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Showing papers by "NTT DoCoMo published in 2021"


Journal ArticleDOI
TL;DR: In this article, the authors explored human behaviour change impacts on urban climate during the G20 Osaka Summit and the coronavirus 2019 (COVID-19) outbreak and estimated the impact of G20 restrictions on anthropogenic heat (QF) and surface air temperature using a regional climate model coupled with urban canopy and building energy models.
Abstract: Here we explored human behaviour change impacts on urban climate during the G20 Osaka Summit and the coronavirus 2019 (COVID-19) outbreak. The G20 Summit was held in the Asian megacity of Osaka, Japan on 28–29 June 2019. Due to the G20 restrictions, the traffic count in the city centre was lower by 33% compared with that 1 week prior (the usual week). The urban/office area population was reduced by approximately 10%; however, the residential population increased by 1%. Here we estimate the impact of G20 restrictions on anthropogenic heat (QF) and surface air temperature using a regional climate model coupled with urban canopy and building energy models. The results showed that the daytime QF and air temperature decreased by 15.6 W land-m−2 and 0.05 °C, respectively, in commercial areas of the city. The method described here is expected to be useful for estimating the impacts of similar political events and more extensive stay-at-home restrictions due to the recent COVID-19 pandemic on urban climates. A simple estimation showed that the COVID-19 restrictions resulted in QF of 76.3 W land-m−2 and a 0.13 °C temperature reduction in urban areas, thus, three- to five-fold the impact of the G20 Summit.

31 citations


Journal ArticleDOI
TL;DR: The explanations provide detailed rate calculations for this use case and show that millimeter wave is the only technology able to achieve the requirements, including cover-age enhancement and beam alignment.
Abstract: Millimeter wave provides high data rates for Vehicle-to-Everything (V2X) communications. This paper motivates millimeter wave to support automated driving and begins by explaining V2X use cases that support automated driving with references to several standardi-zation bodies. The paper gives a classification of existing V2X stand-ards: IEEE802.11p and LTE V2X, along with the status of their com-mercial deployment. Then, the paper provides a detailed assessment on how millimeter wave V2X enables the use case of cooperative perception. The explanations provide detailed rate calculations for this use case and show that millimeter wave is the only technology able to achieve the requirements. Furthermore, specific challenges related to millimeter wave for V2X are described, including cover-age enhancement and beam alignment. The paper concludes with some results from three studies, i.e. IEEE802.11ad (WiGig) based V2X, extension of 5G NR (New Radio) toward mmWave V2X, and prototypes of intelligent street with mmWave V2X.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the authors considered a NOMA-based transmission strategy in a mmWave UAV-assisted wireless network, and investigated the respective secrecy-rate performance rigorously.
Abstract: The non-orthogonal multiple access (NOMA) and millimeter-wave (mmWave) transmission enable the unmanned aerial vehicle (UAV) assisted wireless networks to provide broadband connectivity over densely packed urban areas. The presence of malicious receivers, however, compromise the security of the UAV-to-ground communications links, thereby degrading secrecy rates. In this work, we consider a NOMA-based transmission strategy in a mmWave UAV-assisted wireless network, and investigate the respective secrecy-rate performance rigorously. In particular, we propose a protected-zone approach to enhance the secrecy-rate performance by preventing the most vulnerable subregion (outside the user region) from the presence of malicious receivers. The respective secrecy rates are then derived analytically as a function of the particular protected zone, which verifies great secrecy rate improvements through optimizing shape of the protected zone in use. Furthermore, we show that the optimal protected zone shape for mmWave links appears as a compromise between protecting the angle versus distance dimension, which would otherwise form to protect solely the distance dimension for sub-6 GHz links. We also numerically evaluate the impact of transmission power, protected-zone size, and UAV altitude on the secrecy-rate performance improvement for the sake of practical deployments.

24 citations


Journal ArticleDOI
TL;DR: In this article, a method that dynamically controls scattering characteristics of metasurfaces while achieving a large area and high optical transparency was proposed, where transparent glass was used as a substrate and meshed metal patterns were used for transparency in the visible light range.
Abstract: Reconfigurable intelligent surfaces (RISs) that dynamically manipulate scattered waves have attracted much attention regarding accommodating coverage holes in wireless communication systems using radio wave frequencies higher than millimeter waves. RISs generally actualized through metasurface technologies must be visually unaffected so that they can be installed in various locations such as existing walls and glass windows in environments where propagation should be controlled. We propose a novel method that dynamically controls scattering characteristics of metasurfaces while achieving a large area and high optical transparency. For transparency in the visible light range, we use transparent glass as a substrate and meshed metal patterns. Furthermore, by stacking a metasurface substrate onto another transparent substrate and controlling the interlayer distance, we achieve dynamic control of the scattered waves over a large area in the 28-GHz band. Fabricated prototypes successfully operate when switching transmission and reflection modes, exhibiting extremely low loss of less than -1 dB. In metasurface lenses that can be attached to glass windows in outdoor-to-indoor scenarios, the lens gain of 25.4 dB is achieved for a static lens, and dynamic switching operation between single focus and dual focus is also successfully verified for a dynamic lens.

20 citations


Journal ArticleDOI
TL;DR: A direction of studies on 6G radio access technologies to explore the higher frequency bands and technical issues on the device technologies are introduced, and basic computer simulations in 100 Gbps transmission using 100 GHz band clarify a potential of extreme high data rate over100 Gbps.
Abstract: In sixth-generation (6G) mobile communication system, it is expected that extreme high data rate communication with a peak data rate over 100 Gbps should be provided by exploiting higher frequency bands in addition to millimeter-wave bands such as 28 GHz. The higher frequency bands are assumed to be millimeter wave and terahertz wave where the extreme wider bandwidth is available compared with 5G, and hence 6G needs to promote research and development to exploit so-called terahertz wave targeting the frequency from 100 GHz to 300 GHz. In the terahertz wave, there are fundamental issues that rectilinearity and pathloss are higher than those in the 28 GHz band. In order to solve these issues, it is very important to clarify channel characteristics of the terahertz wave and establish a channel model, to advance 6G radio access technologies suitable for the terahertz wave based on the channel model, and to develop radio-frequency device technologies for such higher frequency bands. This paper introduces a direction of studies on 6G radio access technologies to explore the higher frequency bands and technical issues on the device technologies, and then basic computer simulations in 100 Gbps transmission using 100 GHz band clarify a potential of extreme high data rate over 100 Gbps. key words: sixth generation mobile communication system, radio access technology, millimeter wave, terahertz wave, extreme high data rate

17 citations


Book ChapterDOI
11 Mar 2021
TL;DR: DBDC4 as discussed by the authors ) is a series of dialogue breakdown detection challenges to detect a system's inappropriate utterances that lead to dialogue breakdowns in chat-oriented dialogue, which used datasets in English and Japanese.
Abstract: To promote the research and development of dialogue breakdown detection for dialogue systems, we have been organizing a series of dialogue breakdown detection challenges to detect a system’s inappropriate utterances that lead to dialogue breakdowns in chat-oriented dialogue. In this paper, we overview Dialogue Breakdown Detection Challenge 4 (DBDC4). As in the previous challenges, we used datasets in English and Japanese. Four teams participated in the challenge, in which all four teams worked on English, and two of the four teams worked on Japanese as well. This paper describes the task setting, evaluation metrics, and datasets for the challenge and the results of the submitted runs of the participants.

15 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a beam aggregation-based mmWave MIMO-NOMA scheme to loosen the requirement of beam alignment and improve the system fairness, which can achieve significant gain on the max-min data rate compared with the conventional scheme.
Abstract: Millimeter wave (mmWave) multiple-input-multiple-output (MIMO) with hybrid beamforming enables high data rate broadband services for 5G. To further improve the spectral efficiency and connectivity, non-orthogonal multiple access (NOMA) has been considered to be integrated with mmWave MIMO. Nonetheless, the existing power-domain mmWave MIMO-NOMA with narrow analog beams suffers from beam misalignments which deteriorate the data rates of the misaligned users as well as the system fairness. Thereby, we propose a beam aggregation-based mmWave MIMO-NOMA scheme to loosen the requirement of beam alignment and improve the system fairness. The proposed scheme generates virtual beams with wider beamwidth by aggregating adjacent analog beams. NOMA transmissions are utilized within each aggregated virtual beam. Then, we propose a non-orthogonal multiuser precoding scheme to ensure the fairness within the aggregated beam by maximizing the minimum achievable rates of the grouped users. To address this issue, a max-min problem is proposed and artificial intelligence (AI) technology is exploited to solve this non-trivial problem. The problem is firstly converted to an equivalent penalized minimization problem and then an unsupervised deep neural network (DNN) is trained to map the instantaneous channel coefficients to the precoders in a data-driven fashion. Specifically, we explicitly introduce the transmit power as the DNN input to achieve better generalization in different signal-to-noise ratio regions. Performance evaluations reveal that the proposed scheme can achieve significant gain on the max-min data rate compared with the conventional scheme.

15 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the superposition of mass-averaged specific absorption rate (SAR) and APD on temperature rise was considered, especially regarding the prevention of excessive surface temperature.
Abstract: In international guidelines and standards for human protection from electromagnetic fields, mass-averaged specific absorption rate (SAR) is used as a metric to prevent excessive temperature rise at frequencies from 100 kHz up to 6 GHz. Above this transition frequency, including the frequency region assigned to fifth-generation (5G) wireless communication systems, area-averaged absorbed power density (APD) or epithelial power density is used as a physical quantity to specify restrictions on human exposure. In 5G wireless systems, frequencies above and below 6 GHz may be used simultaneously. The effect of the superposition of SAR and APD on temperature rise should be considered, especially regarding the prevention of excessive surface temperature. Herein, we considered simultaneous exposure from inverted-F antenna and patch antenna array operating at 2 and 28 GHz, respectively. Computational results showed that the effect of superposition was marginal. This result is attributable to the heat diffusion length in biological tissues ( $\sim 10$ mm). The effect of the superposition was higher than 15% only when the patch antenna array and inverted-F antenna were separated by less than 50 mm for the 5 mm antenna-body separation.

10 citations


Proceedings ArticleDOI
22 Mar 2021
TL;DR: In this paper, the frequency dependency of human blockage, building shadowing, and scattering effects from a rough building surface up to 150 GHz was analyzed for 6G networks, and the frequency dependence of path loss and channel properties was analyzed.
Abstract: The 6th generation (6G) mobile communication system is being actively pursued worldwide. To satisfy extreme-high-speed-communication, one solution is to utilize terahertz bands above 100 GHz because a remarkably wider frequency bandwidth can be utilized than in 5G. To determine the service frequency bands on the basis of system performance for 6G, frequency dependency of path loss and channel properties needs to be understood. In this paper, we introduce our concept of a new network topology for 6G and then show the frequency dependency of human blockage, building shadowing, and scattering effects from a rough building surface up to 150 GHz.

9 citations


Proceedings ArticleDOI
01 Aug 2021
TL;DR: In this paper, the development status of a 5G network backhaul system using HAPS in the millimeter wave band is described, and the research and development is carried out from 2020 to 2023 by the Ministry of Internal Affairs and Communications "Research and Development for Expansion of Radio Resources".
Abstract: In order to support the mid-2020 and beyond, the development of high-speed, high-capacity wireless communication systems for 5G (5th Generation) networks has become an urgent and important issue in areas where optical fiber installation has not progressed due to geographical and economic reasons. Toward the 5G and beyond networks, HAPS (High Altitude Platform Station) which is located at an altitude of 20km can provide communication links to aircraft, drones, flying cars, ships, and expand the coverage to the sky and the sea. The HAPS makes it possible to provide low latency, high speed 5G communication services in these areas, and it is also possible to realize a communication system that can handle all use cases. This paper describes the development status of a 5G network backhaul system using HAPS in the millimeter wave band. This research and development is carried out from 2020 to 2023 by the Ministry of Internal Affairs and Communications "Research and Development for Expansion of Radio Resources".

7 citations


Journal ArticleDOI
22 Mar 2021
TL;DR: This paper conducted an experiment to compare two types of scenario-based dialogue systems with different types of bodies-physical and virtual robots-to investigate the effects of embodying such dialogue systems.
Abstract: In recent years, communication robots aiming to offer mental support to the elderly have attracted increasing attention. Dialogue systems consisting of two robots could provide the elderly with opportunities to hold longer conversations in care homes. In this study, we conducted an experiment to compare two types of scenario-based dialogue systems with different types of bodies-physical and virtual robots-to investigate the effects of embodying such dialogue systems. Forty elderly people aged from 65 to 84 interacted with either an embodied desktop-sized humanoid robot or computer graphic agent displayed on a monitor. The elderly participants were divided into groups depending on the success of the interactions. The results revealed that (i) in the group where the robots responded more successfully with the expected conversation flow, the elderly are more engaged in the conversation with the physical robots than the virtual robots, and (ii) the elderly in the group in which robots responded successfully are more engaged in the conversation with the physical robots than those in the group in which the robots responded with ambiguous responses owing to unexpected utterances from the elderly. These results suggest that having a physical body is advantageous in promoting high engagement, and the potential advantage appears depending on whether the system can handle the conversation flow. These findings provide new insight into the development of dialogue systems assisting elderly in maintaining a better mental health.

Journal ArticleDOI
TL;DR: This is the first study to predict gestational age in normal and complicated pregnancies by using urinary metabolite information, and the predicted gestational ages of cases with hypertensive disorders of pregnancy exhibited significant progression, compared with actual Gestational ages.
Abstract: The elucidation of dynamic metabolomic changes during gestation is particularly important for the development of methods to evaluate pregnancy status or achieve earlier detection of pregnancy-related complications. Some studies have constructed models to evaluate pregnancy status and predict gestational age using omics data from blood biospecimens; however, less invasive methods are desired. Here we propose a model to predict gestational age, using urinary metabolite information. In our prospective cohort study, we collected 2741 urine samples from 187 healthy pregnant women, 23 patients with hypertensive disorders of pregnancy, and 14 patients with spontaneous preterm birth. Using gas chromatography-tandem mass spectrometry, we identified 184 urinary metabolites that showed dynamic systematic changes in healthy pregnant women according to gestational age. A model to predict gestational age during normal pregnancy progression was constructed; the correlation coefficient between actual and predicted weeks of gestation was 0.86. The predicted gestational ages of cases with hypertensive disorders of pregnancy exhibited significant progression, compared with actual gestational ages. This is the first study to predict gestational age in normal and complicated pregnancies by using urinary metabolite information. Minimally invasive urinary metabolomics might facilitate changes in the prediction of gestational age in various clinical settings.

Journal ArticleDOI
TL;DR: Abstract Owing to recent advances in information communication technologies, trail data, i.e., movement logs of people on the road or on trains, can be acquired on a 24-h, 365-day basis, some of which are disturbing to say the least.
Abstract: Owing to recent advances in information communication technologies, trail data, i.e., movement logs of people on the road or on trains, can be acquired on a 24-h, 365-day basis, some of wh...

Proceedings ArticleDOI
10 Oct 2021
TL;DR: In this article, the authors present HMK, an effective text input method that mounts split keyboards on the left and right side of the head mounted display (HMD) to make it easier to find the home position.
Abstract: Text input is essential in a variety of uses in virtual and augmented reality (VR and AR). We present HMK: an effective text input method that mounts split keyboards on the left and right side of the head mounted display (HMD). Users who can touch-type are able to type using HMK by relying on their familiarity with the normal QWERTY keyboard. We develop custom keycaps to make it easier to find the home position. A study with three participants shows that users retain most of their normal keyboard typing skills. The participants achieved, on average, 34.7 words per minute (WPM) by the end of three days of use, retaining 81 percent of their regular entry speed.

Journal ArticleDOI
TL;DR: In this paper, the relationship between power, delay time, and direction of arrival was clarified using a 48-element massive array in the 20 GHz band in urban Japan, and the dominant path was estimated using an iterative reduction threshold algorithm (ISTA).
Abstract: The super-high-frequency band is used in the fifth-generation (5G) mobile communication system, 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 letter, 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 (DoA) 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.


Journal ArticleDOI
12 May 2021-Sensors
TL;DR: In this paper, a hybrid CTC/attention model was used to detect the balance of chewing and swallowing in a series of eating behaviors, including chewing, front biting, and front chewing.
Abstract: A series of eating behaviors, including chewing and swallowing, is considered to be crucial to the maintenance of good health. However, most such behaviors occur within the human body, and highly invasive methods such as X-rays and fiberscopes must be utilized to collect accurate behavioral data. A simpler method of measurement is needed in healthcare and medical fields; hence, the present study concerns the development of a method to automatically recognize a series of eating behaviors from the sounds produced during eating. The automatic detection of left chewing, right chewing, front biting, and swallowing was tested through the deployment of the hybrid CTC/attention model, which uses sound recorded through 2ch microphones under the ear and weak labeled data as training data to detect the balance of chewing and swallowing. N-gram based data augmentation was first performed using weak labeled data to generate many weak labeled eating sounds to augment the training data. The detection performance was improved through the use of the hybrid CTC/attention model, which can learn the context. In addition, the study confirmed a similar detection performance for open and closed foods.


Journal ArticleDOI
TL;DR: In this article, the authors proposed a method to improve the conversion efficiency by loading a high-impedance microstrip line as a feedback line in part of the rectifier circuit.
Abstract: Research on wireless power transmission technology is being actively conducted, and studies on spatial transmission methods such as SSPS are currently underway for applications such as power transfer to the upper part of steel towers and power transfer to flying objects such as drones. To enable such applications, it is necessary to examine the configuration of the power-transfer and power-receiving antennas and to improve the RF-DC conversion efficiency (hereinafter referred to as conversion efficiency) of the rectifier circuit on the power-receiving antenna. To improve the conversion efficiency, various methods that utilize full-wave rectification rather than half-wave rectification have been proposed. However, these come with problems such as a complicated circuit structure, the need for additional capacitors, the selection of components at high frequencies, and a reduction in mounting yield. In this paper, we propose a method to improve the conversion efficiency by loading a high-impedance microstrip line as a feedback line in part of the rectifier circuit. We analyzed a class-F rectifier circuit using circuit analysis software and found that the conversion efficiency of the conventional configuration was 54.2%, but the proposed configuration was 69.3%. We also analyzed a measuring circuit made with a discrete configuration in the 5.8-GHz band and found that the conversion efficiency was 74.7% at 24 dBm input. key words: wireless power transfer, rectifier circuit, feedback line, microwave frequency, quasi-millimeter and millimeter-wave frequency

Proceedings ArticleDOI
11 Oct 2021
TL;DR: In this paper, an enhanced non-orthogonal waveform (eNOW) was proposed to improve the SE of DFT-s-OFDM by designing the frequency domain power allocation to efficiently suppress OOBE and reduce SNR loss.
Abstract: Non-linearity of power amplifiers (PA) is the restriction of waveform design for 5G Evolution (5GE) and 6G in high frequency bands with large bandwidth. The low peak to average power ratio (PAPR) single carrier waveform discrete fourier transform spreading orthogonal frequency division multiplexing (DFT-s-OFDM) can be used as a candidate waveform for 5GE and 6G. To satisfy the extremely high data rate requirement in 6G, how to keep the low PAPR of single carrier waveform and improve its spectral efficiency (SE) will be the challenge. In our previous study, a novel non-orthogonal waveform (NOW) design was proposed by combining DFT-s-OFDM with FTN to improve SE with low PAPR. However, due to the spectrum extension caused by FTN, large out of band emission (OOBE) and signal-to-noise ratio (SNR) loss were observed. In this paper, we propose an enhanced non-orthogonal waveform (eNOW) to improve the SE of DFT-s-OFDM by designing the frequency domain power allocation to efficiently suppress OOBE and reduce SNR loss. Simulation results demonstrate that the OOBE and SNR loss of eNOW can be significantly reduced than that of NOW by design the frequency domain power allocation. With eNOW scheme, OOBE, PAPR and throughput gain can be achieved, simultaneously.


Journal ArticleDOI
TL;DR: In this article, the origin of resonance excitation in planar metamaterials placed longitudinally at the boundary of a two-layer dissimilar dielectric substrate integrated waveguide, as an approximation of integrated circuit electronics, was investigated.

Journal ArticleDOI
TL;DR: In this paper, the authors developed a talking robot that could converse with elderly people over an extended period of time by adding a previously proposed active listening function for twining the robot dialogue system to prompt the user to say something.
Abstract: The number of isolated elderly people with few opportunities to talk to other people is currently increasing. Research is ongoing to develop talking robots for addressing the situation. The aim of the present study was to develop a talking robot that could converse with elderly people over an extended period. To enable long-duration conversation, we added a previously proposed active listening function for twining the robot dialogue system to prompt the user to say something. To verify the effectiveness of this function, a comparative experiment was performed using the proposed robot system and a control system with identical functions except the active listening function. The results showed that the conversation of the elderly subjects with the proposed robot system was significantly more than that with the control system. The capability of the developed robot system was further demonstrated in a nursing home for the elderly, where its conversation durations with different residents were measured. The results revealed that the robot could converse for more than 30 min with more than half of the elderly subjects. These results indicate that the additional function of the proposed talking robot system would enable elderly people to talk over longer periods of time.


Proceedings ArticleDOI
25 Jan 2021
TL;DR: In this paper, the frequency dependency of scattering effects from the building rough surface up to the 100 GHz band for 6G was clarified by changing the beam width of the directive scattering model according to the frequency.
Abstract: This paper clarifies frequency dependency of scattering effects from the building rough surface up to the 100 GHz band for 6G. From the measurements, it is found that the scattering are diffused as the frequency increases. Based on these results, we modeled scattering using directive scattering model and confirmed that the frequency dependency of the scattering can be predicted by changing the beam width of the directive scattering model according to the frequency.

Journal ArticleDOI
TL;DR: This study proposed a thinner video communication system using a holographic optical element (HOE), which was utilized as a transparent off-axis mirror and helped increase the flexibility of the system configuration, thus reducing the depth of the space in front.
Abstract: Video communication tools, such as video chat and video conferencing, have become common means of communication among users in remote locations, as display/capture devices, such as flat panel displays, projectors, and digital cameras, have evolved, and communication networks have become much faster. In addition, tools, such as PCs and smartphones, have become widely spread around the globe. However, although it is now very easy to use video communication, it has not completely replaced actual face-to-face (F2F) communication. It has been shown that F2F communication leads to longer conversations compared with online video communication [1]. Also, people tend to prefer F2F communication in important scenarios, such as business negotiations. In other words, it is widely considered that the \"quality\" of online video communication is lower than that of F2F communication. In this study, we considered two major factors that affect the quality of video communications. The first factor is the decreased \"sense of presence\" of the other party at a remote location. In F2F, you can perceive that the person you are talking with is actually in front of you, and you can also feel their presence with your eyes. However, generally, video communication systems have several physiological issues that detract the presence of their users, e.g., low image resolution, improper life-size scaling of displayed users, and the stereoscopic effect absence in the display [2]. Therefore, in video communication, users do not properly feel the presence of the other party compared with F2F communication. The second factor is that it is difficult to properly convey non-verbal information in video communication, including facial expressions, eye gaze information, gestures, and postures. For example, a coinciding eye gaze between two communicating parties makes eye contact possible, which contributes to building trust and having new impressions during conversations and when performing tasks between remote locations [3]. A typical video communication system configuration is shown in Fig. 1 (a). As shown in the figure, the camera is placed around the 2D display (typically at the top), and Abstract Online video communication systems are widely used among users between remote locations, but the communication quality is still inferior to face-to-face communication. To enhance the quality of video communication systems, it is necessary to provide a sense of presence of the users at a high level and to realize eye contact for better non-verbal communication. The technologies that realize virtual image projection and frontal image capture are promising for such purposes. However, conventional systems require bulky display screens. Thus, we proposed a thinner system using a holographic optical element (HOE), which was utilized as a transparent off-axis mirror and helped increase the flexibility of the system configuration, thus reducing the depth of the space in front. To verify the feasibility of the proposed system, we established a proof-of-concept system with dispersion compensation optics and a full-color HOE, and the system simultaneously realized virtual image projection and frontal image capture.

Journal ArticleDOI
TL;DR: In this article, the authors present linearization technologies for high efficiency power amplifiers of cellular base stations, which are important to actualizing highly efficient power amplifier that reduce power consumption of the base station equipment and to achieving a sufficient non-linear distortion compensation level.
Abstract: This paper presents linearization technologies for high efficiency power amplifiers of cellular base stations. These technologies are important to actualizing highly efficient power amplifiers that reduce power consumption of the base station equipment and to achieving a sufficient non-linear distortion compensation level. It is well known that it is very difficult for a power amplifier using linearization technologies to achieve simultaneously high efficiency and a sufficient non-linear distortion compensation level. This paper presents two approaches toward addressing this technical issue. The first approach is a feed-forward power amplifier using the Doherty amplifier as the main amplifier. The second approach is a digital predistortion linearizer that compensates for frequency dependent intermodulation distortion components. Experimental results validate these approaches as effective for providing power amplification for base stations. key words: feed-forward, predistortion, power amplifier, cellular base station

Proceedings ArticleDOI
01 Aug 2021
TL;DR: In this article, a weighting factor of less than one to the interfering orthogonal frequency division multiplexing (OFDM) symbol is proposed in a turbo soft interference cancellation (SIC) for OFDM applying faster-than-Nyquist (FTN) signaling.
Abstract: This paper proposes multiplying a weighting factor of less than one to the interfering orthogonal frequency division multiplexing (OFDM) symbol esti-mates in a turbo soft interference canceller (SIC) for OFDM applying faster-than-Nyquist (FTN) signaling. Computer simulation results show that by multiplying the weighting factor of 0.8 or 0.9 to the interfering OFDM symbol estimates, the required average received signal-to-noise ratio (SNR) satisfying the target aver-age block error rate (BLER) is decreased significantly assuming the same improvement level in the spectral efficiency of the FTN signaling compared to cyclic pre x based OFDM using 16QAM associated with the turbo coding rates of 1/3 and 1/2 in multipath Rayleigh fading channels.

Proceedings ArticleDOI
01 Oct 2021
TL;DR: In this article, a novel occlusion handling method using a monocular RGB camera and map data is proposed, which detects the regions of buildings in a camera image using an instance segmentation method and then obtains accurate occlusions handling in the image from each building instance and corresponding building map.
Abstract: Visual consistency between virtual objects and the real environment is essential to improve user experience in Augmented Reality (AR). Occlusion handling is one of the key factors for maintaining visual consistency. In an application scenario for small areas such as indoors, various methods are applicable to acquire a depth information required for occlusion handling. However, in an application scenario in wide environment such as outdoor especially a scene including many buildings, occlusion handling is a challenging task because acquiring an accurate depth map is challenging. Several studies that have tackled this problem utilized 3D models of real buildings, but they have suffered from the accuracy of 3D models and camera localization. In this study, we propose a novel occlusion handling method using a monocular RGB camera and map data. Our method detects the regions of buildings in a camera image using an instance segmentation method and then obtains accurate occlusion handling in the image from each building instance and corresponding building map. The qualitative evaluation shows the improvement in the occlusion handling with buildings. The user study also shows the better performance of the perception of depth and distance than a model-based method.

Patent
Ohara Tomoya1, Harada Hiroki1
24 Feb 2021
TL;DR: In this article, a preamble is transmitted using a resource corresponding to at least one beam of the plurality of beams, where the reception unit measures a reception quality for each beam of a plurality of beacons, and the transmission unit transmits the pre-amble using a beam that satisfies a predetermined condition.
Abstract: A user apparatus in a radio communication system including a base station and the user apparatus, including: a reception unit configured to receive a plurality of predetermined signals transmitted from the base station by a plurality of beams; and a transmission unit configured to transmit a preamble using a resource corresponding to at least one beam of the plurality of beams, wherein the reception unit measures a reception quality for each of the plurality of beams, and the transmission unit transmits the preamble using a resource corresponding to a beam of a reception quality that satisfies a predetermined condition.