Learning Outcomes
• Identify main elements in data communication
systems
• Identify the communication devices
• Explain the basic data transmission concepts
• Describe the common transmission flaws effecting
data signals
• Explain the rule of communication
• Explain how signals transmitted from a host to a
destination in a network

Data Communication System
Elements
 Data Elements
 Communication Devices
 Electronic Communication Methods
 Transmission Media

Data Elements
• Message - information to be communicated
• Sender - device that sends the message
• Receiver - device that receives the message
• Medium - physical path from sender to
receiver
• Protocol - set of rules that govern data
communication

Data Elements (cont…)
 Message
 Sender
 Receiver
 Medium
 Protocol

Communication Devices
 A hardware component that enables a
computer to send and receive data,
instructions and information and from one or
more computers.
 Type of communication devices:
 Wired (Data Terminal Equipment
(DTE))
 Wireless (3G,GPRS, Laptop, Mobile
Phones)

Wired Communication
• Wired communication is transmission of
data over a wire-based communication
technology.
• One of common wired-based communication
is an Ethernet.
• DTE ( data terminal equipment) and DCE
(data circuit-terminating equipment / data
communications equipment).

Wireless Communication
• Wireless communication is the transfer of information
between two or more points that are not connected by
an electrical conductor

Electronic communication methods
• Fax
• Email
• Instant Messenger
• Telephone/ Mobiles
• Video Conferencing
• Intranet
• Chat / IRC

Transmission Media
 Guided Media
 Twisted-Pair Cable – Unshielded Twisted-Pair (UTP) and
Shielded Twisted-Pair (STP)
 Coaxial Cable
 Fiber Optic Cable
 Unguided Media: Wireless
 Transport electromagnetic waves without using a physical
conductor

Twisted Cable
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
STP cable consists of twisted wire
pairs that are individually insulated
and surrounded by shielding
made of metallic substance
UTP cable consists of one or more
insulated wire pairs encased in a
plastic sheath

Comparing STP and UTP
 Throughput - Both can transmit up to 100 Mbps
 Cost - Typically, STP is more expensive
 Connector - Both use RJ-45 connectors
 Noise immunity - STP is more noise-resistant
 Size and scalability - Maximum segment length for
both is 100 meters
Throughput refers to the
volume of data that can flow
through a network

RJ-45
RJ45 is a standard type of connector for
network cables
Crossover cable must be used between 2 devices from the same
level like (PC-PC, Router-Router, Switch-Hub, PC-Router)
Straight through cable used between two different levels like
(PC-Switch, Router-Switch) – T-568A / T-568B

Coaxial Cable
• Coaxial cables are a type of
cable that is used by cable TV
and that is common for data
communications.
• There are two types of
coaxial cable:
 Thinnet (thin)
 Thicknet (thickness)
• The coaxial cable using
connectors - BNC (British
Naval Connector)

Fiber Optic
 Contains one or several glass fibers at its core
 Surrounding the fibers is a layer of glass called
cladding

Fiber Optic (cont…)
 Single-mode fiber
 Carries light pulses along single path
 Multimode fiber
 Many pulses of light generated by LED travel at
different angles

Unguided Media: Wireless
 Infrared transmission
 Infrared networks use infrared light signals to
transmit data through space
 Direct infrared transmission depends on
transmitter and receiver remaining within line of
sight
 In indirect infrared transmission, signals can
bounce off of walls, ceilings, and any other
objects in their path

Unguided Media: Wireless
 RF transmission
 Radio frequency (RF) transmission relies on
signals broadcast over specific frequencies
 Two most common RF technologies:
Narrowband
Spread
spectrum

Data Transmission Concept
 Analog and digital
signaling
 Data modulation
 Simple, half-duplex
and full-duplex
 Multiplexing
 Point-to-point
transmission
 Broadcast
transmission
 Bluetooth, 3G
 Throughput
 Bandwidth
EXERCISE

Transmission Flaws
FLAW is any defect that can affect the
quality of data signal send in networking.
Most common flaws is
• Noise
• Attenuation
• Latency
• Radio frequency interference (RFI)
• Electromagnetic interference (EMI)

Transmission Flaws
 Noise
 Occurred when devices act as a sending antenna and
the transmission medium act as the receiving antenna.
Analog Signal Digital Signal

Transmission Flaws
 Attenuation
 Loss of signal strength as transmission travels away
from source (for long network cable)
 Analog signals pass through an amplifier, which
increases not only voltage of a signal but also noise
accumulated
An analog signal
distorted by
noise, and then
amplified
Amplifier - device for increasing the power
of a signal by use of an external energy
source

Transmission Flaws
 Latency
 Latency is the delay between requesting data and the
receipt of a response, or in the case of one-way
communication, between the actual moment of a signal's
broadcast and the time it is received at its destination

Transmission Flaws
 Radio frequency interference (RFI)
 Interference that may be generated by motors, power
lines, televisions, copiers, fluorescent lights, or broadcast
signals from radio or TV towers
 Electromagnetic interference (EMI)
 Interference that may be caused by motors, power lines,
television, copiers, fluorescent lights, or other sources of
electrical activity

Transmission Flaws
 Regeneration
 Process of retransmitting a digital signal
 Repeater
 Device used to regenerate a signal
A digital signal distorted by noise, and then
repeated

I don’t stop when I’m tired.
I only stop when I’m done…