On the Frequency Dependency of Radio Channel's Delay Spread: Analyses and Findings From mmMAGIC Multi-frequency Channel Sounding

This paper analyzes the frequency dependency of the radio propagation channel's root mean square (rms) delay spread (DS), based on the multi-frequency measurement campaigns in the mmMAGIC project. The campaigns cover indoor, outdoor, and outdoor-to-indoor (O2I) scenarios and a wide frequency range from 2 to 86 GHz. Several requirements have been identified that define the parameters which need to be aligned in order to make a reasonable comparison among the different channel sounders employed for this study. A new modelling approach enabling the evaluation of the statistical significance of the model parameters from different measurements and the establishment of a unified model is proposed. After careful analysis, the conclusion is that any frequency trend of the DS is small considering its confidence intervals. There is statistically significant difference from the 3GPP New Radio (NR) model TR 38.901, except for the O2I scenario.Comment: This paper has been accepted to the 2018 12th European Conference on Antennas and Propagation (EuCAP), London, UK, April 201

Radiowave propagation and antennas for high data rate mobile communications in the 60 GHz band

The 60 GHz MIMO systems are seen as some of the best candidates for the implementation of future high data-rate short range communications systems such as wireless personal area networks (WPAN). Although the performance of MIMO systems has been studied thoroughly theoretically and experimentally at lower frequencies like at 2 and 5 GHz, there is a clear lack of measurement data and experimental performance evaluations of MIMO techniques at 60 GHz. Furthermore, more effort is still needed in the design and evaluation of compact low cost 60 GHz antennas for communication applications. In the first part of the thesis, the first 60 GHz MIMO channel measurement system is presented. It is based on a previously developed 2 and 5 GHz sounder and frequency converters. This system uses virtual antenna arrays to create the channel matrix. A measurement campaign is reported. In order to improve the delay resolution, two other MIMO measurement systems are presented, based on an ultra wide band (UWB) sounder and a vector network analyzer (VNA). Those systems allow full characterization of the MIMO channel in the delay and angular domains. In the second part of this work, the performance of multi-antenna techniques is evaluated based on the measurement data obtained in the first part of the thesis. Three of the most promising multi-antenna techniques, namely MIMO, antenna selection MIMO, and beam steering, are analyzed and compared. The presented results indicate that the mutual information of the measured MIMO channel is quite close to that of the independent and identically distributed (i.i.d.) MIMO Rayleigh channel. Furthermore, in realistic conditions it is seen that MIMO-antenna selection often leads to lower mutual information than traditional MIMO with the same number of RF chains. Moreover, it is shown that when considering phase shifters with realistic losses, MIMO technique almost always outperforms beam steering technique. In the last part of the thesis a 60 GHz planar omnidirectional antenna is presented. This antenna is very suitable for communications applications since it has low profile and uses a metal layer only on one side of the substrate. Therefore, it can be manufactured easily and at very low cost. In addition, an advanced quasi full 3-D radiation pattern measurement system has been developed to evaluate probe-fed antennas. Very good measurement repeatability is reported. The radiation of the probe is analyzed and is seen to be the main limitation of the dynamic range of the measurement setup

Survey of millimeter-wave propagation measurements and models in indoor environments

The millimeter-wave (mmWave) is expected to deliver a huge bandwidth to address the future demands for higher data rate transmissions. However, one of the major challenges in the mmWave band is the increase in signal loss as the operating frequency increases. This has attracted several research interests both from academia and the industry for indoor and outdoor mmWave operations. This paper focuses on the works that have been carried out in the study of the mmWave channel measurement in indoor environments. A survey of the measurement techniques, prominent path loss models, analysis of path loss and delay spread for mmWave in different indoor environments is presented. This covers the mmWave frequencies from 28 GHz to 100 GHz that have been considered in the last two decades. In addition, the possible future trends for the mmWave indoor propagation studies and measurements have been discussed. These include the critical indoor environment, the roles of artificial intelligence, channel characterization for indoor devices, reconfigurable intelligent surfaces, and mmWave for 6G systems. This survey can help engineers and researchers to plan, design, and optimize reliable 5G wireless indoor networks. It will also motivate the researchers and engineering communities towards finding a better outcome in the future trends of the mmWave indoor wireless network for 6G systems and beyond

Indoor Channel Measurements and Analysis in the Frequency Bands 2 GHz and 60 GHz

This paper describes the wideband measurements conducted at the frequencies 58 GHz and 2.25 GHz in an indoor environment. Normalized received power (NRP) and root-meansquared (RMS) delay spread are calculated and used to compare the characteristics of radio wave propagation in both line-of-sight and non-line-of-sight areas at the two frequencies. The results show that on top of the difference in free space, the NRP at 58 GHz is several dBs lower than at 2.25 GHz in average. This difference is also reflected in the fitted log-(virtual) distance NRP models. In the deep shadow region, the poor diffraction level at 58 GHz will reduce the power level, but meanwhile the reflected waves from walls have a strong contribution to the received signal. In addition, it is observed that the radio channel at 58 GHz shows much less time dispersion in terms of RMS delay spread. The results can be quite useful for the 60 GHz system design, which might be very different from the design of conventional systems which operate in the lower frequency bands

Wide-band channel sounding in the bands above 2GHz

Modem telecommunication services require increasing data rates for both mobile and fixed applications. At frequencies in the range 2.5 GHz to 6 GHz physical constraints on the size of equipment result in antenna with moderate directivity typically with an antenna beam width of 20 degrees or greater. Thus building and ground clutter is present within the first Fresnel zones of the antenna system which gives rise to multi-path propagation. This multi-path propagation (average delay and RMS delay spread) has been investigated using a wideband FMCW channel sounder that is capable of operation at a number of frequencies. The channel sounder has been based upon a parallel architecture sounder operating within the 2 GHz band with a number of frequency conversion modules to translate operation to the new frequency bands under study. Two primary configurations have been explored. In the first of these, propagation has been measured simultaneously within the 2.5 GHz, 3.4 GHz and 5.7 GHz bands. This is believed to be novel and original. In the second configuration four parallel channels operating within the 5.7 GHz band may be operated simultaneously. This configuration supports multiple antennas at the receiver. To support the work in the bands from 2.5 GHz to 6 GHz wideband discone antenna have been designed and fabricated. A system to provide relative gain and phase calibration for up to four antennas has been developed and demonstrated. This is also believed to represent a novel method of performing antenna and array calibration. Finally, the frequency converters have been used in conjunction with additional components to provide an FMCพ sounder operating within the 60 GHz Oxygen absorption band. This work is novel in that up to 1 GHz of spectrum can be swept. To support this work a significant number of microwave components have been designed and developed. In particular a novel wide band balanced X3 multiplier and a novel impedance-matched amplitude-equaliser (to provide amplifier gain-slope equalisation) has been developed. Channel soundings have been performed at three frequencies simultaneously using band specific and common antenna. The average delay and RMS delay spread have been demonstrated to be essentially frequency independent for the environments evaluated

Connectivity, throughput, and end-to-end latency in infrastructureless wireless Networks with beamforming-enabled devices

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 181-188).Infrastructureless wireless networks are an important class of wireless networks best fitted to operational situations with temporary, localized demand for communication ability. These networks are composed of wireless communication devices that autonomously form a network without the need for pre-deployed infrastructure such as wireless base-stations and access points. Significant research and development has been devoted to mobile ad hoc wireless networks (MANETs) in the past decade, a particular infrastructureless wireless network architecture. While MANETs are capable of autonomous network formation and multihop routing, the practical adoption of this technology has been limited since these networks are not designed to support more than about thirty users or to provide the quality of service (QoS) assurance required by many of the envisioned driving applications for infrastructureless wireless networks. In particular, communication during disaster relief efforts or tactical military operations requires guaranteed network service capabilities for mission-critical, time-sensitive data and applications. MANETs may be frequently disconnected due to device mobility and mismatches between routing and transport layer protocols, making them unsuitable for these scenarios. Network connectivity is fundamentally important to a network designed to provide QoS guarantees to the end-user. Without network connectivity, at least one pair of devices in the network experiences zero sustainable data rate and infinite end-to-end message delay, a catastrophic condition during a search and rescue mission or in a battlefield. We consider the use of wireless devices equipped with beamforming-enabled antennas to expand deployment regimes in which there is a high probability of instantaneous connectivity and desirable network scalability. Exploiting the increased communication reach of directional antennas and electronic beam steering techniques in fixed rate systems, we characterize the probability of instantaneous connectivity for a finite number of nodes operating in a bounded region and identify required conditions to achieve an acceptably high probability of connectivity. Our analysis shows significant improvements to highly-connected regimes of operation with added antenna directivity. Following the characterization of instantaneous network connectivity, we analyze the achievable network throughput and scalability of both fixed and variable rate beamforming-enabled power-limited networks operating in a bounded region. Our study of the scaling behavior of the network is concerned with three QoS metrics of central importance for a system designed to provide service assurance to the end-user: achievable throughput, end-to-end delay (which we quantify as the number of end-to-end hops), and network energy consumption. We find that the infrastructureless wireless network can achieve scalable performance that is independent of end-user device density with high probability, as well as identify the existence of a system characteristic hopping distance for routing schemes that attain this scaling-optimal behavior. Our results also reveal achievable QoS performance gains from the inclusion of antenna directivity. Following these insights, we develop a scalable, heuristic geographic routing algorithm using device localization information and the characteristic hopping distance guideline that achieves sub-optimal but high network throughput in simulation.by Matthew F. Carey.S.M