Showing papers in "IEEE Communications Magazine in 1990"
TL;DR: The general technique of parallel transmission on many carriers, called multicarrier modulation (MCM), is explained, and the performance that can be achieved on an undistorted channel and algorithms for achieving that performance are discussed.
Abstract: The general technique of parallel transmission on many carriers, called multicarrier modulation (MCM), is explained. The performance that can be achieved on an undistorted channel and algorithms for achieving that performance are discussed. Ways of dealing with channel impairments and of improving the performance through coding are described, and implementation methods are considered. Duplex operation of MCM and the possible use of this on the general switched telephone network are examined. >
3,995Â citations
TL;DR: A set of performance specifications that seem appropriate for real-time computer communication services is proposed, and various types of delay bounds, throughput bounds, and reliability bounds are proposed.
Abstract: A set of performance specifications that seem appropriate for real-time computer communication services is proposed. They include various types of delay bounds, throughput bounds, and reliability bounds. Other requirements and desirable properties are described from a client's viewpoint, and the ways in which each requirement is to be translated to make it suitable for lower levels in the protocol hierarchy are examined. Some examples of requirements specification are presented, and possible objections to the approach are discussed. >
400Â citations
TL;DR: A tutorial overview of the salient features of SS7 is provided and the SS7 network services part (NSP), which corresponds to the first three layers of the Open Systems Interconnection (OSI) Reference Model, is described.
Abstract: A tutorial overview of the salient features of SS7 is provided. Its history is briefly reviewed, and the SS7 network services part (NSP), which corresponds to the first three layers of the Open Systems Interconnection (OSI) Reference Model, is described. Signaling network structures that, in conjunction with the NSP, provide integrated services digital network (ISDN) nodes with a highly reliable and efficient means of exchanging signaling messages are discussed. The nodal capabilities of connection (call) control and remote process invocation and management and other functions of the user parts of SS7 are examined. The very stringent performance requirements of signaling systems, which reflect the critical nature of signaling functions and their real-time exigencies, are stressed. A broad outline of the likely evolution of ISDN signaling systems in the remaining years of this century is sketched. >
209Â citations
TL;DR: A personal view of an extended concept of personal communications is discussed and the relationship between low-power digital cordless technology and some alternatives (analog cordless, digital mobile radio, and cellular mobile radio) is examined.
Abstract: A personal view of an extended concept of personal communications is discussed. The relationship between low-power digital cordless technology and some alternatives (analog cordless, digital mobile radio, and cellular mobile radio) is examined. Personal communication network (PCN) power requirements, circuit quality, level of network integration, and access to network intelligence (e.g. call forwarding, call transfer, and personal number calling) are emphasized. >
162Â citations
TL;DR: The use of adaptive equalization to increase storage density and equalization methods for peak detection and for sampling detection are discussed, and gains in both linear and areal density are addressed.
Abstract: The use of adaptive equalization to increase storage density is discussed. Adaptive equalization is attractive since it permits a significant reduction in manufacturing costs by allowing a greater component yield due to relaxed tolerances and also permits a reduction in servicing costs because of a reduced need for fine-tuning on the customer's premises. The differences between data storage and data transmission channels are examined. The storage channel's important signal-processing characteristics are described, covering read and write processes, detection methods, and various types of distortion that can occur in storage channels. The use of signal-to-noise ratio as a performance measure is considered. Equalization methods for peak detection and for sampling detection are discussed. Gains in both linear and areal (track) density are addressed. Some of the basic performance advantages of using adaptive equalization are illustrated. The future of communication technology in storage systems is assessed. >
150Â citations
TL;DR: The task of speaker verification, a subset of the general problem of speaker recognition, is defined and the feature selection and pattern matching steps of the recognition procedure are examined.
Abstract: The task of speaker verification, a subset of the general problem of speaker recognition is defined. The feature selection and pattern matching steps of the recognition procedure are examined. Speaker verification system design and performance are discussed, and databases for evaluating them are briefly considered. An example of a speaker verification system is described. An overview of industry research in this area is given. >
146Â citations
TL;DR: Practical echo cancellation techniques, in particular, those used in telecommunications, are reviewed and current international standardization activities are discussed, and echo canceler implementation considerations are set forth.
Abstract: Practical echo cancellation techniques, in particular, those used in telecommunications, are reviewed. The various situations in which echoes are generated are examined. Echo path modeling techniques and adaptive algorithms for coefficient control are reviewed. Current international standardization activities are discussed, and echo canceler implementation considerations are set forth. These include echo cancelers for telephone circuits, echo cancelers for full-duplex data transmission over voice channels, acoustic echo cancelers, and echo cancelers for ISDN digital loop transmission. >
102Â citations
TL;DR: The strengths and limitations of the photonic technology are reviewed, beginning with the temporal bandwidth limitations of photonic devices and then focusing on spatial bandwidth, commonly referred to as the parallelism of optics, and how it can be used in photonic fabrics.
Abstract: The strengths and limitations of the photonic technology are reviewed, beginning with the temporal bandwidth limitations of photonic devices and then focusing on spatial bandwidth, commonly referred to as the parallelism of optics, and how it can be used in photonic fabrics. Some of the proposed photonic switching fabrics that are based on guided-wave devices are discussed, comprising switching fabrics based on space channels, using directional couplers and optical amplifiers, and those based on time channels. The latter include active reconfigurable fabrics based on TDM, time-slot interchangers, and universal time slots, in addition to passive shared media fabrics. Some of the switching fabrics that have been proposed using wavelength channels are outlined, and multidimensional fabrics are briefly reviewed. Photonic switching fabrics based on free-space devices are described, covering free-space relational switching fabrics, the basic hardware required for digital free-space optical fabrics, and digital free-space switching fabrics. >
90Â citations
TL;DR: The layered performance modeling approach is refined and extended to cover the latest CCITT Blue Book specifications, and generic models for signaling points and signaling transfer points are constructed.
Abstract: The layered performance modeling approach is refined and extended to cover the latest CCITT Blue Book specifications. Specific submodels for the higher-level functional blocks, such as the message transfer part (MTP) level 3, the signaling connection control part (SCCP), the ISDN user part (ISDN-UP), and the transaction capabilities application part (TCAP), are given in a generic way, explicitly. With these submodels, generic models for signaling points and signaling transfer points are constructed. The major functional parts of the layered protocol architecture of SS7 are modeled in a generic way by extended queuing network elements such as full duplex flow controlled links, priority processors, multiple-chain multiple-class traffic streams, or elements for segmenting and reassembling of messages. The analysis of the whole network starts from a global traffic flow analysis, which takes all the different signaling message types, their paths through the network, and the load into account. The overall performance measures, such as end-to-end transfer times, are found from all the component delays. The analytical results have been validated by simulation, revealing a high degree of accuracy. >
77Â citations
TL;DR: These are networks that allow mass communications between users who are generally mobile, and represent a significant extension of the capabilities of today's cellular mobile telephone networks with much smaller cells and far lower station power requirements.
Abstract: Present plans for personal communication networks (PCNs) in Great Britain are described. These are networks that allow mass communications between users who are generally mobile. They represent a significant extension of the capabilities of today's cellular mobile telephone networks with much smaller cells and far lower station power requirements. The relationship between PCNs and current cellular networks is examined. Technical approaches that will promote widespread PCN availability are explored. >
76Â citations
TL;DR: An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided and a representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture.
Abstract: At the transport layer in interoffice and interexchange networks, shared protection rings (SPRINGS) interconnected at matched nodes can provide 100% restoration in milliseconds after cable cuts and central office failures. The author introduces the SPRING and explains how its capacity advantage over other ring configurations enables it to be the most economical solution in more applications. Transport restoration technologies-1+1 diversity, digital crossconnect systems, and SPRINGS-in interoffice and interexchange environments are compared. A representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture. Recommendations on how to evolve today's asynchronous networks in preparation for a fully survivable SONET ring-based network are also provided. Generic ring planning guidelines and network examples are presented to demonstrate how today's networks can be evolved to provide end-to-end survivable SONET transport. An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided. >
TL;DR: The key factors deterring the use of visual telephony are identified, and an overview of a typical system architecture is given.
Abstract: The key factors deterring the use of visual telephony are identified, and an overview of a typical system architecture is given. The video signal formats and video and audio coding algorithms used are described. Video codec implementation is considered, and an implementation based on application-specific integrated circuits is presented. In particular, three key signal processing modules in the video codec are examined: a discrete cosine transform chip, a motion estimation chip, and a variable-length codec chip. Standardization activities in the video coding area are discussed. >
TL;DR: The economic feasibility of using SONET self-healing-ring (SHR) architecture in survivable interoffice fiber networks is studied and results of two case studies based on a metropolitan local access and transport area (LATA) network are discussed.
Abstract: The economic feasibility of using SONET self-healing-ring (SHR) architecture in survivable interoffice fiber networks is studied. The model used is discussed, and the selection criterion for the candidate area in this study, the SHR cost model, the hubbing network cost model, the network survivability measure, and the network growth model are described. Results of two case studies based on a metropolitan local access and transport area (LATA) network are discussed. One involves a single- and the other a dual-homing interoffice network. Sensitivity analysis and network impact results are highlighted. >
TL;DR: The main design considerations are reviewed, focusing on the update cycle, protective allowance, multiple alternate routes, congestion-control thresholds, and algorithm extensions.
Abstract: Dynamic traffic management (DTM) is described. The overall system architecture and data flow, routing, and congestion control are addressed. The main design considerations are reviewed, focusing on the update cycle, protective allowance, multiple alternate routes, congestion-control thresholds, and algorithm extensions. The immediate benefits that automation and near-real-time responsiveness entail in traffic management are outlined. These lie in the areas of capital savings, traffic management automation, and trunk servicing. >
TL;DR: Four key timing parameters that are used as performance measures are defined; reframe time, false in-frame time, out-of-frame detection time, and misframe time.
Abstract: Four key timing parameters that are used as performance measures are defined; reframe time, false in-frame time, out-of-frame detection time, and misframe time. Several strategies that improve frame alignment performance are considered for the case of a burst frame alignment word (FAW). With a little modification, the same strategies could also be applied to the case of a distributed FAW. The probability generating function is introduced, and its derivation from a state transition diagram is presented. The probability generating function is used in the timing parameters estimation. As an example, the frame alignment of a SONET (synchronized optical network) STS-3 signal is discussed. >
TL;DR: The TCS-V2 traffic-control system, an advanced automatic code-blocking system that uses area and subscriber congestion control, is considered, and the simulated performance of proportional control and threshold control is compared for this system.
Abstract: The objectives of network management control are outlined, and two categories of control are defined: network traffic controls and network configuration controls. Network traffic controls are further classified into traffic volume controls and routing controls, and advanced techniques for achieving each of them are examined. Two classes of methods for specifying the amount of traffic to be controlled are described. In proportional control, a certain proportion of the traffic offered by each exchange is admitted; in threshold control, there is a maximum rate at which the traffic offered by each exchange is admitted. The TCS-V2 traffic-control system, an advanced automatic code-blocking system that uses area and subscriber congestion control, is considered, and the simulated performance of proportional control and threshold control is compared for this system. For routing control, an advanced state-dependent dynamic routing scheme is examined, and the results of a comparative evaluation of dynamic routing schemes are presented. >
TL;DR: Digital speech technology is reviewed, with the emphasis on applications demanding high-quality reproduction of the speech signal, which include the important subclass of wideband speech.
Abstract: Digital speech technology is reviewed, with the emphasis on applications demanding high-quality reproduction of the speech signal. Examples of such applications are network telephony, ISDN terminals for audio teleconferencing, and systems for the storage of audio signals, which include the important subclass of wideband speech. Depending on the application, the bandwidth of input speech can vary from about 3 kHz to nearly 20 kHz. Coding for digital telephony at 4 and 8 kb/s, network quality coding at 16 kb/s, and coding for audio at 7 and 20 kHz are examined. Future directions in the field are discussed with respect to anticipated technology applications and the algorithms needed to support these technologies. >
TL;DR: A video coding algorithm developed at Bellcore that has been proposed as a contribution to the standardization activity of ISO/MPEG is described and the following characteristics of the algorithm are described.
Abstract: The Moving Picture Experts Group (MPEG) of ISO is considering a standard for storage applications below 1.5 Mb/s. A video coding algorithm developed at Bellcore that has been proposed as a contribution to the standardization activity of ISO/MPEG is described. The following characteristics of the algorithm are described. The following characteristics of the algorithm are described in detail: frequent periodic reset of the temporal predictor (to provide random access), interpolative coding of every second frame, flexibility of providing adaptive Huffman code tables for digital-storage-media (DSM)-based applications (not feasible for real-time transmissions), 1/2-pel accuracy in motion estimation, and optional quantization matrix. Additional features of reverse playback, fast searches, and random access are described. >
TL;DR: Schemes that do not explicitly use much information about the state of networks are briefly surveyed, with the focus on dynamic alternative routing (DAR), a simple but highly effective routing method currently planned for the British Telecom Network.
Abstract: Schemes that do not explicitly use much information about the state of networks are briefly surveyed, with the focus on dynamic alternative routing (DAR), a simple but highly effective routing method currently planned for the British Telecom Network. State-dependent routing and how some of the methodology also has bearing on the control issue are discussed. The problem of dimensioning a network that uses dynamic routing (i.e. how much capacity is needed and where it should be put to provide an acceptable performance) is addressed. A practical example, which refers to routing in an international access network, is discussed. Some conclusions are drawn on the benefits and drawbacks of distributed routing. >
TL;DR: It is shown how end-to-end service reliability can be improved by using the techniques described, applying them to AT&T 800 Service as an example.
Abstract: Modern telecommunications network design and examples of possible causes of service interruption are examined, using AT&T 800 Service for illustration. Different methods of assuring service technically are presented. It is shown how end-to-end service reliability can be improved by using the techniques described, applying them to 800 Service as an example. Techniques used to restore generic switched services or private line services after a failure within a network are also presented. >
TL;DR: Text analysis for speech synthesis is described in relation to the information needed in speech production, including a pronouncing dictionary and letter-to-sound rules, morphological analysis and accent assignment, and syntactic analysis.
Abstract: Text analysis for speech synthesis is described in relation to the information needed in speech production. This includes a pronouncing dictionary and letter-to-sound rules, morphological analysis and accent assignment, and syntactic analysis. Prosody control rules (fundamental frequency control and segmental duration control) are examined. Speech units for synthesis and parametric representation of speech signals are discussed. Applications and development tools are considered. >
TL;DR: The characteristics of international 24-h traffic profiles are examined, and proposed dynamic routing schemes are described, and results on circuit savings and fault tolerance of international dynamic routing networks are outlined.
Abstract: Major issues that should be examined in evaluating the performance of networks with dynamic routing are reviewed The characteristics of international 24-h traffic profiles are examined, and proposed dynamic routing schemes are described Gain allocation principles are discussed, and results on circuit savings and fault tolerance of international dynamic routing networks are outlined >
TL;DR: Applications are discussed, including key management for conventional encryption equipment, electronic mail and data interchange, access control and audit trails, software verification and virus detection, counterfeit-proof currency, nuclear test ban treaty detectors, and challenge response systems such as in aircraft identification of friend or foe.
Abstract: A tutorial on digital signatures is presented, covering the basic concepts of public-key cryptography and digital signatures based on public-key techniques. Applications are discussed, including key management for conventional encryption equipment, electronic mail and data interchange, access control and audit trails, software verification and virus detection, counterfeit-proof currency, nuclear test ban treaty detectors, and challenge response systems such as in aircraft identification of friend or foe. >
TL;DR: The evolution of dynamic routing with respect to several future directions is highlighted, including extension to new networks and services, robust design and real-time adaptivity, and extension to interconnecting networks, including the Worldwide Intelligent Network.
Abstract: Dynamic routing concepts are described, and the design and control of dynamic routing networks is discussed. The vastly improved performance of the networks is illustrated with examples from operational experience. The evolution of dynamic routing with respect to several future directions is highlighted. These directions are extension to new networks and services, robust design and real-time adaptivity, and extension to interconnecting networks, including the Worldwide Intelligent Network. >
TL;DR: Fundamental design issues and/or parameters of specific relevance to MB communication systems are discussed and some historical and more recent MB systems are examined.
Abstract: The characteristics of meteor burst communications are described and compared to those of HF and satellite systems. The two generic types of MB systems, broadcast and channel-probing systems, are explained. In systems using the broadcast protocol, the transmitter knows nothing about the occurrence of bursts or trails and transmits continuously for a sufficient duration to permit all recipients to receive the message/data with the desired probability. For practical purposes, the optimum burst or block duration for such systems is around 100-200 ms, based on the characteristics of the predominant trails. Channel-probing MB systems are more common and are commercially available in several versions. Here the transmitter repeatedly sends a short (typically 5-20 ms) probe signal until it receives a similarly short message response, indicating the availability of a suitable trail. A third, intermediate type of protocol with hybrid features does not probe the channel with a short signal, but starts repeatedly transmitting the first packet, in effect using it as a probe signal. Fundamental design issues and/or parameters of specific relevance to MB communication systems are discussed. Some historical and more recent MB systems are examined. >
TL;DR: Experimentation with screen-based telephony is discussed in the framework of Apple Computer's user-centered design philosophy, which enables programs to be developed for the most ubiquitous technologies today-plain old telephone service and proprietary private branch exchanges-but also allows for an easy, logical upgrade to future technologies like ISDN.
Abstract: Experimentation with screen-based telephony is discussed in the framework of Apple Computer's user-centered design philosophy. The approach described enables programs to be developed for the most ubiquitous technologies today-plain old telephone service (POTS) and proprietary private branch exchanges (PBXs)-but also allows for an easy, logical upgrade to future technologies like ISDN. The model has been built in three layers, which reflect the three constituencies who must cooperate to bring ISDN applications (and their forerunners) to market, in the volume required to spark the growth of this area: telecommunications vendors, personal computer vendors, and independent software developers. The Call Manager Application Programmers Interface is the code/specification from Apple that enables voice and data applications to be written independently of the vendor or technology. Telecommunications vendors can write drivers to the Application Program Interface (API) and build the appropriate hardware interfaces, without having to support thousands of software developers. Some of the features of Apple's prototype human interface to the voice network on this API are described. >
TL;DR: The main concepts and interfacing and multiplexing techniques for an NNI (network node interface) as set forth in CCITT (International Consultive Committee for Telephone and Telegraph) Recommendations are described in this article.
Abstract: The main concepts and interfacing and multiplexing techniques for an NNI (network node interface) as set forth in CCITT (International Consultive Committee for Telephone and Telegraph) Recommendations are described. The objectives and history of the NNI standardization are reviewed together with concepts, basic requirements, and features of the NNI. The nine-row-based frame structure and the virtual container (VC) concept, which are the main features of the NNI, are introduced. The multiplexing principle and method, the detailed frame structure and overhead, and mapping methods related to the NNI are described. Applications of the NNI in the synchronous network and international interworking are presented. The future application of asynchronous transfer mode (ATM) is discussed. >
TL;DR: The nature of the traffic-routing problem is described, and early studies of state-dependent routing are noted; how the relative costs can be determined for the case of direct routing is shown.
Abstract: The nature of the traffic-routing problem is described, and early studies of state-dependent routing are noted. A state-dependent scheme seeks to route each call so as to minimize the risk of blocking future calls, and thus responds to the current state of the network on the basis of certain assumptions about future traffic demands. State-dependent routing is considered as a Markov decision process. How the relative costs can be determined for the case of direct routing is shown. >
TL;DR: The performance levels for increasing cell loss are compared for various speech coding methods, in combination with methods for dividing coded speech signals into cells and discarding cells.
Abstract: A type of speech coding for asynchronous transfer mode (ATM) is described. Cell processing, which improves service quality, is taken into account. Missing-cell recovery methods are discussed, and the distinctive features of missing-cell recovery methods used with low-bit-rate coding are examined. An example of the speech quality obtained using speech coding techniques in the ATM networks is described. The performance levels for increasing cell loss are compared for various speech coding methods, in combination with methods for dividing coded speech signals into cells and discarding cells. Representative feasible network applications of coding technologies are considered. >
TL;DR: Suggestions are presented for strategies to increase the representation of women at all levels: precollege, undergraduate, graduate, and industry.
Abstract: Reasons for the low numbers of women entering the engineering profession are explored. Suggestions are presented for strategies to increase the representation of women at all levels: precollege, undergraduate, graduate, and industry. Insights gained from a recent Cooper Union survey are discussed. Actions that can be taken at the precollege, community college, engineering baccalaureate, graduate, and industry levels are proposed. >