TELECOMMUNICATION NETWORKS

*

UNIT-1

Introduction to Telecommunication Networks

*

TELECOMMUNICATION SYSTEMS Definition A telecommunication system is two things: (1) a communication systemthat is, a system in which information is transmitted from one physical location, A, to a second physical location, B; and (2) a system which allows this information to be sent beyond the range of usual vocal or visual communications. The human eardrum can actually pick up vibrations between 50 Hz and 16,500 Hz*In telephone communication, the person who originates a call is referred to as the calling subscriber and the person for whom the call is originated is known as the called subscriber.

FOUR EXAMPLES AND AN ERRATIC HISTORY LESSON Smoking UpWild HorsesTelegraphThe Telephone *

THE TELEPHONE

*

*

SIGNIFICANCE OF TELECOMMUNICATIONS:

Banking, automatic teller machines, telebanking Aviation, booking of tickets Sales, wholesale and order handling Credit card payments at gasoline stations Booking of hotel rooms by travel agencies Material purchasing by industry Government operations, such as taxation

*

TELECOMMUNICATION NETWORKSThe following figure shows a small part of a telecommunication network. It mainly consists of

exchanges trunks subscriber lines*

*

*

SET UP AND RELEASE .*

STANDARDIZATIONStandards enable competitionStandards lead to economies of scale in manufacturing and engineeringPolitical interests often lead to different standards in Europe, Japan, and the United StatesInternational standards are threats to the local industries of large countries but opportunities to the industries of small countriesStandards make the interconnection of systems from different vendors possibleStandards make users and network operators vendor independent and improve availability of the systems*

EXAMPLES OF INTERNATIONAL STANDARDIZATIONScrew thread pitches International telephone numbering and country codesTelephone subscriber interfacesTelevision and radio systemsFrequencies used for satellite and other radio communicationsConnectors and signals for PC, printer, and modem interfacesCellular telephone systems*

NATIONAL STANDARDIZATION AUTHORITIESEuropean Organizations The European Telecommunications Standards Institute (ETSI) The European Committee for Electro technical Standardization/European Committee for Standardization (CEN/CENELEC) The Confrence Europenne des administrations des Postes et des Tlcommunications or Europen Confrence of Postes and Tlcommunications Administrations (CEPT)*

AMERICAN ORGANIZATIONSThe Institute of Electrical and Electronics Engineers (IEEE)The Electronic Industries Association (EIA)The Federal Communications Commission (FCC)The Telecommunications Industry Association (TIA) has been developing global third generation cellular systems together with ETSI from Europe and the Association of Radio Industries and Broadcasting (ARIB) from Japan*

GLOBAL ORGANIZATIONSThe International Telecommunication Union (ITU) is a specialized agency of the United Nations responsible for telecommunicationsInternational Telegraph and Telephone Consultative Committee (CCITT/ ITU-T) is presently called ITU-T, where the T comes from telecommunicationsInternational Radio Consultative Committee (CCIR/ITU-R) is presently known as ITU-R, where the R stands for radio*

OTHER ORGANIZATIONSThe Internet Engineering Task Force (IETF) is responsible for the evolution of the Internet architectureThe Universal Mobile Telecommunications System (UMTS) Forum is an open organization of cellular system manufacturersThe Telemanagement Forum (TMF) is an organization of system manufacturers that works to speed the development of network management standards. *

NETWORK TRAFFIC LOAD PARAMETERSBusy hour: Continuous 1-hour period lying wholly in the time interval concerned, for which the traffic volume or the number of call attempts is greatest.Time consistent Busy Hour: The 1-hour period starting at the same time each day for which the average traffic volume or the number of call attempts is greatest over the days under consideration.Call Completion rate (CCR): is defined as the ratio of the number of successful calls to the number of call attempts.Busy hour call attempts (BHCA): The number of call attempt in the busy hour is called Busy hour call attempts (BHCA), which is an important parameter in deciding the processing capacity of a common control or a stored program control system of an exchange.Traffic intensity: The traffic on the network may be measured in terms of the occupancy of the servers in the network. Such a measure is called the Traffic intensity. A0 =Period for which a server is occupied/total period of observationA0 is dimensionless and is called earlang (E). 1E=36 CCS = 3600 CS =60 CM

*

Grade of Service: The amount of traffic rejected by the network is an index of the quality of the service offered by the network. This is termed grade of service (GOS) It is defined as the ratio of lost traffic to offered traffic.Offered traffic is the product of the average number of calls generated by the users and the average holding time per call.The actual traffic carried by the network is called the Carried traffic and is the average occupancy of the servers in the network as given by GOS=A-A0/A Where A=offered traffic A0=carried traffic A-A0 =lost traffic

*

EXAMPLES:1. An exchange serves 2000 subscribers. If the average BHCA is 10,000 and the CCR is 60%, calculate the busy hour calling rate.2. In a group of 10 servers, each is occupied for 30 minutes in an observation interval of two hours. Calculate the traffic carried by the group.3. A group of 20 servers carry a traffic of 10 erlangs. If the average duration of a call is three minutes, calculate the number of calls put through by a single server and the group as a whole in a one-hour period. 4. A Subscriber makes three phone calls of three minutes, four minutes and two minutes duration in a one-hour period. Calculate the subscriber traffic in erlangs, CCS and CM. *

*Timing diagram illustrating how a call to a mobile user initiated by a land line subscriber is established

Explain Timing diagram illustrating how a call to landline user initiated by a mobile subscriber is established? Answer to Examples: 1. Given N = 2000 suscriber BHCA = 10000 CCR = 60% = 60/100 = 0.6 Calculate BHCR = ? Solution: BHCR is given by BHCR = Average busy hour calls Total number of subscriber*

but Average busy hour calls = BHCA x CCR = 10000 x 0.6 = 6000 calls BHCR = 6000/2000 = 3 2.

*3

*4