RMS delay spread vs. coherence bandwidth from 5G indoor radio channel measurements at 3.5 GHz band

Our society has become fully submersed in fourth generation (4G) technologies, setting constant connectivity as the norm. Together with self-driving cars, augmented reality, and upcoming technologies, the new generation of Internet of Things (IoT) devices is pushing the development of fifth generation (5G) communication systems. In 5G architecture, increased capacity, improved data rate, and decreased latency are the objectives. In this paper, a measurement campaign is proposed; we focused on studying the propagation properties of microwaves at a center frequency of 3.5 GHz, commonly used in 5G cellular networks. Wideband measurement data were gathered at various indoor environments with different dimensions and characteristics. A ray-tracing analysis showed that the power spectrum is dominated by the line of sight component together with reflections on two sidewalls, indicating the practical applicability of our results. Two wideband parameters, root mean square delay spread and coherence bandwidth, were estimated for the considered scenarios, and we found that they are highly dependent on the physical dimension of the environment rather than on furniture present in the room. The relationship between both parameters was also investigated to provide support to network planners when obtaining the bandwidth from the delay spread, easily computed by a ray-tracing tool

Millimeter-Wave Massive MU-MIMO Performance Analysis for Private Underground Mine Communications

In this article, a performance analysis of millimeter wave (mmWave) massive multiuser multiple-input and multiple-output (MU-MIMO) channel within an underground mine is performed. The analysis is based on channel measurements conducted at 28 GHz using a base station of 64 virtual antenna elements serving multiple users. Channel characteristics such as large-scale path loss, time dispersion, coherence bandwidth and sum-rate capacity are reported and evaluated. The results indicate that multislope path loss model is better suited for precise prediction of path loss across various propagation segments within the mining gallery. The time dispersion analysis reveals that the underground mine channel does not cause significant time dispersion, as 90% of the root-mean-square (rms) delay spreads are below 4 ns. In addition, it was found that the rms delay spread is not dependent on the propagation distance. The study on sum-rate capacity highlights the potential of employing massive MIMO technology to improve the channel’s spectral efficiency. The analysis reveals that the capacity, with eight active users, can reach up to 33.54 bit/s/Hz. The outcomes of this article offer valuable insights into the propagation properties of underground mine environment, which is characterized by rich-scattering and irregular topology

Wireless channel analysis between 25 and 40 GHz in an intra-wagon environment for 5G using a ray-tracing tool

Metro and railway systems are one of the most used transportation systems for people in almost all countries. Nevertheless, the access to high throughput wireless services is still very limited inside the wagons (cars). A deep analysis of the wireless channel inside wagons is needed to deploy new efficient and high throughput networks as the ones provided by fifth-generation (5G) systems. Although several works have analyzed the intra-wagon channel, some limitations are usually present: only certain user equipment-access point situations were considered, the number of studied propagation mechanisms was limited, and only some channel parameters were extracted. For these reasons, in this work the wireless channel in an intra-wagon environment is thoroughly analyzed using simulations performed with a ray-tracing tool calibrated and validated with wideband measurements. Thanks to the accurate ray-tracing tool the main replicas are identified in different typical user equipment-access point positions; the contribution of each propagation mechanism to the total power is extracted; and the angular spread in azimuth and elevation for the direction of arrival and departure are obtained. This analysis is performed in the frequency range from 25 to 40 GHz, where spectrum for several 5G bands has been already allocated.This work was supported in part by the Ministerio de Ciencia e Innovación of the Spanish Government through the National Projects under Grant PID2019-107885GB-C33 and in part by the Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER) under Grant PID2020-119173RB-C21

Path loss modelling at 60 GHz mmWave based on cognitive 3D ray tracing algorithm in 5G

The objective of the study is to consider the foremost high-tech issue of mobile radio propagation i.e. path loss for an outdoor and indoor environment for mmWave in a densely populated area.60 [GHz] mmWave is a win-win for the 5th Generation radio network. Several measurements and simulations are performed using the simulator “Smart Cognitive 3D Ray Tracer” build in MATLAB. Two of the main parameters (pathloss and received signal strength (RSS)) of the radio propagation are obtained in this study. To compute the pathloss and RSS, 5G 3GPP mobile propagation model is selected due to its flexibility of scenario and conditions beyond 6 GHz frequency. For indoor simulations, we again chose 5G 3GPP mobile propagation model. It is evident from the recent previous studies that there is still not enough findings in the ray tracing specially cognitive 3D ray tracing. The suggested alternative cognitive algorithm here deals with less iterations and effective use of resources. The conclusions of this work also comprise that the path loss is reliant on separation distance of base station and receiver. The above mentioned frequency and interconnected distance reported here provide better knowledge of mobile radio channel attributes and can be also used to design and estimate the performance of the future generation (5G) mobile networks

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

Dynamic mmWave Channel Emulation in a Cost-Effective MPAC with Dominant-Cluster Concept

Millimeter-Wave (mmWave) massive multiple-input multiple-output (MIMO) has been considered as a key enabler for the fifth-generation (5G) communications. It is essential to design and test mmWave 5G devices under various realistic scenarios, since the radio propagation channels pose intrinsic limitations on the performance. This requires emulating realistic dynamic mmWave channels in a reproducible manner in laboratories, which is the goal of this paper. In this contribution, we firstly illustrate the dominant-cluster(s) concept, where the non-dominant clusters in the mmWave channels are pruned, for mmWave 5G devices applying massive MIMO beamforming. This demonstrates the importance and necessity to accurately emulate the mmWave channels at a cluster level rather than the composite-channel level. Thus, an over-the-air (OTA) emulation strategy for dynamic mmWave channels is proposed based on the concept of dominant-cluster(s) in a sectored multiprobe anechoic chamber (SMPAC). The key design parameters including the probe number and the angular spacing of probes are investigated through comprehensive simulations. A cost-effective switchcircuit is also designed for this purpose and validated in the simulation. Furthermore, a dynamic mmWave channel measured in an indoor scenario at 28-30 GHz is presented, where the proposed emulation strategy is also validated by reproducing the measured reality.Comment: Accepted by IEEE Transactions on Antennas and Propagatio