Pub Date : 2025-09-10DOI: 10.23919/comex.2025XBL0099
Takumi Senaha;Taito Baba;Takuya Asaka
Maximizing the bottleneck bandwidth of communication paths is a critical challenge for bandwidth-intensive applications. This study proposes a distributed-routing method based on ant colony optimization that dynamically adjusts pheromones according to locally learned path quality. The method's key feature is its ability to adapt to changing network conditions using local statistics, making it suitable for dynamic environments such as information-centric networking, where content sources change frequently. Simulation results indicate high convergence and effective selection of optimal paths with the proposed method.
{"title":"A Distributed Approach for Maximum-Bandwidth-Path Discovery Using Ant Colony Optimization","authors":"Takumi Senaha;Taito Baba;Takuya Asaka","doi":"10.23919/comex.2025XBL0099","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0099","url":null,"abstract":"Maximizing the bottleneck bandwidth of communication paths is a critical challenge for bandwidth-intensive applications. This study proposes a distributed-routing method based on ant colony optimization that dynamically adjusts pheromones according to locally learned path quality. The method's key feature is its ability to adapt to changing network conditions using local statistics, making it suitable for dynamic environments such as information-centric networking, where content sources change frequently. Simulation results indicate high convergence and effective selection of optimal paths with the proposed method.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"398-401"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157913","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674832","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}
In this study, we propose a text-based CAPTCHA that utilizes human visual completion to prevent automated programs from getting through, without affecting human cognition. This CAPTCHA requires users to enter the reading of the kanji strings, whose centers are hidden behind a black bar. This method makes it challenging for machines to recognize the characters, while still allowing humans to identify the original text through their visual completion ability. We evaluate both the usability and security of the proposed CAPTCHA. To assess usability, we observed how humans respond to the CAPTCHA challenge. For the security evaluation, we tested the machine's ability to read the kanji using a Convolutional Neural Network (CNN). The results showed that the proposed CAPTCHA achieves a success rate comparable to traditional CAPTCHAs, with a slightly shorter response time than a similar type of CAPTCHA. Furthermore, security experiments have shown that it exhibits a certain degree of resistance against simple convolutional neural networks.
{"title":"Evaluating the Usability and Security of the Text-Based CAPTCHA that Asks to Recognize Hidden Text with the Help of Human Visual Completion Function","authors":"Shotaro Usuzaki;Nobuya Takahashi;Taiki Kamada;Kentaro Aburada;Hisaaki Yamaba;Mirang Park;Naonobu Okazaki","doi":"10.23919/comex.2025COL0018","DOIUrl":"https://doi.org/10.23919/comex.2025COL0018","url":null,"abstract":"In this study, we propose a text-based CAPTCHA that utilizes human visual completion to prevent automated programs from getting through, without affecting human cognition. This CAPTCHA requires users to enter the reading of the kanji strings, whose centers are hidden behind a black bar. This method makes it challenging for machines to recognize the characters, while still allowing humans to identify the original text through their visual completion ability. We evaluate both the usability and security of the proposed CAPTCHA. To assess usability, we observed how humans respond to the CAPTCHA challenge. For the security evaluation, we tested the machine's ability to read the kanji using a Convolutional Neural Network (CNN). The results showed that the proposed CAPTCHA achieves a success rate comparable to traditional CAPTCHAs, with a slightly shorter response time than a similar type of CAPTCHA. Furthermore, security experiments have shown that it exhibits a certain degree of resistance against simple convolutional neural networks.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"441-444"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157905","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665749","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}
This paper shows that loading ferrite beads on feeding lines causes significant errors in direction estimation in a loop array antenna in a borehole radar. This contradicts the conventional wisdom that ferrite bead loading avoids undesirable scattering. The numerical simulation of a plane wave incidence on the loop array found that the ferrite loading worsened the DOA estimation by about 30°. We conducted a field experiment of cross-hole measurement in soil. The azimuth angle estimation error of the loop array without the ferrite loading was less than 25°, while that with the ferrite loading ranged between 30° and 120°.
{"title":"Influence of Ferrite Loading on Feeding Lines Near a Loop Array Antenna in a Borehole","authors":"Satoshi Ebihara;Ruuku Aoki;Takumi Orihashi;Ryuga Maeda;Sota Odagawa","doi":"10.23919/comex.2025XBL0112","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0112","url":null,"abstract":"This paper shows that loading ferrite beads on feeding lines causes significant errors in direction estimation in a loop array antenna in a borehole radar. This contradicts the conventional wisdom that ferrite bead loading avoids undesirable scattering. The numerical simulation of a plane wave incidence on the loop array found that the ferrite loading worsened the DOA estimation by about 30°. We conducted a field experiment of cross-hole measurement in soil. The azimuth angle estimation error of the loop array without the ferrite loading was less than 25°, while that with the ferrite loading ranged between 30° and 120°.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"406-410"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157904","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674792","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}
This study investigates the system capacity of orbital angular momentum multiple-input multiple-output (OAM-MIMO) systems employing parabolic reflectors at both the transmitter and receiver and evaluates its effectiveness in comparison with conventional OAM-MIMO systems, which use a parabolic antenna only at the transmitter. Specifically, the system capacity of OAM-MIMO with parabolic antennas applied at both ends is calculated based on the planar antenna reception analysis. The impact of applying parabolic reflectors at both the transmitter and receiver is examined by varying the number of multiplexed streams and carrier frequency, using the case with a parabolic antenna at the transmitter alone as a reference. In particular, performance evaluation ensures a fair comparison by fixing the total number of antenna elements and the total transmit power, thereby considering the trade-off between stream power reduction and bandwidth expansion.
{"title":"System Capacity Enhancement Analysis in OAM-MIMO Systems Using Parabolic Reflectors","authors":"Shuhei Saito;Yasunori Yagi;Doohwan Lee;Fumiaki Maehara","doi":"10.23919/comex.2025XBL0096","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0096","url":null,"abstract":"This study investigates the system capacity of orbital angular momentum multiple-input multiple-output (OAM-MIMO) systems employing parabolic reflectors at both the transmitter and receiver and evaluates its effectiveness in comparison with conventional OAM-MIMO systems, which use a parabolic antenna only at the transmitter. Specifically, the system capacity of OAM-MIMO with parabolic antennas applied at both ends is calculated based on the planar antenna reception analysis. The impact of applying parabolic reflectors at both the transmitter and receiver is examined by varying the number of multiplexed streams and carrier frequency, using the case with a parabolic antenna at the transmitter alone as a reference. In particular, performance evaluation ensures a fair comparison by fixing the total number of antenna elements and the total transmit power, thereby considering the trade-off between stream power reduction and bandwidth expansion.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"381-385"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157910","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674839","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 : 2025-09-10DOI: 10.23919/comex.2025COL0015
Badr Mochizuki
Elastic Optical Networks (EON) can support high data bit rates efficiently and network virtualization technology manages network resources flexibly by running multiple virtual networks (VN) on a substrate network. However, it is difficult to provide an acceptable Quality of Service (QoS) during network congestion due to bandwidth unavailability. Bandwidth degradation, which corresponds to allocating a smaller amount of bandwidth than requested, is one solution to this problem. In this paper, we propose an adaptive bandwidth degradation algorithm for VN construction in EONs that is QoS assured. The performance of the proposed method has been evaluated by simulation, and numerical results show that the proposed method has significantly reduced the blocking probability.
{"title":"QoS Assured Bandwidth Degradation for Virtual Network Embedding in Elastic Optical Networks","authors":"Badr Mochizuki","doi":"10.23919/comex.2025COL0015","DOIUrl":"https://doi.org/10.23919/comex.2025COL0015","url":null,"abstract":"Elastic Optical Networks (EON) can support high data bit rates efficiently and network virtualization technology manages network resources flexibly by running multiple virtual networks (VN) on a substrate network. However, it is difficult to provide an acceptable Quality of Service (QoS) during network congestion due to bandwidth unavailability. Bandwidth degradation, which corresponds to allocating a smaller amount of bandwidth than requested, is one solution to this problem. In this paper, we propose an adaptive bandwidth degradation algorithm for VN construction in EONs that is QoS assured. The performance of the proposed method has been evaluated by simulation, and numerical results show that the proposed method has significantly reduced the blocking probability.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"449-452"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157903","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665728","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}
This paper proposes a novel method for controlling the directional pattern of array antennas using a quantum computer. Phase shifters are attached to each element of the array antenna, and the problem of controlling the directional pattern is formulated as a QUBO (Quadratic Unconstrained Binary Optimization) format. The optimal weight coefficients of the phase shifters are determined using quantum annealing. It is shown that a high-gain beam is formed in the desired direction by the proposed method. Also, a formula for forming multiple beams has been proposed. Furthermore, it is confirmed that the executing time remains stable even as the number of antenna elements is increased. Effectiveness of the proposed method for high-speed control of large-scale array antennas is demonstrated.
{"title":"Multiple Beamforming of Array Antenna Using Quantum Annealing","authors":"Kayako Yuda;Mitoshi Fujimoto;Ryo Yamaguchi;Kazuma Tomimoto;Tomonori Ikeda","doi":"10.23919/comex.2025COL0009","DOIUrl":"https://doi.org/10.23919/comex.2025COL0009","url":null,"abstract":"This paper proposes a novel method for controlling the directional pattern of array antennas using a quantum computer. Phase shifters are attached to each element of the array antenna, and the problem of controlling the directional pattern is formulated as a QUBO (Quadratic Unconstrained Binary Optimization) format. The optimal weight coefficients of the phase shifters are determined using quantum annealing. It is shown that a high-gain beam is formed in the desired direction by the proposed method. Also, a formula for forming multiple beams has been proposed. Furthermore, it is confirmed that the executing time remains stable even as the number of antenna elements is increased. Effectiveness of the proposed method for high-speed control of large-scale array antennas is demonstrated.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"445-448"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157914","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665819","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 : 2025-09-10DOI: 10.23919/comex.2025XBL0085
Grant Lewis Bulaong;Takuichi Hirano
This paper proposes a positioning-enabled embedded system designed for the spatial characterization of indoor Wi-Fi propagation. The proposed system integrates received signal strength indicator (RSSI) data from a commercial off-the-shelf (COTS) device, signal-to-noise ratio (SNR) measurements from a software-defined radio (SDR), and position information from optical 2-D markers. The system was deployed in two indoor environments, and the measurements were compared with ray tracing simulations. The results show agreement in spatial trends between the measured and simulated data, supporting the validity of the proposed system.
{"title":"Spatial Characterization of Indoor Wi-Fi Propagation using an Embedded System with Optical 2-D Marker-Based Positioning","authors":"Grant Lewis Bulaong;Takuichi Hirano","doi":"10.23919/comex.2025XBL0085","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0085","url":null,"abstract":"This paper proposes a positioning-enabled embedded system designed for the spatial characterization of indoor Wi-Fi propagation. The proposed system integrates received signal strength indicator (RSSI) data from a commercial off-the-shelf (COTS) device, signal-to-noise ratio (SNR) measurements from a software-defined radio (SDR), and position information from optical 2-D markers. The system was deployed in two indoor environments, and the measurements were compared with ray tracing simulations. The results show agreement in spatial trends between the measured and simulated data, supporting the validity of the proposed system.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 11","pages":"386-389"},"PeriodicalIF":0.3,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11157909","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145674744","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.2025COL0010
Toki Miyazaki;Kenji Mikawa;Takashi Fuchino
Packet classification is used to determine the behavior of pack-ets incoming to network devices based on a predefined policy. In linear search, the increasing number of comparisons between packets and rules can cause communication latency. The problem of optimizing the rule order to minimize the number of comparisons has been actively studied. Since this problem is known to be NP-hard, various heuristic approaches have been proposed. In this paper, we propose a new approach to optimizing communication latency by focusing on rule order that reduces latency involved in parts of the rule list. We conduct computational experiments to demonstrate that the proposed algorithm is faster and more efficient than existing algorithms.
{"title":"An Efficient Algorithm for Reordering Rules based on Latency Differences","authors":"Toki Miyazaki;Kenji Mikawa;Takashi Fuchino","doi":"10.23919/comex.2025COL0010","DOIUrl":"https://doi.org/10.23919/comex.2025COL0010","url":null,"abstract":"Packet classification is used to determine the behavior of pack-ets incoming to network devices based on a predefined policy. In linear search, the increasing number of comparisons between packets and rules can cause communication latency. The problem of optimizing the rule order to minimize the number of comparisons has been actively studied. Since this problem is known to be NP-hard, various heuristic approaches have been proposed. In this paper, we propose a new approach to optimizing communication latency by focusing on rule order that reduces latency involved in parts of the rule list. We conduct computational experiments to demonstrate that the proposed algorithm is faster and more efficient than existing algorithms.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"428-431"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130689","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665750","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}
For the faster and higher capacity communication using higher frequencies in Beyond 5G era, we have proposed the switched analog radio over fiber (Switched-RoF) system, in which optical switches are inserted between antennas and Central units (CUs)/ Distributed units (DUs), in order to efficiently use and provide additional features to a large number of small optically powered antennas using the power over fiber technology with the hollow core fiber. One of the features of Switched-RoF is DU aggregation, which reduces system power consumption by optical path switching. This paper presents analytical results of the effectiveness of Switched-RoF in terms of power consumption and call blocking rate based on two different user equipment distribution scenarios.
{"title":"Power Saving Impact of Distributed Unit Aggregation in Switched Radio Over Fiber Mobile Fronthaul Network","authors":"Ryuta Murakami;Kojiro Nishimura;Satoru Okamoto;Yoshihiko Uematsu;Takashi Kurimoto;Naoaki Yamanaka","doi":"10.23919/comex.2025XBL0065","DOIUrl":"https://doi.org/10.23919/comex.2025XBL0065","url":null,"abstract":"For the faster and higher capacity communication using higher frequencies in Beyond 5G era, we have proposed the switched analog radio over fiber (Switched-RoF) system, in which optical switches are inserted between antennas and Central units (CUs)/ Distributed units (DUs), in order to efficiently use and provide additional features to a large number of small optically powered antennas using the power over fiber technology with the hollow core fiber. One of the features of Switched-RoF is DU aggregation, which reduces system power consumption by optical path switching. This paper presents analytical results of the effectiveness of Switched-RoF in terms of power consumption and call blocking rate based on two different user equipment distribution scenarios.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 10","pages":"365-368"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130690","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145479364","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.2025COL0008
Hiroto Sakaki;Kazutomi Mori;Kenjiro Nishikawa
We propose a model that combines a neural network composed of LSTM units with polynomials corresponding to each average input power level. This combination enables high-precision modeling of the rectifier's output signals in response to modulated signal inputs at multiple average power levels. The accuracy of the proposed model was evaluated using the Normalized Mean Square Error (NMSE). The evaluation results confirmed that, for all average input power levels, the proposed model reproduces the actual rectifier's output signals more accurately than a model using that uses only the a neural network.
{"title":"Hybrid LSTM and Polynomial-Based Rectifier Modeling for Modulated Signals Under Varying Average Input Power Levels","authors":"Hiroto Sakaki;Kazutomi Mori;Kenjiro Nishikawa","doi":"10.23919/comex.2025COL0008","DOIUrl":"https://doi.org/10.23919/comex.2025COL0008","url":null,"abstract":"We propose a model that combines a neural network composed of LSTM units with polynomials corresponding to each average input power level. This combination enables high-precision modeling of the rectifier's output signals in response to modulated signal inputs at multiple average power levels. The accuracy of the proposed model was evaluated using the Normalized Mean Square Error (NMSE). The evaluation results confirmed that, for all average input power levels, the proposed model reproduces the actual rectifier's output signals more accurately than a model using that uses only the a neural network.","PeriodicalId":54101,"journal":{"name":"IEICE Communications Express","volume":"14 12","pages":"424-427"},"PeriodicalIF":0.3,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11130687","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665835","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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