We designed and fabricated a 300-GHz-band fundamental mixer in indium phosphide (InP) high electron mobility transistor (HEMT) technology for 6G wireless communications.We devised a widely split frequency matching network to widen the bandwidth of a resistive mixer.The mixer IC achieved a conversion gain of -15 and -6-dB RF bandwidth of 100 GHz (220-320 GHz), the widest ever reported.We implemented the mixer IC as a WR3.4 waveguide mixer module and performed a back-to-back data transmission experiment in three different frequency bands.Data rates of 120, 152, and 168 Gbps were achieved in each band.We also developed a dual-band data transmission system with a local oscillator (LO) leakage canceling method.It was capable of transmitting data at 240 Gbps, the highest rate reported to date, and suppressing LO leakage by 60 dB.

In this study, the morphology and electronic properties of semiconducting polymer films were investigated in relation to a different drying behavior induced by the spinning time variation. Morphology changes related to the decreased spinning time were evaluated for p-type (P3HT, PQT-12) and n-type (N2200, PDBPyBT) polymer films fabricated at different preparation conditions. Based on the improved morphology, OFET devices were fabricated showing a 2.5 times carrier mobility increase (0.044 +/- 0.012 cm2V- 1s- 1 for 3 s spin to 0.018 +/- 0.011 cm2V- 1s- 1 for 30 s spin) for P3HT films, and 3 times improvement (0.088 +/- 0.023 cm2V- 1s- 1 for 50 s to 0.28 +/- 0.017 cm2V- 1s- 1 for 5 s) for N2200 films. For short spinning times, the slow drying of residual solvent allowed for the self-organization of polymer chains improving the crystallinity of polymer films. The presented approach synergizes the benefits of the spin coating method, like highly controlled film uniformity and thickness, with improved film morphology provided by other methods, like drop casting, or dip-coating.

A 300-GHz-band transmission-type multilayer metasurface beamformer based on a Jerusalem cross geometry is presented. A metamaterial cell with a continuous 2π phase variation for the radius change was designed and used in the fabrication of a reference device and three types of beamforming devices. The beamforming metasurface devices achieved steering angles of θ = 18°, θ = 30°, and θ = 38°, which were in good agreement with simulated results. A broadband operation in a 40 GHz band, from 280 GHz to 320 GHz was evaluated, showing only minor frequency dependence of the beamforming angles. The design and fabrication methodology can be applied to various types of metasurface devices, such as circular and fan lenses, beamformers, polarization switches, and so on for millimeter-wave frequency bands that are considered to be used in future 6 G wireless network systems.

Existing recommender systems often make recommendations based on the previous actions and preferences of the user, and do not always provide new experiences. Recommendations based on the concept of serendipity can be adapted to such problems. However, in such recommendations, the user may not be able to evaluate the value of the recommended content correctly; this may result in non-acceptance of the recommendation. To increase acceptability, we believe that reviews that users are likely to write themselves (known as predicted reviews) may be more interesting than reviews written by others. Hence, in this study, we propose a method for generating predicted reviews using GPT-3.5-Turbo as a large-scale language model based on the travel purpose of the user and information on the target spot. We explain the method of review generation and describe experiments using a prototype system in which the proposed method is applied to randomly selected spots instead of recommendations based on serendipity. We conducted an evaluation experiment to compare the reviews with those written by others, and confirmed that the predicted reviews based on the proposed method arouse interest in tourist attractions and encourage people to incorporate them into their travel plans. This effect is particularly pronounced for unfamiliar tourist spots.

In this invited paper, we introduce a 300-GHz-band power amplifier (PA) IC and module designed and fabricated in 250-nm InP DHBT technology and a 300-GHz-band InP-CMOS hybrid phased array transmitter for 6G. Our PA module achieved a maximum gain of 30 dB around 260 GHz and maintained over 20 dB within a range from 220 to 310 GHz. It also achieved a saturation power of 9 dBm at 270 GHz and demonstrated pointto-point wireless data transmission with a data rate of 100 Gbps at a distance of 40 m. Our phased array transmitter, in which four InP-HBT PA ICs and CMOS ICs containing mixers and control functions are integrated onto the same printed circuit board, achieved a maximum EIRP of 8.4 dBm and steering range of 36 degrees and successfully demonstrated wireless data transmission of up to 30 Gbps over a distance of 50 cm with beam steering.

In recent years, video streaming platforms such as YouTube have been offering a genre of video streaming known as “working streaming.” Despite its potential to enhance work productivity through self-explanation and listener reactions, it faces challenges related to confidentiality and the need for a substantial number of listeners. This study introduces a novel method to overcome these issues by automatically generating viewer comments in response to user utterances, thereby simulating real-time interaction. We conducted experiments with four undergraduate students to validate our method. The results indicate that our approach successfully stimulates user interaction, offering a potential solution that can be as effective as working streaming without streaming.

To achieve high-speed, large-capacity communication, next-generation mobile communication systems will require manipulation of the propagation of sub-terahertz waves in the propagation channel. In this paper, we propose the use of a novel split-ring resonator (SRR) structure as a metasurface unit cell for manipulating the linearly polarized incident and transmission waves used in mobile communication systems. In this SRR structure, the gap is twisted by 90° to efficiently use cross-polarized scattered waves. By changing the twist direction and gap size of the unit cell, 2π phase designability can be achieved, which enables linear polarization conversion efficiencies of -2 dB with a backside polarizer and -0.2 dB with two polarizers. In addition, a complementary pattern of the unit cell was fabricated, and a measured conversion efficiency of more than -1 dB at the peak with only the backside polarizer on a single substrate was verified. In the proposed structure, the 2π phase designability and efficiency gain are obtained independently by the unit cell and polarizer, respectively, thus enabling alignment-free characteristics, which are highly advantageous from an industrial viewpoint. Metasurface lenses with binary phase profiles of 0 and π were fabricated using the proposed structure with a backside polarizer on a single substrate. The lenses' focusing, deflection, and collimation operations were experimentally verified with a lens gain of 20.8 dB, which agreed well with our calculated results. Our metasurface lens has the great advantages of easy fabrication and implementation, and it has the potential to enable dynamic control by combining it with active devices because of the simple design methodology, which entails only changing the twist direction and the gap's capacitance component.

A 300-GHz-band fundamental mixer was designed and fabricated in indium phosphide (InP) high electron mobility transistor (HEMT) technology for 6G wireless communications. To achieve a wide bandwidth, we proposed a resistive mixer with a widely split frequency matching network. The fabricated mixer IC achieved a conversion gain of -15 dB, a -3-dB RF bandwidth of 60 GHz (235-295 GHz), and a -6-dB RF bandwidth of 100 GHz (220-320 GHz), the widest ever reported. We implemented the mixer IC as a WR3.4 waveguide mixer module and used a single mixer module in the TX and in the RX in a back-to-back data transmission experiment in three different frequency bands in the range from 220 GHz to 320 GHz. Data rates of 120, 152 and 168 Gbps were achieved in the three frequency bands, with 168 Gbps being the highest data rate achieved so far by a single mixer.

A 300-GHz-band fundamental mixer was designed and fabricated in indium phosphide (InP) high electron mobility transistor (HEMT) technology for 6G wireless communications. To achieve a wide bandwidth, we proposed a resistive mixer with a widely split frequency matching network. The fabricated mixer IC achieved a conversion gain of -15 dB, a -3-dB RF bandwidth of 60 GHz (235-295 GHz), and a -6-dB RF bandwidth of 100 GHz (220-320 GHz), the widest ever reported. We implemented the mixer IC as a WR3.4 waveguide mixer module and used a single mixer module in the TX and in the RX in a back-to-back data transmission experiment in three different frequency bands in the range from 220 GHz to 320 GHz. Data rates of 120, 152 and 168 Gbps were achieved in the three frequency bands, with 168 Gbps being the highest data rate achieved so far by a single mixer.

Toward further enhancement of the fifth generation (5G) mobile communication system, referred to as 5G Evolution (5GE), more stable high data-rate transmission should be required even in high-mobility environments such as high-speed trains. By using 28 GHz-band experimental equipment with beamforming and beam tracking, a 5GE experimental trial had been conducted in the actual high-speed bullet train running at a speed of 283 km/h. However, it is important to evaluate transmission performances and robustness against the higher mobile speed in sub-6 GHz band in addition to millimeter-wave band. Thus, we conducted 4.85 GHz-band 5GE experimental trial aboard Shinkansen test train running at 360 km/h, which is the fastest experiment trial in Japan. This trial deployed two base station antennas along the Shinkansen railways, and a mobile station was mounted in the rolling stock of the Shinkansen test train. This paper introduces 4.85 GHz-band 5GE experimental equipment, an overview of the experimental trial, and measured transmission performances.

In order to further utilize the high frequency band represented by millimeter wave, it is one of the issues to construct an economical indoor area. One of the solutions is to efficiently bring the radio waves from outdoor base stations to indoors. In this study, we have confirmed that the indoor radio wave strength can be significantly improved by using three elemental technologies: (1) radio wave transmission structure design technology (FSS technology), (2) metasurface technology (radio wave aggregation technology), and (3) relay stations.

In this work, toward an intelligent radio environment for 5G/6G, design methodologies of active split-ring resonators (SRRs) for more efficient dynamic control of metasurfaces are investigated. The relationship between the excitation of circulating-current eigenmode and the asymmetric structure of SRRs is numerically analyzed, and it is clarified that the excitation of the circulating-current mode is difficult when the level of asymmetry of the current path is decreased by the addition of large capacitance such as from semiconductor-based devices. To avoid change in the asymmetry, we incorporated an additional gap (slit) in the SRRs, which enabled us to excite the circulating-current mode even when a large capacitance was implemented. Prototype devices were fabricated according to this design methodology, and by the control of the intensity/phase distribution, the variable focal-length and beamsteering capabilities of the transmitted waves were demonstrated, indicating the high effectiveness of the design. The presented design methodology can be applied not only to the demonstrated case of discrete varactors, but also to various other active metamaterials, such as semiconductor-integrated types for operating in the millimeter and submillimeter frequency bands as potential candidates for future 6G systems.

When acquiring knowledge in a certain field, it is important to obtain comprehensive information. However, it is difficult for users to extract missing information in unknown fields by themselves. Therefore, this study proposes a subtopic extraction method that can supplement missing information step-wise by presenting the user with important unknown phrases related to the topic the user is currently learning about by performing Web searches; the phrases are such that they are highly relevant to the user’s browsing history. We then conducted small-scale experiments and found that topic extraction using phrase co-occurrence as a reference for the next search keyword to be entered is effective compared to conventional topic extraction using LexRank.

We cannot acquire cooking skills overnight; although our skills can be improved through repeated practice. This study proposes a method to recommend recipes that amateurs should attempt to turn failures into successes, based on their logs of cooking failures and successes. Initially, the user classifies past recipes and labels them as failures and successes. Next, we use a naive Bayes classifier to find the factors of failures and successes from the recipe's ingredients and cooking actions. By recommending recipes with multiple success factors and some failure factors, we aim to lower the psychological hurdle for attempting recipes with difficult factors that have resulted in failure earlier.

When users perform a fashion coordination search, they tend to select their “preferred styles,” or styles that match their personal tastes, from among the search results. However, for effective fashion coordination, it is also important for one's fashion style to not only be suited to one's own preferences but also be highly evaluated by other people. In this paper, we propose a method that displays the evaluation values, such as the number of favorites, of fashion coordinates in the search results not when the search results are first displayed, but after the user has selected his/her preference from among the search results. The purpose of this method is to emphasize the difference between how a user perceives his/her own preference and how it is evaluated by other people, and to help users become aware of the differences between their preferred styles and others' preferences and perceptions. In this study, we implemented a system for fashion coordination search wherein the inputs are the desired items and styles from the user. In addition, we designed an experiment wherein we would vary the presentation timing of metadata such as user evaluation and style information in the search results. This experimentation method would clarify the effect of the system on changing users' attitudes toward fashion styling with respect to the timing of the presentation of user evaluation scores.

There have been many studies on automatic generation of artificial maps, but few have focused on the objects displayed on artificial maps. Therefore, in this research, we analyzed an object extraction method for automatically generating artificial map. In this research, objects are extracted using Biased Page Rank. Biased Page Rank is a method for improving the quality of search results by changing the rank source according to the interests and interests of individual users. By using this method for object extraction, it is possible to display the objects with a high evaluation value among the objects existing in a specific area on artificial map.

5th generation mobile communications systems (5G) have already gone into commercial operation around the world, and NTT DOCOMO also launched commercial services in March 2020. However, as challenges and further expectations for 5G are identified, research and development to further 5G technological development will be required into the 2020s. NTT DOCOMO began examining requirements for 5G evolution and 6G from around 2017 [1], and released 6G technical concepts (a white paper) in January 2020 [2]. A number of initiatives are also underway regarding field experiments for 5G evolution. This article describes field experiments using the 28 GHz band, a 5G frequency band, as part of efforts to further develop millimeter-wave*1 radio technology, a crucial issue in 5G evolution. Specifically, we describe a coverage improvement experiment with a metasurface*2 reflector [3] [4], a 5G highspeed travel experiment on the Tokaido Shinkansen [5] [6], and a field experiment of fishing area remote monitoring using an underwater drone [7] [8]. Field Experiments Millimeter Wave 5G Evolution

The introduction of 5G commercial services has begun throughout the world, and at present, research toward the further development of 5G (5G evolution) and the development of 6G as the next-generation mobile communications system is being actively pursued. In this article, we describe IRE, an important concept in “New Radio Network Topology” now under discussion on the road to 5G evolution & 6G. We also describe NTT DOCOMO’s initiatives toward RIS, an important component of IRE, and metamaterial/metasurface technologies as elemental technologies of RIS.