but not much dependency is observed in the LOS environment. By dividing the wideband channel transfer function into subbands of 1 GHz each, we study the frequency dependence of pathloss, shadow fading, Ricean factor, delay spread, and coherence bandwidth in the 3–18 GHz band. The pathloss exponents vary significantly with frequency, but not-monotonically. The shadow fading and the Ricean factor increase with frequency. The RMS delay spreads decrease with frequency in the LOS environments, but they do not change significantly in the NLOS environments. The coherence bandwidth values do not change significantly with frequency in either environment.
ResearchGate has not been able to resolve any references for this publication.