The concept of wireless ad hoc networking has unique features in which neither base stations nor wired backbone networks are required and a mobile node can communicate with a partner beyond the transmission range by multihopping. In this paper, innovations and issues in ad hoc network technologies are reviewed. The concept of a general-purpose ad hoc network is identified as a step toward next-generation ad hoc network development. The concept of an open community network is then presented as a vision for general-purpose ad hoc networks. An open community network is a novel information infrastructure for local communities based on wireless multihopping technologies, which may support an advanced information-oriented society in the twenty-first century. As a case study, an experimental system using PHS (Personal Handy Phone System) is described and some research issues for developing an open community network are identified.

We introduce efficient algorithms for scalar multiplication on elliptic curves defined over FP. The algorithms compute 2k P directly from P, where P is a random point on an elliptic curve, without computing the intermediate points, which is faster than k repeated doublings. Moreover, we apply the algorithms to scalar multiplication on elliptic curves, and analyze their computational complexity. As a result of their implementation with respect to affine (resp. weighted projective) coordinates, we achieved an increased performance factor of 1.45 (45%) (resp. 1.15 (15%)) in the scalar multiplication of the elliptic curve of size 160-bit.

NOR self-decimated sequences are attractive for stream ciphers because they have a good statistical property and the hardware construction is very simple. This paper presents an analysis of NOR self-decimation system for any parameter. We first determine the period. Then we show the exact distribution of consecutive two bits and three bits, which are shown to be almost uniform distribution.

B-ISDN is expected to be applied in the near future to video delivery systems for the broadcast of news and television programs. The demand for such services is increasing, and in particular, on-demand services are becoming more desirable. On-demand services allow viewers to request their favorite programs at the time that is convenient, hence catering for the wide range of modern lifestyles. As for on-demand services, there already exist Video on Demand (VoD) systems such as the original VoD or Near VoD. However, such systems have not yet been widely implemented because of the inefficient cost of communication resources, and storage. The authors' research is aimed at producing an efficient VoD system based on a high speed network. We are focused in particular on the forms of data transmission, and in this paper, we propose a new VoD system called Burst VoD. Burst VoD aggressively utilizes the multicasting technique, and involves dividing the program resource data into block files and transmitting them to viewer terminals as burst traffic over a high speed network. Simulation results comparing Burst VoD with conventional VoD show that Burst VoD achieves lower request blocking rates, efficient utilization of networks with multicasting, and almost on-demand response time to requests.

The capability of frequency-swept cross-borehole radar to detect an empty rectangular cylinder embedded in a dielectric medium is simulated numerically by employing the boundary element method. The frequency loci providing the strongest double dips in the received signal pattern are plotted as functions of the observation distance and the cross-sectional width. It is found that, regardless of the shape of the rectangular cross-section, the strongest double dips become double nulls in the near-field region.

An electromagnetic wave scattering by a material loaded rectangular trough on a ground plane is approximately analyzed by using standard impedance boundary condition (SIBC). The validity of the derived approximate solution is examined by comparing with the rigorous one not only for the oblique incidence but also for the variation of both the filled material's parameters and the trough dimension. An applicability condition has been derived here for this trough structure.

We introduce a refined definition of semantic security. The new definition is valid against not only chosen-plaintext attacks but also chosen-ciphertext attacks whereas the original one is defined against only chosen-plaintext attacks. We show that semantic security formalized by the new definition is equivalent to indistinguishability, due to Goldwasser and Micali for each of chosen-plaintext attacks, non-adaptive chosen-ciphertext attack, and adaptive chosen-ciphertext attack.

The diffraction problem of a Gaussian beam by finite number of periodic slots in a parallel-plate waveguide filled with a homogeneous dielectric is considered. The integro-differential equation for the unknown equivalent surface magnetic current density over the slots is derived and solved by the method of moments (piecewise sinusoidal Galerkin method). From some theoretical results for the angular diffraction pattern, the present geometry is observed to simulate well the previous rectangular groove geometry from the viewpoint of scattering behaviour. In addition, two types (resonance and non-resonance types) of Bragg blazing phenomena are discussed. Simultaneous Bragg and off-Bragg blazing is also demonstrated.

The term pilot pollution in IS-95 CDMA systems is used to indicate that a large number of equally strong pilot signals is present. Those pilots compete with each other to become the serving one and this causes a very high rotation of pilot leadership at the mobile station. As a consequence, the signaling rate on the traffic channel increases, thus degrading the call quality. We present a method of alleviating the pilot pollution problem by means of repeaters. Simulation studies have been carried out on an actual CDMA network suffering from pilot pollution and the results have been verified by field trials. They indicate that repeaters can effectively improve call quality by altering the spacial distribution of pilot signal strength.

A single-chip MPEG-2 video, audio, and system encoder LSI has been developed. It performs concurrent real-time processing of MPEG-2 422P@ML video encoding, 2-channel Dolby Digital or MPEG-1 audio encoding, and system encoding that generates a multiplexed transport stream (TS) or a program stream (PS). Advanced hybrid architecture, which combines a high performance VLIW media-processor D30V and hardwired video processing circuits, has been adopted to satisfy the demands of both high flexibility and enormous computational capability. A unified control scheme has been newly proposed that hierarchically manages adaptive task priority control over asynchronous video, audio, and system encoding processes in order to achieve real-time concurrent processing using a single D30V. Dual dedicated motion estimation cores consisting of a coarse ME core (CME) for wide range searches and a fine ME core (FME) for precise searches have been integrated to produce high picture quality while using a small amount of hardware. Adopting these features, a single-chip encoder has been fabricated using 0.25-micron 4-layer metal CMOS technology, and integrated into a 14.2 mm 14.2 mm die with 11 million transistors.

We formalize a model of "demonstration of program result-correctness," and investigate how to prove this fact against possible adversaries, which naturally extends Blum's theory of program checking by adding zero-knowledge requirements. The zero-knowledge requirements are universal for yes and no instances alike.

This paper describes how the image sequences taken by a stationary video camera may be effectively processed to detect and track moving objects against a stationary background in real-time. Our approach is first to isolate the moving objects in image sequences via a modified adaptive background estimation method and then perform token tracking of multiple objects based on features extracted from the processed image sequences. In feature based multiple object tracking, the most prominent tracking issues are track initialization, data association, occlusions due to traffic congestion, and object maneuvering. While there are limited past works addressing these problems, most relevant tracking systems proposed in the past are independently focused to either "occlusion" or "data association" only. In this paper, we propose the KL-IMMPDA (Kanade Lucas-Interacting Multiple Model Probabilistic Data Association) filtering approach for multiple-object tracking to collectively address the key issues. The proposed method essentially employs optical flow measurements for both detection and track initialization while the KL-IMMPDA filter is used to accept or reject measurements, which belong to other objects. The data association performed by the proposed KL-IMMPDA results in an effective tracking scheme, which is robust to partial occlusions and image clutter of object maneuvering. The simulation results show a significant performance improvement for tracking multi-objects in occlusion and maneuvering, when compared to other conventional trackers such as Kalman filter.

For distributed multimedia applications, the development of adaptive QoS (quality of service) management mechanisms is needed to guarantee various and changeable end-to-end QoS requirements. In this paper, we propose an adaptive QoS management framework based on multi-agent systems. In this framework, QoS management mechanisms are divided into two phases, the flow establishment and renegotiation phase and the media-transfer phase. An adaptation to system resource changes and various user requirements is accomplished by direct or indirect collaborations of the agents in each phase. In the flow establishment and renegotiation phase, application agents determine optimal resource allocation with QoS negotiations to maximize the total users' utility. In the media-transfer phase, stream agents collaborate to adjust each stream QoS reactively. In addition, personal agents help a novice user to specify stream QoS without any a priori knowledge of QoS. To make the interworking of agents tractable, a QoS mapping mechanism is needed to translate the QoS parameters from level to level, since the expression of QoS differs from level to level. As an example of multimedia application based on the proposed framework, a one-way video system is designed. The experimental results of computer simulation show the validity of the proposed framework.

A passive branched optical network unified for broadcasting and communication utilizing a set of Fabry-Perot etalons with different cavity lengths is proposed and its basic operation including thermal stability of broadcasting channel is demonstrated. It is confirmed that a high transmission frequency in common for a pair of fiber Fabry-Perot etalons is always found however environmental temperature changes.

Terahertz radiation imaging has been employed to diagnose the supercurent and vortex distribution in high-Tc superconductive thin film strips. We observe them in the YBCO films patterned into the strip with and without ordered arrays of small antidots. Comparison with the theoretically expected distribution reveals that the present technique can provide a powerful tool for the noncontact, nondestructive, and free-space evaluation of the supercurrent and the vortex distribution with good quantitative agreement. The effect of the antidot formation in the strips is explained by the decrease of the effective critical current. The remanent state after removal of the relatively large magnetic field cannot be explained by the conventional model for the superconductive thin films, and the discrepancy is more notable in the antidot-formed area.

A uniquely parsable unification grammar (UPUG) is a formal grammar with the following features: (1) parsing is performed without backtracking, and (2) each nonterminal symbol can have arguments, and derivation and parsing processes accompany unification of terms as in Prolog (or logic programming). We newly introduce a uniquely parallel parsable unification grammar (UPPUG) by extending the framework of a UPUG so that parallel parsing is also possible. We show that, in UPPUG, parsing can be done without backtracking in both cases of parallel and sequential reductions. We give examples of UPPUGs where a given input string can be parsed in sublinear number of steps of the length of the input by parallel reduction.

This paper describes a random access memory (RAM, sometimes also called an array) test scheme that has the following attributes: (1) Can be used in both built-in mode and off chip/module mode. (2) Can be used to test and diagnose naked arrays. (3) Fault diagnosis is simple and is "free" for some faults during test. (4) Is never subject to aliasing. (5) Depending upon the test length, it can detect many kinds of failures, like stuck-cells, decoder faults, shorts, pattern-sensitive, etc. (6) If used as built-in feature, it does not slow down the normal operation of the array. (7) Does not require storage of correct responses. A single response bit always indicates whether a fault has been detected. Thus, the storage requirement for the implementation of the test scheme is zero. (8) If used as a built-in feature, the hardware overhead is very low.

Recently, antenna selection diversity has been widely used for hand-held phones to overcome a fading problem. A monopole antenna (MPA) and an inverted-F antenna (IFA) are the typical antennas used for this purpose. However, strong mutual coupling generally appears between these two antennas and often makes the diversity antenna design difficult. In particular, in the case that the MPA is unselected antenna the mutual coupling can be minimized using the open terminating impedance. On the other hand, in the case that the IFA is unselected antenna the terminating impedance, which can minimize the mutual coupling, has not been clarified. This paper presents a novel analytical method for optimizing the terminating impedance of the IFA. The method exploits the Z-matrix, and the final expression of the terminating impedance is expressed by self- and mutual-impedance. The numerical and experimental results confirm that the proposed optimization method is effective for minimizing the mutual coupling.

This paper examines similarities between the Decision Diffie-Hellman (DDH) assumption and the Quadratic Residuosity (QR) assumption. In addition, we show that many cryptographic protocols based on the QR assumption can be reconstructed using the DDH assumption.

This paper, for the first time, presents a provably secure signature scheme with message recovery based on the elliptic-curve discrete logarithm. The proposed scheme is proven to be secure in the strongest sense (i.e., existentially unforgeable against adaptively chosen message attacks) in the random oracle model under the discrete logarithm assumption. We give a concrete analysis of the security reduction. When practical hash functions are used in place of truly random functions, the proposed scheme is almost as efficient as the elliptic-curve version of the Schnorr signature scheme and existing schemes with message recovery such as the elliptic-curve version of the Nyberg-Rueppel and Miyaji schemes.