View
215
Download
0
Category
Preview:
Citation preview
Corso “Telematica e Reti”
Università Degli Studi Di Roma “Tor Vergata” – Facoltà Di Ingegneria
DIPARTIMENTO DI INGEGNERIA DELL’IMPRESA
“Mario Lucertini”
Anno Accademico 2012-2013
Prof. Francesco Vatalaro
Prof. Romeo Giuliano
1
Definition of Telecommunications
Telecommunications technology:
• evolved from mechanical to electrical form
• electrical and/or optical signals
• mono- or bi-directional communication
What is telecommunications? Webster’s calls it “communications at a distance”. The
IEEE Standard Dictionary defines telecommunications as “the transmission of signals
over long distance, such as by telegraph, radio, or television”.
Telecommunication encompasses the
communication at a distance
3
Telecommunications networks interconnected
into a global system
4
Telecommunications
communication at a distance
of voice, data, and image information
“Telematica e Reti” -- From Wikipedia →
-Telematics typically is any integrated use of
telecommunications and informatics, also known as ICT
(Information and Communications Technology)
- A computer network, or simply a network, is a collection of computers and
other hardware components interconnected by communication channels that
allow sharing of resources and information
Role of Telecommunications
Telecommunications plays an essential role on many areas of everyday life.
Each of us uses telecommunications services and services that rely on
telecommunications daily.
Here are some examples of services that depend on telecommunications:
4
• 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.
5
End-Users, Nodes, ConnectivityEnd-users (clients, subscribers, etc.) provide the inputs (“source”) to the network and are
recipients (“destination”) of network outputs.
End-user employs what is called an I/O (input/output device): it may be a PC, telephone,
cellular phone, smart phone, facsimile, conference TV equipment, etc.
End-users usually connect to nodes: a node is a point or junction in a transmission
system where lines and trunks meet.
A connectivity links an end-user to a node, and from there possibly through other nodes
to some final end-user destination with which the initiating end-user wants to
5
6
to some final end-user destination with which the initiating end-user wants to
communicate. Figure below illustrates this concept.
The IEEE defines a connection as “an association of channels, switching systems, and
other functional units set up to provide means for a transfer of information between
two or more points in a telecommunications network.”
Functions of end-users, nodes, and connectivity
1800: Alessandro Volta discovers the primary battery
1836: Samuel Morse invents Telegraphy
1876: Alexander Bell perfects acoustic
transducer and is accredited inventor
of Telephony
1901: Guglielmo Marconi’s first successful transatlantic
Radio transmission (“Can you hear anything, Mr. Kemp?”)
1918: H. C. Armstrong perfects
the superheterodyne radio receiver Development of telecommunications
Telecommunications: a Bit of History6
the superheterodyne radio receiver
1937: Alec Reeves conceives pulse code modulation (PCM)
1948: Claude Shannon publishes his founding paper
on information theory
1954: J. R. Pierce proposes satellite communications
1969: ARPANET, the precursor of INTERNET, is created
1976: Ethernet LAN invented by Metcalfe et al.
1980: Cellular mobile networks start being put into service
1989: Proposal for a World Wide Web (WWW) by Tim Berners-Lee7
Development of telecommunications
Villa Griffone, Pontecchio (BO),
where Marconi invented the
Radio (1895)
2000: Launch of the UMTS service.
Transoceanic Telegraphy Network in 19017
8Source: http://matt-welsh.blogspot.com/2010/08/book-review-victorian-internet.html
Standardization
Standards are necessary to achieve interoperability, compatibility, and required
performance in a cost-effective manner:
• enable competition
• lead to economies of scale
8
Different standards in Europe, Japan, and the United States
Standards make the interconnection of systems from different vendors possible
Standards make users and network operators vendor-independent
Standards make international services available
Interested parties: groups that are interested in
standardization and participate in standardization work.
9
Standards Organizations
National
Standardization
Authorities
9
European Standards Organizations American Standards Organizations
Global Organizations Other Organizations10
An example of standard: ISO/OSIThe seven-layer stack structure, called ISO-OSI (International Standards Organization - Open
Systems Interconnection) architecture, is a useful conceptual reference to organize the
functions of a telecommunications network.
In general the functions of the generic layer, say layer n, regardless of its location in the ISO-
OSI stack, are to provide a set of services to the upper layer, i.e. layer n+1, hiding the details
of how the services are actually implemented by layer n-1.
Data Link Layer: task of transferring data
between adjacent nodes, providing the
Examples: Layer 1 e Layer 2
10
11
MEDIUM
Physical
Data Link
Network
Transport
Session
Presentation
Application
MAC
LLC
1
3
4
5
6
7
2Physical Layer (PHY): includes equipment for
physical cabling or wireless connection, and
also deals with the electrical and mechanical
specifications, control of interference and
collisions, and any other basic aspects of the
transmission in order to transmit the
information in raw form.
between adjacent nodes, providing the
functional and procedural means to transfer
data between network entities and the means
to detect and possibly correct errors that may
occur in the underlying physical layer.
ISO/OSI functional stack
The Telecommunications Business
In the past, telecommunications were a protected business area.
PTTs had control over standardization in international standardization
bodies and monopoly in providing telecommunications services in their respective
Countries.
Competition was not allowed.
Latter part of the 1980s: the deregulation of the telecommunications business
started in the USA and in Europe (first in UK, then in the EU).
11
started in the USA and in Europe (first in UK, then in the EU).
New operators obtained licenses to provide local and long-distance
telephone and data services, as well as mobile telecommunications services.
Deregulation of the telecommunications business promoted economical
efficiency: reduced tariffs and one driver for increased service quality.
12
Competition became the rule: liberalization and (very often) privatization.
Main public tariffs dynamics (Italy) TLC services prices dynamics (EU)
-15 -32
-26
-15
+40
+66 0
0
+27
Tariffe telefoniche (Italia)Tariffe TLC (Italia)
Reduced Tariffs in a Liberalized Economy12
AGCOM annual report (year 2010)
13
Italy: over the past decade the basic telephone service was the only one among public
services to become cheaper. Telephone prices fall by 15% in absolute value (while water
increase was +66%, transport, gas, energy was about +40% and post was + 27%).
Europe: in the past decade the portfolio of TLC services tariffs fell everywhere, with an
average of about 26%. With an average decrease of over 30%, Italy is the country where
tariffs fell more (in Spain and France decrease was only 15%).
Note: in Telecommunications, tariffs decrease both for the effect of competition and
for the effect of technology innovation (“Moore-law related”). It is difficult to separate
the relative impact.
Recommended