Transcript Information Technology

Information Technology
Essentials
2nd
Edition
CHAPTER 5
COMMUNICATIONS AND NETWORKS
Prepared by: Arlene N. Baratang
OBJECTIVES
• Gain introductory knowledge about communication system.
• Know the similarities and differences about communication,
telecommunication and computer communication.
• Learn and define the different components and devices for a
successful communications.
• Define the different communication channels used in
communications.
• List and distinguish the different network connection devices.
• Be familiar of the different network connection services and
providers.
COMPUTER COMMUNICATION
• Communication is the transfer or exchange of data or
information from a sending device to a receiving
device across a distance or from one geographic area
to another using electric pulse representing messages.
These representations of messages using packet may
be transmitted in different frequencies in a form of
electricity, electromagnetic wave, light waves or radio
waves through a physical transmission media or
through the atmosphere.
• Telecommunication. The process of transmitting and
receiving of voice, video, or computer data in a form
that could be send and/or receive by the different
communication devices over a long distance channel
• Computer communication is when computer are used
as a device for transmitting and receiving or exchange
of messages or information this refers to. The
interchange of information may happen in real time
called as synchronous or not in real time called
asynchronous.
Communication Channel used in
transmitting messages
COMMUNICATION DEVICES
• Communication devices are types of hardware capable of
sending data, instruction, or information between a
transmitting devices and receiving devices.
– Sending device or terminal are used to transmit data,
instructions, or information
– Communication device (modulator) that are used to convert data,
instructions, or information into a form that could be transmitted
through a channel
– Communication channels serve as a media or path on which the
signals travel
– Communication device (demodulator) that are used to convert
data, instructions, or information into a form that could be
received by the receiving devices.
– Receiving devices or host computers accept the transmitted data,
instructions, or information
Transmission of signal in
communication devices
• Data or information is transmitted in a form that could
travel along a particular communication channel. The
communication device sends the signal to a converter
called modulator before it could be transmitted along
the communication channels. The signal may be
transmitted using a telephone lines, microwave
system, or satellite stations. The transmitted signals
are then receive by another device for a translation to
a format that could be interpreted by the receiving
devices. This device is called demodulator.
Elements of Communication
• Sender is an electronic device that serves as a transmitter of the source of
messages or information on the network.
• Receiver is an electronic device on the network that accepts messages or
information from the sender.
• Communication channel is a medium where the message or information are
transmitted from the sender to the receiver’s electronic devices. Medium
could be physical transmission media or wireless transmission media using
electromagnetic waves transmitted over the atmosphere or air.
• Operating System is software that supports network features installed on
the electronic receiving and transmitting devices.
• Network Devices are collection of electronic component and circuitry that
are used to augment the performance of the transmission of messages or
information between the transmitter and receiver. Network devices come
with Network Interface Card (NIC), Hub, Switch, Bridge, Router, and
Gateway.
Network Devices:
• Network Interface Card (NIC) is a printed circuit board installed in the
expansion slot of the motherboard that connects with the network cable.
• Hub is a central common point of connection joining multiple electronic
devices on the local area network (LAN). Hub rebroadcast signals to all other
devices intended for a particular device connected on the network
• Switch is similar to a hub that every device on the network is connected to it
but function differently in rebroadcasting signals to all other devices. Switch
does not retransmit signals but instead it makes direct link between
transmitting and receiving device while other devices are unaware of the
communication taking place.
• Bridge is used to connect one local area network (LAN) to another local area
network using the same protocol. Bridge examines every messages on a
LAN, letting those known belonging to be within the same LAN, and
forwarding those known belonging to the other interconnected LANs.
Network Devices…
• Router is a device used to link two or more computer or electronic
device to the internet either wirelessly or through physical media.
• Gateway serve as an entrance and exit point of a network wherein
all data routed inward or outward first pass through and
communicated with it in order to use routing path. Network
gateway is capable of joining together two networks using
different base protocols.
• Modem, also known as Data Communication Equipment (DCE),
stands for modulate and demodulate is used for data conversion.
Modulator is used to changed digital to analog; and demodulator
is used to convert analog signal to digital signal. For a computer to
establish communication it needs a modem for transformation of
data from one form to another
NOISE
• Noise is the unnecessary electrical energy which
interferes with the communication channels during
the process of transmitting and receiving of
information or signal from the transmitter to the
receiver.
Types of Noise:
• Internal noise
• Thermal agitation noise are unwanted noise arises from
the random movement of electrons in the resistors due
to heat
• Shot noise these are noise produced from electron
movement in active devices like vacuum tubes and
transistors that are found in amplifier & oscillators.
• Flicker noise or modulation noise resulted from the
movement of electrons in voltage or current transit time
found in capacitor and inductor.
Types of Noise…
• External Noise
• Atmospheric Noise (static) are noise generated from
Lightning (Thunderstorm), any electrical disturbances in the
atmosphere
• Man made noise are noise from Industries like automobile
when starting the engine, aircraft, electric motor, switching
gears in switch yard, leakage from high voltage, fluorescent
lamp, welding machines.
• Extraterrestrial noise – these are Solar noise – constant
radiation of the sun, cosmic noise – noise from the stars,
galactic noise - noise from the center of milky way, Radiofrequency radiation - originating outside the solar system
but from within the Milky Way galaxy.
COMMUNICATION CHANNELS
• Channel is an essential aspect in data
communications. This serves as the pathway for
communicating devices to send and receive data and
information. Communication channel have
bandwidth. This is the breadth of the channels where
the signal travels. The higher the bandwidth, the more
data or information can be transmitted through the
channel.
• Transmission media are made up of different
materials or techniques capable of carrying one or
more signals for transmission. When a transmission
media can transmit only one signal at a time, it is
called Baseband. But when a media can transmit
multiple signals simultaneously, this refers to as
Broadband. DSL, CATV, and satellite offer broadband
transmission.
• Two types of transmission media:
1. Physical transmission media use insulated wire,
cable, fiber optics, or other materials for
transmitting communication signals.
2. Wireless transmission media uses air or space for
sending communication signals through
electromagnetic wave or infrared signals.
Physical Connection
• Twisted-pair cable is a
transmission medium
consisting of one or more
insulated twisted-pair of
wire bundled together as
one cable. Twisting pair
of insulated wire reduces
electrical disturbance or
interferences called noise
that affects the
communication.
• Coaxial cable is a shielded high frequency transmission
medium consisting of a single copper wire surrounded
by insulating materials, woven or braided metal, and
plastic outer covering. Coaxial cable has 80 times the
transmission capacity of twisted-pair cable.
• Fiber optic cable is insulated thin strand of glass or plastic
(2/1000 of an inch) where signals converted to light fires by
laser burst pass through. A fiber optic cable may consist of
dozens or hundreds of thin strands of glass or plastic called
optical fiber.
WIRELESS CONNECTIONS
• Radio frequency is an electromagnetic (EM) field energy from
an alternating current (AC) radiated from an antenna. This
oscillating magnetic field energy generates perpendicularly
oriented electric field energy that propagates and travels at long
distance through space inducing energy at the receiver’s
antenna. RF is a form of wireless communication enabling users
to communicate via electromagnetic energy at a speed closer to
that of the speed of light. Wireless communication
technologies are based on RF field propagation which is part of
electromagnetic radiation spectrum.
Electromagnetic Spectrum
Wireless transmission media have various data transmission transfer rate.
This is the speed at which a line carries data and information.
Wireless connection…
• Communication Satellite is a space station 22,300
miles above the earth’s equator. This receives
microwave signals from earth-based station,
amplifying the signals and transmitting it back over a
wide area to any number of earth-based stations as
fast as 50 Mbps. The transmission of signal from earthbased station to space satellite is called uplink. And
the transmission of signal from space satellite to earthbased station is called downlink.
Users of communication satellite
• Television and radio
broadcasting stations
• Global positioning system
(GPS)
• Video conferencing
• Weather forecasting
Users of communication satellite …
• Air navigation
Uplink and downlink transmission
of signal via Communication Satellite
How triangulation works with satellite
and cell site antennas
• GPS is a satellite based navigational system that uses triangulation to
determine the exact location of the users on anywhere in the world.
There are 24 satellites make up the GPS that are orbiting twice a day at
a speed of 7,000 miles an hour and 12,000 miles above the earth.
• GPS is used for mapping of countries, land surveying, scientific
applications, surveillance, and analyzing earthquake activity.
• Twenty-four satellites make
up the GPS
• General Packet Radio Services
(GPRS) where a particular
location in the map can easily
be located. GPRS is a packetbased wireless communication
service providing continuous
internet connection for mobile
phone at data rate speed
ranging from 56 to 114 Kbps.
• Microwave radio transmission involves transmitting of
electromagnetic signals from one microwave station to another
at a rate of 45 Mbps. Microwave stations are earth-based
stations that have a reflective disc containing antenna,
transceiver, and other equipment used in line-of-sight
transmission of signals.
• Electromagnetic signals transmitted via Microwave stations
• Broadcast radio is a wireless transmission that involves sending or
distributing of signals through the air either over short distance or long
distance. Radio transmission requires a transmitter and receiver to transmit
and receives radio signals. The receiver of the broadcast signal must have an
antenna located within the range of signals being transmitted.
• Broadcast Radio transmission
• Bluetooth is a technology
that uses short range radio
wave transmission among
other users using Bluetooth
enabled-device. It has a
small chip that allows it to
communicate with other
Bluetooth enabled devices.
Short range radio wave
transmitted using Bluetooth
• Infrared (IR) is similar to microwave radio that needs no
obstruction on the line of its signal transmission. Infrared is a
transmission media that transmit signals using infrared light
waves at the speed of 1 to 4 Mbps.
• Signals transmitted using Infrared
• Cellular radio is a form broadcast radio that is widely used for
mobile communication like the cellular telephone and wireless
modem. The data transfer rate for cellular radio ranges from
9,600 bps to 14.4 Kbps.
Cell phone signal from a user is
transmitted to the nearest cell-base
station. From the cell-based station
signals may travel through landline or
through one cell-based station to
another to reach the Mobile Telephone
Switching Office (MTSO). The signal
will then be transmitted to the Public
Switched Telephone Network (PSTN)
via landline for retransmission to the
recipient.
• Wi-Fi (Wireless Local Area Network) is the most popular
method of communicating data or information within a
permanent location. This is a wireless networking standards
allowing devices to communicate without physical
transmission media. Computers connect through wireless LAN
card to a nearby access point, wireless router or any hotspots
operating in the 2.5, 3.6, and 5 GHz frequency bands.
• Acronym Wi-Fi does not correspond to ”Wide Fidelity” but
rather it correspond to the trade mark of the Wi-Fi Alliance.
The Wi-Fi Alliance is an industry trade group promoting
wireless LAN technology and certifies products conforming to
a particular standard of interoperability.
Wi-Fi, Wireless Local Area Network
•
WiMAX stands for Worldwide Interoperability for Microwave
Access. This is another wireless technology providing
broadband internet service over long distance at a radius of 10
Km. WiMax network connectivity is composed of two parts:
WiMax Base Station (WiMAX tower or WiMAX booster) and
WiMax Receiver
MODEMS
• Modem, also known as Data Communication Equipment (DCE),
stands for modulate and demodulate is used for data
conversion. Modulator is used to changed digital to analog; and
demodulator is used to convert analog signal to digital signal.
The sending computer that generate digital signal must be
connected to a modem that convert the signal to analog before
transmission. Similarly, the receiving computer must also be
connected to a modem that converts the transmitted signal
from analog to digital that the computer understands. There
are varieties of modem such as internal and external and
internal devices.
Modem hardware…
• Serial (RS-232)
communication
interface
• RJ-11 telephone line
interface (four-wire
telephone line)
• RS 232 System Programmer
Types of modem
• Wireless modems are for mobile users that allow access
to the web or network without telephone wire
connection. The signal in electromagnetic wave
generated by wireless modem is the same with the signal
transmitted by cellular phones.
• ADSL Wireless Modem
• USB Wireless Modem
• The internal modem is a
separate card that is use
to be inserted into an
expansion slot of the
mainboard of the
computer. Within this
separate device, a
telephone cord is inserted
to a port and the other
end is plug in a telephone
outlet for connection to
the network.
• The external modem is a
separate device that is
used to plug into a special
port (RS-232) on a
computer with the
telephone line connected
to a telephone outlet.
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eq=7334#
Category of Modem
• Analog or Dial up modem are usually internal connected to the
computer through PCI slot of the motherboard. Dial-up modems have
operational speeds of around 28.8 kbps up to 56 kbps.
• Integrated Services Digital Network (ISDN) modem can be of internal
or external type that can transmit data in either digital or analog
phone lines at a typical speed from 64 kbps to 128 kbps.
• Digital Subscriber Line (DSL) modem is an external modem
supporting standard xDSL technologies providing “always-on” Internet
connections. Standard xDSL technologies includes network modems
for Asymmetric DSL (ADSL), and ADSL+2, Symmetric DSL (SDSL), High
Data Rate DSL (HDSL), and Very High DSL (VDSL). xDSL typical speed
ranges from 128 Kbps to 8 Mbps.
Category of modem …
• Cable modem connects to the internet using coaxial cable television
lines providing greater bandwidth for fast access to the internet with
downstream speed at a rate of 38 Mbps and an upstream at a speed
of 1 Mbps.
• 3G modem is another interface that allows electronic devices like
computer, and cell phone to connect to the Internet via a high speed
mobile broadband connection which is being transmitted over the
airwaves.
• Global System for Mobile Communication (GSM) modem is a
particular modem like a mobile phone which accepts Subscriber
Identity Module (SIM).
• Wireless modem is a device that let computers to connect to a
wireless local area network (WLAN) using cellular, satellite or WiFi
protocols for connectivity without physical transmission media.
Category of modem …
• Analog modem
• Integrated Services Digital Network
(ISDN) is a set of communication
standards for simultaneous digital
transmission of voice, video, data, and
other network services
• Cable modem
• 3G USB Modem
• 3G Wireless Modem
• Huawei E58836 3G Modem
• 3G Networking
• USB 3G Wireless Modem
• Wireless modems
Connection Services
• Dial-up connection also called dial-up access, is a method of
connecting to the internet wherein there is only one telephone line
connected to the computer.
• Digital Subscriber Line (DSL) Connection is an all digital, high speed
line utilizing ordinary telephone wires with special modems on
receiving and sending end.
• Integrated Services Digital Network (ISDN) Connection is all digital
similar with DSL but slower in accessing the internet.
• Cable TV Internet Connections. Cable modem connection provides
broadband internet connection that is designed to operate over cable
Television lines using channel space for data transmission.
Connection Services …
• Satellite Internet Connection allows user to access the Internet via
satellite. Two types of satellite used in communication are Geostationary
satellite place at a height of 36,800 km above the surface of the earth
and Low Earth Orbiting satellite placed at 400 km. above the earth’s
surface. This satellite changes position relative to the ground position
quickly.
• Wireless Internet Connections, also known as broadband, is one of the
latest Internet connection types using radio frequency band instead of
telephone lines or cables for Internet connections.
• Cellular Internet Connection is a technology that provides cell phone
network to access the Internet. The performance is restricted by the
capabilities of the mobile phone and the cell tower signal strength where
it is connected.
• Geostationary Stationary and Low Earth Orbiting Satellite
Internet Broadband Service Providers
• Bayan Telecommunications, through BayanDSL (formerly
SkyDSL)
• Globe Telecom, through its subsidiary Innove offers ADSL from
512 kbit/s to 4 Mbit/s
• PLDT offers ADSL from 384 kbit/s to 5 Mbit/s.
• PT&T offers ADSL and SDSL from 384 kbit/s to 2 Mbit/s.
• Smart Communications offers wireless fixed broadband at 384
kbit/s 512 kbit/s and 4 Mbit/s for corporate lines
• Sun Cellular offers 3.5G-enabled wireless Internet up to 2
Mbit/s.
• Wi-Tribe offers Wi-Max Internet up to 2Mbit/s, and 4Mbit/s.
COMPREHENSION CHECK
1. What are the different network devices that are used
to increase the performance of the transmission of
messages or information in communication?
2. What are the elements of communication?
3. What are the three types physical transmission
media?
4. What are the connection services used in
communication?
NETWORKS
• Computer network refers to
the connection of computers
by a media. It can be wired or
wireless and the connections
is managed by a network
operating systems.
• Each computer connection in
this topology is an example of a
node.
Terminology
• Nodes refer to the one connection of the network.
• Client is the requestor for the data or files from the server. The
client is connected to one of the available nodes.
• Server is the provider of files or information coming from the
database to the client computer.
• Directory server its serves as the authenticator. It gives rights to
those who log in to the networks. It also identifies and stores
the profiles of the user in the network.
• Host refers to the computers that contain the server’s files
where the clients made their request for connections.
• Switch is the one that establish connections to all computers.
Terminology …
• Network interface card or NIC card is the one that provides
interface from the computer mothers boards to the network
which is directly connected to the switch.
• Network operating system is the operating system that
manages the network. It gives privileges and rights to all
computers connecting to the networks.
• Network administrator is the person in charge of administering
the networks. He enforces the policies on how people will use
and access the networks.
Network Topologies
• Bus topology computers are connected in a common
media. This media is shared by computers in the
network.
• Star topology all computers are connected to central
hub sometimes it is the switch that manage the data
that is passing through it.
• Ring topology is the node
connected to other node
forming a circular
connection of computers.
The packets pass thru the
nodes until it reach its
destination. The LAN
protocol for this topology
is token passing.
• Hierarchical
topology has a
central root node
and it can branch to
the next level and it
can branch down
the line of the
hierarchy.
• Mesh Topology has at
least two nodes that
are connected to other
nodes. This topology
establishes redundant
connections. The node
does not only used to
receive and transmit
their messages but
serves as relays of
messages.
Network Security
• Firewall is hardware or a software base that filters the
incoming and outgoing traffic in your network. This is based
on the policies set on the firewall.
Firewall software
Career in IT: Network Administrator
• Network Administrator maintains computing
environment by identifying network requirements;
installing upgrades; monitoring network performance.
COMPREHENSION CHECK
1. Discuss the advantages and disadvantages of the
following network topologies: bus topology, ring
topology, star topology, hierarchical and mesh
topologies.
2. Describe the different types of modem.
REFERENCES
• Freshnel, Louis E. Communication Electronics. 2nd Ed. McGraw-Hill:
Singapore,1994
• Mcleod, Raymund, Jr. Management Information System. USA: Prentice-Hall
International, Inc., 1998
• Reference:O'Leary, T.J., O'Leary, L.I. Computing Essentials Introductory
Edition Ashford University. Boston: McGraw Hill, 2000
• Shelly, Gary B., Thomas J. Cashman, and Misty E. Varmaat. Discovering
Computers, Cooncept for Digital World 2002. USA: Course Technology,
Thomson Learning, 2001.
• Stair, Ralph, and George W. Reynolds. Fundamentals of Information Systems.
USA: Course Technology, Thomson Learning, 2006.
• http://beta.globalspec.com/learnmore/communications_networking/netwo
rking_equ
ipment/network_modems