Lecture#04 Plain Old Telephone Service (part II) The Bonch-Bruevich Saint-Petersburg State University of Telecommunications Series of lectures Telecommunication networks Instructor: Prof. Nikolay Sokolov,
Telephone communications system "Telephone communications system" term is usually refers to base principles of telephone networks construction, operation and development. These principles usually include the following positions: purpose of the system; supported services; network structure; quality of service ratings; numbering plan; maintenance; equipment requirements; main directions of system development.
Supported services (1) Service (ITU-T, Q.1290): That which is offered by an Administration or ROA (recognized operating agency) to its customers in order to satisfy a telecommunication requirement.
Supported services (2) Source:
Supported services (3) Source: ITU
Supported services (4) Basic service: the fundamental type of service, or the most commonly provided service in a telecommunications network. It forms the basis upon which supplementary services may be added.
Supported services (5)
Supported services (6) Examples of the basic services: 1. Bi-directional (full duplex) voice band path with limited frequency range of 300 to 3400 Hz between two terminals for local, long-distance and international connections, 2. Access to operator services, 3. Access to emergency service.
Supported services (7) Examples of the supplementary services: 1.Call waiting (If a calling party places a call to a called party which is otherwise engaged, and the called party has the call waiting feature enabled, the called party is able to suspend the current telephone call and switch to the new incoming call, and can then negotiate with the new or the current caller an appropriate time to ring back if the message is important, or to quickly handle a separate incoming call.). 2.Centrex is a PBX-like service providing switching at the central office instead of at the customer's premises. Typically, the telephone company owns and manages all the communications equipment and software necessary to implement the Centrex service and then sells various services to the customer.
Supported services (8)
Quality of service (1) The collective effect of service performance which determines the degree of satisfaction of a user of the service (ITU).
Quality of service (2) Quality of service is specified in ITU-T Recommendations and ETSI standards. Each national Telecommunication Administration has established a lot of QoS indices. These indices are obligatory for all Operators and Service Providers.
Quality of service (3)
Quality of service (4) Recommendation E.800: Four viewpoints of QoS. Recommendation E.800: QoS and network performance.
Numbering plan (1) Number (Recommendation E.164): A string of decimal digits that uniquely indicates the public network termination point. The number contains the information necessary to route the call to this termination point. A number can be in a format determined nationally or in an international format. The international format is known as the International Public Telecommunication Number which includes the country code and subsequent digits, but not the international prefix. Numbering plan specifies the format and structure of the numbers used within that plan. It typically consists of decimal digits segmented into groups in order to identify specific elements used for identification, routing and charging capabilities, e.g. within E.164 to identify countries, national destinations, and subscribers. A numbering plan does not include prefixes, suffixes, and additional information required to complete a call (Recommendation E.164).
Numbering plan (2) Dialling plan (Recommendation E.164): A string or combination of decimal digits, symbols, and additional information that defines the method by which the numbering plan is used. A dialling plan includes the use of prefixes, suffixes, and additional information, supplemental to the numbering plan, required to complete the call. A prefix is an indicator consisting of one or more digits, that allows the selection of different types of number formats, networks and/or service. Country code (CC): The combination of one, two or three digits identifying a specific country, countries in an integrated numbering plan, or a specific geographic area. National (significant) number N(S)N : That portion of the number that follows the country code for geographic areas. The national (significant) number consists of the National Destination Code (NDC) followed by the Subscriber Number (SN). The function and format of the N(S)N is nationally determined.
Numbering plan (3) Russian PSTN: CC=7, NDC=3 digits (Area code), SN=7 digits (within urban and rural areas it is possible to use 5 or 6 digits), Area code of St. Petersburg is 812, Long-distance prefix is 8, International prefix is 8-10, access to Emergency services will be 112 (currently 01, 02, 03, 04).
Equipment requirements There are the number of requirements related to hardware, software, channels, maintenance system, etc. These requirements depend on type of network, installed equipment, market situation, adopted standards, etc. All requirements are radically changed for new generation of the telecommunication equipment.
Equipment requirements (1)
Equipment requirements (2)
Equipment requirements (3)
Equipment requirements (4)
Equipment requirements (5)
Equipment requirements (6) Requirements for the existing cable between main distribution frame and distribution cabinet (cross connect point) can be presented by the following parameters: R – resistance of the loop, L – series inductance, C – earth capacity. Evidently, these parameters will be of no interest after replacement of the existing cable by the fiber-optic one. For the fiber-optic cable, we have to specify another parameters: λ – wavelength, D – chromatic dispersion, etc.
PSTN development (ITU) OSS – operational support system, SLA – service level agreement.
PSTN evolution
Instructor: Prof. Nikolay Sokolov, Questions? Plain Old Telephone Service (part II)