A channel equalization technique on a time division duplex CDMA/TDMA system for wireless multimedia networks is investigated, and the bit error rate performance of the system is theoretically analyzed. The assumed network connects mobile terminals to a node of ATM based high speed LAN through a radio central unit. Only human interface facilities are implemented into the terminal so that users access integrated services through the node of the network. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit human interface signals and the downlink employs a TDMA scheme to transmit display interface signals. Both the CDMA and the TDMA signals occupy the same frequency band. To mitigate bit error rate degradation due to fading, the radio central unit estimates the impulse response of the channel from the received CDMA signals and subtracts the replica signal to cancel the major intersymbol interference (ISI) component. Numerical results using the Nakagami-m fading model and recent propagation measurements show that the proposed TPC technique compensates the fading attenuation and the proposed CEQ cancels the major ISI component. The bit error rate performance of the downlink with the proposed CEQ is superior to that with the DFE by 12dB of the symbol SNR at the BER=10-6 over a specular channel, and the system with the proposed CEQ achieves a BER=10-6 at the symbol SNR=12dB. Furthermore, the channel equalizer is implemented without increases in complexity of the terminal because all the processing on the equalization is carried out only in the radio central unit.

The firing squad synchronization problem is considered for defective cellular automata. A lower bound of time tf for the problem is derived. The state complexity to solve the problem is investigated and it is shown that the state set has to be arbitrary large to obtain solutions of time complexity (n). For memory-augmented defective cellular automata a tf-time solution is given.

This paper describes a flexible point-to-multipoint access protocol for the fiber-optic passive double star (PDS) system. To provide various types of services, and permit flexibility in changing transport capacity, a time division multiple access (TDMA) scheme for the PDS system is considered. Dynamic time slot multiplexing based on TDMA is proposed to provide required time slots efficiently according to service changes. The effectiveness of dynamic time slot multiplexing is calculated and compared to fixed time slot multiplexing for telephony services. A TCM/TDMA frame structure and an access protocol enabling dynamic time slot multiplexing are proposed. ONU bandwidth is dynamically assigned by using a set of pointers. The ONU access protocol causes no interruption to operating ONUs on the same PDS system during the configuration or reconfiguration of an ONU. The access time is analyzed to estimate the performance of the access protocol. The probability density of access time is calculated for the number of ONUs connected. The calculation results indicate that a PDS system can accommodate up to around 60 ONUs within the maximum access time specified by ITU-T. The experimental results also agree fairly well with the theoretical values.

This paper describes analytical results of high-Tc superconducting asymmetric coplanar strip lines using the frequency-dependent finite-difference time-domain method. The propagation constants of the YBa2Cu3O7-x asymmetric coplanar strip line fabricated on the LiNbO3 substrate are reported. The effect of the SiO2 buffer layer is also investigated.

New multimedia applications have emerged on top of information infrastructures, such as on-demand services, digital libraries and museums, online shopping, information Q & A, concurrent engineering, document management, and desktop program production, which require new databases. That is, next-generation database systems must enable users to efficiently and flexibly develop and execute such advanced multimedia applications. Moreover, in some applications, there is no existent data; in others, there are databases or files to be integrated. This requires both top-down and bottom-up database development. To this end, we focus on development of a database system which enables flexible and efficient acquisition, storage, access and retrieval, and distribution and presentation of large amounts of heterogeneous media data. In particular, we propose a multimedia data model as an integration of structural, temporal, spatial, and control functionality. That is, we take an approach based on an object-oriented database, which is more suitable for description of media structures and operations than a traditional relational database. And we extend the object-oriented approach by providing temporal and spatial operators, and control of distributing computing and QOS (quality of service). In this paper, we describe a multimedia data model and its efficient implementation.

Multimedia communication services are being made available with the advent of broadband optical fiber networks. As many different services will be accommodated in such networks, network survivability has been recognized to be a crucial concern. In this paper, we propose a new restoration algorithm for ATM networks providing multimedia services. Our proposed restoration algorithm adopts the message bundling scheme of the Multi-Destination Flooding (MDF) algorithm which was previously proposed for STM-based networks to handle catastrophic failures such as multiple link and node failures. Virtual Paths (VP) with the same communication speed are bundled and Operation Administration and Maintenance (OAM) cells are used for communication of restoration messages. In addition, the following modifications are made on the original MDF to improve restoration performance. The pre-cancellation scheme is adopted to arbitrate reservation contention to realize high restoration ratio. The dual queue scheme is applied to avoid congestion of restoration messages. Moreover, the connection control scheme for VPI connections is proposed to prevent alternative routes from being misconnected. This paper describes the design concept of our restoration algorithm, processes in each restoration phase, and the performance evaluation by computer simulation.

This paper gives several explicit formulas for the waiting times in each stage in an alternating-service, two-stage tandem queue (M/G/1 type queue) with a gate in the first stage and server vacations (or setup time). These formula are obtained by using simple conversion relationships between the performance measures. This study has been motivated by the performance evaluation of call (packet or message) processing in telecommunication switching systems.

This paper presents a general method for computing quantitative information about finite-state real-time systems. We have developed algorithms that compute exact bounds on the delay between two specified events and on the number of occurrences of an event in a given interval. This technique allows us to determine performance measures such as schedulability, response time, and system load. Our algorithms produce more detailed information than traditional methods. This information leads to a better understanding of system behavior, in addition to determining its correctness. The algorithms presented in this paper are efficiently implemented using binary decision diagrams and have been incorporated into the SMV symbolic model checker. Using this method, we have verified a model of an aircraft control system with 1015 states. The results obtained demonstrate that our method can be successfully applied in the verification of real-time system designs.

Synchronization of media streams is recognized as an important requirement not only in media retrieval such as a video on-demand service but also in groupware such as a remote conferencing system. In a remote conferencing system, synchronization is more complicated because Live Media Streams (LMS) such as the live raw voice of some participants must be taken into consideration as well as Retrieved Media Streams (RMS) such as media streams retrieved from video equipment. In this paper, we propose a mechanism to synchronize RMSs and LMSs in a remote conferencing system DMSIC (Distributed Multimedia System with Interactive Control) which has been implemented on UNIX workstations connected by Ethernet. In this mechanism, synchronization among RMSs (we call it R & R synchronization) is kept by maintaining the Current Presentation Positions (CPP) on Media Buffers (MB) close to the Ideal Presentation Position (IPP). Synchronization among RMSs and LMSs (we call it R & L synchronization) is kept by adjusting the IPPs among multiple nodes. We have implemented the synchronization mechanism in DMSIC to confirm the effectiveness of it.

At the beginning of the 21st century, 1 Gb DRAMs will be in practical use, and sufficient in terms of memory capacity for most memory applications systems. The key technologies for multimedia systems include data compression, communication, storage, and human interfaces. Image data processing, ATM switch, and microprocessor in multimedia applications require the high data transfer rate from several 100 Mbits/s to Tbits/s. Storage systems, on the other hand, require the reduction of the price per bit to less than 10 cents/Mbytes. Application specific design approaches towards a system-on-chip are strongly needed for ULSI memories in the multimedia era.

Recently, through high speed computer networks, multifarious information such as text, moving and still images, video, voice and control data is available. There is a natural demand to store such multimedia data in databases to facilitate their reuse in a wide variety of applications. Therefore, important research issues pertain to the investigation of appropriate database systems in multimedia computer network environments. In this paper, we first discuss the required technologies for multimedia information systems. Then we look at many multimedia information services through computer networks, and consider the importance of storing and effectively reusing such available multimedia data. To facilitate developing databases for use in these environments, we discuss the evolution of the notion of database systems. Finally, we demonstrate, as practical examples of such database systems, two prototype systems that we are currently implementing, i.e., the campus wide news on demand system and the ASN. 1 database system.

The goal of this paper is to propose a new symbolic model checking approach named time-space modal model checking, which could be applicable to verification of bit-slice microprocessor of infinite bit width and one dimensional systolic array of infinite length. A simple benchmark result shows the effectiveness of the proposed approach.

A novel wireless multimedia network employing a time division duplex CDMA/TDMA scheme is proposed. The network connects mobile multimedia terminals to an ATM based LAN through a radio central unit, and provides both uplink and downlink with unbalanced data rates in the same frequency band. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit low speed human interface signals (-2.4kbit/s), and the downlink employs a TDMA scheme to transmit high speed video signals (-24Mbit/s). The data rates of both links are independent from that of the LAN. The uplink also employs a RAKE receiver and a forward error correction (FEC) scheme using a BCH code in order to reduce bit errors caused by multipath fading. To mitigate channel degradation caused by the near-far problem and multipath fading, a transmission power control (TPC) method for both links and a channel equalizer (CEQ) for the downlink are proposed. The control signals for the TPC and the CEQ are estimated from the impulse response of the channel which is extracted as the output of the matched filters in the CDMA receiver. Theoretical analyses are performed to evaluate the bit error rate (BER) characteristics of the proposed network. The BER performance is derived for a general multipath fading condition modeled by the Nakagami-m distribution and a typical delay profile. Numerical calculation using recent propagation measurements shows the bit error rates of both uplink and downlink to be less than 10-6 when both of the TPC and the CEQ are employed if there are some specular components in the received signals. This excellent performance can cut a way to realize a mobile multimedia terminal for customer premises. Furthermore, the configuration of the mobile terminal is quite simple even if the high speed TDMA signals are received over a multipath fading channel.

This paper proposes a functional video handling technique based on structured video. The video handling architecture, which includes a video data structure, file management structure, and visual interface structure, is introduced as the core concept of this technique. One of the key features of this architecture is that the newly proposed video indexing method is performed automatically based on image processing. The video data structure, which plays an important role in the architecture, has two kinds of data structures: content and node. The central idea behind these structures is to separate the video contents from the processing operations and to create links between them. Video indexes work as a backend mechanism in structuring video content. A prototype video handling system called the MediaBENCH, a hypermedia basic environment for computer and human interactions, which demonstrates the actual implementation of the proposed concept and technique, is described. Basic functions such as browsing and editing, which are achieved based on the architecture, exhibit the advantages of structured video handling. The concept and the methods proposed in this paper assure various video-computer applications, which will play major roles in the multimedia field.

A multi-layer perceptron (MLP) acting directly in the time-domain is applied as a speech signal enhancer, and the performance examined in the context of three common classes of degradation, namely low bit-rate CELP degradation is non-linear system degradation, additive noise, and convolution by a linear system. The investigation focuses on two topics: (i) the influence of non-linearities within the network and (ii) network topology, comparing single and multiple output structures. The objective is to examine how these characteristics influence network performance and whether this depends on the class of degradation. Experimental results show the importance of matching the enhancer to the class of degradation. In the case of the CELP coder the standard MLP with its inherently non-linear characteristics is shown to be consistently better than any equivalent linear structure (up to 3.2 dB compared with 1.6 dB SNR improvement). In contrast, when the degradation is from additive noise, a linear enhancer is always, superior.

The recursive least-squares filter and fixed-point smoother are designed in linear discrete-time systems. The estimators require the information of the system matrix, the observation vector and the variances of the state and white Gaussian observation noise in the signal generating model. By appropriate choices of the observation vector and the state variables, the state-space model corresponding to the ARMA (autoregressive moving average) model of order (n,m) is introduced. Here,some elements of the system matrix consist of the AR parameters. This paper proposes modified iterative technique to the existing one regarding the estimation of the variance of observation noise based on the estimation methods of ARMA parameters in Refs. [2],[3]. As a result, the system matrix, the ARMA parameters and the variances of the state and observation noise are estimated from the observed value and its sampled autocovariance data of finite number. The input noise variance of the ARMA model is estimated by use of the autocovariance data and the estimates of the AR parameters and one MA parameter.

A noise cancelling sonar-ranging system based on the adaptive filtering technique, which can automatically adapt itself to the changes in environmental noise-field and improve the passive sonar-ranging/goniometric precision, was introduced by this paper. In the meantime, the software and hardware design principle of the system using high speed VLSI (Very Large Scale Integrated) DSP (Digital Signal Processing) chips, and the practical test results were also presented. In comparison with the traditional ranging system, the system not only enhanced obviously the ranging precision but also possessed some more characteristics such as simple structure, rapid operation, large data-storage volume, easy programming, high reliability and so on.

Recent advances of processing speed and window systems in computers, especially workstations, accelerate multi-media data processing (MMDP). Then, a variety of data such as numerics, characters, voice, video, animation and so on, are processed concurrently in a workstation. In data processings, concurrent execution of transactions is a key to improve through-puts. However, concurrent execution without concurrency control may cause inconsistent results. Thus, the concurrency control must be introduced in such systems. However, in MMDP it is ineffective to adopt previous concurrency control methods for ordinal databases since multi-media data are huge and possess a real-time property. This paper discusses concurrency control for MMDP. We propose some new concepts for MMDP, and define a new serializability class called Permissible Serializability which provides high concurrency in MMDP compared with ordinal classes. Then, we propose a concurrency control algorithm TYPE for the Permissible Serializability, and show some simulation results.

Over the last decade, the Internet has been extremely successful by distinguishing between overlaying applications and underlying networking technologies. This approach allows rapid and independent improvement in both networking and application technologies. The internetworking layer that divides applications and the network enables the Internet to function as a general and evolving infrastructures for data communications. The current Internet architecture offers only best-effort data delivery. However, recent emerging computer and networking technologies, demand the Internet guaranteed performance. In particular, audio and video applications have more rigid delay requirement than those applications which the current Internet supports. To offer guaranteed services in addition to best-effort services, both a new service model and a new architecture are necessary in the Internet architecture. The paper surveys researches and experiments conducted in the Internet community to accommodate a wide variety of qualities of services.

In this paper, the ATM Mini-Bar System (AMBS) which is a future information providing service infrastructure is proposed. The purpose of AMBS is to provide a multi-media environment in which a user can (1) select and get quickly any needed information, in low cost, at any time, among very large amount of different media information provided by a variety of providers, (2) be charged only for the information which is selected and used, (3) edit or process informations into users' individually requested style or format before using them. The basic concept and configurations of AMBS are also addressed. This system is basically a center-end oriented one-way information providing system. The information center broadcasts its contents to all user equipments based on a user request forecast, and every user equipment stores the delivered contents in its large storage. A user can select one's needed informations from the storage, and may edit or process them within the user equipment. The charge is only on the read informations from the storage, not on all contents in it. The key points of this system are the following three. (A) Introduction of a broadcast (or multicast) media for economical information delivery (exactly speaking, it is a predelivery which means a delivery before request) to user equipments. (B) Introduction of a 1 to 1 communication network for selective charging and control of each user equipments. (C) Introduction of the user equipment storage for Quick response to user information request in most cases with the broadcast (or multicast) information delivery media described above, Separation of information delivery speed and replay speed to increase system flexibility, Local user information processing or editing. As an example of technical solutions, a memory architecture, which is based on hierarchical architecture, is described. AMBS is expected to give some impacts to information industries because it can integrate many kinds of services into the same platform, but some standerdization items are needed to realize it.