This paper describes a mobile information access system based on a multi-agent architecture. With the rapid progress of wireless data communications, mobile Internet access will be more and more popular. In mobile environments, user location plays an important role for information filtering and flexible communication service. In this paper, we propose a mobile information service system where a user with a handy terminal accesses Internet in an open air to look up map information and related town information. Each user information is managed by an independent agent process. And the agent provides each user with a personal service collaborating with other applications. A map-based information service example based on this architecture is also described.

In this paper, we propose a scalable service networking architecture as a TINA-like environment for providing flexibly various mobility services. The proposed architecture provides an environment that enables the advent of service providers and rapidly introduces multimedia applications, considering networks scalability. For supporting customized mobility services, this architecture adopts a new service component, which we call Omnipresent Personal Environment Manager (OpeMgr). In order to support mobile users who move between heterogeneous networks, for instance, between the TINA-like environment and the Internet environment, we propose a structure of a gateway. In addition, the proposed architecture uses the fixed and mobile agent approaches for supporting the user's mobility, and we evaluated their performances with comparing those approaches.

Service interaction resolution is an important study subject to realize a network supporting various advanced communication services. This paper proposes service interaction resolution by service node connected with the communication network via the user-network interface. By executing various advanced services on the service node, service interactions can be efficiently resolved without adding new functions to the existing network. In other words, the service node enables a unified execution control of all the services including those for the originating side and those for the terminating side. This prevents the signalling system and the signalling procedure from being expanded to resolve service interactions. Moreover, the interactions between the services initiated at the conversation active state can be resolved by the service node equipped with function of receiving plural types of in-band signals. This avoids functional expansion of the switching systems in the network. In this paper, feasibility of the proposed resolution scheme is proved by showing a structure of the service node and a detailed procedure to resolve interactions on that service node. In the proposed service node, the application part is divided into basic call processing part and service processing part, and the basic call processing part is represented by three kinds of basic call processing state models. The proposed method for resolving service interactions can control services execution with high flexibility by using feature interaction table.

Connectionless data from existing network applications compose a large portion of the workload during an early ATM deployment, and are likely to make up an important portion of ATM's workload even in the long term. For providing a connectionless service over the ATM network, we compare two approaches; an indirect and a direct approaches, which are adopted by International Telecommunication Union-Telecommunication (ITU-T) as generic approaches. Our main subject of this paper is to compare network costs of two approaches by taking into account several cost factors such as transmission links, buffers, and connectionless servers in the case of the direct approach. Since the cost of the direct approach heavily depends on the configuration of a virtual connectionless overlay network, we propose a new heuristic algorithm to construct an effective connectionless overlay network topology. The proposed algorithm determines an optimal number of connectionless servers and their locations to minimize the network cost while satisfying QoS requirements such as maximum delay time and packet loss probability. Through numerical examples, we compare the indirect and direct approaches, the latter of which is constructed by means of our proposed algorithm.

Recently, many types of high-density recording technologies for future MO (Magneto-Optical) storage have been reported. MSR (Magnetically Induced Super Resolution) technology is one of the most promising candidates, and over ten types of MSR technologies have been already proposed. However, they are not well-discussed from the viewpoint of total recording technology which would include the recording and readout methods, the pick-up technology and the signal processing technology. Key technologies for realizing MO storage of over 7 GBytes in a CD-sized disk using a red laser are proposed, and the experimental results pertaining to each key technology are described. The write/read characteristics were examined for the CAD (Center Aperture Detection)-MSR disk. From the characteristics of the CAD-MSR disk combined with laser pumped magnetic field modulation recording, it was shown that land/groove (0.7 µm width) recording with the linear density of 0.27 µm/bit and track pitch below 0.7 µm can be realized. It was also shown that CAD-MSR disk is well combined with an OSR (Optical Super Resolution) pick up, laser pumped read-out and PRML (Partial Response Maximum Likelihood) technologies which are very useful to achieve a high density MO disk. Using CAD-MSR disk combined with above technologies together, high density write/read with a bit length of 0.2 µm and a track pitch of 0.6 µm should be realized with using the laser of 635 nm wavelength. Applying the CAD-MSR disks to a CD sized MO disk, the capacity becomes over 7 GBytes (Format efficiency: 80%), which is 20 times higher than 5.25 inches MO disk and 1.5 times than DVD-ROM.

Since the introduction of magnetoresistive (MR) heads, the areal density of hard disk drives (HDDs) has been increasing at a rate of 60% a year, and has now reached 1.4 Gb/sq. in. The data rate has also been increasing at a rate of 40% or more, and this has recently become a key factor in the ability of multimedia applications to transfer stored data rapidly from the HDD to the PC or workstation. Currently, data rates of around 150 Mb/sec are being implemented in products. In this study, key technologies for increasing both the areal density and the data rate of HDDs are proposed. If they are implemented, an areal density of around 10 Gb/sq. in. and a data rate of 200 Mb/sec or more can be achieved.

Microcellular radio direct-sequence code division multiple access (DC-CDMA) system using optical link to connect their base stations to a central station is a solution of cost-effective and efficient spectrum reuse to meet the growing demand for mobile communications. In addition to the inherent multiuser interference (MUI) of CDMA signals, the system capacity is significantly reduced by a nonlinear distortion (NLD) due to the nonlinearity of optical link. In this paper, a two-stage cancellation technique is introduced into the system to cancel both the MUI and the NLD. It is performed at the receiver of the central station where the random ingredients of all user signals are estimated, and the MUI and the NLD are rebuilt and removed from the received signal. The validity of the cancellation technique is theoretically analyzed and shown by the numerical results. The analytical method and its results are also applicable to other general nonlinear CDMA.

This paper proposes a new multiuser detector, quasi-decorrelating detector (QDD), for a synchronous CDMA system. The QDD has the same complexity as that of decorrelator detector (DD) although it uses feedback loops, the number of which is adjustable to balance the near-far resistance and noise enhancement. The results show that the QDD outperforms the DD under various operational conditions. The impact of different spreading codes on the performance of the QDD is studied. It is shown that the Gold code is the best spreading code suitable for the QDD.

In this paper, a new trial for the signal processing is proposed along the same line as a previous study on the extended regression analysis based on the Bayes' theorem. This method enables us to estimate a response probability property of complicated systems in an actual case when observation values of the output response are roughly observed due to the quantization mechanism of measuring equipment. More concretely, the main purpose of this research is to find the statistics of the joint probability density function before a level quantization operation which reflects every proper correlation informations between the system input and the output fluctuations. Then, the output probability distribution for another kind of input is predicted by using the estimated regression relationship. Finally, the effectiveness of the proposed method is experimentally confirmed by applying it to the actually observed input-output data of the acoustic system.

We have constructed a new concept device with combination of ferroelectric and ferromagnetic materials by a laser ablation technique. An ideal hetero-epitaxy can be obtained owing to the similar crystal structure of perovskite type ferroelectric Pb (Zr, Ti) O3; (so called PZT) and ferromagnetic (La, Sr) MnO3. The ferromagnetic (La, Sr) MnO3 compounds are well known for their colossal magnetoresistance (CMR) properties. The CMR effect is strongly affected by the lattice stress. The PZT, on the other hand, is famous for its large piezoelectrics. We can introduce the lattice stress easily by applying voltage for the piezoelectric compounds. In the heterostructured ferromagnetic/ferroelectric devices, there are remarkable interesting phenomena. Electric properties of the ferromagnetic material can be controlled by piezoelectric effect via distortion of crystal structure.

In client-server database management systems (DBMSs), inter-transaction caching is an effective technique for improving the performance. However, inter-transaction caching requires a cache consistency maintenance (CCM) protocol to ensure that cached copies at clients are kept mutually consistent. Such a protocol could be complex to implement and expensive to run, since several rounds of message exchange may be required. In this paper, we propose a new CCM scheme based on the primary-copy locking algorithm. In the proposed scheme, a number of lock requests and a data-shipping request are combined into a single message packet to reduce client-server interactions, which are known to be very critical to the performance of clientserver DBMSs. We examine its performance tradeoffs on the basis of a simulation model under a wide range of workloads. The performance results indicate that the proposed scheme improves the overall system throughput significantly over the caching two-phase locking and the optimistic two-phase locking scheme. Its higher performance mainly results from its lower communication overhead and lower degree of transaction blocking ratio.

In this paper, we propose a quasi-optimum multiuser detector using co-channel interference cancellation technique in an asynchronous code-division multiple-access communication system, and evaluate its performance by computer simulations. In the proposed detector, maximum likelihood sequence estimation is performed to compare the original received signal with replicas of the signal which are produced from the demodulation data bit sequence of a co-channel interference canceller. In several conditions, the proposed detector is compared with the co-channel interference canceller, and it is shown that the average bit error rate characteristics of the propose detector are improved considerably.

In this work, the performance evaluation of a voice and data integrated fast PRMA has been done. In this newly proposed protocol, every data terminal has an infinite buffer and voice terminals can work independently of data terminals. Thus voice terminals have the higher priority over data terminals. We can, therefore, analyze voice and data subsystems separately. For voice analysis, we use a Markov analysis, and we use the EPA method for data analysis in order to create an analytic form. As performance measures, the voice packet dropping probability, the average voice and data delays, and the total throughput have been derived. It is shown how many voice and data terminals the fast PRMA protocol can accommodate in a frame under the constraints that the voice packet dropping probability should be less than 0.01, and average data packet delay should be less than 250 msec. We also discuss the stable region for this system. Numerical results show close agreement between analysis and computer simulation.

Event-related are the kind of signals that are time-related to a given event. In this work, we will study the effect of bias and overlapping noise on Fourier linear combiner (FLC)-based filters, and its implication on filtering event-related signals. We found that the bias alters the weights behaviour, and therefore the filter output, and we discuss solutions to the problem of spectral overlap.

This paper presents a character recognition method based on a dynamic model, which can be applied to character patterns from both on-line and off-line input. Other similar attempts simply treat on-line patterns as off-line input, while this method makes use of the on-line input's characteristics by representing the time information of handwriting in the character pattern representations. Experiments were carried out on the Hiragana character set. Without non-linear normalization, this method achieved recognition rates of 92.3% for on-line input and 89.1% for off-line input. When non-linear normalization is used, there is an increase in performance for both types of input with on-line input achieving 94.5% and off-line input achieving 94.1%. The reason for the difference in the effectiveness of non-linear normalization on off-line and on-line patterns could be that while the method used for off-line input was an established and proved one, we used our own initial attempt at non-linear normalization for the on-line patterns. If the same level of effectiveness of non-linear normalization as off-line input is achieved on the on-line input, however, the recognition rate for on-line input again improves becoming 96.3%. Since only one standard pattern was used per category for the dictionary patterns, the above results show the promise of this method. This result shows the compatibility of this method to both on-line and off-line input, as well as its effective use of on-line input's characteristics. The effectiveness of this use of the time information is shown by using an actual example. The data also shows the need for a method of non-linear normalization which is more suitable for on-line input.

With the dramatic rise in the number of Internet users, the expansion of international corporate activity and the arrival of multimedia services, highly-competitive information and communication services are entering a period of severe global change. There is widespread recognition that as these changes take place, it is important to establish operation and management (O&M) that will enable "seamless" end-to-end communication services between any points on the earth. With worldwide trends moving toward automation, the study of automation of O&M is being energetically pursued. This paper describes the requirements for service O&M and gives an overview of the technology believed to be essential to achieve them. The progress of developments is also reported.

This paper proposes the Snow Crystal method, which aims to present the hierarchies of a large-scale telecommunication network on one screen. This will improve the user interface of a network operation system for network operations and management. With the proposed presentation method, locations of nodes are automatically set based on the number of hierarchy levels and the number of nodes. The nodes in the same hierarchy level are located on the same circle at even intervals. The center of the circle that corresponds to the top hierarchy level is set at the center of the screen. The radius of the circle is determined by the number of nodes. The centers of circles that correspond to the second hierarchy levels belonging to the nodes of the top hierarchy level, are located on a larger circle with the same center point as the top level circle at even intervals. The centers of circles that correspond to the third hierarchy levels are located at even intervals on a circle with the same center point as the second level circle, which the third levels belong to. The nodes of the subsequent levels are located in the same way. The proposed presentation method is successfully applied to a large-scale telecommunication network. Moreover, the results of an operating experiment with the proposed method show its effectiveness for presenting hierarchies of large-scale telecommunication networks.

Given the recent advances in telecommunication services, new service operations are needed that support not only existing network services, but also information and communication providing services, such as multimedia services. It is particularly important that service usage information should be gathered, processed, analyzed and presented properly for smooth service provisioning and business support. This paper defines a reference model for service usage information and an implementation model for establishing the functions needed to gather and process this information. The results of an service operation system as implemented in NTT multimedia service trials, currently underway in the city of Urayasu, are also described.

Rapid advancing technology and customer demand for sophisticated services are driving the global telecommunications environment into fully competitive and multi service providers environment. To cope with this new environment successfully, open network and open telecommunication management are essential. Telecommunication management is becoming more and more important to realize flexible and dynamic telecommunication services. This paper first gives a view of the new environment in the telecommunication industry and discusses the direction to be taken by service providers. Then, a concept of multi-domain management is proposed to meet a dynamically changing environment. Finally, the paper describes the subjects for the development of telecommunication management system and suggests that a competition based on harmony between the users, service providers and vendors is needed to make customers satisfied with telecommunication services.

Several multiuser detectors have been recently proposed to combat multiple-access interference and near-far problem for CDMA systems. The performance of a multi-user receiver in combining the decorrelating decision-feedback scheme for a synchronous DS/CDMA system is considered. Using the Gaussian approximation on the multiple-access interference and amplitude estimation errors, we derive a closed form expression for the BER performance of the decorrelating decision-feedback detector in single-path Rayleigh fading channel and power controlled system. And, we show that our analysis agrees with the results of simulations. A modified decision-feedback detector is also proposed and analyzes. Numerical results show that the modified dicision-feedback detector proposed in this paper results in enhanced performance.