This paper presents an approach that uses the Viterbi algorithm in a stereo correspondence problem. We propose a matching process which is visualized as a trellis diagram to find the maximum a posterior result. The matching process is divided into two parts: matching the left scene to the right scene and matching the right scene to the left scene. The last result of stereo problem is selected based on the minimum error for uniqueness by a comparison between the results of the two parts of matching process. This makes the stereo matching possible without explicitly detecting occlusions. Moreover, this stereo matching algorithm can improve the accuracy of the disparity image, and it has an acceptable running time for practical applications since it uses a trellis diagram iteratively and bi-directionally. The complexity of our proposed method is shown approximately as O(N2P), in which N is the number of disparity, and P is the length of the epipolar line in both the left and right images. Our proposed method has been proved to be robust when applied to well-known samples of stereo images such as random dot, Pentagon, Tsukuba image, etc. It provides a 95.7 percent of accuracy in radius 1 (differing by 1) for the Tsukuba images.

With the increase of commercial multimedia applications using digital video, the security of video data becomes more and more important. Although several techniques have been proposed in order to protect these video data, they provide limited security or introduce significant overhead. This paper proposes a video security scheme for MPEG video compression standard, which includes two methods: DCEA (DC Coefficient Encryption Algorithm) and "Event Shuffle." DCEA is aim to encrypt group of codewords of DC coefficients. The feature of this method is the usage of data permutation to scatter the ciphertexts of additional codes in DC codewords. These additional codes are encrypted by block cipher previously. With the combination of these algorithms, the method provides enough security for important DC component of MPEG video data. "Event Shuffle" is aim to encrypt the AC coefficients. The prominent feature of this method is a shuffling of AC events generated after DCT transformation and quantization stages. Experimental results show that these methods introduce no bit overhead to MPEG bit stream while achieving low processing overhead to MPEG codec.

In this paper, we propose an angle of arrival (AOA)-based beamforming structure with strong interference resistant capability for OFDM systems. First, we present novel interference resistant angle of arrival (AOA) estimation schemes for each multipath without training sequences or symbols as the pre-processing of the proposed structure. The generalized sidelobe canceler (GSC) structure is thus applied with the AOA information to avoid calculating the beamforming weight vector individually on a per subcarrier basis, wherein the GSC structure with the reduced-rank multistage Wiener filter (MSWF) is adopted. We also propose a signal transformation scheme to improve performance before the signals are fed into the GSC receiver. The proposed receiver offers better performance than the GSC form of the constrained Wiener filter-based receiver due to the faster convergence property of reduced rank processing and the signal transformation scheme.

This paper presents a multi-matcher on-line signature verification system which fuses the verification scores in pen-position parameter and pen-movement angle one at total decision. Features of pen-position and pen-movement angle are extracted by the sub-band decomposition using the Discrete Wavelet Transform (DWT). In the pen-position, high frequency sub-band signals are considered as individual features to enhance the difference between a genuine signature and its forgery. On the other hand, low frequency sub-band signals are utilized as features for suppressing the intra-class variation in the pen-movement angle. Verification is achieved by the adaptive signal processing using the extracted features. Verification scores in the pen-position and the pen-movement angle are integrated by using a weighted sum rule to make total decision. Experimental results show that the fusion of pen-position and pen-movement angle can improve verification performance.

It has been a very important issue to evaluate the performance of transmission control protocol (TCP), and the importance is still growing up because TCP will be deployed more widely in future wireless as well as wireline networks. It is also the reason why there have been a lot of efforts to analyze TCP performance more accurately. Most of these works are focusing on overall TCP end-to-end throughput that is defined as the number of bytes transmitted for a given time period. Even though each TCP's fast recovery strategy should be considered in computation of the exact time period, it has not been considered sufficiently in the existing models. That is, for more detailed performance analysis of a TCP implementation, the fast recovery latency during which lost packets are retransmitted should be considered with its relevant strategy. In this paper, we extend the existing models in order to capture TCP's loss recovery behaviors in detail. On the basis of the model, the loss recovery latency of three TCP implementations can be derived with considering the number of retransmitted packets. In particular, the proposed model differentiates the loss recovery performance of TCP using selective acknowledgement (SACK) option from TCP NewReno. We also verify that the proposed model reflects the precise latency of each TCP's loss recovery by simulations.

Syntax and prosody are closely related to each other. This paper is concerned with the problem of exploiting pause information for recovering dependency structures of read Japanese sentences. Our parser can handle both symbolic information such as dependency rule and numerical information such as the probability of dependency distance of a phrase in a unified way as linguistic information. In our past work, post-phrase pause that immediately succeeds a phrase in question was employed as prosodic information. In this paper, we employed two kinds of pauses in addition to the post-phrase pause: post-post-phrase pause that immediately succeeds the phrase that follows a phrase in question, and pre-phrase pause that immediately precedes a phrase in question. By combining the three kinds of pause information linearly with the optimal combination weights that were determined experimentally, the parsing accuracy was improved compared to the case where only the post-phrase pause was used as in our previous work. Linear combination of pause and fundamental frequency information yielded further improvement of parsing accuracy.

This paper introduces the concept of "revocable unlinkability" for unlinkable anonymous signatures and proposes a generalized scheme that modifies the signatures to include revocable unlinkability. Revocable unlinkability provides a condition in which multiple messages signed using an unlinkable anonymous signature are unlinkable for anyone except the unlinkability revocation manager. Noteworthy is that the identifier of the signer is kept secret from the manager. In addition, examples are presented in which the proposed scheme is applied to existing group/ring signatures. The proposed scheme employs a verifiable MIX-net to shuffle the identifiers of all potential signers, thus giving it the potential for wide application to unlinkable anonymous signatures.

There is redundancy in instruction sequences, which can be utilized for information hiding or digital watermarking. This study quantitatively examines the information capacity in the order of variables, basic blocks, and instructions in each basic block. Derived information density was 0.3% for reordering of basic blocks, 0.3% for reordering instructions in basic blocks, and 0.02% for reordering of global variables. The performance degradation caused by this method was less than 6.1%, and the increase in the object file size was less than 5.1%.

This paper presents an improved gate drive circuit for high power GTO thyristors. The energy-storage/transfer characteristics of an air-core reactor and the fast switching characteristics of FET are employed to make a high gate current of sharp pulse form. The power loss in the gate drive circuit is reduced by using the low resistance and the hysteresis comparator to detect and control the steady on-gate current. The proposed gate drive circuit is analyzed and its usefulness is confirmed by experiments.

In this paper, we propose a framework for virtual reality, I2-NEXT, which enables users to interact with virtual objects by tangible objects in immersive networked virtual environment. The primary goal of this framework is to support rapid development of immersive and interactive virtual reality systems as well as various types of user interfaces. The proposed framework consists of user interface for interactions, immersive virtual environment, and networking interface. In this framework, we adopt several design patterns to guarantee that either developers or users (artists) can easily implement their VR applications without strong knowledge of VR techniques such as programming, libraries etc. One of the key features of this framework is the presence of the device module which supports a natural user interaction in a virtual environment. For example, the proposed framework provides users with tangible objects so that the users are able to manipulate virtual objects by touching real objects. The proposed framework also supports large scale stereoscopic display through clustering technique. To realize the effectiveness of the proposed framework, we have been developing an application for digital heritage reconstruction. Having been through development of the system, we believe that virtual reality technology is one of the promising technologies which enable users to experience realities in a digital space. Detailed explanations of each component and system architecture are presented.

This letter describes four-branch open-loop transmit diversity schemes that are based on group-coherent codes using space-time block codes (STBC-GCC), for orthogonal frequency-division multiplexing and code-division multiplexing (OFDM-CDM) systems. Open-loop STBC-GCC is designed for transmitting control data by two-dimensional spreading, which is achieved by applying two distinct Walsh-Hadamard (WH) codes within the same mother-code group to two different groups of transmit antennas. The simulation results demonstrated that open-loop STBC-GCC applied to two-dimensional spreading provides space diversity gains and frequency diversity gains. It can therefore be concluded that open-loop STBC-GCC is suitable for transmitting common control data or broadcast data via two-dimensional spreading OFDM-CDM.

Recently, the direct conversion scheme has been actively investigated for the purpose of cost miniaturization and low power consumption of wireless receivers. IQ imbalance is one of the problems for the direct conversion receiver. In the case of OFCDM modulations, this IQ imbalance causes intercarrier interference (ICI) in the demodulated signals. In this paper, the decision directed scheme for IQ imbalance compensation is proposed. In the proposed scheme, the combination of received symbols which satisfies orthogonality conditions is used for compensation of IQ imbalance. Therefore, in addition to the pilot symbols, the received symbols can be used in order to improve the accuracy of the compensation matrix and BER can be reduced.

For emission from a printed circuit board (PCB) by the common-mode current, the suppression method based on the image theory by placing a conducting plate under the PCB is presented. In order to evaluate the suppression effect by this method the radiation power from the PCB is calculated by using FDTD method. The numerical results show that placing the conducting plate suppresses the emission by the common-mode current. Especially, using the conducting plate bent the sides, it is possible to suppress the emission by the small conducting plate. Further, the experimental results of a radiation power and a maximum electric field intensity show the validity of the numerical results.

This paper investigates the 10 m semi anechoic chamber using a new type hybrid EM wave absorber consisted of the grid-ferrite and the open-top hollow pyramidal EM wave absorber. We designed a new type hybrid EM wave absorber, which length could be slightly realized 65 cm. The 10 m semi anechoic chamber was constructed in the size of L21.5 mW13.5 mH8.9 m as the result of the ray-tracing simulation using this absorber. Then, the site attenuation in the constructed anechoic chamber was measured by using the broadband calculable dipole antennas. As the result, the maximum deviations between the measured site attenuation and theoretical calculated one were obtained within 3.6 dB in the frequency range of 30 MHz to 300 MHz. It was confirmed the validity of a new type hybrid EM wave absorber. Moreover, it was confirmed that the measured results agree with the ray-tracing simulation results, in which the differences are about 1.5 dB.

Our group is exploring interactive multi- and hypermedia, especially applied to virtual and mixed reality multimodal groupware systems. We are researching user interfaces to control source→sink transmissions in synchronous groupware (like teleconferences, chatspaces, virtual concerts, etc.). We have developed two interfaces for privacy visualization of narrowcasting (selection) functions in collaborative virtual environments (CVES): for a workstation WIMP (windows/icon/menu/pointer) GUI (graphical user interface), and for networked mobile devices, 2.5- and 3rd-generation mobile phones. The interfaces are integrated with other CVE clients, interoperating with a heterogeneous multimodal groupware suite, including stereographic panoramic browsers and spatial audio backends & speaker arrays. The narrowcasting operations comprise an idiom for selective attention, presence, and privacy-- an infrastructure for rich conferencing capability.

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.

To support international medical collaboration activities carried out among Japan, Sri Lanka and other countries in Asia, we have been developing a collaboration system, which incorporates synchronous and asynchronous collaboration paradigms through network-effective persistent information sharing. The designed system facilitates synchronous collaborative work on maxillo-facial cases through real-time high-quality image delivery and by bringing the system database objects to a shared-workspace. The asynchronous activities are supported through a web based collaborative environment that enables both activity-centric and object-centric navigation of collaboration contents incorporated with email notifications of the system updates. Multimedia records of synchronous sessions are posted to the system database for later reviewing. Geographically dispersed groups experiencing different scales of network heterogeneities are served by a distributed application level multicast overlay and an adaptive multimedia delivery mechanism. The designed collaboration system also features several useful collaboration tools, user friendly GUI and ubiquitous connectivity.

In this paper, we demonstrate an immersive and interactive broadcasting production system with a new haptically enhanced multimedia broadcasting chain. The system adapts Augmented Reality (AR) techniques, which merges captured videos and virtual 3D media seamlessly through multimedia streaming technology, and haptic interaction technology in near real-time. In this system, viewers at the haptic multimedia client can interact with AR broadcasting production transmitted via communication network. We demonstrate two test applications, which show that the addition of AR- and haptic-interaction to the conventional audio-visual contents can improve immersiveness and interactivity of viewers with rich contents service.

XML query processing is one of the most active areas of database research. Although the main focus of past research has been the processing of structural XML queries, there are growing demands for a full-text search for XML documents. In this paper, we propose XICS (XML Indices for Content and Structural search), which aims at high-speed processing of both full-text and structural queries in XML documents. An important design principle of our indices is the use of a B+-tree. To represent the structural information of XML trees, each node in the XML tree is labeled with an identifier. The identifier contains an integer number representing the path information from the root node. XICS consist of two types of indices, the COB-tree (COntent B+-tree) and the STB-tree (STructure B+-tree). The search keys of the COB-tree are a pair of text fragments in the XML document and the identifiers of the leaf nodes that contain the text, whereas the search keys of the STB-tree are the node identifiers. By using a node identifier in the search keys, we can retrieve only the entries that match the path information in the query. The STB-tree can filter nodes using structural conditions in queries, while the COB-tree can filter nodes using text conditions. We have implemented a COB-tree and an STB-tree using GiST and examined index size and query processing time. Our experimental results show the efficiency of XICS in query processing.

Security protocols flaws represent a substantial portion of security exposures of data networks. In order to evaluate security protocols against any attack, formal methods are equipped with a number of techniques. Unfortunately, formal methods are applicable for static state only, and don't guarantee detecting all possible flaws. Therefore, formal methods should be complemented with dynamic protection. Anomaly detection systems are very suitable for security protocols environments as dynamic activities protectors. This paper presents an intrusion detection system that uses a number of different anomaly detection techniques to detect attacks against security protocols.