Multimedia Communication Networks Research Articles

Study of self-similarity in variable bit rate video sources

Variable bit rate (VBR) video will be the predominant application in the future’s multimedia communication networks. Understanding the characteristics of VBR video is important for us to utilize network resources effectively. A brief description of MPEG-1 video sources is given. The essentials of self-similarity and long-range dependence are also presented. Furthermore, some methods of estimating Hurst parameter are described in details. We analyze an hour-long MPEG-1 video trace, and the details of statistical results are discussed. The results highlight that the trace generated by MPEG-1 code has both the short-range dependence and long-range dependence structures.

Vets on the Net.

THE Internet is a multimedia communications network which spans 100 nations across the globe and incorporates 61,000 individual computer networks. Currently undergoing explosive growth, the Internet is expected to reach...

A MAC protocol supporting wireless video transmission over multi-code CDMA personal communication networks

Code Division Multiple Access (CDMA) has become an attractive technique for medium access control in multimedia Personal Communication Networks (PCN). In this paper, a multi-priority medium access protocol for multimedia PCN is proposed and studied. The multimedia PCN uses H.263 implementation to transmit video data. We exploit the features of CDMA to maximize the utilisation of the system capacity. A random access control scheme is proposed for the mobile hosts to contend for spectrum resource. Both Forward Error Correction (FEC) and Automatic Repeat Request (ARQ) schemes are used to handle video transmission error. Simulation results have been presented to show how several system parameters can be tuned to improve the system performance.

ALPEN: An ATM multi-protocol emulation network based on periodical performance checks between edge nodes

This paper proposes a new network architecture, ALPEN (ATM multi-protocol emulation network), based on a new concept for realizing full-scale multimedia communication networks. In ALPEN, various communication protocols, such as ABR (available bit rate), FRM (fast resource management), or SHM (short hold mode), can be handled using a single, simple transit network. Each protocol is emulated at the edge node of the WAN (wide area network), and the status of the transit network is checked by periodically examining the residual bandwidth information of each route. ALPEN is a cost-effective and flexible network architecture because it enables us to implement new services or protocols easily by modifying only the edge nodes. In ALPEN, since individual edge nodes periodically obtain the bandwidth information, it is possible to respond promptly to a user's request to change his bandwidth. In particular, when the network's RTT (round trip time) is long, as in a WAN, ALPEN is a promising way to resolve the problem of performance responsibility. Although each edge node periodically checks the disperse information to all destination edge nodes on a residual bandwidth, the information might be old, or it might be necessary to process it independently at the multiple edge nodes. Therefore, the parameter of “effective residual bandwidth” is estimated by a statistical method; the estimation also considers that bandwidth resources may be overbooked by multiple edge nodes. The statistical method is described in this paper. The ALPEN introduced in this paper is an effective architecture that makes it possible to implement new or various unforeseeable network services in the future multimedia era, in which various services and protocols may exist simultaneously. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(8): 19–31, 1998

Source-based delay-bounded multicasting in multimedia networks

In multimedia communication networks, the problem of multicasting assumes a new dimension. Apart from minimizing the cost of multicast communication, it is also necessary to ensure that each of the destination nodes receives the message within a bounded delay. Such delay-bounded multicast applications typically arise in multimedia conferencing. In this paper, we present a genetic algorithm for solving the delay-bounded multicast problem. We assume source-based routing, i.e. each source node completely determines the Steiner tree along which multicasting is performed. The genetic algorithm is a powerful optimization tool, and our experimental results reveal that a genetic algorithm provides fast and superior quality solutions to the delay-bounded multicast problem.

The Neural Network Approach To A Parallel Decentralized Network Routing

With the progress of high-speed optical transmission and packet switching, a large capacity packet-based multi-media communication network is expected to spread rapidly. One of the key issues in these networks is the network routing that chooses the route to the destination for packet transmission in the network. In most previous work, the whole network is mapped to a large size-Hopfield-type neural network. Hence, the network routing by this method is not beyond the centralized control. In this paper, a parallel decentralized Network Routing method is presented. The model comprises an interconnection of groups of an intraconnected network, which is fully connected, and resides at each node of the communication network. Since the dynamics of each neuron in the whole system follows a unique state equation, we can see easily how the update of a neuron maps to real world network routing problems. Most important, becauase of the dynamics of the neurons with such a high speed of convergence, the model has the ability to achieve a sub-optimum routing solution in a real-time application. Finally, simulation results validate the proposed method.

A Psychophysical Evaluation of Frame Rate in Desktop Video Conferencing

The quality of digital video transmitted over computer networks can suffer from a variety of degradations. Little research has addressed perceptions of degraded digital video image quality. This paper reports on a study in which a psychophysical method, magnitude estimation, was used to develop a ratio scale of image quality for frame rates between 1 and 28 frames per second (fps). Five different scenes were used as stimuli, each varying in terms of filming speed, level of detail, and content. Results indicate that for non-traditional conferencing applications, image quality is not perceived to be better at rates greater than 10 fps. For a traditional conferencing application, a linear increase in image quality perception is associated with a linear increase in frame rate. Results are presented in terms of trend analysis, Steven's Power Function, and parametric statistics. Implications are made for the design of multimedia communication networks.

Broadcast scheduling in packet radio networks by Hopfield neural networks

A multihop packet radio network is a packet switching network where nodes communicate by radio signals. When used in real-time multimedia or military communication networks, it is very important to broadcast a packet from a source node to all other nodes as quickly as possible. Unfortunately, the problem of finding an optimal schedule to minimize the time needed to complete the broadcast for a general multihop packet radio network is NP-complete. We propose a Hopfield neural network solution for one-source-node broadcasting in a multihop packet radio network. The proposed neural network model always finds a good solution by trying to maximize the number of correctly receiving nodes in every time slot. Experiments indicate good results. The model requires n processing elements (neurons) for an n-node radio network.

Flexible multi-QoS logical ATM network (full-net)

This paper proposes Full-Net (Flexible Multi-QoS Logical ATM Network), a simple, flexible, and cost-effective network architecture that will enable the development of an advanced multimedia communications network. The backbone of this Full-Net is a VP (virtual path) network where mesh interconnection is made possible between all VCH (virtual channel handler) switches. End-to-end QoS (quality of service) control is executed at access points to the VP network to map out each optimum VC (virtual channel) according to the VCs' respective service characteristics. This is done independently and simultaneously on the same physical ATM network. In the proposed network, a relatively small size switching system is utilized as a transit switch or a local switch depending on the service request. That is, the logical topology of the VC network is altered in response to individual service requests, and multiple VC networks are realized by overlapping them on the same physical network. In order to assure high QoS and construct an optimum VC network, two parameters which characterize the VC network topology are introduced; one is the disjoint route D and the other is the hop limit H. Traffic reliability is the most important QoS factor, and it is shown that an optimum disjoint number D can be determined to maximize the network resource. In the Full-Net, it is clearly shown that it is possible to control easily the end-to-end delay characteristic, also a critical QoS factor, at one or two VCH access points to VP network. The flexible node system PUN (programmable unified node) used in the Full-Net is also described in this paper. The Full-Net described is proposed as an efficient solution for sophisticated network architectures which will satisfy the demand for new services and will flexibly meet the varying demands of the future multimedia age. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(6): 47–58, 1997

NeuroNet: collaborative intraoperative guidance and control

Neurophysiological monitoring assesses CNS structure function relationships during surgery. NeuroNet supports remote performance of this task through real time multimodal data processing and multimedia network communication. The system is fully integrated, transparently combining the collection, processing, and presentation of real time data sources, including all physiological monitoring functions, with non real time functions and extensive online database information. Workstations are mounted in instrumentation racks and configured with appropriate electronics to support various data acquisition tasks including electroencephalograms (EEGs), electromyograms (EMGs), and multimodality evoked potentials. Multiple racks can be used in parallel on the same case if the number of variables to be monitored exceeds the capacity of a single tack. The data acquired on these systems is transparently accessible, in real time, across the network for both review and analysis.

Advances in satellite CDMA transmission for mobile and personal communications

An ubiquitous network for multimedia personal communications (Personal Communications Network (PCN)) with small, individual low-cost terminals is one of the most ambitious worldwide projects for the 21st century that are being pursued nowadays. In the development of such PCN, Geostationary, Medium, and Low Earth Orbiting (GEO, MEO, LEO) satellite constellations will play a fundamental role to provide worldwide coverage for most services required by the end-user. The characteristics of efficiency and flexibility inherently required by that scenario suggest, amidst other possibilities, to take into special consideration a radio interface based on code division multiple access (CDMA) to ensure, in addition to the features mentioned above, a sufficient grade of power and spectral efficiency of the relevant satellite radio link. The aim of this paper is a review of the current status of those issues in the field of satellite CDMA transmission systems design that, in our opinion, appear fundamental to the successful operation of an efficient PCN. In particular, we survey the techniques for multiplexing, coding and transmission of direct-sequence spread spectrum (DS/SS) signals, and we touch upon the techniques for the minimization of the self-noise effect, and the related topics of power-control and multiuser detection. We also shortly address in this respect some technological aspects related to an efficient modem design via digital signal processing techniques. The final part of the paper deals more specifically with some typical issues of satellite transmission, namely the minimization of the detrimental effects of the nonlinear satellite transponder and of multipath propagation; the applicability of diversity reception to a multisatellite network is also addressed as possible means of performance boost.

Multimedia communication era and network technologies

Multimedia communication era and network technologies

Capacity assignment algorithm for packet switching network with different grades of service

A multimedia communication network is expected to treat various kinds of information, e.g., voice, image, and data which have different demands of grade of service. Furthermore, in new high-speed networks, end-to-end delay distributions or packet-loss probabilities rather than average delays become more important performance measures. This paper presents a new heuristic design algorithm for packet switching communication networks in which the end-to-end delay distribution and packet-loss probabilities are adopted as design constraints. It is shown that, while the total cost is increased slightly when compared with the former approach, end-to-end delays and packet-loss probabilities between every two end-nodes can satisfy predefined constraint as expected.

特集 次世代画像メディアへの期待 ３． 次世代画像メディアの基礎技術 ３‐４ 移動通信網の展望とマルチメディア化の課題

特集 次世代画像メディアへの期待 ３． 次世代画像メディアの基礎技術 ３‐４ 移動通信網の展望とマルチメディア化の課題

Multimedia communications for users

Research on next-generation multimedia communications services and technologies within a highly interdisciplinary research program that encompasses behavioral science, computer science, and electrical engineering is discussed. The authors state that they have taken an approach to their research that allows the needs of users and the demands of end-to-end applications to shape the future of the multimedia communications network. They use several examples to show how such a perspective affects the development of practical, advanced communications services. These examples span a wide range, including: empirical studies of people's use of technology to communicate in collaborative work settings; the design of software supporting the real-time network delivery of interactive multimedia documents for casual information users in the home; and the creation of next-generation prototypes that support the transmission and viewing of multimedia information in homes, offices and classrooms.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Baseband emulators for the protocol testing of multimedia communication networks

The testing of protocols for survivable computer communications networks that use different propagation media, so that the vulnerability of any one medium is offset by the availability of another, is considered. The design and construction of a prototype testbed that can emulate the effects of a stressed medium at either a packet or bit level is discussed, with particular reference to the Multi-Media Link Emulation currently under development. The design incorporates emulation-service protocols that fit in below the user packet switch network protocol and replace the actual user physical link layer and makes use of a seven-event fault set. The components of the ultimate system and its present implementation status are described. >

THE HUMAN INTERFACE IN A MULTIMEDIA COMMUNICATION TERMINAL

New multimedia communication networks such as ISDN and office Automation communication systems are being rapidly introduced into existing communication networks. Easy-to-use human interfaces are important to bring out the full potential of these advanced networks. This paper describes the human interface in a multimedia communication terminal, the Image Station.