Mitsuki Nakamura’s research while affiliated with Nippon Telegraph and Telephone and other places

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Publications (26)


Frequency Dependence and Propagation Mechanisms of Path Loss in Indoor Environments
  • Article

October 2024

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8 Reads

IEEE Antennas and Wireless Propagation Letters

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Minoru Inomata

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Wataru Yamada

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[...]

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Tomoaki Ogawa

This paper presents the frequency dependence of the path loss exponent (PLE) based on measurement results of multiple frequency bands in indoor environments and explains the propagation mechanisms that cause frequency dependence. Path loss measurements from 0.8 GHz to 66.5 GHz in two indoor open office environments were used to derive the parameters of a close-in free space reference distance model (CI model) and an alpha-beta-gamma model (ABG model). We revealed that the PLE of the single-frequency CI model tended to decrease with increasing frequency, while the frequency coefficient of the ABG model was smaller than that of the free space loss (FSPL), indicating a different frequency dependence than FSPL in these environments. Furthermore, the propagation mechanisms of the waveguide effect and the first Fresnel zone shielding cause this frequency dependence. Ray-tracing simulations revealed that the PLE becomes large and small in the low- and high-frequency bands, respectively, when the ceiling height is low, consistent with the measurements. The PLE becomes small regardless of the frequency band when the ceiling height is high, indicating frequency dependence along the propagation mechanism in both the ray-tracing simulation and measurement results.






A method of path loss prediction based on computer graphics technologies

March 2023

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5 Reads

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1 Citation

IEICE Communications Express

In this letter, a method for path loss prediction in outdoor urban environments based on computer graphics technologies is presented. Each wall of buildings in an evaluation area is assigned to a different RGB color. We create two types of color images that are viewed from a transmission point (Tx) and receiving points (Rxs). By analyzing and comparing the colors of these images, the visible colors existed in both images corresponding to the single scattering walls are detected all at once. The numbers of pixels of the visible colors are used to calculate received powers of the single scattering waves. The average and RMSE of difference between predicted path loss results and measurement results are small with -0.5 dB and 7.6 dB, respectively. The computation time is extremely short.






Citations (17)


... This setup fails to capture the omnidirectional multipath characteristics, where significant multipath rays can arrive from 360° in the azimuth plane, as demonstrated in this study. An exception is the work in [24], which conducted measurements in a real office desk environment within the 110 [31]. However, these studies typically focused on longer-range communications, such as cellular or WLAN-type communications, where the propagation characteristics differ significantly from those in personal office desk environments. ...

Reference:

105 GHz Multipath Propagation Measurement and Comparison with 60 GHz in Office Desk Environment for Ultra-High Speed Sub-THz WPAN Systems
Analysis of Propagation Channel Characteristics in an Indoor Office Environment at 160 GHz
  • Citing Conference Paper
  • June 2024

... This technology is ideal for processing video information and other applications that generate a lot of network traffic. In order to keep up with the ever-increasing volume of video data, eMBB in 6G will likely take advantage of high-bandwidth channels to provide even greater usable bitrates according to the study by Nakamura et al. [16]. ...

6th Generation Mobile Communication System Supported by New Radio Wave Propagation Research新しい電波伝搬研究が支える第6世代移動通信システム
  • Citing Article
  • September 2023

IEICE Communications Society Magazine

... For DOA measurement, methods using array antennas with super-resolution algorithms [4,5] and methods using physically rotating large aperture antennas [6,7] are employed. For frequencies beyond 100 GHz, the first method is not easy to prepare array antennas. ...

Measurement of Multipath Waves at 160 GHz and 300 GHz in an Indoor Conference Room
  • Citing Conference Paper
  • March 2023

... In next-generation mobile communications, the proactive use of millimeter-wave (mm-wave) and terahertz-wave (THz-wave) frequencies, which can secure a wide frequency bandwidth, is anticipated to achieve further high-speed and large-capacity communications. Various studies have reported on the characteristics of path-loss, delay, and direction-of-arrival (DOA) for these frequencies in different scenarios [1][2][3]. ...

Path-loss Characteristics and Modeling for 2-300-GHz bands in Urban Microcell Environment
  • Citing Conference Paper
  • March 2023

... In this letter, we present a method to predict the path loss in outdoor urban environments based on computer graphics technologies (CGTs) [5]. Two types of color images that are viewed from a transmission point (Tx) and receiving points (Rxs) are created. ...

A Study on Path Loss Prediction Based on Computer Graphics Technologies
  • Citing Conference Paper
  • October 2022

... Despite promising features, major challenges in the effective usage of higher frequency bands include high free space path loss (FSPL), atmospheric attenuation in gasses and rainfall, and non-line of sight (NLOS) propagation issues, that lead to the degradation of signal-to-noise ratio (SNR) and data rates [11][12][13][14][15]. To solve these issues, high-gain and highly-directive antennas have been commonly used; however, as a result, the beam coverage has become quite narrow, limiting the practicality of such systems. ...

Sub-terahertz propagation characteristics up to 150 GHz for 6G mobile communication systems
  • Citing Article
  • Full-text available
  • April 2022

International Journal of Microwave and Wireless Technologies

... 10 to 100 times of the current 5G peak rate [4]. The other characteristics encompass remarkable penetrability [5], the capacity to traverse non-metallic materials without inflicting any damage, and the low energy levels that minimize harm to living organisms, thereby facilitating non-destructive testing. ...

Terahertz Propagation Characteristics for 6G Mobile Communication Systems
  • Citing Conference Paper
  • March 2021

... Because 6G has not been pushing out a wide range of applications and is still in the research stage, there is a vacancy in the next 6G after the success of the development of a wide range of commercial and application. At present, the research direction of 6G mainly includes research on 6G band and bandwidth [1], AI, and 6G communication. This paper mainly studies the application or service industry of 6G in the future by comparing the technical characteristics of 5G. ...

Scattering Effect up to 100 GHz Band for 6G
  • Citing Conference Paper
  • January 2021

... Also, since the input images do not change with frequency, frequency as a scalar parameter is added to the later fully connected neural network (FNN) part to take the frequency characteristics into account. The validity of the proposed model was evaluated by learning and validating the model with measured data [10] and then determining the error between the measured and estimated values. Fig. 1 shows the structure of the proposed model. ...

Extension of ITU-R Site-General Path Loss Model in Urban Areas Based on Measurements from 2 to 66 GHz Bands
  • Citing Article
  • January 2021

IEICE Transactions on Communications

... The presence of people in an environment has been considered in [21], where empirical path-loss and delay spread models for an office environment have been proposed, being shown that there is little impact of people and their mobility on the modelled radio channel parameters. In [22], a path loss model for a crowded indoor environment has been proposed, but without the comparison with the empty room, so the influence of people's presence has not been evaluated. On the other hand, in [23], it has been shown that the average path loss may be higher, even by 4 dB, when there are people present in the office, and that variations may be as high as 9 dB when their mobility is high. ...

Path Loss Model in Crowded Outdoor Environments Considering Multiple Human Body Shadowing of Multipath at 4.7 GHz and 26.4 GHz
  • Citing Article
  • February 2019

IEICE Transactions on Communications