In 6G design, radio propagation analysis with high accuracy is required. Radio wave propagation analysis with ray-tracing (RT) is based on searching for ray-paths between Tx and Rx. Here, in order to improve the analysis accuracy, it is necessary to search for multiple ray-paths that contribute to the propagation characteristics, but the amount of calculation increases exponentially as the number of structures to be considered and the number of interactions with structures increase. On the other hand, at present, attention is focused on quantum annealing (QA) computer that enable ultra-high-speed operations for combinatorial optimization problems. Here, it can be said that the searching for ray-paths is one of the combinatorial optimization problems. Therefore, this paper proposes novel ray-path search method applicable to QA. And the validation results are shown.

This study applied to improve the mobile radio propagation prediction utilizing a ray tracing method. Mobile radio propagation simulation based on ray tracing methods has been extensively used to estimate channel characteristics. Related works have reported the modeling of propagation with tuning parameters. Optimizing the parameters structurally impacted the channel prediction. In this paper, an optimization system using a genetic algorithm was proposed, and system performance was evaluated by measured data.

This paper proposes 28-GHz band compatible vehicle glass mounted antenna that actualizes cellular-V2X communications and report on the downlink performance when distributing that antennas on the glass surfaces in high mobility environments up to 100 km/h. The antennas can be installed on vehicle glass surfaces without affecting the vehicle design. Based on measurement results when utilizing a distributed antenna installation on the glass surfaces, we confirmed proper beam selection according to the vehicle position. We also achieved the maximum throughput of approximately 8 Gbps while moving at high speeds of approximately 100 km/h, and achieved the maximum throughput of approximately 11 Gbps at a speed of approximately 30 km/h. We confirmed the feasibility of high-speed in-vehicle communications using a 28-GHz band compatible vehicle glass mounted antenna.

For fifth generation mobile communication systems (5G) utilization of the band from 6 to 100 GHz is investigated to increase the system capacity, because it is relatively easy to ensure the wide bandwidth in these frequencies. Considering the capital investment involved in establishing 5G service areas, utilizing non-line-of-sight (NLOS) environments for service areas is desirable. Moreover, since beamforming will be utilized to compensate large path loss in higher frequencies, it is important to understand the relationship between the multipath and the city structure in a NLOS environment in which compensating for path loss is more important than LOS environment. In this report, we investigate the relationship between the multipath and the city structure around intersections based on delay profiles measured using a horn antenna in a NLOS street cell environment. The results clarify that diffraction waves from building corners and reflected waves from building walls that exist along the street on which a mobile station is deployed are dominant paths.

This paper presents path loss frequency dependence on the basis of measurement campaign results in two urban macro (UMa) cell environments using four frequencies between 2 and 66 GHz. For a 3rd Generation Partnership Project (3GPP) UMa model above 6 GHz band, the dependence is shown by 20log(f). However, some studies for the environments show the frequency dependence more than 20log(f) and its propagation phenomena as its cause. The 3GPP model is based on measurements whose dynamic range and distance are limited. So, we measured the path loss characteristics using wide dynamic range equipment capable, for example, of measuring the path loss more than 170 dB at 26 GHz. The measurement results show that the dependence is similar to 3GPP model in Line-of-Sight areas, but that in Non-Line-of-Sight (NLoS) areas it increases more than the dependence of 20log(f). The measured path loss also show that the high frequency dependence can be seen in far distance area and the high path loss area. Taking into account the geographical and urban environment, the high frequency dependence in the far distance NLoS area may be explained by the dominance of diffraction over reflective propagation along the buildings. These results can contribute to clarify the site-specific path loss characteristics and design the cell area for the high frequency bands.

For the development of new 5G systems to operate in bands up to 100 GHz, there is a need for accurate radio propagation models at these bands that currently are not addressed by existing channel models developed for bands below 6 GHz. This document presents a preliminary overview of 5G channel models for bands up to 100 GHz. These have been derived based on extensive measurement and ray tracing results across a multitude of frequencies from 6 GHz to 100 GHz, and this document describes an initial 3D channel model which includes: 1) typical deployment scenarios for urban microcells (UMi) and urban macrocells (UMa), and 2) a baseline model for incorporating path loss, shadow fading, line of sight probability, penetration and blockage models for the typical scenarios. Various processing methodologies such as clustering and antenna decoupling algorithms are also presented.

Fifth generation (5G) mobile communication systems are being actively investigated to increase the system capacity. For 5G, utilizing frequency bands above 6 GHz is being investigated because it is considered that ensuring a wide frequency band above 6 GHz is relatively easier than that under 6 GHz, which is used for IMT-Advanced systems. In this report, a site general type path loss prediction model for 5G system radio link design is investigated for the above mentioned frequency band in a non-line-of-sight (NLOS) microcell environment. More specifically, based on measurement data, extending the applicable frequency range of the path loss prediction model for a hexagonal layout in a NLOS microcell environment for under 6 GHz, which is defined in Report ITU-R M.2135, is investigated. The root mean square of the prediction error (RMSE) of the original M.2135 prediction model increases with an increase in frequency; however, the model modifies the frequency term of M.2135 which improves the RMSE at higher frequencies.

In recent years, MIMO channel models for the crowded areas such as indoor offices, shops, and outdoor hot spot environments have become a topic of great interest. In the crowded environments, the propagation paths are blocked frequently by users walking around the mobile terminal, and it causes severe shadowing and fading of channel. In this paper, to take the impact of pedestrians on the channel model into consideration, we proposed the estimation method of clusters' power variation properties from the channel sounding data. We carried out the MIMO channel sounding experiments in a cafeteria in a weekday lunch time in the 3 GHz band assuming the use of LTE based cellular systems. We estimated the propagation parameters of clusters from the measured data and estimated the cluster power variation properties. The measurement results showed that the mean cluster power varied from -11.3 dB to 1.3 dB compared to the no pedestrian environment. The mean cluster powers tended to decrease as the clusters' propagation delay increased. The cluster power variation standard deviations. ranged from 0.9 dB to 2.4 dB and the cluster power variation correlation times ranged from 0.7 sec. to 1.1 sec.

The user traffic volume in the cellular network has been growing rapidly. Recent capacity enhancement techniques based on the small-cell architecture are examined for crowded areas such as urban railway stations and environs. Although small-cell propagation environments are characterized by short distances and low antenna heights, the applicability of current MIMO channel models in those environments has not been adequately investigated. In addition, although there are a great number of pedestrians and vehicles in urban areas, the influence of pedestrians on the MIMO channel models remains unclear. In this paper we carried out channel sounding experiments outside a crowded urban railway station in the 2 GHz band assuming the use of LTE-based cellular systems. To elucidate the influence of pedestrians on the channel properties, the measurements were carried out both in the daytime and in the midnight. The measurements result showed that the received power decreased about 4-5 dB in the daytime due to the shadowing by the pedestrians. In addition, the delay spreads decreased and AoAelv and AoDelv spreads increased in the daytime due to the change of propagation environment caused by the pedestrians.

To address the rapid increase in the volume of data traffic in mobile communication networks, small cells that enable data transmission at a high bit rate and use very high frequency bands (over 6 GHz) have been studied recently. Considering that the environment into which small cells are introduced is crowded and dominated by line of sight communications with very high data traffic loads, the characteristics of human body shadowing (HBS) are important propagation parameters. In this paper, we propose a method for analyzing HBS characteristics based on the uniform geometrical theory of diffraction and lossy dielectric flat plates. Calculated results are compared to measured results to show that the proposed method is effective in analyzing the HBS characteristics.

In LTE-Advanced heterogeneous networks, a typical cell layout to enhance frequency utilization is to incorporate picocells and femtocells in a macrocell. However, the co-channel interference between the marcocell and picocell/femtocell is an important issue when the same frequency band is used between these systems. %We have already clarified how the interference from the femto(macro)cell affects on the macro(femto)cell. In this paper, we evaluate the interference rejection characteristics by an adaptive array for user equipment#126;(UE) with Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) algorithms. The characteristics are evaluated based on the #36;K#36;-factor used in the Nakagami-Race Fading model and the spatial correlation that is obtained in an actual outdoor environment. It is shown that a two-element adaptive array at the macro UE(M-UE) can sufficiently reduce the interference from the femto base station(F-BS) to the M-UE even if the number of total signals exceeds the degrees of freedom of the array. Moreover, 1.5dB SINR difference is observed when comparing ZF and MMSE algorithms when the number of interfering signals is two.

In order to employ MIMO techniques the number of antenna branches must be increased and as a consequence the installation space requirements are increased. Since the installation space is limited, much attention is now focused on the utilization of polarization characteristics for MIMO configuration in order to relax the requirements. This is called Polarization-MIMO in this paper. In accurately evaluating the performance of Polarization-MIMO, a channel model that can handle the polarization dispersion characteristics of propagation paths is essential. Up to now, the spatial-temporal dispersion characteristics of the paths have been investigated in detail. However, there are few reports on the polarization dispersion characteristics. In this paper, we propose a new power profile for the linear polarized direction as an evaluation model for polarization dispersion, and clarify the analyzed power profile from measurement data in an urban macrocell environment.

In indoor environments, although models using parameters such as the K-factor and Cross-Polarization Discrimination (XPD) were proposed as a method for estimating the throughput in polarized Multiple-Input-Multiple-Output (MIMO), the values for the K-factor and XPD are assumed. In order to estimate the throughput of actual indoor environments, it is necessary to measure the value of the K-factor and XPD in actual indoor environments. However, there are few studies that measured both the K-factor and XPD of a polarized MIMO channel in an indoor environment. So, in this report, we clarify the characteristics of the K-factor, XPD, and channel correlation of the polarized MIMO channel obtained through measurements and simulations in a line-of-sight indoor environment.

This paper proposes interference cancellation that utilizes relay stations (RSs). In Long Term Evolution (LTE) Advanced, heterogeneous networks in which femto and picocells are overlaid onto macrocells are extensively discussed. However, interference between macro and pico(femto)cells arises due to their different transmit power levels. Unlike conventional cooperative transmission schemes, the RS decodes interference in the first transmit timing period and forwards it to the user equipment (UE) in the second period. Moreover, cooperative transmission can be achieved without stopping the transmission from the base station (BS) to UE when forwarding the interference from the RS to the UE by utilizing the fact that signal to noise power ratio (SNR) between the RS and UE is much greater than that between the BS and UE. The effectiveness of the proposed method and the optimal relay arrangement are shown based on computer simulation when considering heterogeneous pathloss models.

MIMO transmission technologies have been investigated and are expected to realize the wide-band and high-speed radio communication in LTE and IMT-A systems. To put those technologies into practical use, the accurate MIMO channel is required. To estimate the propagation parameters of rays from the channel data measured by the channel sounder, the SAGE based estimation algorithms have been used. SAGE algorithm is able to be applied to any patterns of antenna arrays, and can estimate the several propagation parameters such as AoA, AoD, delay and amplitude in parallel. However it has the resolution degrading problem in the case that there are close rays that have the close propagation parameters. In the paper, we propose the novel channel estimation methods. In our proposal, after the global parameter estimation using SAGE algorithm, we extract the signal component of the close rays from the measured data. Then we execute detailed parameter estimation for those rays using MODE based algorithm with the array interpolation. We show the effectiveness of our proposal through the computer simulation.

The ray-based channel models with parameters derived from measured data such as the 3GPP Spatial Channel Model has been widely used as the standard for evaluating the performance of MIMO transmission technologies used in next generation cellular systems such as LTE and IMT-Advanced. Recently, for evaluating the temporal evolution of MIMO transmission performance, demand has been rising for enhanced channel models that include not only the static channel behavior but also dynamic and time-variant channel behavior. In this paper, we propose a Dynamic Channel Model. In our model, we estimate the dynamic properties of rays such as the ray's birth time, death time, and propagation parameter drift using Rao-Blackwellized particle filter. Experiments show that our dynamic channel model yields AoA, ToA, and AoD attributes, spread and auto-correlation, that agree with data measured in an urban environment well.

This paper describes an evolution and standardization trends of the wireless channel modeling activities towards IMT-Advanced. In particular, the new developed and standardized ITU-R IMT-Advanced multiple-input-multiple-output (MIMO) Channel Model (IMT-Adv MCM) is detailed. The IMT-Adv MCM is compared with the well-known the 3GPP/3GPP2 Spatial Channel Model (SCM), and their main similarities and differences are pointed out. The performance of MIMO systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. Here, we investigate the spatial-temporal correlation characteristics of the 3GPP/3GPP2 SCM and the IMT-Adv MCM in term of their spatial multiplexing and spatial diversity gains. The main goals of this paper are to summarize the current state of the art, as well as to point out the gaps in the wireless channel modeling works, and thus hopefully to stimulate research in these areas.

This paper presents a path-shadowing model in indoor populated environments based on computer simulations. The propagation paths between the transmitting and receiving points in an empty rectangular space are determined by a ray tracing method, moving quasi-human bodies modeled as a cylinder with finite height are generated in this space, and intersections of the paths with the bodies are counted. As a result, the shadowing probabilities, durations, and intervals are evaluated for each propagation path, and this shadowing process is characterized as a Markov process. This paper proposes a method for individually generating the shadowing effects on each propagation path. The results of 5.2 GHz propagation measurements in indoor populated space using a high resolution channel sounder is also presented, and the validity of this model is confirmed.

In this paper, the prediction of received power in the out-of-zone of a dedicated short range communications (DSRC) system operating inside a typical arched highway tunnel is discussed. By conducting wideband directional channel sounding inside the tunnel, the gain, angle-of-arrival and delay of each propagation path are estimated by means of a multidimensional maximum likelihood estimation algorithm from the measured data. Using these estimated parameters and by employing simulations of application antennas according to the DSRC standard, the received power in the out-of-zone is predicted for 2 roadside unit (RSU) antenna positions. The dominant scatterers causing the over-reach of radiated power to the out-of- zone were identified and attributed to the ground and sidewalk. These scatterers can affect the received power level in the out- of-zone by as much as 10 dB. It can therefore be concluded that suppressing ground and sidewalk scatterings in the vicinity of RSU by installing composite pavement materials are needed to increase the electromagnetic absorption in order to guarantee DSRC services.

To analyze the radio propagation channel inside a tunnel, a wideband directional measurement campaign was managed inside an arched tunnel which was constructed to be used for a highway. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver (Rx), the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The dominant scatterers are classified into 5 classes based on the structure of the tunnel as follows: ceiling, light-frames, walls, sidewalk or ground. The power contribution and cross polarization ratio for different Rx positions along the tunnel are compared

A channel model for line-of-sight (LoS) small street microcell in dense urban areas is proposed. The scattering power distribution (SPD) in the channel seen from the receiver (Rx) based on the physical phenomenon is obtained. The coefficients of the distribution are derived by approximation to a set of urban street microcell measurement data. The azimuth-power spectrum (APS) for the proposed model is compared to those for conventional elliptical model as well as to the experimental results obtained from measurements in three different streets of a dense urban area. It is shown that the proposed model in contrast to the conventional models produces results that closely agree with the experimental results

This paper proposes a delay profile measurement scheme for estimating W-CDMA systems performance in practical service areas. The scheme uses the P-CPICH continuously transmitted from each base station. Its two key points are; detecting the synchronization timing from just P-CPICH and measuring the SIR delay profile in addition to the power delay profile. We clarify the performance of the measurement system analytically and show the results of tests conducted on a prototype.

In mobile communication systems, especially digital wireless PBX systems, it is very important to clarify the service area in case of indoor base stations. However it is very difficult to estimate the propagation characteristics accurately under these environments because the indoor components, ex. wall partition, etc., are not only positioned randomly, but also made from complex materials. An indoor micro cell area prediction system, which can be easily estimate the propagation characteristics using the ray-tracing method, is proposed and its system configuration and major performance are described.