In recent years, along with the increasing popularity of multi-hop wireless networks, there has been a growing demand in the coupling of these networks to external ones such as the Internet. As traffic destined for external networks increases, special attention is required not only in gateway selection, but also in optimized routing and scheduling in order to maximize the network performance. In this paper we introduce the Ideally Scheduled Route Optimization (ISRO) method to address this concern. ISRO is the combination of three separate optimization problems: optimal routing of gateway traffic under ideal conditions, interference-free scheduling to determine link capacity, and route adjustment in light of the new link capacities. The performance of ISRO is evaluated by experiment which shows significant potential in maximizing the throughput and capacity of the network.

Recently, much effort aiming at achieving ubiquitous networks has been made. A ubiquitous network refers to a network environment, which enables anytime and anywhere access, by possibly any given device or by any user. In a ubiquitous network, applications require many types of information such as temperature and so forth. A great deal of attention has been paid to aggregate this information in Wireless Sensor Networks (WSNs). A WSN consists of tiny nodes comprising sensing and communication devices. The information sensed by each node is relayed via other nodes in the WSN to the destination node called the ``sink''. One of the most significant challenges pertaining to any WSN is to reduce the energy consumption of its nodes, which run on scarce battery resources. An effective scheme to reduce this energy consumption is to exploit the sink node's mobility, which however presents new challenges to the sink node's routing and information aggregation. In this paper, we propose a new routing and data aggregation scheme based on clustering. Simulation results demonstrate that our scheme can provide better energy efficient data aggregation as compared to the KAT (K-means And Traveling salesman path) mobility.

Today, with the rapid advance in broadband technology, streaming technology is applied to many applications, such as content delivery systems and web conference systems. On the other hand, we must implement digital rights management (DRM) to control content spreading and to avoid unintended content use. Traitor tracing is one of the key technologies that constructs DRM systems, and enables content distributors to observe and control content reception. General methods make use of watermarking to provide users' individual information unique to each user. However, these methods need to produce many individual contents. Especially, this is not realistic for real-time streaming systems. Furthermore, watermarking, which is a key technology adopted by contemporary methods, has known limitations and attacks against it. This is why the authors have proposed a method to monitor the content stream using traffic patterns constructed from only traffic volume information obtained from routers. The proposed method can determine who is watching the streaming content and whether or not a secondary content delivery exists. This information can be also used with general methods to construct a more practical traitor-tracing system. A method to cope with random errors and burst errors has also been investigated. Finally, the results of simulation and practical experiment are provided demonstrating the effectiveness of the proposed approach.

Application layer multicast (ALM) is highly expected to replace IP multicasting as the new technological choice for content delivery. Depending on the streaming application, ALM nodes will construct a multicast tree and deliver the stream through this tree. However, if a node resides in the tree leaves, it cannot deliver the stream to its descendant nodes. In this case, quality of service (QoS) will be compromised dramatically. To overcome this problem, topology-aware hierarchical arrangement graph (THAG) was proposed. By employing multiple description coding (MDC), THAG first splits the stream into a number of descriptions, and then uses arrangement graph (AG) to construct node-disjoint multicast trees for each description. However, using a constant AG size in THAG creates difficulty in delivering descriptions appropriately across a heterogeneous network. In this paper, we propose a method, referred to as network-aware hierarchical arrangement graph (NHAG), to change the AG size dynamically to enhance THAG performance, even in heterogeneous networks. Finally, we evaluate the proposed scheme by experiments using the network simulator ns-2. By comparing our proposed method to THAG and SplitStream, we show that our method provides better performance in terms of throughput and QoS. The results indicate that our approach is more reliable than other methods in heterogeneous networks.

During the last several years, the Internet has evolved from a wired infrastructure to a hybrid of wired and wireless domains by spreading worldwide interoperability for microwave access (WiMAX), Wi-Fi, and cellular networks. Therefore, there is a growing need to facilitate reliable content delivery over such heterogeneous networks. On the other hand, application layer multicast (ALM) has become a promising approach for streaming media content from a server to a large number of interested nodes. ALM nodes construct a multicast tree and deliver the stream through this tree. However, if a node leaves, it cannot deliver the stream to its descendant nodes. In this case, quality-of-service (QoS) is compromised dramatically. Especially, this problem is exacerbated in wireless networks because of packet errors and handovers. In order to cope with this problem, multiple-tree multicasts have been proposed. However, existing methods fail to deliver contents reliably in combined wired and wireless networks. In this paper, we propose a method to ensure the robustness of node departure, while meeting various bandwidth constraints by using layered multiple description coding (LMDC). Finally, we evaluate the proposed method via extensive simulations by using the network simulator (ns-2). By comparing our proposed method with the existing ones, we demonstrate that our method provides better performance in terms of total throughput, relative delay penalty (RDP), and relative delay variation (RDV). The results indicate that our approach is a more reliable content delivery system when compared with contemporary methods in the context of heterogeneous networks containing wired and wireless environments.

Broadcasting, in the context of ad-hoc networks, is a costly operation, and thus topology control has been proposed to achieve efficient broadcasting with low interference and low energy consumption. By topology control, each node optimizes its transmission power by maintaining network connectivity in a localized manner. Local Minimum Spanning Tree (LMST) is the state-of-the-art topology control algorithm, which has been proven to provide satisfactory performance. However, LMST almost always results in a 1-connected network, without redundancy to tolerate external factors. In this paper, we propose Local Tree-based Reliable Topology (LTRT), which is mathematically proven to guarantee k-edge connectivity while preserving the features of LMST. LTRT can be easily constructed with a low computational complexity of O(k(m + n log n)), where k is the connectivity of the resulting topology, n is the number of neighboring nodes, and m is the number of edges. Simulation results have demonstrated the efficiency of LTRT and its superiority over other localized algorithms.

For the management of early stage atherosclerosis, the concept of metabolic syndrome is important. An inexpensive, ultra-mobile ultrasound imaging device is proposed for the accurate diagnosis of the atherosclerosis. A linear probe capable of transmitting and receiving 64 ultrasound beams with the central frequency of 7.5 MHz is made. Echo images are displayed on a 5.7 inch LCD screen. The dimension of the device is 270 times 184 times 62 mm and the total weight including the probe is 1.9kg. For the popularization of the echo images for the patients' education and motivation, ultrasound movie client systems were proposed using a mobile phone or PlayStation Portabletrade. The entire procedure proposed in the paper consists of the development of electronic devices and configuration of this system including to the training of community health nurses to use this device.

Recent advances in solid state and packaging technologies have enabled production of more efficient and reasonably small devices such as micro electro mechanical systems (MEMS). Wireless sensor networks (WSNs) can gather data from sensor nodes and are now at the practical stage of realizations because of the above advances. Conventional researches have mainly focused on extending the lifetime of WSNs because sensor nodes are only equipped with small-capacity batteries. Mobile ubiquitous LAN extension (MULE) is one of the approaches to meet such demand, and it can gather data from isolated nodes. The KAT mobility scheme is one of the mobility schemes on MULE focusing on the efficiency. Therefore, this scheme is expected to prolong the lifetime of the network. However, this scheme cannot ensure that the mobile sinks can gather the data from all of the nodes. In this paper, we focus on the fairness issue of data gathered by the mobile sinks while also considering the efficiency of data gathering. We propose a new mobility scheme based on a new clustering method and the set cover algorithm to ensure that the mobile sinks can gather data from all of the nodes, and simulation results show that fairness of data gathering by the proposed mobility scheme is greatly improved as compared to conventional KAT mobility scheme.

Currently, mobile ad hoc network (MANET) has drawn great attention for being part of the ubiquitous network. Unlike the conventional network, MANETs have many unique features such as node resource constraint. That is why several efficient routing protocols have been proposed specifically for MANETs. Among these protocols, optimized link state routing (OLSR) is one of the four important routing protocol identified by IETF. The current OLSR protocol assumes that all nodes are trusted. However, in hostile environment, the OLSR is known to be vulnerable to various kinds of malicious attacks. In this paper, we propose a new security aware optimized link state routing (SA-OLSR) which is a secured version of current OLSR. Our approach is based on exchanging acknowledgement between 2-hop neighbors when the control traffic is successfully received. The main advantage of our approach is that it can protect against many sophisticated attacks such as link spoofing, colluding misrelay attack, and wormhole attack without requiring any location information as well as the knowledge of complete network topology. Our simulation results show that the proposed solution can achieve higher packet delivery ratio compared to the network using the standard OLSR in the presence of malicious nodes.

The coupling of mobile ad-hoc networks (MANETs) and the Internet is gaining attention by researchers working towards future ubiquitous computing environments. In this work, we focus on the situation that occurs when specialized, sensitive data are sent to the Internet from MANET nodes. These special data types are especially susceptible to security risks such as information leak and data falsification. Therefore, it is necessary for such special data to be forwarded by a secure/trusted gateway which is under control of a trusted network administrator. However, we assume there can be multiple gateways deployed in a MANET, where the cost ineffectiveness makes it difficult for a network administrator to simultaneously manage every gateway. Because of the risk of forwarding special data through an unmaintained gateway, we propose a routing protocol which allows a source node to have all data forwarded to the Internet through a trusted gateway. To achieve desirable performance, we improve upon one of the newest routing protocols, Dynamic MANET On-demand (DYMO). Through simulations, we evaluated our proposal in comparison with the conventional DYMO protocol. The results show that our proposal achieves performance allowing MANET source nodes to choose gateways for specific data.

Data confidentiality is one of the most important concerns in security of ad-hoc networks which have been widely studied in recent years. In this paper, we consider the public-key cryptography which is one of the simplest and viable means to maintain data confidentiality. There are several ways to distribute a public key. Flooding is an intuitive approach to distribute each node’s public key. However, the normal flooding approach is costly, and can cause MAC-level contention in a dense region of nodes. Tree based topology flooding can be appied to mitigate these problems. The construction algorithm should use ideally only local information. In this paper, we propose a completely localized algorithm called the Local Tree-based Reliable Topology (LTRT) algorithm, which achieves both reliability and efficiency. LTRT is a localized version of TRT that has 2-edge connectivity. Each node can distribute its public key to all other nodes in the network by LTRT. Simulation results show the efficiency of LTRT and its superiority over other localized algorithms.

Application Layer Multicast (ALM) is highly expected to be the new technological choice contents delivery in lieu of IP multicast. Depending on each node's streaming application, ALM constructs multicast trees and delivers the stream through those trees. The problem of ALM is that when a node resides in tree leaves, the stream cannot be delivered to descendant nodes. To overcome this problem, Topology-aware Hierarchical Arrangement Graph (THAG) was proposed. By employing Multiple Description Coding (MDC), THAG first splits the stream into a number of sub-streams, and then uses Arrangement Graph (AG) to construct an independent tree for each sub-stream. However, using the same size of AG in THAG has a difficulty delivering a stream appropriately across a heterogeneous network. In this paper, we propose a method to change the size of AG dynamically in enhancing THAG performance well even in a heterogeneous network. Finally, we evaluate the proposed scheme by experiments in ns -2. By comparing with THAG, we show that our proposal scheme provides a better performance in throughput and Bandwidth Satisfaction Rate (BSR).

To distinguish similar characters, it is preferable to construct a classifier using a projective feature space which differentiates two similar categories. The classifier CMF has been proposed for a discriminant function, in similar characters recognition. In the CMF, a subspace is constructed by some eigenvectors, that corresponds to the smallest eigenvalues, is applied as projective feature space. A difference vector of two class-mean feature vectors are assumed as the difference between two similar categories, the CMF is constructed by projecting a feature vector onto this difference vector. In this paper, we propose new discriminant function expanding the CMF. In proposed method, we treat the Difference Subspace, which is difference between two subspaces as difference between two similar categories. The efficiency of the proposed new discriminant function has been demonstrated in similar characters recognition through extensive experiments on hand-written Japanese characters derived from the ETL9B database.

Today, with the rapid advance in broadband technology, digital contents delivery applications have been used widely and the streaming technology has made the contents delivery more popular. Nowadays, there is high expectation on Digital Rights Management (DRM). Traitor Tracing is one of the DRM technologies and enables us to observe user's contents streaming and detect illegal contents streaming. However, malicious users can interrupt tracing with illegal processes at user-side computers. To prevent all illegal processes at the user- side, routers should analyze information embedded into packets, which is unrealistic. In this article, we propose a system to detect illegal contents streaming by using only traffic patterns which are constructed from the amount of traffic traversing routers. We also investigate a method to cope with random errors and burst errors which occur frequently in wireless environment and show the satisfactory result which we have obtained in a practical testing environment.

Rapid advances in wireless networking technologies have made it possible to construct a mobile ad hoc network (MANET) which can be applied in infrastructureless situations. However, due to their inherent characteristics, MANETs are vulnerable to various kinds of attacks which aim at disrupting their routing operations. To develop a strong security scheme to protect against these attacks it is necessary to understand the possible form of attacks that may be launched. Recently, researchers have proposed and investigated several possible attacks against MANET. However, there are still unanticipated or sophisticated attacks that have not been well studied. In this paper, we present a collusion attack model against optimized link state routing (OLSR) protocol which is one of the four standard routing protocols for MANETs. After analyzed the attack in detail and demonstrated the feasibility of the attack through simulations, we present a technique to detect the attack by utilizing information of two hops neighbors.

Mobile ad hoc networks (MANET) are usually formed without any major infrastructure. As a result, they are relatively vulnerable to malicious network attacks and therefore the security is a more significant issue than in infrastructure-type wireless networks. In these networks, it is difficult to identify malicious hosts, as the topology of the network changes dynamically. A malicious host can easily interrupt a route for which the malicious host is one of the forming nodes in the communication path. In the literature, there are several proposals to detect such malicious host inside the network. In those methods usually a baseline profile is defined in accordance to static training data and then they are used to verify the identity and the topology of the network, thus avoiding any malicious host to be joined in the network. Since the topology of a MANET is dynamically changing, use of a static profile is not efficient. In this paper, we propose a new intrusion detection scheme based on a learning process, so that the training data can be updated at particular time intervals. The simulation results show the effectiveness of the proposed technique compared to conventional schemes