Pub Date : 2025-08-19DOI: 10.23919/comex.2025COL0013
Hayato Moriyasu;Shotaro Ishikura;Miki Yamamoto
BBR is a new congestion-based congestion control algorithm proposed by Google to address the bufferbloat problem. It is designed to achieve the maximum throughput with the minimum RTT by continuously estimating the available bandwidth. Our preliminary evaluation results in this paper show that delay jitters in ACK packets cause overestimation of available bandwidth and accordingly increase of RTT. In this paper, we propose a new BBR rate calculation algorithm, Low-Pass-Filter-based BBR (LPF-BBR), which mitigating fluctuations of calculated delivery rate. Our evaluation results by computer simulation show that our proposing LPF-BBR can estimate bottleneck bandwidth accurately and prevent increase of RTT caused by overestimation, even in the case that ACK packets suffer delay jitter. As far as we know, this is the first work focusing on influence of backward path congestion in BBR.
{"title":"A New BBR with the Low-Pass Filter","authors":"Hayato Moriyasu;Shotaro Ishikura;Miki Yamamoto","doi":"10.23919/comex.2025COL0013","DOIUrl":"https://doi.org/10.23919/comex.2025COL0013","url":null,"abstract":"BBR is a new congestion-based congestion control algorithm proposed by Google to address the bufferbloat problem. It is designed to achieve the maximum throughput with the minimum RTT by continuously estimating the available bandwidth. Our preliminary evaluation results in this paper show that delay jitters in ACK packets cause overestimation of available bandwidth and accordingly increase of RTT. In this paper, we propose a new BBR rate calculation algorithm, Low-Pass-Filter-based BBR (LPF-BBR), which mitigating fluctuations of calculated delivery rate. Our evaluation results by computer simulation show that our proposing LPF-BBR can estimate bottleneck bandwidth accurately and prevent increase of RTT caused by overestimation, even in the case that ACK packets suffer delay jitter. As far as we know, this is the first work focusing on influence of backward path congestion in BBR.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"432-435"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130686","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MACKEY II (Meta-surface inspired Antenna Chip developed by KIT EOE Laboratory) has been proposed as a functional compact antenna that is not affected by surrounding metals. The aim of the study is to further miniaturize the MACKEY. To lower the resonance frequency, we focused on increasing the capacitance of the antenna. Focusing on the laminated structure of 3 conductor layers and the surplus space in the intermediate layer of MACKEY II, two metal plates composed of conductor strips were newly installed. The antenna's capacitance has successfully reduced the resonance frequency by increasing the antenna's capacitance, resulting in reducing the antenna size. In this paper, the performance of the antenna is evaluated by comparing the analyzed and measured values.
{"title":"Study of MACKEY Miniaturized by Loading Capacitance Structure","authors":"Yoichi Murakami;Ryoya Kishi;Toru Fukasawa;Shimpei Akimoto;Shigeru Makino","doi":"10.23919/comex.2025XBL0089","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0089","url":null,"abstract":"MACKEY II (Meta-surface inspired Antenna Chip developed by KIT EOE Laboratory) has been proposed as a functional compact antenna that is not affected by surrounding metals. The aim of the study is to further miniaturize the MACKEY. To lower the resonance frequency, we focused on increasing the capacitance of the antenna. Focusing on the laminated structure of 3 conductor layers and the surplus space in the intermediate layer of MACKEY II, two metal plates composed of conductor strips were newly installed. The antenna's capacitance has successfully reduced the resonance frequency by increasing the antenna's capacitance, resulting in reducing the antenna size. In this paper, the performance of the antenna is evaluated by comparing the analyzed and measured values.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"373-376"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130695","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-19DOI: 10.23919/comex.2025XBL0086
Makoto Sano
This letter presents a numerical method for analyzing the radiation characteristics of beam-steering folded reflectarray (FRA) antennas. With the aid of the fast Fourier transform, near-field to near-field transformation between the two surfaces constituting the FRA antenna, as well as the computation of the co- and cross-polar far-field patterns and directivity, are performed computationally efficiently using the plane-wave spectrum. The proposed method was used to analyze a beam-steering FRA antenna with a $16{-}lambda$ diameter ($lambda$: wavelength). The radiation characteristics were computed in the order of milliseconds.
{"title":"Computationally Efficient Radiation Analysis of Beam-Steering Folded Reflectarray Antennas Using Plane-Wave Spectrum","authors":"Makoto Sano","doi":"10.23919/comex.2025XBL0086","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0086","url":null,"abstract":"This letter presents a numerical method for analyzing the radiation characteristics of beam-steering folded reflectarray (FRA) antennas. With the aid of the fast Fourier transform, near-field to near-field transformation between the two surfaces constituting the FRA antenna, as well as the computation of the co- and cross-polar far-field patterns and directivity, are performed computationally efficiently using the plane-wave spectrum. The proposed method was used to analyze a beam-steering FRA antenna with a <tex>$16{-}lambda$</tex> diameter (<tex>$lambda$</tex>: wavelength). The radiation characteristics were computed in the order of milliseconds.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 10","pages":"361-364"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130681","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145479428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-19DOI: 10.23919/comex.2025XBL0084
Takahiro Ishiyama;Satoru Okamoto;Naoaki Yamanaka
An ultra-high splitting ratio passive optical network (PON) architecture using a hollow-core fiber cable has been proposed. To verify whether existing PON implementation is applicable to emulate the proposed architecture using the small number of actual equipment environment, we examined commercially available 10 Gbps Ethernet PON (10G-EPON) equipment. The verification was performed by configuring a dual-fiber transmission 10G-EPON with a maximum distance difference of 11 km between the upstream and downstream fibers. We report that we confirm the stable operation of dynamic bandwidth allocation under high load conditions with actual traffic flows.
{"title":"Non-Equidistance Dual-Fiber 10G-EPON for Evaluating Emulated Ultra-High Splitting Ratio Passive Optical Network Architecture Using Hollow-Core Fibers","authors":"Takahiro Ishiyama;Satoru Okamoto;Naoaki Yamanaka","doi":"10.23919/comex.2025XBL0084","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0084","url":null,"abstract":"An ultra-high splitting ratio passive optical network (PON) architecture using a hollow-core fiber cable has been proposed. To verify whether existing PON implementation is applicable to emulate the proposed architecture using the small number of actual equipment environment, we examined commercially available 10 Gbps Ethernet PON (10G-EPON) equipment. The verification was performed by configuring a dual-fiber transmission 10G-EPON with a maximum distance difference of 11 km between the upstream and downstream fibers. We report that we confirm the stable operation of dynamic bandwidth allocation under high load conditions with actual traffic flows.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 10","pages":"369-372"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130696","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145479426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-19DOI: 10.23919/comex.2025XBL0083
Hideo Tatsuno
I show an LTE/4G wireless cell network that uses existing OFDMA telephone mobile nodes with the ability to detect 1.5, 1.25 and 1.75 wavelength peak-to-peak distance between 2 peaks of peak voltage beyond threshold, respectively for 3 each neighbor BS 4 wavelength PSK carrier wave-form for data bit 1, enabling receiving high speed data. Also, I showed good performance of proposed methods by simulation with 4 carrier wavelength for data bit 0 by using diversity antenna far by about 0.5 wave-length distance from main antenna in case that 2 other neighbor BS 0.4 v microwave signals and 2 0.4v fading add to present BS 1v direct microwave signal after LCR resonant filter of MN microwave receive circuit.
{"title":"A Mobile Node with Counters that Distinguish Peak-to-Peak Distance Between 2 Peaks Beyond Threshold of Wave-Forms for Data Bit 1","authors":"Hideo Tatsuno","doi":"10.23919/comex.2025XBL0083","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0083","url":null,"abstract":"I show an LTE/4G wireless cell network that uses existing OFDMA telephone mobile nodes with the ability to detect 1.5, 1.25 and 1.75 wavelength peak-to-peak distance between 2 peaks of peak voltage beyond threshold, respectively for 3 each neighbor BS 4 wavelength PSK carrier wave-form for data bit 1, enabling receiving high speed data. Also, I showed good performance of proposed methods by simulation with 4 carrier wavelength for data bit 0 by using diversity antenna far by about 0.5 wave-length distance from main antenna in case that 2 other neighbor BS 0.4 v microwave signals and 2 0.4v fading add to present BS 1v direct microwave signal after LCR resonant filter of MN microwave receive circuit.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"377-380"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130692","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-19DOI: 10.23919/comex.2025XBL0094
Ryoya Kishi;Toru Fukasawa
This paper presents the design and evaluation of a compact dipole antenna optimized for ear-mounted devices, aiming to mitigate radiation efficiency loss caused by proximity to the human body. By analyzing current distribution, antenna orientation, and antenna size, it was found that placing the antenna perpendicular to the body, setting high-current regions away from the human body, and increasing the antenna size to reduce power absorption within the human body significantly improves efficiency. A novel “in-ear dipole antenna” was proposed and compared to a folded dipole design, achieving approximately 4 dB improvement in radiation efficiency. These findings contribute to the development of high-performance wireless ear-worn devices with minimal interference from human body proximity.
{"title":"A High-Efficiency Antenna for in-Ear Wearable Devices","authors":"Ryoya Kishi;Toru Fukasawa","doi":"10.23919/comex.2025XBL0094","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0094","url":null,"abstract":"This paper presents the design and evaluation of a compact dipole antenna optimized for ear-mounted devices, aiming to mitigate radiation efficiency loss caused by proximity to the human body. By analyzing current distribution, antenna orientation, and antenna size, it was found that placing the antenna perpendicular to the body, setting high-current regions away from the human body, and increasing the antenna size to reduce power absorption within the human body significantly improves efficiency. A novel “in-ear dipole antenna” was proposed and compared to a folded dipole design, achieving approximately 4 dB improvement in radiation efficiency. These findings contribute to the development of high-performance wireless ear-worn devices with minimal interference from human body proximity.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"411-414"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130682","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-11DOI: 10.23919/comex.2025XBL0079
Yuki Shimizu;Kiyoshi Ueda
In the development of large-scale communication software, various methods have been investigated to address challenges such as increasing development costs and shortages of skilled personnel by leveraging machine learning to automatically generate system test cases from requirement specifications. To further improve the accuracy of automatically generated test cases, this study proposes a method that employs deep learning to structure requirement specifications and generate test cases. In particular, we introduce an Attention Seq2Seq model. The proposed model achieved significantly higher accuracy than theLSTM model presented in previous studies.
{"title":"Test Case Generation Using an Attention Seq2Seq Model for Structuring Requirement Specifications","authors":"Yuki Shimizu;Kiyoshi Ueda","doi":"10.23919/comex.2025XBL0079","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0079","url":null,"abstract":"In the development of large-scale communication software, various methods have been investigated to address challenges such as increasing development costs and shortages of skilled personnel by leveraging machine learning to automatically generate system test cases from requirement specifications. To further improve the accuracy of automatically generated test cases, this study proposes a method that employs deep learning to structure requirement specifications and generate test cases. In particular, we introduce an Attention Seq2Seq model. The proposed model achieved significantly higher accuracy than theLSTM model presented in previous studies.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 9","pages":"346-348"},"PeriodicalIF":0.3,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11078829","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144916320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-11DOI: 10.23919/comex.2025XBL0082
Shohei Ogura;Takashi Tomura
This letter presents a novel method for designing the radiating elements of a corporate-feed array antenna using eigenmode analysis. This approach numerically determines the eigenmodes, resonant frequencies, and radiation Q-factors of the radiating elements, enabling their evaluation without requiring impedance matching. A printed circuit board (PCB) slit array antenna structure was designed with three eigenmodes contributing to the primary polarization and low radiation Q-factors. Through parameter optimization, a 300-GHz-band antenna was designed, achieving a 24% bandwidth while satisfying manufacturing constraints of a PCB process. The proposed method offers a universal approach for realizing wideband performance in various antenna designs.
{"title":"A Wideband Antenna Design Method Using Eigenmode Analysis: Application to a 300-GHz Corporate-Feed PCB Slit Array Antenna","authors":"Shohei Ogura;Takashi Tomura","doi":"10.23919/comex.2025XBL0082","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0082","url":null,"abstract":"This letter presents a novel method for designing the radiating elements of a corporate-feed array antenna using eigenmode analysis. This approach numerically determines the eigenmodes, resonant frequencies, and radiation Q-factors of the radiating elements, enabling their evaluation without requiring impedance matching. A printed circuit board (PCB) slit array antenna structure was designed with three eigenmodes contributing to the primary polarization and low radiation Q-factors. Through parameter optimization, a 300-GHz-band antenna was designed, achieving a 24% bandwidth while satisfying manufacturing constraints of a PCB process. The proposed method offers a universal approach for realizing wideband performance in various antenna designs.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 10","pages":"357-360"},"PeriodicalIF":0.3,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11078827","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145479417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To increase data rate of screen camera communication (SCC), rolling shutter camera-based SCCs (RS-SCCs) have been studied. Among modulation schemes, inverse pulse position modulation (I-PPM) is the simplest to maintain constant screen luminance. However, image overlay properties of I-PPM have yet to be elucidated. In this study, the properties were clarified for uplink SCC that combined with a small liquid crystal display and a telephoto RS camera. Type of overlay standard image for I-PPMs and variable PPMs (VPPMs) was altered as parameters. Comparison of symbol error rates among I-PPMs and VPPMs demonstrated the most suitable scheme for image overlay RS-SCC.
{"title":"Image Overlay Properties of I-PPM and VPPM Schemes for Rolling Shutter Camera-Based Uplink Screen Camera Communication","authors":"Hayate Ohtani;Wataru Chujo;Kanta Takayanagi;Shodai Kawaguchi;Hideaki Funabashi;Kentaro Kobayashi","doi":"10.23919/comex.2025XBL0067","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0067","url":null,"abstract":"To increase data rate of screen camera communication (SCC), rolling shutter camera-based SCCs (RS-SCCs) have been studied. Among modulation schemes, inverse pulse position modulation (I-PPM) is the simplest to maintain constant screen luminance. However, image overlay properties of I-PPM have yet to be elucidated. In this study, the properties were clarified for uplink SCC that combined with a small liquid crystal display and a telephoto RS camera. Type of overlay standard image for I-PPMs and variable PPMs (VPPMs) was altered as parameters. Comparison of symbol error rates among I-PPMs and VPPMs demonstrated the most suitable scheme for image overlay RS-SCC.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 9","pages":"338-341"},"PeriodicalIF":0.3,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11078824","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144918347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-11DOI: 10.23919/comex.2025XBL0063
Weichuang Yu;Hui Wang;Huiheng Liu;Gang Li
This paper proposes three novel sparse-optimized nested L-shaped array (LA) configurations (ISNA-LA, ANCADiS-LA, AINA-LA) to address the challenges of limited degrees of freedom (DOFs) and mutual coupling in conventional LAs. These configurations optimize element placement in two-level nested arrays (TLNAs) to enhance DOFs and reduce mutual coupling via sparse spatial distribution. A hybrid 2-D DOA estimation framework integrating the least absolute shrinkage and selection operator (LASSO) and the pair-matching method by signal covariance matrices (PSCM) is established, enabling full utilization of difference coarray DOFs and automatic azimuth-elevation pairing. Numerical simulations show that the proposed arrays outperform conventional LAs in DOFs and mutual coupling reduction, while the LASSO-PSCM algorithm achieves superior 2-D estimation accuracy.
{"title":"Sparse-Optimized Nested L-Shaped Arrays with Hybrid LASSO-PSCM Framework for Enhanced DOA Estimation in Mutual Coupling Environments","authors":"Weichuang Yu;Hui Wang;Huiheng Liu;Gang Li","doi":"10.23919/comex.2025XBL0063","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0063","url":null,"abstract":"This paper proposes three novel sparse-optimized nested L-shaped array (LA) configurations (ISNA-LA, ANCADiS-LA, AINA-LA) to address the challenges of limited degrees of freedom (DOFs) and mutual coupling in conventional LAs. These configurations optimize element placement in two-level nested arrays (TLNAs) to enhance DOFs and reduce mutual coupling via sparse spatial distribution. A hybrid 2-D DOA estimation framework integrating the least absolute shrinkage and selection operator (LASSO) and the pair-matching method by signal covariance matrices (PSCM) is established, enabling full utilization of difference coarray DOFs and automatic azimuth-elevation pairing. Numerical simulations show that the proposed arrays outperform conventional LAs in DOFs and mutual coupling reduction, while the LASSO-PSCM algorithm achieves superior 2-D estimation accuracy.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"15 1","pages":"1-4"},"PeriodicalIF":0.3,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11078830","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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