Modern Telecommunication Networks Research Articles

Non-intrusive speech-quality assessment using vocal-tract models

It is increasingly vital that there are effective quality of service (QoS) metrics to describe the performance of telecommunications networks. Speech quality is a major contributor to users' perception of QoS, and the ability to design for and monitor this quality is paramount. The authors describe work towards a non-intrusive speech quality assessment algorithm, capable of making predictions of the speech quality received by a customer, utilising the in-service signal. Modern telecommunications networks contain complex nonlinear elements that cannot be assessed with traditional engineering metrics. A novel use of vocal-tract modelling techniques is described, which enables predictions of the quality of a network degraded speech stream to be made. Details of the algorithm's adaptation to different talker characteristics are presented, together with a summary of the performance of the system.

Out-of-hours service in rural areas: An observational study of accessibility, attitudes and quality standards among general practitioners in Iceland

Objectives - To examine the access, workload, duties, commitments and quality standards of primary care physicians (GPs) resulting from out-of-hours service. Setting - All GPs (n=96) in rural Iceland. Main outcome measures - Answers to a postal survey. Results - The participation rate was 80%. The GPs estimated that in 97% of the cases they could be contacted within 5 minutes in an emergency. Under usual circumstances (weather conditions) and within a distance of 10 km, 70% of them could reach the patient within 30 minutes of receiving the call. In severe weather conditions, 50% of the GPs in smaller districts (650-6000 inhabitants) estimated that it could take up to 5 hours or more to reach the patient (which could happen once a year). In the least populated districts, 84% of the GPs had to be on call 14 days or more per month. Serious emergencies (involving special training such as cardiac resuscitation or tracheal intubation) were relatively rare, and GPs expressed the necessity for regular refresher courses in such fields. Conclusions - Modern telecommunication networks guarantee good access to out-of-hours service. The workload and on-call duties are great and do not comply with European Union (EU) recommendations regarding minimal rest time. If GPs in rural areas are to be expected to provide frontline health care, including in severe emergency situations, regular training courses are needed.

Jitter performances of STM-16 line regenerator in SDH system

In the modern high-speed telecommunication networks on fiber optic (SDH standard), the long distance transmission links (e.g. a transoceanic transmission line) employ several cascaded regenerators. To ensure the synchronization of these networks, the jitter at each regenerator span has to be limited rigorously and maintained within permissible levels, according to ITU-T Recommendations and ETSI Standards. In this paper the architecture of an STM-16 line regenerator (bit rate equal to 2·48832 Gbits/s) is analyzed with particular consideration to the traffic timing characteristics. The influence of traffic timing blocks on jitter performances of the regenerator is investigated more in depth. © 1997 John Wiley & Sons, Ltd.

Are telecommunications facilities ‘infrastructure?’ If they are, so what?

It is obvious that modern telecommunications networks possess at least some of the attributes of what we commonly call ‘infrastructure’. They are essential to modern commerce and, indeed, to modern living. It is essential that all subscribers be able to connect to most other subscribers, but perhaps not through the same network but through interconnected networks. These networks may even have natural monopoly characteristics and may generate substantial externalities. Nevertheless, the speed of technological change in electronics and communications provides a strong argument against government programs to develop or build modern telecommunications infrastructure. The choice of any network architecture is fraught with risk and could require the investment of S1000 or more per subscriber that could easily be obsolete as soon as it is completed. Rather than providing grants of monopoly and relying on the ensuing regulation of network architecture, governments should open their telecommunications sectors to competition, allowing private firms to shoulder the risk of building these expensive new networks. Indeed, the United States has recently moved strongly in this direction after a quarter century of selective telecommunications liberalization that has seen private networks flourish. The evidence on the effect of new telecommunications infrastructure on economic growth is too weak to justify a conclusion that this infrastructure has already created large externalities. As networks proliferate, with private and public systems competing with each other and complementing each other, it will be even more difficult to demonstrate these externalities. Thus, the case for government support and direction of telecommunications infrastructure investment remains very weak.

Letter: Output slave clock short term stability on SDH equipment

AbstractIn the modern synchronous telecommunication networks the quality of distributed clock is of primary importance. Instabilities of slave clocks due to their internal noise sources introduce jitter on transported tributaries. Several parameters can be used to characterize the short term stability of a slave clock. In this paper we use the Time Deviation (TDEV (τ)) to characterize the short term stability of a slave clock based on Phase Locked Loop (PLL), locked to an ideal input reference signal. Different PLL bandwidth values are considered and the possibility to discriminate between the PLL internal noise types is also emphasized, analysing its output TDEV (τ) curves only.

The standards aspects of SS7 network management

Signaling System No7 (SS7) is an internationally standardized general purpose Common Channel Signaling (CCS) system. It is a key component of modern telecommunications networks. Its malfunctioning can cause major problems, as demonstrated in recent history by the spectacular breakdowns induced in public networks by its nonperformance. This paper gives an overview of SS7 management, as represented in the standards. It reviews successively the built-in management mechanisms, the Open Systems Interconnection (OSI) system management-based functions, and the emerging Telecommunications Network Management (TMN)-based approach. It shows that the TMN approach, although still in its cradle, is the most promising.

Data telecommunication network needs for Polish state finance sector

The exploitation of data processing systems in the governmental finance sector in Poland requires designing and implementing modern data telecommunication networks. The key for success of data telecommunication enterprises is a clear understanding of the present customer's need, but also understanding what future customers will want. The goal of the paper is to analyze, on the basis of existing data-processing equipment and telecommunication interfaces, the potential alternatives for establishing efficient, cost-effective, manageable, and high QoS networks. The presently existing facilities, as well as initiatives that may be operational in the subsequent years, are reviewed. The analysis is aimed towards elaborating the general strategy for large modern data telecommunication investments in Poland. >

Traffic routing and link dimensioning in the common channel signaling networks

Signaling can be defined as the exchange of information specifically concerned with the establishment and control of connections, and with network management, in a telecommunications network. It constitutes the command/control infrastructure of the modern telecommunications networks. The Common Channel Signaling (CCS) network not only forms the foundation for control and management in the modern telecommunications environments but also provides database transaction processing capability for special services such as the 800 Service and Alternate Billing Service (ABS). The CCS network is the backbone for providing the Integrated Services Digital Network (ISDN) signaling, the Advanced Intelligent Network (AIN) services, and the Personal Communications Service (PCS). It is therefore critical to provide adequate switching and transmission (link) capacities so that performance of CCS networks can be ensured. This paper describes a flexible link set dimensioning algorithm for supporting CCS network and traffic engineering. We first show that increasing a link set by one or more links may not always increase the link set capacity accordingly because of the current routing procedure defined in the Signaling System No. 7 (SS7) protocol. We then demonstrate a theorem that enables us to construct the number of all possible meaningful links in a CCS link set. Based on the theorem, an efficient and flexible procedure for implementing the link dimensioning algorithm in software is devised to support the mechanization of the CCS network planning traffic engineering functions. Finally, we show an approach to improve the CCS link utilization efficiency and its sufficient and necessary conditions.

Modeling and analysis of communication systems based on computational methods for Markov chains

The authors describe a computational approach for modeling and analyzing modern communication systems based on numerical methods for Markov chains. Advanced direct and iterative procedures for the calculation of the stationary distribution of a homogeneous discrete- or continuous-time Markov chain with finite state space are presented. They are implemented in a convenient software tool called MACOM for interactive modeling and performance evaluation of communication systems. MACOM provides the user with a predefined markovian model world describing modern telecommunication networks with adaptive routing schemes and advanced congestion-control mechanisms. The versatility of these algorithms is illustrated by their application to Markovian queuing models derived from telecommunications networks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Service assurance in modern telecommunications networks

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. >

Guided-wave devices and circuits

Two decades have passed since the first, tentative experiments the first, tentaive experiments in guidedwave electro-optics were performed. During that time, development has been spurred on particularly by the successful penetration of fibre optics into many diverse fields and by the need for associated devices of ever increasing sophistication. Single-mode fibre is well established as the choice for the trunk backbone of modern telecommunications networks and is set for further applications in local networks. Fibre optics is now responsible for high performance sensor systems and is beginning to impact on analogue signal transmission, notably at RF, in fields such as radar systems and satellite communication antennae. These applications have driven research and development in both discrete electro-optic devices and in integrated electro-optic circuits.

High-performance expert system-DBMS interface for network management and control

The field of network management in modern telecommunications networks is discussed along with the need for database and expert systems techniques in this field. It is pointed out that one of the requirements is the capability of inferencing with a very large volume of factual information. A framework is presented for optimization in coupling an expert system and a database management system (DBMS) in such a way to satisfy this requirement. A loose coupling strategy is adopted as a practical solution allowing utilization of an existing DBMS. Specifically, techniques for normalizing the logic query, implementation primitives, and the set of access strategies as mappings between the normalized primitives and implementation primitives is presented. The techniques are discussed in the context of an expert system shell, the SOL Inference Engine for Network Applications (SIENA). >

The evolution of a modern telecommunications network to the year 2000 and beyond

An example of how a general management goes about the formulation of long-term policy and investment programmes, where rapidly changing technology is linked to rapidly changing needs in the market place, in a newly competitive environment, in a time frame extending over the next 15 years. British Telecom is in the middle of an investment programme that will transform analogue network into a digital system. The initial objective was to reduce operating costs, but market demands for new services require additional and substantial investment decisions, with the total running at the rate of £1 billion per year for atleast the next five years. The present ‘layered’ network has been built up by adding services. As the ‘product life cycles’ of the several technologies reach out into the future, new possibilities emerge such as mobile radio where the cellular network can be divided down to accomodate millions of subscribers and, in the longer term, the realisation of an all digital main network serving the business environment, with local intelligence in each subscriber&apos;s PABX. As an example of the pace of technology, a 15000 line exchange as now manufactured is based on the technology of about six years ago, and occupies 15 racks. With currently developed technologies, this can be reduced to 3 racks. Extrapolating to techniques of high-density wafer integration, by 1995 only two circuit boards will be required, a small fraction of one rack. The market needs are changing, and a wide adoption of electronic funds transfer by retailers will generate a heavy demand for short duration calls, increasing the processing load. The area of limited improvement is the production of software, where costs are being reduced by a factor of only two per decade.

Network operating system for telecommunications applications

Computers are being used in modern telecommunications networks to control the switching systems and to assist with other aspects of their operation, such as maintenance or subscriber services. These applications require a range of operating system services in a distributed network environment, hence the term network operating system (NOS). The design concepts and major features of LM Ericsson's NOS are described, emphasis being placed on the use of functional layering to achieve adaptability. Attention is also drawn to the similarity between the problems which the NOS addresses and those that many organizations with face in coping with distributed processing.