Intending to contribute to constructing better multimedia network systems, we propose a new concept of image database system of which form of storage is featuring exponential or graceful oblivion and abrupt recollection like the human memory property. By virtue of this property of database storages that is realized by employing hierarchical or pyramidal image coding, the database memory and transmission costs can be significantly reduced. In this paper we will describe the details of the concept, the results of theoretical analysis based on a simplified model which reveals the effectiveness of the proposed system, the structure of an experimental prototype system and the result of an experimental image retrieval service carried out by implementing it over ATM high speed channels.

This paper is concerned with bandwidth reservation for circuit groups which handle calls requesting asymmetric forward and backward multi-connections. A model of circuit group with sub-group configuration is treated, and two types of the bandwidth reservation schemes for the model are studied in this paper. One is a global scheme with monitoring the whole circuit group, and the other is a local scheme with monitoring each sub-group independently. The problems of optimizing the reservation parameters are formulated, and optimization methods for the problems are proposed. Numerical example are presented, and effectiveness of the reservation schemes with using the optimized parameters is numerically examined.

Intricate Speech Communication Mode (I-SC Mode) is observed in verbal interaction during ISDN-TV conferencing. It is characterized by conflicts and multiple interactions of speech. I-SC Mode might cause mental stress to participants and be obstacles for smooth communication. However, the reasons of I-SC Mode on the environment of information transmission are hitherto unknown. Furthermore, analyses on the talks inside a conference site (LT: local talk or a talk inside a local site) and between remote sites (MT: media talk or a talk between remote sites) are originally conceived on assumed differences in cognitive distance and media intimacy. This study deals with communication effects/barriers and cognitive distance/intimacy of media correlated with audio-video transmission signals and speech modes or talk types and response delay in human speech interactions by using an innovated conference model (decision-making transaction model: DT-Model) in synchronous ISDN-TV conference systems (SYN) and asynchronous ones (ASYN). The effects of intricate communication can be predicted to a certain extent and in some ways. In I-SC Mode, because a timely answer can not be received from recipients (or partner), response time delay and response rate are analyzed. These factors are thus analyzed with an innovated dynamic model, where the recognizable acceptance of delay is evaluated. The nonlinear model shows that the larger the response time delay, the lower the response rate becomes. Comparing the response rate between SYN and ASYN, the latter is notably lower than the former. This indicates that the communication efficiency is lower in ASYN. An I-SC Mode is the main mode that occurs during ASYN conferences, and this in turn causes psychological stress. Statistics show the prevalence of a high incidence of complicated plural talks and a low response rate exists as the main factors preventing smooth human-to-human communication. Furthermore, comparing the response delays in face-to-face LT (Tf) and machine-mediated MT (Tm), human communication delay is significantly extended by the effects of initial mechanical delays. Therefore, cognitive intimacy of media is clearly affected by the existence of physical distance.

In order to pave the way to B-ISDN, one of the most important issues for network providers is to identify the most efficient B-ISDN introduction strategy. This paper focuses on the costs of introducing ATM transmission systems into backbone transport networks which must provide highly reliable broad band transmission capability. In this context, the main rival to ATM is Synchronous Transfer Mode (STM); recent Synchronous Digital Hierarchy (SDH) equipment supports the establishment of advanced STM-based high speed transport networks. This paper offers a cost comparison of ATM and STM based backbone transport networks. A digital path network in STM has a hierarchical structure determined by the hierarchical multiplexing scheme employed. The minimum cost STM path network can only be determined by developing a path design method that considers all hierarchical path levels and yields the optimum balance of link cost and node cost. Virtual paths have desirable features such as non-deterministic path bandwidth and non-hierarchical and direct multiplexing capability into high speed optical transmission links. These features make it possible to implement a non-hierarchical VP network with ATM cross connect systems which can handle any bandwidth VP with a universal cell switching function. This paper shows that the non-hierarchical VP routing, which strongly minimizes link cost, can be implemented without significantly increasing node cost. Network design simulations show that the virtual path scheme, possible only in an ATM network, yields the most cost effective path network configuration.

A goal of a broadband ISDN network is to provide integrated transport for a wide range of applications such as teleconferencing, entertainment video, and file distribution. These require multipoint communications in addition to conventional point-to-point connections. The essential component to provide multipoint communications is a multicast packet switch. In this paper, we propose and analyze a new parallel multicast packet switch which easily approaches a maximum throughput of 100% as the number of fanout and multicast rate are increased. The proposed switch consists of a simple ring network and a point-to-point switch network in parallel. The ring network provides both replication and routing of multicast packets. The point-to-point switch network is responsible for delivering only unicast packets. The ring network provided in this switch overcomes the problems of clock synchronization and unfairness of access in the slotted ring by synchronizing the ring to the time slot used in the point-to-point switch and providing small amount of speed-up. Moreover, the significant drawbacks of the basic cascaded multicast fabric design are removed in this parallel switch which can separate the unicast and multicast packets before entering the switch fabric. The performance analysis shows that this switch with the small size of input/output buffers achieves good performance in delay and throughput, and the packet loss probability less than 10-9.

The transmission and processing of multimedia information requires a high-speed communications network infrastructure. This is especially true for the networks between the user's computer and the information highway. An Ethernet LAN is widely used for these networks, but it has limited throughput. Asynchronous Transfer Mode (ATM) LAN technology is a promising approach to overcome this limitation. We have developed a chip set which can be used to connect personal computers (PCs) and workstations (WSs) to a 156-Mbps ATM LAN. The advanced architecture, optimized performance and efficient buffer management enables a sustained more than 100 Mbps transfer speed to be obtained. The chip set is implemented in a 0.8 µm triple metal-layer CMOS process to integrate total 460 K transistors and consumes total 4 W at 5 V.

Realizing an effective channel connection scheme and a useful human-machine interface is important for popularizing the audio-visual communication services that should become significant in the near future. This paper describes a terminal design that is applicable to various audio-visual communication services. First, future audio-visual services are classified into three types: Videophone, Tele-monitoring and Video On Demand(VOD). The requirements for these services are discussed in detail. Second, a channel connection scheme is specified taking into consideration for the requirements and characteristics of various networks such as N-ISDN and LANs. Terminals based on these specifications are developed as prototypes and demonstrated to confirm the validity of these specifications.

In this paper we propose a congestion control method for interconnecting connectionless MANs with ATM networks which works at the gateway of DQDB. Since connectionless traffic belong to loss sensitive data, they should experience small cell loss rate. Due to the function of congestion control in the gateway, we can prevent the network from overload which not only introduces serious cell loss at remote destination gateway but also lots of undesirable retransmissions and time delay in the ATM network. It neither needs to modify the slot format of DQDB nor to increase the overhead so the implementation is simple and cost effective. Performance results are also provided to verify the effectiveness.

This paper presents a newly developed analytical method which evaluates the virtual path bandwidth control effects for a general topology ATM (Asynchronous Transfer Mode) transport network. The virtual path concept can enhance the controllability of path bandwidth. Required link capacity to attain a specified call blocking probability can be reduced by applying virtual path bandwidth control. This paper proposes an analytical method to evaluate the call blocking probability of a general topology ATM network, which includes many virtual paths, that is using virtual path bandwidth control. A method for the designing link capacities of the network is also proposed. These methods make it possible to design an optimum transport network with path bandwidth control. Finally, a newly developed approximation technique is used to develop some analytical results on the effects of dynamic path bandwidth control are provided to demonstrate its effectiveness.

This paper proposes two algorithms for defining a routing domain in multiclass-of-service networks. One an off-line-based method, whose objective is to optimize dynamic routing performance by using precise knowledge on the traffic levels. The algorithm of the proposed method takes into account the random nature of the traffic flow, which is not considered in the network flow approach. The proposed method inherits the conceptual simplicity of the network flow approach and remains applicable to large and complex networks. In simulation experiments, the proposed off-line-based method performs better than the method based on the network flow approach, but has a similar the computation time requirement. The other method proposed here is an on-line-based method for application to B-ISDNs, where precise traffic data is not expected to be available. In this method, the routing domain is defined adaptively according to the network performance (call-blocking probability) measured in real-time. In simulation experiments, the performance of this method is comparable to that of the off-line-based method--especially when highly efficient dynamic routing is used. This paper also derives and describes methods for approximating the implied costs for multiclass-of-service networks. The approximations are very useful not only for off-line-based routing domain definition (RDD) methods but also for other kinds of network controls or optimal network dimensioning based on the concept of revenue optimization.

This paper describes a fully digitized modem designed for variable baud rate transmission systems with the aim of efficiently providing multimedia services over a wireless communication network. The concept of a variable baud rate wireless communication system is discussed focusing on the access scheme and channel allocation from the viewpoint of frequency utilization efficiency. For easy system construction, we propose a fully digitized variable baud rate modem based on multirate digital signal processing, taking into account the need for even performance and easy clock control for all transmission rates. We also discuss the operational principle of modulation, the degradation factor in the A/D converter, and the configuration of the clock recovery circuit. Steady modulation performance can be kept by generating the same frequency system clock for all transmission rates and using the sampling rate conversion technique without selecting the channel filter for each transmission rate. It is proved by the analysis of the degradation factor in the A/D converter that only the bandwidth of the channel filter in demodulator should be changed for the transmission rate. A double loop clock recovery configuration capable of both tank-limit type and baseband estimation type clock recovery is shown to be suitable for this system. The tank-limit clock recovery circuits can be constructed easily by employing a tank circuit array. Finally, we present experimental results for a modem having transmission rates of 1.544Mbps and 6.312Mbps for the digital hierarchy and information speed of video signals such as MPEG-1 and MPEG-2. The measured basic performance of the proposed modem shows it delivers superior performance without the need for precise adjustment when a QPSK modulation scheme is employed.

Calls using different media which require different transfer quality will arrive at ATM networks. Therefore it is important to develop a method for allocating network resources efficiently to individual calls by judging admission of calls. Various call admission control schemes have been already proposed, and these schemes assume that users specify values of traffic descriptors when they originate calls. However, it is sometimes difficult for users to specify these values accurately. This paper proposes a new ATM call admission control scheme based on cell transfer state monitoring which does not require that users specify values of traffic descriptors in detail when they originate calls. In this proposed scheme, the acceptance or rejection of calls is judged by comparing the monitored cell transfer state value with a threshold prepared in advance. This threshold must be adjusted according to changes in the characteristics of traffic applied to ATM networks. This is one of the most serious problems in the control scheme based on the monitoring of cell transfer state. Herein, this paper proposes neural network application to the control scheme in order to resolve this problem and improve performance. In principle, the threshold can be adjusted automatically by the self-learning function of the neural network, and the control can be maintained appropriately even if the characteristics of traffic applied to ATM networks change drastically. In this paper, the effectiveness of the application of a neural network is clarified by showing the configuration of this proposed control scheme with the neural network, a method for deciding various parameter values needed to implement this control scheme, and finally the results of a performance evaluation of the control scheme. Inputs required by the neural network are also discussed.

The recent progress of B-ISDN signaling systems has enabled networks to handle calls which require a wide variety of ATM connection sets. This paper is concerned with the circuit group which handles calls requesting asymmetric forward and backward multi-connections, and has the capability of both bandwidth negotiation and bandwidth reservation as a traffic control for enhancing call blocking performance. A model of the circuit group is first established focusing on the call level characteristics of the group, and then a method based on the reduced load approximation and an approximate analysis of a multirate group is proposed for calculating approximate blocking probabilities. The accuracy of the approximation method is evaluated numerically by comparing with an exact method and simulation. Further the impact of bandwidth negotiation and reservation on call blockings is examined based on numerical examples.

This paper proposes a hybrid access control scheme for broadcast-based ATM-LANs. Broadcast-based ATM-LANs are shared media networks with star topology. In this network, packets are broadcast to all subscriber terminals by a CPYF (Cell COPY Function) node located in the ATM network and only relevant packets are extracted and sent to the destined user layer function by packet filtering functions in the terminals. The simplicity of the packet transfer mechanism makes the network very economical. In broadcast-based ATM-LANs, the hybrid access control scheme is effective in improving performance. In this scheme, short packets and long packets are transmitted respectively by means of a back-pressure type and a CSMA/CD type access control scheme. Throughput evaluation was performed by computer simulation and the results show that the proposed scheme achieves a high throughput characteristic.

We investigated performance of routing schemes in B-ISDN, for heterogeneous traffic flows under various bandwidths. In particular, we compared the simulated performance of these schemes by evaluating their blocking probabilities. To achieve high performance, these schemes use special kinds of routing algorithm, one which is pre-selection algorithm and one which is cyclic algorithm. We investigated the efficiency of the pre-selection algorithm and the robustness of the cyclic algorithm for nonuniform traffic and network resources. We found that these routing algorithm schemes can compensate for errors in resource design.

A uniquely-structured Usage Parameter Control (UPC) method named Virtual-shaping is proposed which considers cell arrival time jitter between user and UPC point. The method uses a modified Dangerous Bridge UPC circuit (Sliding window type) and virtually (logically) shapes cell traffic using cell arrival time compensation to offset cell delay variation (CDV). In addition, the proposed method is based on a cell-buffer-less structure and can be realized with reasonable hardware. The method yields precise and accurate monitoring. Computer simulations show that the method offers higher network utilization than the conventional Leaky Bucket based UPC method. The proposed method will make it possible to create more effective B-ISDNs, and more cost-effective broadband VBR services.

This paper examines performance study items for ATM connections in B-ISDNs. We consider the characteristics of B-ISDN performance and describe the current status in ITU-T and the ATM Forum. On this basis, we propose a new performance framework and performance criteria. We also describe objectives for ATM cell transfer performance.

This paper deals with network performance of 64kbit/s-based services supported in an ATM network and an ATM interworking network with 64kbit/s-based networks. It first clarifies network performance issues giving a model and objectives of study and experiment. A result of computational analysis is then presented, where a cell loss ratio of an order of 10-4 or 10-5 is obtained to give a performance equivalent to that currently used as objective values in existing networks for a 64kbit/s digital level. In order to capture the impact of cell loss and associated performance for application levels, an experimental test has been carried out using typical applications. Test results show that the cell loss ratio needs to be approximately ten times better than the bit error ratio for comparable performance for application levels. A cell loss ratio of better than 10-5, or an order of 10-6 considering an interworking situation, seems to be necessary according to the test results. It is further clarified by the test that a single cell is more valuable than a multiplexed cell for providing better cell loss resilience characteristics. Although not all applications of 64kbit/s networks have been tested, it is expected that the test results can be used as guidance for considering the support of 64 kbit/s services in an ATM and interworking networks.

Recently as one of attractive applications in the B-ISDN era, LAN/MAN interconnection through an ATM network has been coming up because burstiness of LAN/MAN data traffic is applicable to distinctive features of cell based ATM network. In order to overcome a difference of the connection mode, i.e., CL packet transfer of LAN/MAN and CO cell transfer of ATM network, a number of interworking and bandwidth allocation mechanisms have been proposed. These methods, however, indicate both merits and drawbacks concerning with CL data transfer quality, network resource efficiency and processing overhead in IWU/CLS and the network, and have been mostly evaluated only for a single IWU model. This paper aims at showing the most appropriate method of LAN/MAN interworking for IWU-IWU or IWU-CLSF connection. In the paper, some interworking issues including a general qualitative assessment are clarified. We then evaluate the selected five interworking methods based on Bandwidth Renegotiation (BR) and VC Establishment (VCE), which are combined with Traffic Enforcement Functions (TEFs) based on policing mechanisms and Cell Loss Control (CLC) scheme. By transient and stationary simulation approach for a single IWU and an IWU-CLS connection model, the most applicable method is indicated as a case study from view points of the communication quality, effective use of the bandwidth and processing load.

In current teleteaching systems, video conferencing systems have been used to transmit a motion video from a teacher's site. A video that captures a teacher or his or her chalkboard is transmitted to a remote site through a communication channel. Since the resolution of the video is not very high, a camera captures either a teacher or a chalkboard, but not both at the same time. Thus, remote students have difficulty in obtaining realistic sensation. Another approach to realizing teleteaching is to use a computer-based desktop conferencing system that supports a motion video and a computer-based shared chalkboard. In this approach, a teacher has to use a mouse or a handwriting tablet for input, and therefore cannot use a real chalkboard. Moreover, the teacher cannot use gestures to remote students. This paper presents a multimedia teleteaching system that integrates an electronic whiteboard with a multimedia desktop conferencing system for providing realistic sensation to remote students. The system provides two-way communication of a video and a computerized chalkboard. A teacher uses an electronic whiteboard as a real whiteboard using direct manipulation, and transmits his or her gestures to remote students by using video communication. The system provides dual views; one view is for teacher's gestures and the other is for chalkboard contents. By providing the dual views, the system can transmit teacher's gestures all the time. Since chalkboard contents are processed and displayed as computer data, students can see them clearly. With the computerized chalkboard, a teacher or a student can zoom contents, input data written on a paper using a scanner, or add annotation.