Chapter 5
Introduction to
Telecommunications
Applications of Telecommunications
O’Brien 121
Business
Telecommunications
Telecommunications
Architectures
Electronic communications system
•
•
•
•
•
•
Electronic mail
Voice mail
Bulletin Board systems
Videotex
Fascimile
Public Information Service
Electronic meeting
systems
• Desktop Video
conferencing
• Decision room
conferencing
• Computer
conferencing
• Teleconferencing
•
•
•
•
•
Centralized
Distributed
Client/server
Interorganizational
Global
Business process
systems
• Online transaction
processing
• Inquiry/Response
• EDI / XML
• Electronic Funds Transfer
• Activity monitoring
• Process control
• Telecommuting
Trends
O’Brien 122 - 124
Industry trends
Towards a greater number of competitive vendors, carriers, alliances
and telecommunications network services.
Technology trends
Towards open and interconnected local and global digital networks for voice,
data and video, using high-speed fiber-optics and satellites.
Application Trends
Towards a pervasive use of the internet and enterprise and interorganizational
intranets, to support collaborative computing, online business operations and
strategic advantage in local and global markets.
Technological Developments
General trend: Connect everybody to everybody else.
 Internet-network technologies
 thousands new hardware- and software products
 web-browsers, HTML- editors, firewalls

Open systems: based on standards
 connectivity of systems: middleware
 OSI, TCP/IP

Digital technologies
 higher transmission speed
 larger information streams
 more efficient transmission method
 less errors
text: O’Brien : p. 168
Internet Revolution


Explosive growth
Terminology
 WWW:






E-mail:
Usenet:
IRC:
FTP:
Telnet:
Other:
text: O’Brien : p. 172
inquiry sources of information via
graphical browser software
electronic mail
place messages on bulletin board
real time dialogs
file transfer
login on other systems
telephone, video conferencing, ...
Telecommunication model

O’Brien 125
Terminals
 terminal, office equipment , telephones , ...

Telecommunications processors
 modems, multiplexers, front-end processors, ...

Telecommunications channels and media
 copper wires, coaxial cables, fiber optic cables, satellites, ...

Computers
 host computers, front-end computers, network servers, ...

Telecommunications control software
 telecommunication monitors, network operating systems, ...
Middleware
Interactive usage
Interactive usage :
- increases considerably the productivity
- requires communication networks
Required transmission capacity depends on the application
and on the user interface :
- administrative input
<1000 char/sec
- CAD/CAM millions char/sec

Physical location often crucial factor to decide on the
type of connection between the computer and the
workstation

Standardization is an absolute must in this respect
Telecommunication Components
O’Brien 126
5 components
Telecom
Channels and Media
Telecommunications
software
Telecom
processors
End-user
workstation
Telecom
processors
Computers
LAN
PC-workstation
PC-workstation
O’Brien 127 - 128
PC-workstation
Databases and
Software packages
Shared hard disk
Network
Server
Shared
printer
PC-workstation
PC-workstation
PC-workstation
Port to
other networks
WAN - Internetwork
LAN’s
Mainframe,
hosts
network
in US
network
in Europe
LAN’s
Tymnet
Internet
network
in Australia
Cisco corporation network
Client/server network
Company A
Internet
Router
Firewall
Intranet
Firewall
Router
Company B
text: O’Brien p 178
Intranet
Mainframe host system
Client - Server
Clients
DB.
server
Print
server
CAD
server
comm.
server
Clients
DB.
server
O.A.
server
comm.
server
The Internetwork-enterprise
The Internet
Intranets
Extranets
Enterprise
Intranets
Intranets
Supplier
Client
Intranets
Electronic Commerce
Other Organizations
text: O’Brien p 180
Media and Channels

Signals
Medium
Metal wire
Microwave
Fiber optics
 analog
 digital

Cables
 Twisted-pair
 Coaxial cable
Transmission speed
.0012Mbps - 10 Mbps
.256 Mbps - 100Mbps
.5Mbps - 1,000Mbps
interference
20x more expensive
5.500 simultaneous phone calls
 Fiber-optic
1 fiber 30.000 phone calls

Wireless
 microwave
 satellites


Radio, Infrared, Cellular Radio, Mobile computing
GPS global positioning system
text: O’Brien p183 - 186
Communication hardware


Modems 9.600 14.400 28.800 bps
Transmission mode
Simplex
Half-duplex
 Full duplex

1 circuit , 1 direction
1 circuit, 2 directions, difficult co-ordination
2 circuits, 2 directions
Transmission accurateness
 parity bits forward and backward error correction

Processors
 multiplexers frequency, time or statistic time distribution
 front-end processors to handle routine communication tasks
with peripheral equipment
text: O’Brien p 187 - 189
Network Topology

Star
all communications go via the central system

Bus
can easily be extended at the ends

Ring
more secure
Star network
O’Brien 147 - 148
With direct
connections
Point-to-point lines
- Efficient , also for high speeds
- With a large number of workstations cabling might be a problem
Star network (multiplexed)
Access via
multiplexed
lines
eventually rented
- local speed up to 2000 char/sec , 1M char/sec very expensive
- internationally 1000 char/sec commonly available
Bus network
Shared usage of a
broadband network
Multidrop lines
- more complex hardware
- simpler cabling system
O’Brien 191
Ring Networks
Ring Network
- more equal basis
O’Brien 147
Public data networks
PAD =
Packet Assembler
and Disassembler
Data Network
PAD
E.g..: DCS 1000 - 6000 char/sec , cost / volume data ( X25 )
Due to high connection cost ($ 30.000 year) usage of PAD
ISDN
ISDN
Integrated services
Digital network
ISDN
- universal network for telephone and data
- > 6000 char/sec
Open systems
Definition: An open system is a system where the design has
not been made by a supplier but by an accredited
standardization organization (eg:ISO , IEEE , ANSI ,
CODASYL , ... )




This provides the user a better independence from a
specific hardware or software supplier and therefore a
better guarantee for his investments.
It allows the user to make always the most appropriate
and optimal choice for each of the sub-systems .
Open systems are not yet sufficiently available on the
market.
The best examples are UNIX and the OSI network
model
The OSI model
Defined by ISO ( International Standard Organization ).
OSI ( Open System Interconnect ) describes a framework to
subdivide connection problems in networks into almost
independent sub-problems .
e.g.:
president x
diplomatic
rules
president y
interpreter x
common
language
interpreter y
cryptography
common
key
cryptography
operator
common
channel
operator
physical link
The TCP/IP and the 7 layer OSI model
TCP/IP
OSI
Application layer
Application- or
process layer
Presentation layer
Session layer
Host-to-host
transport layer
Internet-protocol
IP
network-interface
Physical layer
O’Brien 193
Transport layer
Network layer
data link
Physical layer
Communication services
for end users
Correct formatting
and coding
Support for session
initiation
Data transfers between
nodes
routing of
connections
Support for error-free
data transfer
physical access to
communication media
OSI 7-Layer Model
O’Brien 150
7. Application (user application program)
6. Presentation (user interface / screen display )
5. Session ( exchange between two nodes on the network )
4. Transport ( protocol for encoding messages )
3. Network ( mechanism for separating multiple messages )
2. Link ( data encoding schemes )
1. Physical ( wires, connectors , voltage )
Descargar

Introduction to Telecommunications