Wataru Yamada’s research while affiliated with Nippon Telegraph and Telephone and other places

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Publications (85)


Frequency Dependence of Path Loss with Wide Dynamic Range in Urban Macro Cells between 2 and 26 GHz
  • Conference Paper

December 2017

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4 Reads

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1 Citation

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Mitsuki Nakamura

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Minoru Inomata

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[...]

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Yasushi Takatori


ITU-R Study Group 3 Activities towards Use of High Frequency Bands for 5G and Other Wireless Communication Systems

September 2017

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25 Reads

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1 Citation

NTT Technical Review

Before frequencies are allocated to new wireless communication systems, it is important to investigate frequency sharing to avoid interference with existing systems. The International Telecommunication Union Radiocommunication Sector Study Group 3 (ITU-R SG 3) supports activities of other SGs by developing and maintaining recommendations for radiowave propagation characteristics and prediction models necessary for frequency sharing studies. This article introduces the activities of ITU-R SG 3 focused on the use of high frequency bands in new wireless communication systems such as the fifthgeneration mobile communication system (5G).


Frequency Dependency of Path Loss Between Different Floors in An Indoor Office Environment at UHF and SHF Bands

August 2017

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24 Reads

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1 Citation

IEICE Transactions on Communications

This paper describes analytical results obtained for floor penetration loss characteristics and their frequency dependency by measurements in multiple frequency bands, including those above 6 GHz, in an indoor office environment. Measurement and analysis results confirm that the floor penetration loss depends on two dominant components: the transmission path through floors, and the path traveling through the outside building. We also clarify that these dominant paths have different path loss characteristics and frequency dependency. The transmission path through floors rapidly attenuates with large inter-floor offsets and in high frequency bands. On the other hand, the path traveling through outside of the building attenuates monotonically as the frequency increases. Therefore, the transmission path is dominant at short inter-floor offsets and low frequencies, and the path traveling through the outside is dominant at high number of floors or high frequency. Finally, we clarify that the floor penetration loss depends on the frequency dependency of the dominant path on the basis of the path loss characteristics of each dominant path.



Event Report: Tsukuba Forum 2016

April 2017

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7 Reads

NTT Technical Review

Tsukuba Forum 2016 was held on October 25 and 26. The theme of the forum was "Future Social Infrastructure: Co-creating a Better Life with Valued Partners - Innovative Access Network to Actualize the NetroSphere Concept." This article gives a brief overview of the speeches and exhibits presented at the forum.


Effects of building shapes on path loss up to 37 GHz band in street microcell environments

March 2017

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2 Reads

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1 Citation

Measurement results of path loss characteristics up to 37 GHz band in street microcell environments are described. Ray tracing is used to analyze the effects of building shapes on path loss characteristics at an intersection. A comparison between measured and calculated results clarified the dominant paths in which specular reflection from a chamfered shaped building contributes the power. The results show that the median prediction error value ranged from about 4.1 to 7.0 dB for bands between 2.2 and 37.1 GHz. This confirms that the building shapes significantly affect the path loss characteristics in NLOS street microcell environments.


Path Loss Model for Outdoor-to-Indoor Corridor Up to 40GHz Band in Microcell Environments

February 2017

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14 Reads

IEICE Transactions on Communications

This paper proposed that a path loss model for outdoor-to-indoor corridor is presented to construct next generation mobile communication systems. The proposed model covers the frequency range of millimeter wave bands up to 40 GHz and provides three dimensional incident angle characteristics. Analysis of path loss characteristics is conducted by ray tracing. We clarify that the paths reflected multiple times between the external walls of buildings and then diffracted into one of the buildings are dominant. Moreover, we also clarify how the paths affect the path loss dependence on frequency and three dimensional incident angle. Therefore, by taking these dependencies into consideration, the proposed model decreases the root mean square errors of prediction results to within about 2 to 6 dB in bands up to 40 GHz. © 2017 The Institute of Electronics, Information and Communication Engineers.


Path Loss Models for Wireless Access Network Systems Using High Frequency Bands

December 2016

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17 Reads

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2 Citations

NTT Technical Review

To design coverage areas for wireless communication systems and evaluate the performance of the systems, it is necessary to develop a path loss model that can be used for the systems' frequency bands. The fifth-generation mobile communication system (5G) is expected to use high frequency bands above 6 GHz. Therefore, developing a path loss model for wireless access communication systems using high frequency bands has become a pressing issue. NTT Access Network Service Systems Laboratories has developed path loss models for the 20-40 GHz bands that are suitable for use scenarios of mobile phones and wireless local area networks. This article introduces the developed models.



Citations (45)


... 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

... The authors of [17] developed a sub-THz massive multipleinput multiple-output (MIMO) channel sounder using 896 antenna elements, offering a high time-spatial channel resolution. The developed channel sounder could determine how many pathways arrived with a lower received power in real time. ...

Sub-Terahertz MassiveMIMO Channel Sounder for 6G Mobile Communication Systems
  • Citing Conference Paper
  • March 2024

... The authors of [7] utilized visual data obtained from multi-view sensing cameras to predict path loss. The authors of [8] utilized side-view images between the transmitter and receiver, along with frequency information, to predict path loss. The work in [9] employed 2D satellite images of the target area as input to a deep neural network to predict path loss distributions at various UAV altitudes. ...

Deep-learning path loss prediction model using side-view images
  • Citing Article
  • October 2023

IEICE Communications Express

... 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 [74] the imaging method, a variant of ray tracing, is approached with a quantum annealer. Given a number of VOLUME 11, 2023 interactions N and a set of M interaction objects, the problem to be solved is to find the dominant propagation path, i.e., the path that experiences exactly N reflections or diffractions and has minimal propagation loss (PL). ...

Radio Propagation Analysis Using Quantum Annealing
  • Citing Conference Paper
  • December 2022

... Several applications of DNN for the next generation of wireless communication systems (e.g., 6G) have recently emerged [3]. Models utilizing this technique have been proposed for path loss estimation, which is essential for the cell and system design of wireless communications [4,5,6,7]. These models use the convolutional neural network (CNN) as the DNN [5,7], which enables feature quantities (e.g., building profile) to be automatically and internally extracted from input images and utilized for estimation. ...

Deep Learning-Based Path Loss Prediction Using Side-View Images in an UMa Environment
  • Citing Conference Paper
  • March 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

... Against the previous methods, Sotiroudis et al. [19] developed a long short-term memory neural network for the prediction of PL with the frequency of 2-26 GHz. Other relevant works adopted DL or ML to predict PL over a channel [20]- [22]. Some of the methods are support vector machine (SVM) [23], random forest [24], and K-nearest neighbors (KNN) [25]. ...

Deep Learning Based Channel Prediction at 2–26 GHz Band using Long Short-Term Memory Network
  • Citing Conference Paper
  • March 2021