Here is a note explaining the ISO reference model for Open System Interconnection with diagrams: The ISO reference model for Open System Interconnection (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. It defines a framework for implementing protocols in seven layers, from the physical layer dealing with transmission systems up to the application layer, dealing directly with end-user processes. The seven layers of the OSI model are: 1. Physical layer - Defines the physical and electrical specifications for devices. It is concerned with the transmission and reception of unstructured raw bit streams over a communication channel. 2. Data link layer -

1. TELECOMMUNICATION
TRANSMISSION AND
SWITCHING SYSTEMS
VIJAYABASKAR Assistant Professor

2. Objectives
 To equip the students with skills and
knowledge of the current and future
telecommunication networks
 It assumes students have a background in
 Communication Systems
 Computer Communication Networks

3. Books
 Text:
 Telecommunication Switching, Traffic and
Networks by J. E. Flood
 Reference:
 Telecommunication Switching Systems and
Networks by V. S. Bagad

4. Marking Scheme
75% ATTENDANCE IS MANDATORY
FOR SITTING IN THE FINAL EXAM

5. Course Outline
 Development of Telecommunication
 Telecommunication Transmission
 Telecommunication Traffic
 Telecommunication Switching Systems
 Signaling techniques
 Public Switched Data networks (PSDN)
 Integrated Services Digital Network (ISDN)

6. Telecommunication Network
A telecommunications network
consists of
 Transmission systems
 Switching systems
 Stations

7. Transmission Systems
 Transmission (abbreviation: Tx):
 is the process of sending and propagating an analogue or digital
information signal over a physical point-to-point or point-to-
multipoint transmission medium, either wired, optical fiber or
wireless.
 Transmission System:
 is a system that transmits a signal from one place to another.
The signal can be an electrical, optical or radio signal.
 carries messages from an originating station to one or more
distant stations.
 is engineered and installed in sufficient quantity to provide a
quality of service compatible with the cost and expected benefits.

8. Transmission Systems
•The source may be a simple telephone microphone, keyboard
•The destination may be a simple telephone speaker, monitor
•It can be a single electrical medium, or a cascade of electrical media

9. Switching systems
 Switching systems are an assembly of switching
and control devices provided so that any station in a
communications system may be connected as
desired with any other station.
 To enable the transmission facilities to be shared,
stations are connected to and reached through
switching system nodes that are part of most
telecommunications networks.
 Switching Systems act under built-in control to
direct messages toward their ultimate destination or
address.

10. High Availability Network Design
Simplified Using Virtual Switching
System
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11. Review of
Telecommunications

12. Development of
Telecommunications
 1837: Beginning of electrical communication,
invention of Telegraph by Wheatstone and
Morse
 1876: Invention of Telephone by Alexander
Graham Bell
 1878: Opening of the first Telephone
Exchange, at New Haven, Connecticut.

13. Global Telephony Trends
 2008: 1.27 billion fixed line subscribers
according to ITU
 At the end of 2011:
 Total mobile‐cellular subscriptions reached
almost 6 billion corresponding to a global
penetration of 86%.
 more than 1 billion mobile‐broadband
subscriptions worldwide.
 590 million fixed (wired)‐broadband subscriptions
worldwide.
 2.3 billion people were online.

14. Global ICT developments 2001-
2011

15. Business of Telecommunication
 Involves various participants. These include:
 The public telecommunication Operators (PTO)
 Providers of Services that involve
telecommunications
 Manufacturers of equipment and components
 Both hardware and software
 Financial investors
 Governments
 The users
 who must pay charges to cover the cost of providing
the network so they are referred to as Subscribe rs o r
Custo m e rs

16. Telephony in action
 Two-way communication is required, on
demand, between any pair of stations
 It must be possible for many conversations to
take place at the same time
 How?

17. Network Structures
Ring Network N=1
Us
er1
Us
er
2
Us
er
3
Us
er
4
Mesh Network N=1/2n(n-1)
Bus Network N=1
Star Network N=n Tree Network

18. Exchange
 Solution can be provided by connecting a line
from each user’s station to the central switching
center/telephone exchange
 a telephone exchange or telephone switch is a
system of electronic components that connects
telephone calls
Area with a single Area with several

19. T
L
L
L
LL
L
L
L
L
LL
Junction Network
Multi exchange area.
L= Local Exchange
T=Tandem Exchange
Junctio n circuits
Telecommunication networks
hierarchy
 A National Public Switched
Telecommunication Network
(PSTN) consists of:
 Local network
 connects customers’ station to their
local exchanges.
 These are also called subscribers’
distribution networks, customer
access networks or the customer
loop.
 Junction networks
 interconnects a group of local
exchanges serving as area and a
tandem or trunk exchange.
 The trunk network or toll network
 which provides long-distance
circuits between local areas

20. International Gateway
Exchange
(Centre de Transit3)
Satellite Links and Submarine
Cables
International Network
Trunk Network
Local Network
National Tandem Exchanges
(tertiary trunk switching centres)
Regional Tandem Exchanges
(Secondary trunk switching
centres)
Local Tandem Exchanges
(Primary trunk switching
centres) Local
Exchanges
Customer
Lines
National Telecommunication Network
Junction Network
Core
Network
PBX
nodes

21. Elements of a Telecommunication
Network
 Transmission System
 Switching System
 Signaling system
 Responsible for interchange of information
 Which are made up by interconnecting
 Customer nodes
 Switching nodes
 Transmission nodes
 Service nodes

22. Network Services
 Customers of a PTO may require different
services which appear to require different
networks. Examples include:
 Public Switched Telephone Network (PSTN)
 The Public Switched Telegraph Network (Telex)
 Private Networks for voice and data
 Radio networks providing mobile communication
 Public data networks (PDN)
 Special Service Networks

23. Network Services Continued..
 Customers are connected to transmission bearer network at their
local exchange via the local access network or local loop.
 The services provided over the telecommunication network can thus
be divided into two categories:
1. Teleservices
 Provision of the service depends on particular terminal
apparatus ( e.g. telephone or tele-printer).
1. Bearer Services
 Present the customer with transmission capacity that can be
used for any desired function (e.g. private circuits)
Transmission Bearer Network
Visua
l
PD
N
Tele
x
PC
PST
N
Loo
p

24. Terminology
North American British
Customer’s Loop Local network
Access Network
Central office Exchange
End Office Local Exchange
Class 5 Office
Inter-office Trunk Junction
Junctor Trunk
Toll Office Trunk Exchange
Toll network Trunk Network

25. Assignment no. 1
 Write a note, with the help of diagram/s,
explaining the ISO reference model for Open
System Interconnection.