Relevance of the topic and purpose of research
The scientific importance and value of results
The review of the SDH technology
The assessment of parameters of the ring SDH - networks with defined terms of reliability
Intensive development of new information technologies in the seventies years led to the rapid development of microprocessor technology, which has stimulated the development of digital techniques of voice and data, which eventually resulted in the creation of new high-speed global network technologies: PDH, SONET, SDH, ISDN, Frame Relay, ATM . Interest in technology SDH due to the fact that this technology has replaced the pulse-code modulation, PCM (PCM) and digital hierarchy plesiochronous PDH (PTSI) and was intensively deployed in the massive establishment of foreign advanced digital telephone, which allows the management of flows of 2 Mbit / s and the establishment of regional local rings SDH. To date, based on SDH technology major renovations going on the old analogue networks to digital coherent communications network that uses the most advanced technology.
The relevance of the topic: Reliability of a transport telecommunication network is one of the most important indicators of working networks. That's why many national carriers, ISPs and mobile operators seek to increase the reliability of the network, which depends on the reliability of the constituent elements (multiplexers, switches, routers, etc.), as well as the chosen scheme of protection. Modern transport telecommunication networks carrying a large amount of information at high speed, so even short breaks connection lead to the loss of large amounts of information. Thus, the development of methods for improving the reliability of optical networks is relevant for today. The purpose of the research: The study and analysis of the transport network, infrastructure, which is based on the technology of SDH. Constructing SDH-ring network and a study on the same basic characteristics of reliability. As well as development of methods for improving the reliability of the existing SDH-ring.
In the work will be explored existing transport network of Donetsk region and an optimization in terms of bandwidth. Also there will be a study of the reliability of the network, analyzing its indicators and provide effective methods of improving these indicators. The value of results involves the application of more effective methods to improve reliability when designing new or upgrading existing transport networks, thus enabling more efficient use of network resources and minimize the cost of its construction and maintenance.
Currently, the major transport networks use fiber-optic system as a medium of information transmission over long distances. However, most such networks have infrastructure which based on the SDH / SONET technology. It is connected with the following features technology SDH:
— Stability of the technologies and standards. Along with the use of mature technology and steady technological basis of SDH in the equipment used conforms to the latest recommendations and standards, particularly standards ETSI and ITU.
— Compliance with the outcome of the modern level of technology. SDH-solutions correspond to the modern level as from an economic point of view (providing a minimum total cost of ownership) and conceptually (through modularity, programmability and multi) and a technological point of view (through the use of modern standards in equipment, management and data transfer) .
— High-quality communication. As originally developed as a technology of primary networks, SDH provides high bandwidth, guaranteed quality of service and fault tolerance.
— High reliability. Reliability of SDH networks is achieved through redundancy in the architecture, topology, at the level of individual nodes, as well as at the level of critical components.
— Economic efficiency. Decisions based on SDH technology provides a reduction in the time for new services to market (due to the small amount of time required for the establishment, expansion and reconfiguration of systems), reducing the cost of the system, the possibility of savings in the purchase of additional equipment (due to multifunctionality, the combination of different functions on a single platform), the ability to expand with minimal changes due to the modularity of the system, as well as the ability to integrate with legacy infrastructure and equipment from other manufacturers.
Reliability — is the property of the network connection to perform a given function, i. e. provide an opportunity to transfer the required information on the directions given to the established norms of accuracy within the required period of time and subject to the rules of service. It is clear that the reliability of the higher, the less the number of refusals. The reliability of the transport network depends on the reliability of the constituent elements (multiplexers, switches, routers, etc.), as well as the chosen scheme of protection. When it is necessary to optimize the size of an existing ring network with defined indicators of reliability, it is necessary to have a mathematical expression that would identify the required performance parameters. Let all the parts of the network have the readiness coefficient . The readiness coefficient (Kг ) — the probability that the network connection to an arbitrarily selected point in time will be working.
[1]
where T — an average time between failures (MTBF), tв — average time of restoration of an efficient condition. Knowing the readiness coefficient, it is possible to obtain an expression for the reliability of one ring:
[2]
where Kн — the reliability of a ring; N — the number of links in the network. Express from the obtained equation:
[3]
When applying the approximation to this formula can be obtained from the following approximate expression for the calculation N :
[4]
The mathematical expression (4) helps to quickly determine the approximate number of nodes in a ring network, if set the required reliability, specifically the readiness coefficients of network links.
So, in the research were: — Considered the advantages of building a transport network based on technology SDH; — Justified the advantage of building networks for topology «ring»; — Raised the assessment of reliability of transport networks SDH; — Gives mathematical expression to determine the number of nodes in ring networks of different sizes. The goal is to develop effective methods to improve the reliability of transport networks.
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