Language：English   Publishing type：Research paper (scientific journal)   Publisher：Information Processing Society of Japan  

We have developed a system (traditional system) to flexibly provide the requested applications environment on educational Windows PCs. The traditional system dynamically controls the execution of applications installed on each educational PC depending on the rules defined by teachers as well as by administrators. The traditional system, however, has a low tolerance for malicious attacks. If the execution file of a certain application is falsified, the corresponding rules already applied become invalid. In addition, though the traditional system has a function to define groups of controlled applications, it does not support hierarchical groups. This reduces the usability of the traditional system. In order to address these issues, this paper proposes a control method of application execution using digital certificates. The proposed method has a high tolerance for the falsification of execution files by controlling their executions based on the reliability of the corresponding digital certificates. It also improves its usability by introducing hierarchical group management utilizing hierarchical structure for digital certificates.

DOI： 10.2197/ipsjjip.23.449

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Enormous traffic generated by spam mails brings heavy load to networks and mail servers, which causes a large delay on legitimate mail delivery. In order to deliver important e-mails without unnecessary delay, we proposed an e-mail priority delivery system, where a dedicated receiving Mail Transfer Agent (MTA) receives all messages sent from trusted MTAs and performs only simple anti-spam measures. However, this system has some problems such that the dedicated receiving MTA easily receives even spam mails sent from trusted MTAs through only simple anti-spam measures. In this paper, we propose a method to perform full anti-spam measures on suspicious messages sent from trusted sending MTAs, by introducing tempfailing and SMTP session abort on the dedicated receiving MTA.

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Recently, many spam mails associated with "One-click fraud," "Phishing," and so on have been sent to unspecified large number of e-mail users. According to some previous works, most spam mails contained some URLs whose domains were registered relatively recently, such that the age of the domain used in the URL in the messages would be a good criterion for spam mail discrimination. However, it is difficult to obtain the age or the registration date of a specific domain for each message by WHOIS service since most WHOIS services would block frequent queries. In this paper, we propose a domain registration date retrieval system, which updates zone files of some Top Level Domains (TLDs) every day, keeps track of the registration date for new domains, and works as a DNS server that replys with the registration date of the queried domain. According to the performance evaluation, the prototype system could update the registration date for all the domains of "com" TLD in two hours.Recently, many spam mails associated with "One-click fraud," "Phishing," and so on have been sent to unspecified large number of e-mail users. According to some previous works, most spam mails contained some URLs whose domains were registered relatively recently, such that the age of the domain used in the URL in the messages would be a good criterion for spam mail discrimination. However, it is difficult to obtain the age or the registration date of a specific domain for each message by WHOIS service since most WHOIS services would block frequent queries. In this paper, we propose a domain registration date retrieval system, which updates zone files of some Top Level Domains (TLDs) every day, keeps track of the registration date for new domains, and works as a DNS server that replys with the registration date of the queried domain. According to the performance evaluation, the prototype system could update the registration date for all the domains of "com" TLD in two hours.

DOI： 10.2197/ipsjjip.22.480

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Information Processing Society of Japan  

Recently, many educational institutions have had to maintain a large number of PCs (educational PCs). It is common for the administrators of these institutions to use a disk image distribution system to manage them all together. It allows the administrators to keep all of their educational PCs in the same configuration with ease. This method, however, robs them of the flexibility of management. Suppose that use of certain application software is restricted to specific users or sites in those institutions. Suppose also that use of other application software is requested to be prohibited by teachers during classes. It is hard for the administrators to satisfy all of these requirements with the traditional method since it causes heavy administrative burden. This paper proposes a flexible method to manage application software on educational Windows PCs without significant efforts of the administrators even with these requirements. The proposed method controls the execution of individual application software on each educational PC to create the requested environments. Teachers as well as the administrators can directly and dynamically change its configuration during their classes. An execution control system was actually implemented as a prototype to show the feasibility of the proposed method.

DOI： 10.2197/ipsjjip.22.161

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

With advances in communication technologies, network services provided via the Internet have become widely diversified, and people can use these services not only via wired networks but also via wireless networks. There are several wireless systems in practical use such as cellular, WiMAX and WiFi. Although these wireless network systems have developed independently of each other, they should be integrated for seamless access by users. However, each system uses an individual spectrum prescribed by law to avoid radio interference. To overcome such a situation, dynamic spectrum access technology is receiving much attention. We propose a dynamic spectrum assignment method in which a WiFi system temporarily uses a spectrum band of the WiMAX system in WiFi/WiMAX integrated networks to reduce call blocking probability of multimedia communication services. We confirm the effectiveness of the proposed method by simulation experiments.

DOI： 10.1587/transcom.E94.B.3498

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Tempfailing, which temporarily refuses the first delivery attempt of a message from an untrusted Mail Transfer Agent (MTA), is one of typical anti-spam technologies commonly used in many organizations. This method can refuse spam mails considerably. However, it also may refuse legitimate mails sent from domains resending the temporarily failed message with a different MTA or those without resending function. In such a case, an administrator of the receiver MTA has to register those domains by hand. In this paper, in order to reduce these drawbacks, we propose an anti-spam method introducing SMTP session abort function. This method performs the same effect as existing tempfailing methods by means of SMTP session abort during the first delivery attempt. In addition, this method can obtain the header or the whole message even if it would not be resent and can use the header for second delivery checking and can use the whole message of unresent messages in case of false positives. According to the operation tests of the prototype systems, we confirmed that the proposed method received messages from domains using a different MTA for retry.

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Other Link： http://id.nii.ac.jp/1001/00009235/

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Route optimization for network mobility is a key technique for providing a node in a mobile network (Mobile Network Node or MNN) with high quality broadband communications. Many schemes adding route optimization function to Network Mobility (NEMO) Basic Support protocol, the standardized network mobility management protocol from the IETF nemo working group, have already been proposed in recent years. One such scheme, a scheme using Hierarchical Mobile IPv6 (HMIPv6) aims to overcome micromobility management issues as well by applying a mechanism based on HMIPv6. The traditional scheme, however, suffers from a significant number of signaling messages as the number of MNNs and/or the number of their Correspondent Nodes (CNs) increase, because many messages notifying the MNNs' Home Agents (HA_MNNs) and the CNs of the mobile network's movement are generated simultaneously each time the mobile network moves to the domain of another micromobility management router (Mobility Anchor Point or MAP). This paper proposes a scheme to overcome this problem. Our scheme reduces the number of signaling messages generated at the same time by managing the mobility of MNNs using multiple MAPs distributed within a network for load sharing. The results of simulation experiments show that our scheme works efficiently compared to the traditional scheme when a mobile network has many MNNs and/or these MNNs communicate with many CNs.

DOI： 10.1093/ietcom/e91-b.7.2272

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Micromobility management is a key issue for the deployment of broadband mobile communication services. The packet loss during handover and the handover latency need to be minimized to maintain the high quality of these services. We have previously proposed a mobility management scheme that addresses this issue in wide-area mobile networks that employed hierarchical multiple mobility management routers (Mobility Anchor Points or MAPs). Our scheme directs a Mobile Terminal (MT) to a suitable MAP to fully minimize packet loss during handover, and handover latency of the MTs. In our previous work, we confirmed the effectiveness of our scheme using a simple tree network. Actual networks however, always have densely meshed topologies to provide some redundancy for the elimination of single points of failure. In such networks, it is difficult to deduce the relationships between the MAPs, and this makes it difficult for our scheme to select a suitable MAP for an MT, because the selection is performed using both the MT's smoothed speed and the relationships existing between the MAPs located above the Access Router (AR), to which the MT is connected. In this paper, we propose a method to overcome this problem, by autonomously adjusting the selection criteria that are individually configured for use at a particular AR, and we evaluate this method using simulation experiments. The results show that our mobility management scheme works well in densely meshed networks using the proposed additional method.

DOI： 10.1093/ietcom/e89-b.7.2002

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Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Hierarchical Mobile IPv6 (HMIPv6) has been proposed to manage the mobility of Mobile Terminals (MTs) hierarchically to reduce packet losses during local handover. HMIPv6 uses a mobility manageable router in a domain visited by the MTs to manage the micromobility of the MTs. The router is called Mobility Anchor Point (MAP). As a hierarchical mobility management scheme based on HMIPv6, we have already proposed a multilevel hierarchical distributed IP mobility management scheme to manage the mobility of MTs in a decentralized manner using multiple MAPs. Our scheme manages the mobility of an MT using a MAP having a suitable management domain. This usage of MAPs aims to efficiently decentralize the load of mobility management. Our scheme estimates the movement speed of the NIT and then estimates the mobility of the MT based on the estimated movement speed of the MT to achieve the objective. However, recent simulation results obtained with more realistic mobility model indicate that our scheme has two problems in estimating the mobility of MTs: One is that our current scheme misestimates the movement speed of an NIT in some cases, and the other is that our current scheme does not notice the changes in the mobility of an MT when the MT decelerates and stays in the same access area for a long time. Thus, an enhanced mobility estimation method is proposed in this paper. The enhanced method has an ability to estimate the movement speed of MTs more correctly and an ability to urge decelerated MTs to degrade their MAP quickly. Finally, the performance of the proposed mobility estimation method is evaluated using simulation experiments. The simulation results show that the enhanced method allows our scheme to estimate the mobility of MTs more correctly and so achieve more efficient load sharing.

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As various mobile communication systems have developed, dramatically integrated wireless network, where users can communicate seamlessly via several wireless access systems, have become expected. At present, there are many studies of integrated wireless network, but no study of a network design method. Therefore, in this paper, we discuss a network design method for integrated wireless networks. Because of the handover procedure, the network design where adjacent base stations are connected to the same router, regardless of radio system type, is simply considered. However, in such a design, where mobile users crowd into a particular area and users' access to the base stations located there increases, the load of these accesses is centralized to the single router. To overcome this problem, we propose a new network design wherein the base stations of heterogeneous wireless communication systems, the service areas of which overlap, are connected to a different router. In the proposed network design, although users' accesses are concentrated on the base stations located in a particular area, users in that area can be assigned bandwidth of several upper links according to the access conditions of the base stations in neighboring areas. Finally, we show the excellent performance of the proposed design by simulation experiments.

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Hierarchical Mobile IPv6 (HMIPv6) has been proposed to accommodate frequent mobility of terminals within the Internet. It utilizes a router, named Mobility Anchor Point (MAP), so that networks can manage mobile terminals without floods of signaling message. Note here that, particularly in a wide area network, such as a mobile communication network, it is efficient to distribute several MAPs within the same network and make the MAP domains cover overlapped areas. This enables the network to manage the terminals in a flexible manner according to their different mobility scenarios. The method described in the Internet-Draft at the IETF, however, lets mobile terminals select its MAP. This may cause load concentration at some particular MAPs and/or floods of signaling messages, because the terminals may not select a feasible MAP in a desirable manner. In this paper, a MAP selection method in distributed-MAPs environment is proposed. It reduces signaling messages to/from outside networks without load concentration at any particular MAPs. Finally, we show that the proposed method works effectively by simulation experiments.

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Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

To diffuse multimedia information services, communication networks must guarantee the quality of services (QoSs) requested by users. In addition, users should be allowed to observe the network in order to customize their own services. A new network management architecture is therefore essential. It must perceive not only node connectivity, but also network failure points and the traffic situation dynamically. This paper introduces the network map as such an architecture on personalized multimedia communication networks and proposes multiple QoS routing using the network map. Moreover, a prototype system is built in order to verify the availability of the network map. key words: network management, multimedia communication, QoS routing, agent communication.

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DOI： 10.1109/icumt.2017.8255192

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DOI： 10.1109/apnoms.2017.8094198

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DOI： 10.1109/ccnc.2017.7983218

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DOI： 10.1109/noms.2016.7502976

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Mobile terminals such as smartphones and tablets which can use multimedia communication are widespread nowadays. On the other hand, wireless traffic is increasing and lack of spectrum resources has become an important problem. To use spectrum resources efficiently, spectrum sharing technology receives much attention. It use spectrum effectively by dynamically channel assignment between systems which differ in the range of cover area, transmission rate, etc. In a case where all providers are non-cooperative and pursue their own profit, they have to estimate the fluctuation of the number of their connecting users correctly in order to decide the channel price. In this paper, we propose a spectrum sharing method to achieve both higher throughput and providers' profit by appropriate pricing using disaggregate behavioral model.

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Lack of spectrum resources has become an important problem due to the increasing of wireless traffic. To use spectrum resources efficiently, spectrum sharing receives much attention. In a case where all providers are non-cooperative, they need to estimate the income which is decided by the channel rental fee and service charge from users. In this study, we propose an efficient spectrum sharing method based on estimation of users' behavior between non-cooperative WiMAX/WiFi providers.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In Okayama University, we replaced our administrative information system in July 2014. The new system introduces a multi-factor authentication system. Users are to be authenticated with their IC card and PIN code when they use their virtual desktop. Single sign-on for some applications is also controlled using the multi-factor authentication system. Users are to be re-authenticated with their IC card when they use some important applications. This report describes an introduction of multi-factor authentication in the new system. A problem of the multi-factor authentication system emerging when it cooperates with Shibboleth and its countermeasure are also described.

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In recent years, with proliferation of smart phones and tablet PCs, speedup of wireless LAN communication is required for dealing with increase of traffic in wireless networks. However, transmission speed through a wireless network often slows down in comparison with that through a wired network since packets of wireless networks frequently drop due to the influence of surrounding environment such as electromagnetic noise. In this paper, we propose a method to mitigate the impacts caused by packet loss by virtue of SCTP bicasting in lossy multihoming environment with two or more wireless networks. This method bicasts not all packets but only important packets concerning retransmission for efficiency since bicasting all packets would cause congestion. We also implemented a prototype system based on the proposed method. According to the result of performance evaluation experiment, we confirmed the effectiveness of the proposed method by the fact that the prototype system performed faster transmission than normal SCTP transmission even in high packet loss rate environment.

DOI： 10.1109/COMPSAC.2014.78

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Using multiple authentication methods with different Levels of Assurance (LoAs) enables secure and practical federated authentication. Shibboleth, widely deployed at academic institutions like universities, has a practical issue, to realize this. Service Providers (SPs) are supposed to understand all the authentication methods (and their LoAs) on the correspondent Identity Providers (IdPs) beforehand. We develop an authentication method grouping function on Shibboleth IdP, to overcome this issue.

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We have developed an Application Execution Control System (traditional system) which provides individual application environments on each educational PC by controlling its execution. The traditional system uses a hash value of the execution file to control target application. If the execution file is falsified, a rule already set gets invalid. In addition, the traditional system has a function to set rules for multiple application at once. However, it cannot handle multiple groups at once. In order to solve these problems, this paper proposes a control method using digital certificates. It supports strict control and flexible group management by using hierarchical structure of digital certificates.

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With advances of wireless communication technology, people can use multimedia services with mobile terminals. On the other hand, lack of spectrum resources has become an important problem due to the increasing of wireless traffic. To use spectrum resources efficiently, spectrum sharing technology receives much attention. Although providers assign additional channels based on transaction price and income from users, there are few studies that considered the influence of users' behavior on the spectrum sharing. In this paper, we consider the effect that the action of the user gives to spectrum sharing method between uncooperative WiMAX/WiFi providers.

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DOI： 10.1109/compsacw.2013.79

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DOI： 10.1109/compsacw.2013.102

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Language：English   Publisher：IEEE  

In order to deliver important e-mails without unnecessary delay, some priority delivery methods with a whitelist, which includes trusted sending Mail Transfer Agents (MTAs), are proposed so far. However, most conventional methods have some problems with a large sized whitelist such as performance degradation, delivery failure, and so on. To alleviate these problems,we proposed a priority delivery system (Prototype system) by using a layer 3 switch (L3SW) with policy based routing (PBR) function. By updating PBR entries dynamically, prototype system implements a large sized whitelist without performance degradation. In this paper,we investigated the case many sending MTAs same time send Email performance of the prototype system. we also describe prototype system improvements.

DOI： 10.1109/COMPSACW.2013.78

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

With advances in wireless communication tecnology, people can use multimedia services with mobile terminals. On the other hand, lack of spectrum resourses has become an inportant problem with increasing of wireless traffic. To use spectrum resourses efficiently, spectrum sharing technology receives much attension. Some existing spectrum sharing methods achieve to improve mean user throughput. But, it works well only if WiMAX/WiFi providers are cooperative. In this paper, we propose a spectrum sharing method between non-cooperative WiMAX/WiFi providers who cannot guess the right number of their users when spectrum is shared. Finally we confirm the effectiveness of the proposed method by simulation experiments.

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Language：Japanese   Publisher：一般社団法人情報処理学会  

重要な電子メールを遅延なく受信者へ配送するために,信頼できる送信MTAをあらかじめホワイトリストに登録し,優先的に配送する仕組みが考えられている.しかし,従来の方法では大規模なホワイトリストを扱えないか,扱える場合でも速度が遅くなるなどの問題があった.これに対して,我々はレイヤ3スイッチのポリシールーティング機能を用いてホワイトリストを実現し,また登録する送信MTAを動的に変更することにより,大規模なホワイトリストでも速度を落とさずに優先配送できるシステムを提案した.本稿では,提案システムを用いてメール配送を行った場合の評価を行い,その結果をもとに改良すべき点を考察する.

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情報システムの重要性、システムの多様化に伴い、認証基盤システムに対する機能追加が要望されている。また、在校生等の現役に加えて卒業生、退職教職員等の幅広い対象への拡充と、生涯に亘って継続的なサービスの提供も必要になる。さらに、統合認証基盤システムでは提供する各種システムへのシングル・サイン・オン（SSO）に加え、プリンタ等の装置類、ネットワークへのアクセス制限機能と利用者との関係を管理するなど、ICT全体の統合管理を実現する必要がある。 統合認証基盤システムへの複雑化する要求に柔軟に対抗可能な情報管理方法、運用を可能な限り省力化できるサービス提供方法を明確にし、そのシステム構成を明らかにする。

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Recently, with advances in wireless communication technology such as WiFi and WiMAX, the number of users increases more and more. It leads lack of spectrum resources, which becomes an important issue. To overcome this problem, spectrum sharing technology that a WiFi system temporarily uses a spectrum band of WiMAX system receives much attention. Although existing works assumed that WiMAX and WiFi providers were cooperative, it may not be realistic. In addition, users' behavior are not considered. In this paper, we propose a spectrum sharing method that behaves properly even if WiMAX provider, WiFi providers and users are uncooperative. Finaly, we confirm the effectiveness of the proposed method by simulation experiments.

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As one of anti-spam technologies, DNSBL based on the URLs or their corresponding IP addresses in the messages is well used. However, some spam mails cannot be filtered by conventional DNSBLs since the spammers create websites using various techniques such as botnet, fast-flux and Wildcard DNS record. To discriminate such spam mails, we ananalyzed DNS record characteristics corresponding to the domain name in the URLs in actual spam mails. According to this analysis, in this paper we propose a spam mail discrimination system based on the behavior of DNS servers. Since the behavior checking process is likely to wait for a timeout, the system queries some records to a DNS server simultaneously and decides whether the mail is spam or not on receiving the first reply. In addition, the system also introduces a blacklist for the IP addresses of the DNS servers.

DOI： 10.1109/saint.2012.68

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DOI： 10.1109/saint.2012.67

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With advances in wireless communication technologies, people can use multimedia services not only via wired networks but also via wireless networks such as Cellular, WiMAX, and WiFi. On the other hand, however, lack of spectrum resources becomes an important problem for future wireless networks. To overcome this problem, dynamic spectrum sharing method based on genetic algorithm in which a WiFi system temporarily uses a spectrum band of WiMAX system in WiFi/WiMAX integrated network has been proposed. However, this method does not take the handover of users into account. In this paper, we enhance the spectrum sharing method to improve fairness in addition to provide higher throughput considering handover. Finally we confirm the effectiveness of the proposed method by simulation experiments.

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With advances in wireless communication technologies, people can use multimedia services not only via wired networks but also via wireless networks such as Cellular, WiMAX, and WiFi. On the other hand, however, lack of spectrum resources becomes an important problem for future wireless networks. To overcome this problem, dynamic spectrum sharing method based on genetic algorithm in which a WiFi system temporarily uses a spectrum band of WiMAX system in WiFi/WiMAX integrated network has been proposed. However, this method does not take the fairness between WiFi system and WiMAX system into account. In this paper, we enhance the spectrum sharing method to consider intersystem fairness in addition to provide higher throughput. Finally we confirm the effectiveness of the proposed method by simulation experiments.

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DOI： 10.1109/icccn.2010.5560068

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DOI： 10.1109/indin.2010.5549608

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DOI： 10.1109/saint.2010.22

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Recently, as wireless systems diversifies, an integrated wireless network which uses some wireless systems selectively to provide seamless accesses and an effective services to users receives much attention. However, by the spread of multimedia communications via wireless systems leads the spectrum shortage moreover. Although each system uses an individual spectrum prescribed by radio law to avoid radio interference, a number of unused spectrum bands exist on a certain time and/or space in each system. To overcome this problem, dynamic spectrum access technology which can provide an effective spectrum assignment receives much attention. In this paper, we propose a dynamic spectrum assignment method in which a WiFi system temporarily uses a spectrum band of the WiMAX system in WiFi/WiMAX integrated networks to reduce call loss probability of multimedia communication services. The proposed method assigns additional spectrum from WiMAX to WiFi access points based on loss probability prediction.

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Other Link： http://id.nii.ac.jp/1001/00067852/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

With advances in communication technologies, network services provided via the Internet have been widely diversified, and people can use these services not only via wired networks but also via wireless networks. There are several wireless systems in practical use such as Cellular, WiMAX and WiFi. Although these wireless network systems have developed independently of each other, they should be integrated for seamless access by users. On the other hand, each system uses an individual spectrum prescribed by law to avoid radio interference. To overcome this problem, dynamic spectrum access technology receives much attention. We propose a dynamic spectrum assignment method in which a WiFi system temporarily uses a spectrum band of the WiMAX system in WiFi/WiMAX integrated networks to reduce call blocking probability of multimedia communication services. We confirm the effectiveness of the proposed method by simulation experiments.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Okayama University has been operating an external link and many inter-campus links via Science Information Network (SINET) and regional Internet eXchanges (IXes) operated by local governments. However, since there were no redundant links for them, we often experienced problems that external connections and inter-campus connections failed in case of some troubles on these links. To overcome these problems, we added a link between Misasa Campus and SINET via regional IXes and Tottori University in addition to the external link between Tsushima Campus and SINET, so that made redundant logical links for the external link and the inter-campus link between Tsushima and Misasa Campuses. According to operations test, we confirmed fault tolerance of these links was improved.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Recently, one of sender authentication methods called SPF has been popularized as Anti-spam technology. However, SPF has a problem that the forwarded e-mail could not be authenticated. In this paper, we propose a solving method for SPF forwarded mail problem by tracing changing history of recipient address. According to the experiments, 88.3% of mails were authenticated with in the proposed method, and 69.5% of mails failed by the original SPF were authenticated in the proposed method.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

For advanced mobile multimedia services, it is expected that wireless access networks have much wider bandwidth. As a promising technology to realize such a network, a mesh network based on WiMAX or WiFi has attracted attention over the years. Moreover, WiMAX/WiFi interworking mesh network where some APs connect to WiMAX base station as a gateway to the Internet has been proposed and spotlighted. In this paper, we propose the effective spectrum sharing method in such a WiMAX/WiFi interworking mesh network by using the dynamic spectrum access technology in order to improve the network throughput. Finally, we show the effectiveness of the proposed method by simulation experiments.

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Publisher：IEEE  

DOI： 10.1109/icn.2009.43

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Publisher：ACM Press  

DOI： 10.1145/1658997.1659004

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Language：Japanese  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

It is necessary to manage the mobility of a moving network efficiently. The traditional method achieves it in a distributed manner using multiple routers called MAPs (Mobility Anchor Points). However, especially when the moving network having a lot of MNs (Mobile Nodes) moves and then changes its MAP, the traditional method has a problem. It takes a lot of time to resume these MNs' session after MAP handover, causing many lost packets. This is because many MNs send their mobility management messages simultaneously in that case. To address this problem, this paper proposes a method that controls a sending timing of MNs' mobility management messages, according to their traffic volumes. We implemented computer simulation experiments to confirm the effectiveness of the proposed method. As a result, we confirmed that the proposed method can reduce the number of lost packets efficiently.

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Publisher：IEEE  

DOI： 10.1109/lcn.2008.4664210

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

It is necessary to manage the mobility of a moving network having a lot of MNs (Mobile Nodes) efficiently. We have proposed a method that distributedly manages the mobility of MNs within a moving network using multiple MAPs (Mobility Anchor Points) whose management areas partially overlap with each other. The traditional method, however, has a problem that it does not have sophisticated MAP selection method in multi-layered MAPs environment. This disturbs the efficient reduction of the number of lost packets during handovers because the traditional method cannot effectively use higher-level MAPs having wider management areas. To address this problem, this paper proposes a method that lets an MN select its MAP according to its traffic volume. We implemented computer simulation experiments to confirm the effectiveness of the proposed method. As a result, we confirmed that the proposed method can reduce the number of lost packets efficiently thanks to effective use of higher-level MAPs.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Spam mails which bother us are dramatically been increasing. Filtering is one of the effective Anti-spam method. But if it based on analyzing the body of mail, some legitimate mails are not deliver to destination. In this thesis, we focused on Received field in the mail header, and analyze the delivery path. This paper presents delivery delay time at a legitimate mail server tends to be a constant. Furthermore, spam mails delivery delay time are dispersedly. Additionally, we described some spam mais uses wrong summer time, and have special count of Received fields.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, wireless systems develop and multimedia communications spread more and more. Moreover, WiMAX/WLAN integrated network which uses WiMAX and WLAN seamlessly is expected. Although it allows users to select an adequate access system, the number of the unused spectrum band may exists on a certain time and space in each system. Therefore, it is said that the utilization efficiency of the radio frequency spectrum is not so improved. In this paper, we consider the effective usage of the radio frequency spectrum by using cognitive radio technology and propose the effective spectrum sharing method which allocates the unused band of WiMAX to WLAN. Finally, we confirm the effectiveness of the proposed method by simulation experiments.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Streaming services in mobile networks have been realizing with wider bandwidth of wireless networks. Especially, from the perspective of user-friendliness, they can be widely accepted via some TCP-based protocols such as HTTP. However, the throughput of TCP-based communication on heterogeneous wireless networks is drastically degraded by decreasing of TCP congestion window size (cwnd) because of packet losses due to handoff. In this paper, we proposed the method to immediately increase the cwnd by using IEEE 802.11e EDCA. It can be implemented without extension of the existing TCP. Finally, we show the effectiveness of the proposed method by simulation experiments.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

A network mobility management scheme using Hierarchical Mobile IPv6 has been proposed to overcome problems with route optimization and micromobility for moving networks. It manages the mobility of a moving network using a router located in a network the moving network moves to (Mobility Anchor Point or MAP). The traditional scheme, however, cannot manage the mobility of a moving network efficiently, especially when the moving network has many nodes and/or these nodes communicate with many correspondent nodes. This paper proposes a distributed network mobility management scheme overcoming this problem, by managing the mobility of a moving network using multiple MAPs.

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Publisher：IEEE  

DOI： 10.1109/lcn.2006.322153

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, as the performance of mobile hosts rapidly improves and the bandwidth of wireless access networks grows up, the expectation for mobile multimedia communication services including many-to-many communications such as video-conferencing begins building. Multicasting is one of the key technologies to provide such services efficiently. The existing multicast protocol called Core Based Trees (CBT) is suitable for many-to-many communications in wired networks. In mobile networks, however, it has problems that the number of links of the multicast tree may increase and the end-to-end delay may not satisfy the QoS requirement from users due to tree reconstruction after handovers. Thus, we propose to change the core in consideration of the delay from the core to member nodes when a handover occurs and a new path is constructed. As a result, the proposed method decreases both the number of members who do not satisfy the delay constraint and the average number of total links of the multicast tree.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

LAN access control systems are often used at many organizations such as universities, to provide network accessibility to both insiders and guest users. However, most of existing LAN access control systems have some problems such that guest users can access services restricted to insiders. In this paper, we propose a LAN access control system to protect restricted services from guest users, without modifying any existing servers by applying NAT function conditionally. According to a field testing, the proposed system has been confirmed to be effective and practical.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese  

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Language：Japanese   Publisher：学術情報処理研究編集委員会  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：English   Publisher：IEEE  

<p>VLAN (Virtual LAN) is a technology which can configure logical networks independent of the physi cal network structure. With VLAN, users in common spaces (such as meeting rooms) can access to their department networks temporarily because changing of logical network structure is achieved only by con figuration of VLAN switches. However, in the general configuration method, because VLANs are managed statically by admin istrators, various problems such as high adminis trative cost and conflict or insufficiency of VLAN IDs may arise especially in large scale organiza tions where VLANs are managed by each depart ment. To solve these problems, we propose a method which provides an interconnection between a tem porary configured VLAN in a common space and a VLAN of a user's department. In the proposed method, a user in a common space can access to his/her department network seamlessly by convert ing a temporary VLAN-ID in the common space and a VLAN-ID used in his/her department each other automatically. The effectiveness of the pro posed method is confirmed by the experiment on the actual network using VLAN managers, VLAN ID converters and authentication servers based on the proposed method. </p>

DOI： 10.1109/apsitt.2005.203697

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Language：Japanese   Publisher：Forum on Information Technology  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Mobile multicasting is one of key technologies to provide broadband communication services efficiently. In recent years, some mobile multicast protocols with mobile IP have been proposed. In these protocols, however, the total path length from a multicast source to a Foreign Agent is not considered. They are unsuitable for broadband communication services in which transmission delay has great influences on the QoS. This paper proposes a new mobile multicast routing. It constructs an efficient multicast tree while satisfying the delay constraint by a simple procedure. Finally, simulation experiments show the excellent performance of the proposed method.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We have previously proposed a multilevel hierarchical mobility management scheme to balance mobility management load in wide-area mobile networks. Our scheme manages the mobility of Mobile Terminals (MTs) using mobility management routers placed hierarchically in the networks (Mobility Anchor Points or MAPs). More precisely, in our scheme, the mobility of an MT is managed using a MAP matched to the MT's mobility characteristics. This paper proposes an autonomous load balancing criteria configuration method. The proposed method allows our scheme to work well, even when the MAP domains intricately overlap with each other to increase system robustness.

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Language：English   Publisher：IEEE  

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Publisher：IEEE (Comput. Soc.)  

DOI： 10.1109/lcn.2004.83

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

It is effective to distribute several mobility manageable routers within a wide area network with multilevel hierarchy like mobile communication networks with Hierarchical Mobile IPv6 (HMIPv6). This enables the network to manage Mobile Terminals (MTs) in a flexible manner according to their different mobility scenarios, and reduces the number of signaling messages more efficiently. The purposeful management, however, may be disturbed with present HMIPv6, because HMIPv6 lets MTs select their MAP. In this paper, a method which achieves the purposeful management by focusing on the speed of MTs is proposed. This aims to reduce the number of signaling messages without load concentration at any particular routers.

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Publisher：IEEE  

DOI： 10.1109/icccn.2002.1043109

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, the multimedia communication services have much attention with the advancement of high speed networks and the enhancement of users' request for communication networks. To have these services comfortably, it is desirable that networks guarantee multiple QoS requirements. Moreover, the method to search for the location of services considered with multiple QoSs is also required. in general, QoS required for multimedia communication services includes transmission delay, delay jitter, movie quality and so on. Traditional searching methods, however, do not consider link state information. In this paper, we propose an efficient method to search for the location of multimedia communication services by utilizing link state information. It can know the location fast by adopting the method which searches adjacent nodes first. Finally, we show that the proposed method has good performance by simulation experiments.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Publisher：IEEE  

DOI： 10.1109/apcc.1999.824500

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