中山 悠NAKAYAMA Yuナカヤマ ユウ

業績情報

氏名・連絡先

• 氏名

  ナカヤマ ユウ, 中山 悠, NAKAYAMA Yu

主たる所属・職名

• 工学研究院　先端情報科学部門, 准教授

学位

• 博士（情報理工学）
  東京大学
  2018年03月23日

科学研究費助成事業

• 若手研究
  ユーザ参加により自律型Device-to-Device通信を促進するメカニズム
  自 2021年, 至 2023年
• 基盤研究(B)
  無線リレーとPONによって構成される適応的C-RAN
  自 2021年, 至 2021年
• 挑戦的研究（萌芽）
  低遅延システムの実現に向けた不完全なネットワーク伝送とコンピューティングの融合
  自 2021年, 至 2021年
• 基盤研究(B)
  情報鮮度 AoI に関する基礎理論の確立と多様な情報通信システムへの応用
  自 2021年, 至 2021年
• 挑戦的研究（萌芽）
  低遅延システムの実現に向けた不完全なネットワーク伝送とコンピューティングの融合
  自 2020年, 至 2020年
• 基盤研究(B)
  無線リレーとPONによって構成される適応的C-RAN
  自 2020年, 至 2020年

論文

• ITU TWDM-PON module for ns-3
  Nakayama, Yu; Yasunaga, Ryoma
  WIRELESS NETWORKS
  SPRINGER
  Optical fiber access systems are one of the driving forces behind the success of the Internet. Time- and wavelength-division multiplexing passive optical network (TWDM-PON) is regarded as the key technology for future Internet access networks. In this paper, we propose an ITU TWDM-PON module for the ns-3 network simulator and describe its concept and design specifications. The proposed module is developed based on the XG-PON module for ns-3. It can simulate G.989 standard-compliant data packet transmission in the upstream and downstream directions using multiple wavelength channels. It enables us to evaluate the performance issues that arise with the TWDM-PON development, including various dynamic bandwidth allocation and dynamic wavelength allocation algorithms. The proposed module is expected to become a good platform for studying future access networks composed of TWDM-PON and mobile networks by enabling us to simulate dynamic wavelength and bandwidth allocation.
  2021年07月, 研究論文（学術雑誌）, 共同, 27, 5, 1022-0038, DOI(公開)(r-map), 3635, 3646
• Interference Gaussianization: Time-Domain Inter-Symbol Spreading for Blind Adaptive Array Signal Source Identification
  Maruta, Kazuki; Senoo, Katsuya; Hisano, Daisuke; Nakayama, Yu; Nishimori, Kentaro
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  This paper proposes a novel blind adaptive array (BAA) interference suppression scheme incorporated with a time-domain symbol spreading (TISS). It can expand an operational region of BAA irrespective of input signal-to-interference power ratio (SIR) conditions. Independent component analysis (ICA) and constant modulus algorithm (CMA) are expected as the promising BAA approaches to suppress unknown interference which is extensively caused due to the small cell densification and spectrum superposing between a plurality of wireless communication systems. These BAA algorithms basically require an input SIR to be larger than 0 dB to suppress interference by capturing the desired signal appropriately. The proposed scheme applies TISS to the transmission signal for the desired user and then de-spreads it at the receiver side. It Gaussianizes statistical inherence of the interference signals and can bring beneficial effects; reducing the kurtosis for ICA as well as collapsing the constant envelope properties for CMA. Such intentional modification to the interference signals can improve the capture performance of the desired signal and realize its effective identification even at SIR < 0 dB. Its fundamental effectiveness is presented through various perspectives such as input SIR, symbol amount, and modulation orders.
  2021年, 研究論文（学術雑誌）, 共同, 9, 2169-3536, DOI(公開)(r-map), 89539, 89553
• Real-Time Reconfiguration of Time-Aware Shaper for ULL Transmission in Dynamic Conditions
  Nakayama, Yu; Yaegashi, Ryo; Anh Hoang Ngoc Nguyen; Hara-Azumi, Yuko
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Many applications such as Industrial Internet of Things (IIoT), tactile Internet, and 5G/6G mobile require Ultra-Low Latency (ULL) in data transmission. The end-to-end latency is required to be on the order of sub-millisecond in these applications. The IEEE 802.1 Time Sensitive Networking (TSN) standards have been developed to provide ULL networking. The IEEE 802.1Qbv Time-Aware Shaper (TAS), which is a typical flow control mechanism of TSN, is a traffic shaper to provide deterministic end-to-end ULL transmission for express traffic. The Gate Control List (GCL) of all TAS enabled nodes must be configured in a coordinated manner to ensure ULL. However, existing configuration schemes cannot be employed in highly dynamic conditions where the distribution of time-sensitive streams frequently changes. It will be a significant problem to deal with such dynamic conditions in the future. Therefore, this paper proposes a real-time adaptive gate scheduling scheme for TAS. The scheduling problem is formulated as a boolean satisfiability problem (SAT), and the employment of an FPGA-based solver is proposed to achieve runtime fast computation. The proposed scheme enables real-time reconfiguration for high flexibility and high bandwidth utilization to deal with the dynamics of network conditions. The feasibility of the proposed scheme is confirmed with computer simulations.
  2021年, 研究論文（学術雑誌）, 共同, 9, 2169-3536, DOI(公開)(r-map), 115246, 115255
• Horizontal Integrated Framework for Mobile Crowdsensing
  Nakayama, Yu
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Mobile crowdsensing is a promising paradigm to leverage the power of people to collect large-scale spatially distributed data. This concept has been intensely studied to efficiently and securely complete sensing tasks at lower cost. The development of a unified platform designed to provide various types of sensing applications is among the major approaches to economical crowdsourcing. However, existing previous frameworks were not optimized for shared use among multiple organizers because they were largely vertically integrated systems. Security and user trust and confidence is also a significant issue a crowdsensing frameworks, given the potential security concerns. Therefore, in this study, we propose a network-side task allocation (NeSTA) framework to address the existing problems in mobile crowdsensing. The proposed framework enables the horizontal integration of sensing applications, in which mobile networks mediate communication among organizers and participants, significantly reducing the installation cost of individual applications. Privacy preservation is achieved by task distribution and allocation procedures, where the participants were obscured by organizers. The validity of the proposed NeSTA was confirmed by simulations with an analytical model using an open dataset. The results show that the proposed method exhibited computational efficiency over two orders of magnitude greater than the conventional approach. This advantage originates from the reduction of problem size by dividing the original problem into subproblems.
  2021年, 研究論文（学術雑誌）, 単独, 9, 2169-3536, DOI(公開)(r-map), 127630, 127643
• Age-of-Information-Based Host Selection for Mobile User Provided Networks
  Nakayama, Yu; Maruta, Kazuki
  IEEE INTERNET OF THINGS JOURNAL
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  The concept of user-provided networks (UPNs) have been investigated to utilize the power of citizens in the deployment of mobile networks. In addition to conventional fixed host models, mobile models have been proposed to utilize movable hosts including mobile phone users. When mobile UPNs are considered, it becomes difficult for clients to establish a stable connection to hosts because they can be in moving environments, such as public buses and taxis. To address this problem, this article focuses on Age of Information (AoI) which a measure of the freshness of a continually updated piece of information. Thus, this article proposes an AoI-based host-selection algorithm for mobile UPNs for establishing stable connection. It determines the host device to establish a wireless link based on the history of values and AoI of received signal strength indicator (RSSI). The performance of the proposed scheme is confirmed through theoretical analysis and computer simulations.
  2021年01月15日, 研究論文（学術雑誌）, 共同, 8, 2, 2327-4662, DOI(公開)(r-map), 672, 683
• Optical Reflection Interference Equalization for Single-Wavelength Bidirectional WDM-PON Transmission System
  Shibita, Sho; Hisano, Daisuke; Maruta, Kazuki; Nakayama, Yu; Mishina, Ken; Maruta, Akihiro
  IEEE PHOTONICS JOURNAL
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  This paper proposes a novel return light cancellation technique using an adaptive interference equalizer in the wavelength division multiplexed passive optical network (WDM-PON) transmission system employing the single-wavelength bidirectional transmission scheme. In this scheme, the same wavelength is assigned to both the uplink and the downlink. In other words, the number of the wavelengths allocated to optical network units can be half compared with a typical PON system. However, this presents us with a problem in that the reflected component of the transmitted signal light interferes with the received signal light. We investigated the performance of the proposed interference canceling equalizer using back-to-back transmission simulation and a dual-polarizationquadrature-phase-shift-keying signal transmission experiment. The results indicated that the proposed adaptive equalizer enabled reception with no error when the OSNR was sufficiently large, even when the power of the interfering light was large (i.e., SIR >= 2 dB).
  2021年02月, 研究論文（学術雑誌）, 共同, 13, 1, 1943-0655, DOI(公開)(r-map)
• Remotely Pumped All-Optical Wavelength Conversion for WDM-PON-Based Access-Metro Convergence
  Tsuji, Ryota; Hisano, Daisuke; Takano, Hiroki; Nakayama, Yu; Mishina, Ken; Maruta, Akihiro
  IEEE PHOTONICS JOURNAL
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Access-metro convergence networks (AMCN) have been proposed as a future optical communication network to realize flexible and dynamic bandwidth allocation. An AMCN requires transceivers with different wavelengths for the optical network units (ONUs). This causes an increase in production costs. Although an all-optical wavelength converter (AOWC) mitigates this issue, the AOWC increases the installation cost because it consists of many expensive optical devices. We propose the use of a remotely pumped AOWC (RP-AOWC) with an AMCN. The proposed technique can reduce the number of pump light sources in the AOWC. This paper demonstrates this reduction in the number of light sources and the feasibility of wavelength conversion using pump light propagation. We calculate the reduction in the number of pump sources and the number of transceiver types caused by the use of RP-AOWC and experiment with the wavelength conversion using pump light propagation.
  2021年06月, 研究論文（学術雑誌）, 共同, 13, 3, 1943-0655, DOI(公開)(r-map)
• Banket: Bandwidth Market for Building a Sharing Economy in Mobile Networks
  Nakayama, Yu; Yasunaga, Ryoma; Maruta, Kazuki
  IEEE COMMUNICATIONS MAGAZINE
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Device-to-device (D2D) communication is expected to be a promising solution in next generation cellular technologies to efficiently provide connectivity over a wide area at low cost. However, autonomous D2D communication introduces challenging technical issues, and how to achieve the benefit and cooperation of users is an unsolved issue. To address this problem, we propose a novel concept of a bandwidth market called Banket for building a sharing economy in mobile networks. It provides an auction-based free marketplace for mobile users to buy and sell mobile bandwidth without cooperation with network operators. The contribution of the proposed Banket is to achieve dynamic and complete autonomous D2D communication established by market mechanisms without intervention. Banket prompts users to efficiently use network resources, and consequently achieves cost reduction for network operators and social profit by reducing resource and energy consumption. The validity of the proposed auction-based transaction scheme is confirmed through computer simulations. Furthermore, the feasibility of Banket is validated with experimental results using implemented applications.
  2021年01月, 研究論文（学術雑誌）, 共同, 59, 1, 0163-6804, DOI(公開)(r-map), 110, 116
• Small Cells Enabled by Crowdsourced Radio Units Mounted on Parked Vehicles for Smart City
  Nakayama, Yu; Nishio, Takayuki; Hisano, Daisuke; Maruta, Kazuki
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  A large number of small cells are densely deployed in the era of 5G and beyond 5G mobile networks to achieve high rate and low latency data transmission. Small cells are composed with fixed ground radio units (RUs) in the conventional networks, and thus the utilization rate of them is drastically deteriorated due to the spatio-temporal patterns of mobile traffic demand. To address this problem, adaptive network architectures have been investigated to reconfigure networks on demand using small cells mounted on moving objects such as vehicles and drones. However, it has been difficult to establish stable communication link to ground nodes in high-speed environments with these schemes. Therefore, this paper proposes a concept of small cells composed with crowdsourced RUs mounted on parked vehicles. They are activated based on the traffic demand in surrounding area by road side units (RSUs) assuming a smart city. The proposed idea is based on the correlation between the distribution of people and the occupancy rate of parking lots. It can efficiently improve user throughput with relatively small number of RUs. The feasibility of the proposed scheme is validated through numerical analysis, computer simulations, and experimental results.
  2020年, 研究論文（学術雑誌）, 共同, 8, 2169-3536, DOI(公開)(r-map), 17986, 17998
• Adaptive C-RAN Architecture with Moving Nodes Toward Beyond the 5G Era
  Nakayama, Yu; Hisano, Daisuke; Maruta, Kazuki
  IEEE NETWORK
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  The C-RAN architecture has been prevailing in mobile networks for 5G and beyond. Along with the significant increase in the amount of mobile data, network operators must consider the spatio-temporal pattern of traffi c demand due to human mobility and lifestyles. It has been an important problem to efficiently deploy mobile networks avoiding the underutilization of cell capacities in off -peak times. To address this problem, in this paper we propose a concept of an adaptive C-RAN architecture toward the beyond 5G era. The proposed architecture enables flexible reconfi guration of the radio unit (RU) states and movable DU locations considering the changes in demand distribution. The DUs and RUs compose wireless relay fronthaul networks to forward fronthaul streams satisfying the strict latency requirements. This paper also proposes the joint scheduling algorithm to activate RUs, relocate DUs, and determine forwarding paths of fronthaul streams. It was confi rmed with computer simulations that mobile networks can be efficiently reconstructed with the proposed idea by activating/deactivating RUs and relocating/ migrating DUs.
  2020年07月, 研究論文（学術雑誌）, 共同, 34, 4, 0890-8044, DOI(公開)(r-map), 249, 255
• Two-stage optimization of uplink forwarding order with cooperative DBA to accommodate a TDM-PON-based fronthaul link
  Hisano, Daisuke; Nakayama, Yu
  JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING
  OPTICAL SOC AMER
  A fronthaul (FH) link based on a time-division multiplexing passive optical network (TDM-PON) has received attention because it is highly cost effective. The uplink transmission has a long forwarding delay in the TDM-PON link, but this issue can be overcome using a cooperative dynamic bandwidth allocation (CO-DBA) scheme. An optical line terminal receives wireless scheduling information from the distributed unit, which is a part of the mobile base station, and can estimate the amount and arrival timing of the FH signal to an optical network unit (ONU) in advance. However, reports of conventional CO-DBA have not considered a situation involving the accommodation of a large number of ONUs, for which forwarding order control considering the FH characteristics is important. By focusing on maintaining the mobile coverage area as a design criterion, this study proposes a two-step maximization scheme of the number of transmittable ONUs within the FH requirement. Numerical simulation indicates improvements in the number of transmittable ONUs and bandwidth usage efficiency. (C) 2020 Optical Society of America
  2020年05月, 研究論文（学術雑誌）, 共同, 12, 5, 1943-0620, DOI(公開)(r-map), 109, 119
• Wavelength and Bandwidth Allocation for Mobile Fronthaul in TWDM-PON
  Nakayama, Yu; Hisano, Daisuke
  IEEE TRANSACTIONS ON COMMUNICATIONS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Time- and wavelength- division multiplexed passive optical network (TWDM-PON) has attracted considerable attention for the next generation optical access systems. Among potential applications of TWDM-PON, a major application is the support of mobile fronthaul streams between radio units (RUs) and distributed units (DUs) in the centralized radio access network (C-RAN) architecture, which consists of central units (CUs), DUs, and RUs. The upstream fronthaul traffic that an optical line terminal (OLT) receives is expected to become highly bursty due to the variable data rate generated by employing new functional split options and the synchronization of data transmission between neighboring RUs caused by time-division duplex (TDD). However, there has been no wavelength and bandwidth allocation scheme for TWDM-PON that is designed to efficiently accommodate fronthaul streams satisfying the strict delay requirement. Therefore, in this paper we propose a novel wavelength and bandwidth allocation algorithm that can minimize the number of active wavelength channels considering the high burstiness and delay requirement of fronthaul data transmission. Through computer simulations it was confirmed that the number of active wavelength channels can be reduced by 50% with the proposed algorithm, and thus more RUs can be efficiently accommodated using TWDM-PON.
  2019年11月, 研究論文（学術雑誌）, 共同, 67, 11, 0090-6778, DOI(公開)(r-map), 7642, 7655
• Rank-Based Low-Latency Scheduling for Maximum Fronthaul Accommodation in Bridged Network
  Nakayama, Yu; Hisano, Daisuke
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Fronthaul bridged networks have attracted attention to transport time-sensitive fronthaul streams in the centralized radio access network (C-RAN) architecture. When the functional split is changed and time-division duplex (TDD) is employed in the C-RAN architecture, the data rate in fronthaul becomes variable and the global synchronization of fronthaul streams will occur. In this case, it is critical to reduce the queuing delay among fronthaul streams to efficiently accommodate a number of radio equipments in a bridged network. In this paper, we propose a novel rank-based queue scheduling method for achieving low-latency in a fronthaul bridged network. The proposed scheme considers the frame-level queuing delay caused by global synchronization with the TDD. The worst-case delay of fronthaul flows is minimized, and the number of accommodated fronthaul streams is maximized We confirmed with computer simulations that the proposed scheme can minimize the worst case delay and increase the number of accommodated fronthaul streams.
  2018年, 研究論文（学術雑誌）, 共同, 6, 2169-3536, DOI(公開)(r-map), 78829, 78838
• Optically Backhauled Moving Network for Local Trains: Architecture and Scheduling
  Nakayama, Yu; Maruta, Kazuki; Tsutsumi, Takuya; Sezaki, Kaoru
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  The concept of moving cell in cellular systems has been discussed for 5G group mobility where rapidly moving platforms such as trains carry a large number of user terminals. It has been considered to employ wireless backhaul for moving cell, the problem of which is its limited and unstable bandwidth. To realize high bandwidth with wireless backhaul, a large number of base stations (BSs) are required along the railway. Therefore, this paper proposes the concept of optically backhauled moving network (OBMN) for local trains to efficiently provide backhaul links for local trains. In the OBMN, an autonomous BS (ABS) is set on the top of a train and is connected to a gateway via optical backhaul. While the user terminals onboard move, the ABS set on the train always satisfies the moving demands through high-bandwidth optical backhaul. The effectiveness of the proposed architecture and scheduling was confirmed by examining two case studies in the suburban and urban areas in Tokyo. The number of required BSs and deployment cost are reduced by half with the proposed OBMN compared with the existing static deployment.
  2018年, 研究論文（学術雑誌）, 共同, 6, 2169-3536, DOI(公開)(r-map), 31023, 31036
• Wired and Wireless Network Cooperation for Wide-Area Quick Disaster Recovery
  Nakayama, Yu; Maruta, Kazuki; Tsutsumi, Takuya; Sezaki, Kaoru
  IEEE ACCESS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  It is a significant challenge for telecommunication network operators to immediately restore communication services in the disaster area. To quickly recover telecommunication services in the affected area, this paper proposes a wired and wireless network cooperation system. When the wired communication for leaf nodes of optical tree networks is disrupted, surviving leaf nodes relay packets to and from these nodes via wireless bypass routes. The advantages of the proposed method are promptness and high-throughput, which is achieved with single-hop wireless bypass routes backhauled by wired networks. The optimal routes for wireless links are calculated to maximize the expected throughput by solving a binary integer programming problem. The proposed system is cost effective, because it can be deployed with minimum additional functions for leaf nodes of optical networks. To overcome the limitation of the proposed approach that the distribution of leaf nodes is determined by the demand distribution, additional recovery nodes can be deployed to improve the expected throughput. The numerical simulations including a medium access control level simulation conducting carrier sense multiple access with collision avoidance behavior showed that the proposed method can achieve a higher throughput than an existing bypass routing method, irrespective of the topology of the wired networks.
  2018年, 研究論文（学術雑誌）, 共同, 6, 2169-3536, DOI(公開)(r-map), 2410, 2424
• Predictive Bandwidth Allocation Scheme With Traffic Pattern and Fluctuation Tracking for TDM-PON-Based Mobile Fronthaul
  Hisano, Daisuke; Uzawa, Hiroyuki; Nakayama, Yu; Nakamura, Hirotaka; Terada, Jun; Otaka, Akihiro
  IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  In future radio access systems, since the number of mobile base stations will increase to cope with the increasing mobile traffic, the number of mobile fronthaul (MFH) links will also have to increase. To reduce the MFH link cost, MFH networking has been attracting attention. In particular, the use of a time-division multiplexed passive optical network (TDM-PON) makes the MFH link cost effective. On the other hand, a TDM-PON has a huge latency when forwarding uplink traffic. In a typical dynamic bandwidth allocation (DBA) scheme, an optical network unit (ONU) has a very long transmission waiting time, e.g., several milliseconds. This transmission waiting time in the ONU is a critical problem since the latency requirement for the MFH link is very strict, e.g., less than 250 mu s defined by the Third Generation Partnership Project. In this paper, we propose a novel statistical DBA scheme taking high-speed traffic fluctuation to reduce the transmission waiting time. Our proposed scheme allocates bandwidth based on the only ratio of the data amount of each distributed unit and detects the pattern of the transmission interval of the burst signal. We show the feasibility with a numerical simulation and experiments.
  2018年11月, 研究論文（学術雑誌）, 共同, 36, 11, 0733-8716, DOI(公開)(r-map), 2508, 2517
• Requirement Modeling Language for the Dynamic Node Integration Problem of Telecommunication Network
  Nakayama, Yu; Sezaki, Kaoru
  IEICE TRANSACTIONS ON COMMUNICATIONS
  IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
  Efficiently locating nodes and allocating demand has been a significant problem for telecommunication network carriers. Most of location models focused on where to locate nodes and how to assign increasing demand with optical access networks. However, the population in industrialized countries will decline over the coming decades. Recent advance in the optical amplifier technology has enabled node integration; an excess telecommunication node is closed and integrated to another node. Node integration in low-demand areas will improve the efficiency of access networks in this approaching age of depopulation. A dynamic node integration problem (DNIP) has been developed to organize the optimal plan for node integration. The problem of the DNIP was that it cannot consider the requirements of network carriers. In actual situations, network carriers often want to specify the way each node is managed, regardless of the mathematical optimality of the solution. This paper proposes a requirement modeling language (RML) for the DNIP, with which the requirements of network carriers can be described. The described statements are used to solve the DNIP, and consequently the calculated optimal solution always satisfies the requirements. The validity of the proposed method was evaluated with computer simulations in a case study.
  2018年06月, 研究論文（学術雑誌）, 共同, E101B, 6, 0916-8516, DOI(公開)(r-map), 1379, 1387
• TDD-Based Rapid Fault Detection and Recovery for Fronthaul Bridged Network
  Nakayama, Yu; Hisano, Daisuke; Kubo, Takahiro; Fukada, Youichi; Terada, Jun; Otaka, Akihiro
  IEEE COMMUNICATIONS LETTERS
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
  Fronthaul bridged network has been a hot research topic in recent years. A challenge for existing path-control protocols for bridged networks is that the route computation is executed after the advertisement of the link fault based on the updated link state information. To address this issue, this letter proposes a novel fault detection and recovery scheme for fronthaul bridged networks. With the proposed scheme, bridges estimate the fault location utilizing the time-division duplex configuration of fronthaul streams and immediately switch the forwarding paths for the affected flows to backup paths. Consequently, the end-to-end communication of fronthaul streams is rapidly recovered compared with the existing protocols.
  2018年03月, 研究論文（学術雑誌）, 共同, 22, 3, 1089-7798, DOI(公開)(r-map), 498, 501
• TDD Pattern Estimation and Auto-Recovery from Estimation Error for Accommodations of Fronthaul and Secondary Services in TDM-PON
  Hisano, Daisuke; Uzawa, Hiroyuki; Nakayama, Yu; Shimada, Tatsuya; Terada, Jun; Otaka, Akihiro
  JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING
  OPTICAL SOC AMER
  Time division multiplexing passive optical networks (TDM-PONs) are attracting attention as a cost-effective way of realizing mobile fronthaul (MFH), which is an optical link between a central unit (CU) and a distributed unit (DU) in a centralized radio access network (C-RAN). To realize an even more cost-effective network, we have studied the accommodation of MFH and secondary services in a single TDM-PON. We focus on the fact that a time division duplex (TDD) scheme will be applied to future radio access (FRA). Since a PON link is a wavelength division multiplexing (WDM) scheme, whereas a radio propagation link is a TDD scheme, unallocated intervals occur periodically in the PON link. For the above reason, we have already proposed a technique for estimating unallocated intervals in a TDD-based MFH link that involves pre-learning based on a test signal transmission, and the signal of the secondary service is accommodated in the unallocated intervals. However, a scheme for recovering from an error when the estimation is wrong and the test signal is not transmitted has yet to be studied. This paper proposes an estimation technique without a test signal transmission and an estimation-error recovery scheme. The proposed estimator calculates the correlation coefficient between captured uplink traffic and the seven types of uplink and downlink ratio patterns standardized by the third generation partnership project (3GPP: http://www.3gpp.org/).We evaluate the effectiveness of the proposed estimation technique by using a numerical simulation. The recovery scheme detects the estimation error and re-allocates the bandwidth. We implement the estimator and the recovery scheme in a 10 Gigabit Ethernet PON (10G-EPON) prototype. We report the feasibility of the proposed scheme along with experimental results.
  2018年02月, 研究論文（学術雑誌）, 共同, 10, 2, 1943-0620, DOI(公開)(r-map), 104, 113
• Low-Latency Routing Scheme for a Fronthaul Bridged Network
  Nakayama, Yu; Hisano, Daisuke; Kubo, Takahiro; Fukada, Youichi; Terada, Jun; Otaka, Akihiro
  JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING
  OPTICAL SOC AMER
  A fronthaul bridged network has attracted attention as a means of efficiently constructing the centralized radio access network (C-RAN) architecture. If we change the functional split of C-RAN and employ time-division duplex (TDD), the data rate in fronthaul will become variable, and the global synchronization of fronthaul streams will occur. This feature results in an increase in the queuing delay in fronthaul bridges among fronthaul flows. To address this problem, this paper proposes a novel low-latency routing scheme designed to minimize the worst-case delay in fronthaul networks with path-control protocols. The proposed scheme formulates the worst-case delay of each fronthaul stream based on the distribution of nodes, the propagation delay, and metric of the links. It selects the set of paths that minimizes the maximum value of the worst-case delay from the candidate path sets for fronthaul flows generated with the k-th shortest path algorithm. We confirmed with computer simulations that the proposed scheme can adequately minimize the worstcase delay, irrespective of the network topology. The maximum queuing delay is minimized by considering the time synchronization between fronthaul flows and the burst size determined by the TDD subframe length.
  2018年01月, 研究論文（国際会議プロシーディングス）, 共同, 10, 1, 1943-0620, DOI(公開)(r-map), 14, 23

メディア報道

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  学位取得後のキャリア選択とその後について、先輩研究者として、東京農工大学の中山悠准教授のお話しが紹介される。
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  自 2021年12月13日, 至 2021年12月13日
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  “The improvement of throughput by locating and activating a radio unit near users was far higher than expected,” says Yu Nakayama, a member of the research team who is a professor at Tokyo University of Agriculture and Technology.
  　
  自 2020年01月28日, 至 2020年01月28日