Showing papers on "Broadband networks published in 1988"

Resource allocation for broadband networks

Abstract: The major benefit of a broadband integrated ATM (asynchronous transfer mode) network is flexible and efficient allocation of communications bandwidth for communications services. However, methods are needed for evaluating congestion for integrated traffic. The author suggests evaluating congestion at different levels, namely the packet level, the burst level, and the call level. Congestion is measured by the probabilities of packet blocking, burst blocking, and call blocking. He outlines the methodologies for comparing these blocking probabilities. The author uses the congestion measures for a multilayer bandwidth-allocation algorithm, emulating some function of virtual circuit setup, fast circuit switching, and fast packet switching at these levels. The analysis also sheds insight on traffic engineering issues such as appropriate link load, traffic integration, trunk group and switch sizing, and bandwidth reservation criteria for two bursty services. >

Nonblocking copy networks for multicast packet switching

Abstract: In addition to handling point-to-point connections, a broadband packet network should be able to provide multipoint communications that are required by a wide range of applications. The essential component to enhance the connection capability of a packet network is a multicast packet switch, capable of packet replications and switching, which is usually a serial combinations of a copy network and a point-to-point switch. The copy network replicates input packets from various sources simultaneously, after which copies of broadcast packets are routed to their final destination by the switch. A nonblocking, self-routing copy network with constant latency is proposed. Packet replications are accomplished by an encoding process and a decoding process. The encoding process transforms the set of copy numbers, specified in the headers of incoming packets, into a set of monotone address intervals which form new packet headers. The decoding process performs the packet replication according to the Boolean interval splitting algorithm through the broadcast banyan network, the decision making is based on a two-bit header information. This yields minimum complexity in the switch nodes. >

The impact of the ATM concept on video coding

Abstract: The induction of the asynchronous transfer mode (ATM) concept may significantly influence the coding of video services for broadband networks. The authors show how the absence of a physical channel structure and the ability to switch bursty traffic can be used to enhance video coding. Packetization defects and their impact on picture quality, coding algorithms, and synchronization schemes are studied. The authors describe variable-bit-rate coding and report on the results obtained with a hardware implementation of a variable-bit-rate video codec. Statistical multiplexing gain figures are given. The influence of cell loss on image quality is discussed and simulation results are given. A layered coding model offering good cell loss concealment properties and high flexibility is described. >

A congestion control framework for high-speed integrated packetized transport

Abstract: The authors briefly discuss general congestion control design approaches in the context of integrated, packetized transport for a public, broadband ISDN (integrated services digital network) environment. A framework is developed for the congestion control design that is applicable to asynchronous transfer mode (ATM), and related performance issues and standardization requirements are identified. The proposed congestion control approach is simple, fair, and non-service-optimized, and it allows an explicit tradeoff to be made between transport performance and bandwidth efficiency. Through this framework, the authors envision future integrated multimedia networks where terminals could efficiently shape their traffic flow characteristics to match those required by transport controls. >

Flow control schemes and delay/loss tradeoff in ATM networks

Abstract: Performance and flow control mechanisms, which represent ATM (asynchronous transfer mode) flexibility, are discussed. To control performance, delay- and/or loss-sensitive service classes, and two mechanisms to realize these classes, are proposed. It is shown that it is possible to have better performance than with other mechanisms, such as no-class distinction or simple priority methods. It is further suggested that this performance controllability results in the provision of multiple logical services, including quasi-STM (synchronous transfer mode; compatible with circuit switching), by an ATM network. ATM flow control is based on a call-oriented resource allocation mechanism similar to circuit switching. The concepts of call/line bit rate ratio and multiplexing degree are seen to be significant for efficient use of resources. When the network handles calls with large call/line bit rate ratios, user-specified flow control parameters at the call setup phase are important for resource assignment. The definition of two types of maximum throughput of each call and its usage for resource management are proposed. >

Multichannel bandwidth allocation in a broadband packet switch

Abstract: The problem of bandwidth allocation in a packet switch supporting broadband services is addressed. To reduce the performance constraints imposed by limiting a data link to a single broadband packet channel, the author introduces the concept of channel group as a set of broadband packet channels that is viewed as a single data-link connection by routing entities. He uses a two-step bandwidth allocation scheme. At connection setup time, a call is allocated to a channel group. At transmission time, specific channels of a group are optimally allocated to the packets destined to the group. Because of the statistical smoothing of the large number of sources served by a channel group, the traffic performance of the switch is improved. This scheme also allows super-rate switching, i.e., the support of services with peak bandwidth exceeding the capacity of a single packet channel. The author shows the feasibility of this scheme in a Batcher-banyan switch, by implementing in hardware the bandwidth allocation at transmission time. Performance improvements obtained by this scheme are also provided in different traffic environments. >

Survivable network architectures for broad-band fiber optic networks: model and performance comparison

Abstract: A class of survivable network architectures and a fiber network design model to study quantitative tradeoffs between cost and survivability for each candidate network architecture are discussed. The network architectures studied fall into two categories: conventional architectures are those using present and future technologies, respectively. The model network used in this study is a metropolitan intralocal access transport area (LATA) network. For the near term, the study show that a 'single homing' architecture with 1:N diverse protection provides affordable survivability for fiber cable cuts. The percentage of model circuits protected from link failures is raised from 50%-72% for only 6.3% increase in cost. For future architectures, the self-healing rings could both improve survivability and reduce costs. >

HYPASS: an optoelectronic hybrid packet switching system

Abstract: An architecture is presented for an optoelectronic hybrid packet switching system (HYPASS) for the distribution of multiple-bit-rate broadband services. HYPASS is based on an input-buffered/output-controlled arbitration protocol. The internal routing and interconnection utilizes a passive optical transport network with wavelength-tunable laser transmitters and fixed wavelength receivers. The single-stage multiwavelength optical interconnect provides an internally nonblocking network for large throughput routing of the bit-serial optical signals. An internal optical control network, with fixed-wavelength trouble receivers, sends output port information to the input nodes for arbitration and control. Packet buffer storage and control processing is performed by word-parallel electronic circuitry. The characteristics and device requirements for this design are presented along with results of a performance analysis of the arbitration and control protocol. >

A fast packet switch for the integrated services backbone network

Abstract: With the projected growth in demand for bandwidth and telecommunication services will come the requirement for a multiservice backbone network of far greater efficiency, capacity, and flexibility than ISDN (integrated-services digital network) is able to satisfy. This class of network has been termed the broadband ISDN, and the design of the switching nodes of such a network is the subject of much research. The author investigates one possible solution. The design and performance, for multiservice traffic, is presented for a fast packet switch based on a nonbuffered, multistage interconnection network. It is shown that for an implementation in current CMOS technology, operating at 50 MHz, switches with a total traffic capacity of up to 150 Gb/s can be constructed. Furthermore, if the reserved service traffic load is limited on each input port to a maximum of 80% of switch port saturation, then a maximum delay across the switch of on the order of 100 mu s can be guaranteed, for 99% of the reserved service traffic, regardless of the unreserved service traffic load. >

An experimental multi-media bridging system

Abstract: The prototype system, which is described in this paper and called the Multi-Media Bridge, is designed to test service concepts and evolving technologies that make possible the deployment of multi-media group communications in future broadband networks. It incorporates such features as extended quality audio, full-motion video, graphics and data multi-point communications capability. The Bridge could serve as either a separate vendor entity or as an integral part of a network-based complex. The multi-shelf architecture of the experimental system allows a variety of technical problems and issues to be autonomously addressed. The shelves, designated Audio, Video, Graphics, and Data, are functionally integrated by a distributed control capability. A graphics user interface was developed which can be realized on any PC or workstation that supports the MIT X-Windowing system. It provides users with the flexibility to dynamically invoke each medium at any time and control various modes of media integration.

Multi-media information services: a laboratory study

Abstract: An overview is given of the work of a research group studying advanced information services. The general form of today's information services is discussed as a baseline for considering the future, and some key technological advances (including a broadband public-switched network) that are expected to greatly influence the continuing evolution of such services are listed. A description is given of a multimedia information services laboratory, consisting of a services testbed and application prototypes, which was constructed to illustrate and study important aspects of future services. The end-to-end performance requirements for these services are examined. Two examples are given to illustrate universal communications. >

Virtual-circuit load control in fast packet-switched broadband networks

Abstract: The authors consider the bandwidth management issues in a congestion control framework proposed for fast packet-switched broadband networks Specifically, they study a simple threshold-based strategy where the threshold parameters are determined so as to minimize a weighted sum of call blocking probabilities while providing a required GOS (grade of service) in terms of blocking performance to each class of calls They develop an efficient integer optimization algorithm using the penalty function method to find optimal threshold values This optimization process requires blocking probabilities of each class of calls as a function of the threshold parameters The authors derive a simple approximation technique to obtain the probabilities using first-moment matching This technique can be readily used to solve large problems (eg many classes of calls and/or large amount of bandwidth) Simulation results show that the technique yields accurate call blocking probabilities for a wide range of parameter values of practical interest >

Personal multi-media multi-point communication services for broadband networks

Abstract: Discuss attributes for multimedia multipoint communications services and describe a prototype system which is targeted at testing service concepts and evolving technologies that will stimulate the widespread deployment of multimedia group communications in future broadband networks. Personal teleconferencing in various forms is included in this service environment. A framework is proposed for categorizing various forms of communications media interrelationships. Users are provided with the flexibility to invoke each medium at any time and control various modes of media integration dynamically. An experimental graphical user interface has been proposed and implemented in the X Window System. The attributes of a high-end workstation matched to the proposed service are discussed. >

A dynamically controllable ATM transport network based on the virtual path concept

Abstract: Studies were carried out on an ATM (asynchronous transfer mode) transport network based on the virtual path concept. An arrangement of node functions in this network is proposed in which the call set-up process is excluded from transit nodes. This leads to a reduction in node processing and simplification of equipment by specialization of transit node functions. Virtual path control is shown to bring benefits in efficiency and flexibility. Among them a transmission efficiency improvement due to bandwidth control, a simple three-value bandwidth control algorithm improves the efficiency considerably with only a slight processing increase. It is concluded that the virtual path concept can provide simple, economical, flexible, and high-performance networks. >

TPON-a passive optical network for telephony

Abstract: A passive optical local access network for telephony applications is proposed which can be evolved to the future broadband ISDN. A laboratory demonstrator is described which can deliver a 144kbit/s ISDN channel, or equivalent, to 128 customers from a single fibre exchange feed. >

Compatible HDTV coding for broadband ISDN

Abstract: A compatible digital HDTV (high-definition television) coding scheme is proposed for broadband ISDN (integrated services digital network) applications. This scheme is capable of compressing HDTV for transmission at the H4 access rate of roughly 135 Mb/s with an embedded signal for delivering EQTV (extended quality TV) over a subchannel of 45 Mb/s. Two major processing components are introduced in this system to facilitate compatible coding; one is decimation in the frequency domain and the other is progressive coding. The decimation, performed in the DCT (discrete cosine transform) domain, results in a low pass filtered and decimated version of HDTV. The progressive coding squeezes the decimated signal into the 45 Mb/s subchannel and properly refines it for 135 MB/s HDTV coding. Simulation results show that high quality HDTV can be achieved at 135 Mb/s and that the quality of the embedded 45 Mb/s signal is also very good. >

Asynchronous transfer mode switching architecture for broadband ISDN-multistage self-routing switching (MSSR)

Abstract: The authors propose an architecture for asynchronous-transfer-mode (ATM) switching which is based on a self-routing switching principle. It is constructed by connecting self-routing switching modules in a three-stage link configuration, an architecture called multistage self-routing (MSSR). The cell-loss probability and delay have been evaluated. The results show that even when voice signals occupy 70% of the transmission capacity and burst data occupy 20%, the average delay per node is less than 60 mu s and the cell-loss probability is less than 10/sup -9/. This shows that this system has a larger traffic capacity than existing circuit switches, which are designed for an average loading of 70 to 80%. >

The knockout switch under nonuniform traffic

Abstract: A novel high-performance packet-switching architecture, called the knockout switch, has been recently proposed. It is a nonblocking, cost-effective switch suitable for broadband packet switching. The authors give equations which can be used to derive the packet loss probability and investigate the knockout switch under various uniform traffic patterns. They also compare the knockout switch with the multistage switch under various nonuniform traffic patterns. >

The 'policing function' to control user access in ATM networks-definition and implementation

Abstract: The authors define a policing function to be any mechanism that controls subscriber access to network capacity during exchange of information in a virtual circuit. While little is needed in circuit-switched networks, a policing function is of fundamental importance in future communication networks using asynchronous transfer modes (ATM), a new packet-oriented transmission principle for multiservice digital broadband networks providing connections in a wide range of bandwidth. The authors define parameters that can be used to specify the demand for both static and dynamic bandwidth allocation and define the practical form of the access to a network to ensure an acceptable grade of service. They present and compare some techniques that control subscriber access to a network to prevent an individual subscriber from exceeding the permitted bandwidth. >

Very high speed and high capacity packet switching for broadband ISDN

Abstract: The authors discuss and propose a very-high-speed and high-capacity packet-switching (HPS) architecture for a future broadband ISDN (integrated-services digital network). The HPS network accommodates various communication services, such as voice, high-speed data, high-speed still picture, and video services. The proposed architecture has three significant principles: a high-speed oriented simple network protocol, separation of signaling and network control from data transfer, and hardware switching. These principles provide fast- and high-throughput transmission for data packets and reliable transmission and processing for call-control packets. The HPS protocol structure is addressed, which provides high flexibility for various communications services as well as high-speed capability. A 3-Gb/s capacity and building-block-structured packet-switching system architecture, using bus- and loop-type switch fabric, is also presented. >

A coherent photonic wavelength-division switching system for broadband networks

Abstract: A photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch, is proposed. Design consideration shows that over 1000 line capacity is possible, using a multi-stage switching network with 32 WD channels. The switching function was confirmed through two channel switching experiments, using 8 GHz-spaced 280 Mb/s optical FSK signals.

Experimental broadband ATM switching system

Abstract: The authors describe an ATM (asynchronous transfer mode) switching architecture based on a self-routing principle and an experimental system constructed by connecting self-routing modules in a three-stage link configuration. The architecture is called multistage self-routing (MSSR). It is confirmed that MSSR switching can deal with various media such as voice, data, and video. >

Broadband ISDN — service visions and technological realities

Abstract: Two forces, service needs and technological advances, are driving the extension of the Integrated Services Digital Network (ISDN) into the broadband area. First, this paper identifies several business and residential services which provide a market pull for broadband ISDN (BISDN). Secondly, it reviews recent advances in optical transmission and broadband switching which provide a technological push. Finally, it describes an experimental broadband prototype constructed to help us better understand the transmission, switching, signaling protocol, software, and service capabilities required for BISDN.

Statistical multiplexing of variable bit rate video sources in asynchronous transfer mode networks

Abstract: The advent of the asynchronous time division (ATM) concept has created the opportunity to use variable bit rate (VBR) coding techniques for the coding of video services in broadband networks The principles of VBR coding are explained, and the benefits-stabilized picture quality combined with a high bandwidth efficiency-are indicated The results obtained with a hardware model of a VBR video codec are presented, and statistical multiplexing gain figures are given A bandwidth allocation scheme is proposed that is based on the statistical characterization and policing of the VBR sources It is concluded that this scheme offers high performance with a limited impact on the network and encoder complexity >

Digital video transmission and coding for the broadband ISDN

Abstract: An overview of visual communication in the broadband network is presented with particular attention to the transmission aspect of full-motion video. A detailed analysis of the quality requirements for digital video transmission is provided. Some significant coding algorithms presently under investigation by international bodies are reviewed. >

Information transfer protocols for the broadband ISDN

Abstract: A refinement of the OSI (open systems interconnection) reference model for broadband ISDN (integrated services digital network) is presented which introduces several additional sublayers in the network layer and one additional sublayer in the link layer. The purpose of these sublayers is to enhance the performance of the network, especially availability, while at the same time reducing capital and operational costs. Central to this improved performance of the network is the concept of a virtual direct route, i.e. a virtual circuit connection between two nodes in the network which is used by one or more calls as though it were a direct route. One of the sublayers in the proposed broadband ISDN reference model corresponds to the transfer of packets on virtual direct routes. The other sublayers all relate to service protection, i.e. techniques for maintaining service in the presence of equipment failure. >

Videomatic switching: systems and services

Abstract: An overview is provided of the trends in videomatic services and systems now coming into being with the advent of ISDN (integrated-services digital networks) and the prospect of broadband ISDN. Service aspects are discussed, including videoconferencing, videocoding, and videotelephony, and the LVX (local video exchange) system, an integrated video-voice-data local area network, is described from implementation and technical standpoints. >

Architecture and technology considerations for multimedia broadband communications

Abstract: The author highlights some of the rules and design tradeoffs which have to be considered in the evolution to an asynchronous transfer mode (ATM) based transport network. The first rules addressed refer to the connection control partitioning between out-of-band and in-band signalling for the design of generic ATM transport and recommend that the split should consider differentiation between connection-specific and generic control functions. The second set of rules refers to ATM system design for performance and efficiency and indicates the critical service parameters responsible for optimum system operation. The third set of rules refers to services integration under performance constraints for different traffic volumes and recommends transport separation of certain performance-sensitive applications in the early network-evolution phases. >

Definition of network options for the Belgian ATM broadband experiment

Abstract: The definition of a system requires the selection of a number of basic options. PTM (packet transfer mode) is a generic concept grouping a number of similar techniques which enable very flexible switching and transmission. The author describes the options and parameters which have been selected for a Belgian experiment planned in the early 1990s. Discussed are the following aspects: ATD (asynchronous time division) versus FPS (fast packet switching), including fixed or variable packet length, the optimal packet length, transmission and switching speed, and the number of lower-layer capabilities. >

Evolution of ISDN towards broadband ISDN

Abstract: Efforts to enhance the ISDN (integrated-services digital network) concept in order to include all forseeable kinds of broadband applications are described. The current state of the discussion is reported in terms of broadband services, interface structures, and reference configurations. The work of several standardization organisations (CCITT, T1, CEPT) is also discussed. >