This paper proposes two types of network architectures using UMTS Release 5 architecture and wireless LAN suitable for context-aware information delivery and personal communication services, and it reports on preliminary evaluations of their performance. The first type of network architecture is the NCA (network-centric architecture) and the second is the ECA (end-user-centric architecture). The two architectures are modeled with a queuing network and their response times are compared through theoretical analysis and simulation. The results indicate that with low-performance servers, the response times of the ECA are generally shorter or almost the same as those of the NCA. However with high-performance servers, the response times of the NCA are generally shorter except during high server utilization.

Delay and Disruption Tolerant Networks (DTN) can provide an underlying base to support mobility environments. DTN is equipped with advanced features such as custody transfer and hop by hop routing which can tackle the frequent disconnections of mobile devices by buffering bundles and dynamically making hop-by-hop routing decisions under intermittent connectivity environment. In this paper, we have proposed a DTN routing protocol HALF (Handoff-based And Limited Flooding) which can manage and improve performance of disrupted and challenging communication between mobile nodes in the presence of an infrastructure network consisting of fixed interconnected nodes (routers). HALF makes use of the general handoff mechanisms intended for the IP network, in a DTN way and also integrates a limited flooding technique to it. Simulation results show that HALF attains better performance than other existing DTN routing protocols under diverse network conditions. As the traffic intensity changes from low to high, delivery ratio of other DTN routing protocols decreased by 50% to 75% whereas in HALF such ratio is reduced by less than 5%. HALF can deliver about 3 times more messages than the other protocols when the disrupted network has to deal with larger size of messages. If we calculate the overhead ratio in terms of 'how many extra (successful) transfer' is needed for each delivery, HALF gives less than 20% overhead ratio while providing a good delivery ratio.

Future wireless/mobile system is expected to have heterogeneous wireless overlay networks for ubiquitous multimedia communication. In a such network environment, mobile users are likely to try to get attached to higher bandwidth network as bandwidth-hungry multimedia applications are increasing. However, the users have to perform vertical handoff to lower bandwidth network, as high bandwidth network become unavailable due to various reasons (such as its limited coverage, network congestion, etc.). In this paper, we discuss the problem of vertical handoff from a user's perspective. For this purpose, we formulate user satisfaction as a function of bandwidth utility and handoff latency. Then, we investigate the effect of call holding time, user movement probability, etc. on the satisfaction that a user derives from the use of network service for multimedia applications. In addition, based on the evaluation, we present an algorithm for selecting a wireless network, which maximizes the effective user satisfaction.

In wireless ad hoc networks, network services are provided through the cooperation of all nodes. Albeit that good teamwork could smoothly run a mobile network, selfish node behaviors would probably cause it to break down. Some examples of these selfish node behaviors would include, "listening only" for saving energy or "receiving the valuable" without forwarding the packets to others. To cope with this problem, we propose PDM, a price-demand function based pricing model, to restrains the selfish behaviors of mobile nodes. PDM is based on the packet sending requirements of the source nodes and the forwarding cost of relay nods. Using this pricing methodology, the packet forwarding activities will be profitable for the relay node and further stimulate cooperation in the network. In particular, the new model enjoys the merit of giving relay nodes no reason to dishonestly report their forwarding costs, because an honest cost claim has proven to be an optimal strategy for relay nodes. Furthermore, our new model uses a price-demand function to reflect the relationship between the service demand of the source nodes and the service supply of the relay nodes. As a consequence, our approach reduces the source nodes' payments to send packets, and at the same time guarantees that the packets sent by the source nodes are delivered to the destination.

This paper discusses the implementation and cost- and performance- evaluations of a distributed processing network, called DONA-α, which is one of the possible physical networks mainly implementing connection-oriented public switched network functions corresponding to OSI layers 1 to 3. The first feature of the DONA-α network is that it separates a switching subsystem and a control subsystem of a conventional switching system and independently allocates them over distributed nodes as a switching node and a control node. Each DONA-α switching node is given a much smaller switching capacity than the switching subsystem of the conventional switching system and is located near subscribers. In contrast, each DONA-α control node has much higher performance than the control subsystem of the conventional switching system. This allows a large number of switching nodes to share the same control node, which controls their connection setups. This separation provides the network with greater flexibility and allows more effective utilization of network resources, such as control processors, switching fabrics, and transmission links, than ever before. The second feature of DONA-α is that it provides a network with network-wide distribution transparency. This allows network resources including software such as databases and application programs to be shared and therefore to be utilized in the network more easily and more efficiently. The results of a network performance simulation and cost calculation confirm the viability of the DONA-α network.

This paper proposes an advanced hybrid network architecture and a comprehensive network design of the next-generation science information network, called SINET3. Effectively combining layer-1 switches and IP/MPLS routers, the network provides layer-1 end-to-end circuit services as well as IP and Ethernet services and enables flexible resource allocation in response to service demands. The detailed network design focuses on the tangible achievement of providing a wide range of network services, such as multiple layer services, multiple virtual private network services, advanced qualities of service, and layer-1 bandwidth on demand services. It also covers high-availability capabilities and effective resource assignment in the hybrid network. The cost reduction effect of our network architecture is also shown in this paper.

The IETF (Internet Engineering Task Force) has developed a Network Mobility (NEMO) basic support protocol by extending the operation of Mobile IPv6 to provide uninterrupted Internet connectivity to the communicating nodes of mobile networks. The protocol uses a mobile router (MR) in the mobile network to perform prefix scope binding updates with its home agent (HA) to establish a bi-directional tunnel between the HA and MR. This solution reduces location-update signaling by making network movements transparent to the mobile nodes behind the MR. However, delays in data delivery and higher overheads are likely to occur because of sub-optimal routing and multiple encapsulation of data packets. To resolve these problems, we propose a mobile router-assisted route optimization (MoRaRo) scheme for NEMO support. With MoRaRo, a mobile node performs route optimization with a correspondent node only once, at the beginning of a session. After that the MR performs route optimization on behalf of all active mobile nodes when the network moves. The virtue of this scheme is that it requires only slight modification of the implementation of the NEMO basic support protocol at local entities such as the MR and mobile nodes of the mobile network, leaving entities in the core or in other administrative domains untouched. MoRaRo enables a correspondent node to forward packets directly to the mobile network without any tunneling, thus reducing packet delay and encapsulation overheads in the core network. To enable the scheme to be evaluated, we present the results of both theoretical analysis and simulation.

Detecting a variety of anomalies caused by attacks or accidents in computer networks has been one of the real challenges for both researchers and network operators. An effective technique that could quickly and accurately detect a wide range of anomalies would be able to prevent serious consequences for system security or reliability. In this article, we characterize detection techniques on the basis of learning models and propose an unsupervised learning model for real-time anomaly detection in computer networks. We also conducted a series of experiments to examine capabilities of the proposed model by employing three well-known machine learning algorithms, namely multivariate normal distribution, k-nearest neighbor, and one-class support vector machine. The results of these experiments on real network traffic suggest that the proposed model is a promising solution and has a number of flexible capabilities to detect several types of anomalies in real time.

This paper describes an architectural design and related services of a new Japanese academic backbone network, called SINET5, which will be launched in April 2016. The network will cover all 47 prefectures with 100-Gigabit Ethernet technology and connect each pair of prefectures with a minimized latency. This will enable users to leverage evolving cloud-computing powers as well as draw on a high-performance platform for data-intensive applications. The transmission layer will form a fully meshed, SDN-friendly, and reliable network. The services will evolve to be more dynamic and cloud-oriented in response to user demands. Cyber-security measures for the backbone network and tools for performance acceleration and visualization are also discussed.

Large Area Synchronized (LAS)-CDMA, actually composed of LA codes and pulse compressing LS codes, has been proposed as a most promising scheme in 3G and 4G wireless communications. LS codes are famous for the Zero Correlation Zone (ZCZ) in the auto-correlation and cross-correlation functions, which endows the codes with the capability to perfectly reduce the Multiple Access Interference (MAI) and Inter Symbol Interference (ISI) if the maximum transmission delay is less than the length of ZCZ. In this letter, we provide a general and systematic method to construct LS codes from the set of complete complementary sequences. Our method is much more general than the ordinary LS construction method revealed previously.

Ubiquitous computing (ubicomp) demands new security and privacy enhancing technologies for the new information and communication environments where a huge number of computers interact with each other in a distributed and ad hoc manner to access various resources and services. This paper surveys emerging security and privacy enhancing technologies, focusing on access control in ubiquitous computing environments because this is the underlying core technology to enforce security and privacy policies. We classify access control technologies into three types associated with the three access control phases of prevention, avoidance, and detection, and provide an overview of ubiquitous computing-oriented technologies and solutions, ranging from security and privacy models and policies to the enforcement of policies and system implementation.

Sequence set with Three Zero Correlation Zones (T-ZCZ) can efficiently mitigate the Multiple Access Interference (MAI) and Inter Symbol Interference (ISI) caused by multi-path in CDMA system. In this paper, an algorithm for generating T-ZCZ sequence set is presented. Moreover, in order to study the restrictions among the parameters such as the length of the sequence, the number of the sequences and the length of the T-ZCZ etc., the corresponding theoretical bound is investigated and proved. Additionally, the performance of T-ZCZ sequence in MC-CDMA system is evaluated to confirm the capability of interference cancellation as well as system capacity improvement.

To support multimedia applications effectively in mobile networks, the handover latency or packet losses during handover should be very small. Addressing this issue, we present a cooperative mobile router-based handover (CoMoRoHo) scheme for long-vehicular multihomed mobile networks. The basic idea behind CoMoRoHo is to enable different mobile routers to access different subnets during a handover and cooperatively receive packets destined for each other. In general, packet losses are directly proportional to handover latency; however, the overlapped reception of packets from different subnets makes possible to minimize packet losses even without reducing handover latency. To evaluate the scheme, we carried out performance modeling of the CoMoRoHo scheme in comparison with the Fast Handover for Mobile IPv6 (FMIPv6) protocol in regard to the handover latency, packet loss, signaling overhead, and packet delivery overhead in access networks. The analysis results show that CoMoRoHo outperforms FMIPv6 by reducing the packet losses as well as signaling overheads by more than 50%. Moreover, CoMoRoHo imposes lower packet delivery overheads required for preventing packets from being dropped from access routers. We thus conclude that CoMoRoHo is a scalable scheme because its performance remains intact even when the access network is overloaded.

Privacy is increasingly viewed as a key concern in multi-agent based algorithms for Distributed Constraint Satisfaction Problems (DCSP) such as the Meeting Scheduling (MS) problem. Many algorithms aim for a global objective function and as a result, incur performance penalties in computational complexity and personal privacy. This paper describes a mobile agent-based scheduling scheme called Efficient and Privacy-aware Meeting Scheduling (EPMS), which results in a tradeoff among complexity, privacy, and global utility. It also introduces a privacy loss model for collaborative computation, multiple criteria for evaluating privacy in the MS problem, and a privacy measurement metric called the Min privacy metric. We have utilized a common computational space in EPMS for reducing the complexity and the privacy loss in the MS problem. The analytical results show that EPMS has a polynomial time computational complexity. In addition, simulation results show that the obtained global utility for scheduling multiple meetings with EPMS is close to the optimal level and the resulting privacy loss is less than for those in existing algorithms.