November 2024
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Publications (34)
March 2024
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10 Reads
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2 Citations
July 2022
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2 Reads
February 2021
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32 Reads
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15 Citations
IEEE Antennas and Wireless Propagation Letters
The super-high-frequency (SHF) band is used in the 5th generation mobile communication system (5G), and the introduction of massive multiple-input multiple-output (MIMO) to 5G is being considered. In an environment with substantial propagation loss, such as that in the case of millimeter waves, massive MIMO can realize beamforming according to the position of terminal stations. Therefore, it is important to understand the direction of arrival of millimeter waves. In this paper, we clarify the relationship between power, delay time, and direction of arrival, while focusing on the horizontal direction, using a 48-element massive array in the 20-GHz band in urban Japan. In addition, we obtain direction of arrival estimation results using an iterative reduction threshold algorithm (ISTA), which is based on compressed sensing. It is shown that the dominant path can be estimated by using the ISTA even with approximately five elements.
February 2021
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38 Reads
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2 Citations
IEICE Communications Express
The fifth generation (5G) of mobile communication systems is actively being investigated worldwide. Various systems exist when considering the microwave bands after the introduction of the 5G systems. Considering microwave propagation characteristics is crucial to minimize possible interferences among systems. This study focused on the fact that wireless communication devices such as smartphones and wireless LANs are primarily used in various indoors environments. Previously, we evaluated the loss due to the difference between the incident angles of the vertical plane with respect to a window through which radio waves enter from outdoor to indoor (O2I). In the present study, we measured the loss when radio waves enter from O2I through a window in the 0.9/2.3/5.1 GHz band, where many IoT devices are expected to be used. From the data analysis of the measured results, we proposed a simple O2I penetration path-loss model using incident angles in the vertical and horizontal planes.
January 2021
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4 Reads
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1 Citation
January 2021
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7 Reads
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4 Citations
January 2021
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2 Reads
January 2021
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3 Reads
January 2021
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3 Reads
Citations (14)
... 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. ...
- Citing Conference Paper
March 2024
... Virtual MIMO technology (V-MIMO), which has been deeply studied for wireless sensor networks, can solve some problems of the traditional MIMO technology. V-MIMO technology utilizes multiple single antenna terminals, to cooperate with each other to form an effective antenna array [29]. After receiving the information forwarded by the cooperative partner, the terminal combines the signals to achieve spatial diversity gain. ...
- Citing Conference Paper
January 2021
... DoA-based wave source localization schemes are proposed in [5]- [7]. Takase et al. [5] propose a wave source localization scheme in LOS environments, where each path between a UAV and the wave source includes a direct path by placing the UAV at a sufficient height. ...
- Citing Conference Paper
January 2021
... The selection of frequencies 24 GHz and 27 GHz, which fall within the millimeter-wave spectrum [13], [14], presents notable advantages for 5G applications [15], including elevated data rates, reduced latency, TELKOMNIKA Telecommun Comput El Control 1×2 microstrip patch antennas array for mm-waves 5G application (Karima Benkhadda) 41 and expanded network capacity. Moreover, selecting these frequencies aligns with worldwide initiatives aimed at allocating spectrum for the deployment of 5G technology. ...
- Citing Article
February 2021
IEEE Antennas and Wireless Propagation Letters
... GHz band is used as the microwave band, and the 28 GHz band is used as the millimeter wave band. For such a complex system, it requires a great deal of effort to evaluate its propagation characteristics in multiple frequency bands [1]. In this paper, we propose a method to estimate the datarate based on the received power measurement using continuous wave ("CW") signals, SNR and K-factor [2]. ...
- Citing Article
January 2020
IEICE Communications Express
... To further utilize the spatial DoFs, some regular/irregular array geometries were explored with the objective of yielding a channel with equal singular values, thereby enhancing spatial multiplexing performance [8], [9]. Additionally, the potential of mechanically rotating the uniform linear array was also investigated to achieve better channel conditions [10]. ...
- Citing Article
- Full-text available
January 2020
IEEE Access
... In [3], the focus is on the incident angles in the horizontal plane; further, O2I factors, which show the path-loss coefficient, are presented for the 0.8, 2.2, and 4.7 GHz bands. In our previous study, we evaluated the O2I penetration path-loss characteristics at 2 and 5 GHz for different incident angles considering only the vertical plane [4]. ...
- Citing Article
September 2019
IEICE Communications Express
... In the practical viewpoint, limited statistical CSI feedback constraint was considered and machine learning based user grouping aided hybrid beamforming was proposed [18]. Further, CSI estimation elimination approach, which applies a blind adaptive array signal processing, has been proposed and its practical performance was evaluated with considering medium access control (MAC) layer overhead of IEEE802.11ac and frequency division duplex (FDD) based LTE standards [19]. ...
Reference:
Massive MIMO Systems: Present and Future
- Citing Article
- Full-text available
February 2019
Electronics
... Link adaptation in massive MIMO was analyzed from the perspective of throughput-fairness tradeoff in [11]. Authors in [12] proposed an adaptive modulation scheme which utilizes a lookup table as an index of the modulation type by using the feature of amplitude beam selection. More recently, a learning-based rate adaptation mechanism was proposed for a downlink massive MIMO with underlaid device-to-device links [13]. ...
- Citing Conference Paper
August 2018
... We previously proposed analog-digital hybrid massive MIMO transmission that eliminates CSI estimation by utilizing a multibeam circuit [7] [8]. In this method, the multibeam circuit is in the analog part, and multiple beams with only amplitude information in the multibeam circuit are selected according to the distribution of users [9]. Then, in the digital part, interference is cancelled using only a received signal without CSI estimation. ...
- Citing Article
January 2018
IEICE Transactions on Communications