2.1 b,c

SC015 SDS

Sesi 2020/2021

2.0 INTERNET TECHNOLOGY

2.1 Basic Concept of Network

LEARNING OUTCOME:

At the end of this lesson students will able to:

b) Explain types of communication devices and
transmission media used in a network.

c) Describe the advantages and disadvantages
of a network.

DEFINITION OF TRANSMISSION MEDIA

Materials substances capable of carrying
one or more signals in a communications

signals.
(Discovering Computers 2018)

TYPES OF TRANSMISSION MEDIA

a) Physical transmission media
b) Wireless transmission media

TYPES OF TRANSMISSION MEDIA

a) Physical transmission media

 Use wire, cable and other tangible
materials to send communications signals.
 These wires and cable typically are used
underground or within or between building.
 Examples : twisted-pair cable, coaxial
cable, Fibre-Optic cable.

PHYSICAL TRANSMISSION MEDIA

i) Twisted-Pair Cable

used for network cabling and landline phone systems.

consists of one or more twisted-pair wires bundled
together.

each twisted-pair wire consists of two separate
insulated cooper wire that are twisted together.

the wires are twisted together to reduce noise,
which is an electrical disturbance that can
degrade communications.

PHYSICAL TRANSMISSION MEDIA

ii) Coaxial Cable

CATV network wiring often uses this cable because it
can be cabled over longer distance than twisted-pair
cable.

consists of a single cooper wire surrounded by at
least three layers (insulating material, woven or
braided metal, plastic outer coating)

PHYSICAL TRANSMISSION MEDIA

iii) Fiber-Optic Cable

the core of fiber-optic cable consists of dozen or hundreds of thin strands
of glass or plastic that use light to transmit signals.

advantage using fiber-optic cable:
• Capability of carrying more signals
• Faster data transmission
• Less susceptible to noise from other device
• Better security for signal during transmission
• Smaller size (much thinner and lighter weight)


 Disadvantage: costly and can be difficult to

install and modify.

TYPES OF TRANSMISSION MEDIA

b) Wireless transmission media

Send communications signals through the
air or space.
 More convenient than installing cables.
 Examples : infrared, broadcast radio,
cellular radio, microwaves and
communications satellites.

WIRELESS TRANSMISSION MEDIA

i) Infrared

• A wireless transmission medium that sends signals using
infrared light waves.
• Mobile computer and devices (mouse,
printer, smart phone) often have an IrDA
port that enables to transfer data from
one device to another.

WIRELESS TRANSMISSION MEDIA

ii) Broadcast Radio

A wireless transmission medium that distributes radio signals
through air over long distance(such as between cities, regions
and countries)and short distance (such as within an office or
home)

Bluetooth, UWB and Wi-Fi
communications technologies that use
broadcast radio signals.

WIRELESS TRANSMISSION MEDIA

ii) Broadcast Radio – example

WiMAX-Longer range
• Used to provide internet access to wide geographic
areas

Wi-Fi – Medium range
• Used for wireless LANs & to connect portable
computer users to the internet at public hotspots.

Bluetooth – short range
• Used to connect a wireless device to a computer.
(alternative to Infrared)

WIRELESS TRANSMISSION MEDIA

iii) Cellular Radio

• A form of broadcast radio that is in wide use for
mobile communications, specifically wireless
modems and mobile phones.

WIRELESS TRANSMISSION MEDIA

iv) Microwaves

• Microwaves are radio waves that provide a high-speed
signal transmission over long distance.
• Signals can be send or received using
microwave stations or
communications satellites

WIRELESS TRANSMISSION MEDIA

v) Communications Satellite

• A communications satellite is a space station that
receives microwave signals from an earth based station
and broadcasts the signals back over a wide area to any
number of earth-based stations.

ADVANTAGES OF NETWORK

1) Facilitate Communications

Networks enable people communicate efficiently and
easily through email, Internet messaging, chat rooms,
blogs, wikis, online social networks, etc.

2) Sharing hardware

Networks enable each computer or device on a network
to share hardware such as printers, scanners. Thus, it
saves money on hardware expenses.

ADVANTAGES OF NETWORK

3) Sharing data and information

Networks enable data and information stored on a
network to be accessed by multiple users.

4) Sharing hardware

Networks enable each computer or device on a network
to share hardware such as printers, scanners. Thus, it
saves money on hardware expenses.

DISADVANTAGES OF NETWORK

1) Expensive to Build

Purchasing the network cabling and other hardware
such as hubs, switches, and routers might be very costly
to buy and replace.

2) Security Threats

Virus can spread to other computers throughout a
computer network.

DISADVANTAGES OF NETWORK

3) Network failure

If something goes wrong with the server the whole
network is unable to operate where no one on the
network can access any files.