WIRELESS NETWORKS
LECTURE 1
Introduction to Wireless Networks
WHAT IS WIRELESS COMMUNICATION ?
Wireless communication is the transmission of signals
(information) over a distance without any wires, cables or any
other forms of electrical conductors.
The transmitted distance can be anywhere between a few foot
(for example, a television’s remote control) and thousands of
kilometers (for example, Satellite radio communication).
Examples: Some of the devices used for wireless
communication are:
(1)Cordless telephones
(2)Mobiles Phones
(3)GPS units
(4)Wireless computer parts, such as WLAN Cards
(5)Satellite and terrestrial televisions.
(6)FM/AM Radios
NETWORKING ANYWHERE AND ANYTIME
There is a growing demand of using networks of mobile
devices anywhere and anytime.
In many situations, the Internet may not be an efficient solution
to communicate.
For example, a collection of people trying to communicate in a
hotel or conference hall.
ADVANTAGES AND DISADVANTAGES OF
WIRELESS COMMUNICATION ?
The most important advantages of wireless networks that
have made them spread significantly and replace wired
networks are:
(1) Mobility:
As wireless signals go through air, therefore no need to
connect device at a fixed location like a wired
communications system which limits the user to a fixed
location. for example, you can listen to a radio, talk on your
mobile phone while traveling in your car.
(2) Flexibility (wirelessness):
A wired communications system is limited to the number
of physical connections on the equipment whereas a
wireless device is generous and can connect devices more
frequently
.
ADVANTAGES AND DISADVANTAGES OF
WIRELESS COMMUNICATION ?
(3) Convenience:
You must physically connect a device to a wall jack for
wired communications to work. Wireless devices have no
cables to connect; if the signal has sufficient strength, the
device will work.
(4) Lower Cost:
Wireless communications networks are less expensive to
install and maintain than equivalent wired systems. Not
only do you have to pay the per-foot costs of the cable
itself, you need to invest time and labor to plan wiring
routes and put the wire in place. Any changes to the wiring
plan add to these costs. Although even wireless systems
need some cabling, the amount involved is a small fraction
of that needed for wired .
.
ADVANTAGES AND DISADVANTAGES OF
WIRELESS COMMUNICATION ?
(5) Time effective:
Working professionals can work and access Internet
anywhere and anytime without carrying cables or wires
wherever they go. This also helps to complete the work
anywhere on time and improves the productivity.
(6) Ease of Accessibility:
Doctors, workers and other professionals working in
remote areas can easily be in touch with medical centers
and their offices through wireless communication..
.
ADVANTAGES AND DISADVANTAGES OF
WIRELESS COMMUNICATION ?
Apart from many advantages there are some disadvantages of
Wireless communication as well
(1) Security:
Risk of outsiders accessing your network is greater and
easy unless strong security protocols are enabled.
(2) Interference:
Compared to wired systems, wireless networks are
frequently subject to electromagnetic interference. This
can be caused by other networks or other types of
equipment that generate radio waves that are within, or
close, to the radio bands used for communication.
Interference can degrade the signal or cause the system to
fail.
ADVANTAGES AND DISADVANTAGES OF
WIRELESS COMMUNICATION ?
(3) Less stability:
The network can be less stable. Wireless reception may be
weaken or damaged by a number of factors including large
distances or objects between wireless devices, and other
wireless networks.
(4) Lower speed:
Significantly slower than a wired network (2 – 50 times
slower)
(5) Health Problems:
The extensive use of wireless signals or exposure to it is
dangerous to the health of the human beings. The various
health problems that wireless can pose are memory loss,
mental disease, hormonal disorders and even cancer.
WIRELESS COMMUNICATION LINKS
Types of wireless communication
The different types of wireless communication technologies
include:
(1) Infrared (IR) wireless communication:
IR wireless communication communicates data or information
in devices or systems through infrared (IR) radiation.
IR wireless is used for short and medium-range
communications and security control. For IR communication
to work, the systems mostly operate in line-of-sight mode
which means that there must be no obstruction between the
transmitter (source) and receiver (destination).
Infrared is used in television remote controls and security
systems.
WIRELESS COMMUNICATION LINKS
WIRELESS COMMUNICATION LINKS
(1) Infrared (IR) wireless communication:
A photo LED transmitter and a photodiode receptor are
required for successful IR communication. The LED
transmitter transmits the infrared signal in the form of non-
visible light, which is captured and retrieved as information by
the photo receptor. In this way, the information between the
source and the target is transferred.
The source and/or destination can be laptops, mobile phones,
televisions, security systems and any other device that supports
IR wireless communication.
WIRELESS COMMUNICATION LINKS
(2) Broadcast Radio:
It is basically an audio broadcasting service, It uses a
transmitter to transmit radio waves to a receiving antenna.
A radio broadcast sends data over long distances (across
countries) at up to 2 megabits per second (AM/FM Radio).
Radio waves are electromagnetic signals transmitted by an
antenna. Radio waves have different frequency segments, and
you will be able to pick up an audio signal by tuning into a
specific frequency segment.
WIRELESS COMMUNICATION LINKS
WIRELESS COMMUNICATION LINKS
(2) Broadcast Radio:
Let us take an example of a radio station. When the Radio
station person says “You are listening to 93.7 FM”, what he
actually means is that signals are being broadcasted at a
frequency of 93.7 megahertz, which in turn means that the
transmitter at the station is oscillating at a frequency of
93,700,000 cycles per second.
When you wish to listen to 93.7 FM, all you have to do is tune
the radio to accept that particular frequency and you will
receive flawless audio reception.
WIRELESS COMMUNICATION LINKS
(3) Terrestrial Microwave :
Terrestrial Microwave transmission involves the transfer of
voice and data through the atmosphere as super high-
frequency radio waves called microwaves.
Terrestrial microwave communication uses Earth-based
transmitters and receivers resembling satellite dishes.
Terrestrial microwaves limit all communications to line-of-
sight. Relay stations are spaced approximately 48 km
(30 mi) apart.
WIRELESS COMMUNICATION LINKS
WIRELESS COMMUNICATION LINKS
(3) Terrestrial Microwave :
Antennas used in microwave transmissions are of convenient
sizes and shapes. Microwave transmission depends on
line-of-sight in order to work properly. For two way
communications to take place, two frequencies are used.
However, this does not require two antennas because the
frequencies can be dealt with one antenna at both ends.
The distance covered by microwave signals relies on the height
of the antenna. Each antenna is built with a fitted repeater
to regenerate the signal before passing it on to the next
antenna in line. The ideal distance between each antenna is
approximately 25 miles.
The main drawback of microwave signals is that they can be
affected by bad weather, especially rain and even totally
stopped by a hindrance like mountain.
WIRELESS COMMUNICATION LINKS
(4) Communications Satellites:
A communication satellite is an artificial satellite used
specifically as a communication transmitter/receiver in
orbit. It behaves like a radio relay station above the earth
to receive, amplify, and redirect analog and digital signals
carried on a specific radio frequency.
Data is passed through a satellite using a transponder which is
a signal path. Most satellites have between 24 to 72
transponders.
A single transponder capable of transmitting and receiving 155
mbps information. This huge capability makes
communication satellites an ideal medium for transmitting
and receiving all kinds of content, including audios and
videos.
WIRELESS COMMUNICATION LINKS
WIRELESS COMMUNICATION LINKS
WIRELESS COMMUNICATION LINKS
(4) Communications Satellites:
Satellites communicate via microwave radio waves, which are
not deflected by the Earth's atmosphere.
The satellites are stationed in space, typically in
geosynchronous orbit 35,400 km (22,000 mi) above the
equator.
These Earth-orbiting systems are capable of receiving and
relaying voice, data, and TV signals.
TYPES OF WIRELESS NETWORKS
(1) Wireless PAN:
Wireless personal area networks (WPANs) interconnect
devices within a relatively small area, that is generally
within a person's reach
For example, both Bluetooth radio and invisible infrared light
provides a WPAN for interconnecting a headset to a
laptop. ZigBee also supports WPAN applications.
Wi-Fi PANs are becoming routine as equipment designers start
to integrate Wi-Fi into a variety of consumer electronic
devices.
Intel "My WiFi" and Windows 7 "virtual Wi-Fi" capabilities
have made Wi-Fi PANs simpler and easier to set up and
configure.
TYPES OF WIRELESS NETWORKS
(1) Wireless PAN:
TYPES OF WIRELESS NETWORKS
(1) Wireless LAN:
A wireless local area network (WLAN) links two or more
devices over a short distance using a wireless distribution
method, usually providing a connection through an access
point for Internet access.
The use of spread-spectrum or OFDM technologies may allow
users to move around within a local coverage area, and
still remain connected to the network.
TYPES OF WIRELESS NETWORKS
(1) Wireless LAN:
TYPES OF WIRELESS NETWORKS
(2) Wireless LAN:
Products using the IEEE 802.11 WLAN standards are marketed
under the Wi-Fi brand name. Wi-Fi establishes internet
connection with the Desktop computers, Laptops, and
portable computer devices.
Fixed wireless technology implements point-to-point links
between computers or networks at two distant locations,
often using dedicated microwave or modulated laser light
beams over line of sight paths. It is often used in cities to
connect networks in two or more buildings without
installing a wired link
TYPES OF WIRELESS NETWORKS
(3) Wireless mesh network:
A wireless mesh network is a wireless network made up of
radio nodes organized in a mesh topology.
Each node forwards messages on behalf of the other nodes.
Mesh networks can "self heal", automatically re-routing
around a node that has lost power.
TYPES OF WIRELESS NETWORKS
(4) Wireless MAN:
Wireless metropolitan area networks are a type of wireless
network that connects several wireless LANs.
WiMAX is a type of Wireless MAN and is described by the
IEEE 802.16 standard.
TYPES OF WIRELESS NETWORKS
(5) Wireless WAN:
Wireless wide area networks are wireless networks that
typically cover large areas, such as between neighboring towns
and cities, or city and suburb.
These networks can be used to connect branch offices of
business or as a public internet access system.
TYPES OF WIRELESS NETWORKS
(5) Wireless WAN:
The wireless connections between access points are usually
point to point microwave links using parabolic dishes on the
2.4 GHz band, rather than omnidirectional antennas used with
smaller networks.
A typical system contains base station gateways, access points
and wireless bridging relays. Other configurations are mesh
systems where each access point acts as a relay as well.
TYPES OF WIRELESS NETWORKS
(5) Cellular networks:
A cellular network or mobile network is a radio network
distributed over land areas called cells, each served by at
least one fixed-location transceiver, known as a cell site or
base station.
In a cellular network, each cell usually uses a different set of
radio frequencies from all their immediate neighbouring
cells to avoid any interference.
TYPES OF WIRELESS NETWORKS
(5) Cellular networks:
When joined together these cells provide radio coverage over a
wide geographic area. This enables a large number of
portable transceivers (e.g., mobile phones, pagers, etc.) to
communicate with each other and with fixed transceivers
and telephones anywhere in the network, via base stations
Although originally intended for cell phones, with the
development of smart phones, cellular telephone networks
routinely carry data in addition to telephone conversations:
TYPES OF WIRELESS NETWORKS
(6) Space network:
Space networks are networks used for communication between
spacecraft, usually in the vicinity of the Earth. The
example of this is NASA's Space Network.
(7) Global area network:
A global area network (GAN) is a network used for supporting
mobile across an arbitrary number of wireless LANs,
satellite coverage areas, etc.
The key challenge in mobile communications is handing off
user communications from one local coverage area to the
next.
HISTORY OF WIRELESS COMMUNICATIONS
Wireless technology has a long history, and it began
around the time that in 1830: Professor Joseph Henry
transmitted the first practical electrical signal
James C. Maxwell theoretically predicted
and then proved the existence of electromagnetic waves in the
1860s.
Heinrich R. Hertz experimentally confirmed
the actual existence of the electromagnetic wave in 1888.
HISTORY OF WIRELESS COMMUNICATIONS
Photophone:
The world's first wireless telephone conversation occurred in
1880, when Alexander Graham Bell and Charles Sumner
Tainter invented a telephone that conducted audio
conversations wirelessly over modulated light beams (which
are narrow projections of electromagnetic waves).
HISTORY OF WIRELESS COMMUNICATIONS
Bell and Tainter's photophone, of 1880.
HISTORY OF WIRELESS COMMUNICATIONS
Radio:
In 1895, Guglielmo Marconi succeeded in receiving Morse
code on a radio wave transmitted by a spark-gap transmitter
with a receiver 2.4 km away.
HISTORY OF WIRELESS OMMUNICATIONS
In1946 the first commercial mobile radiotelephone service is
introduced in St. Louis
In 1947, Engineers at Bell Labs develop the concept of cellular
technology.
In 1947 The transistor was invented by scientists John
Bardeen, Walter Brattain and William Shockley who later share
the Nobel Prize. The transistor replaces vacuum tubes, serving
as the foundation for the development of modern electronics
and makes possible the combining of computers and
communications.
HISTORY OF WIRELESS COMMUNICATIONS
In1950 , TD-2, the first terrestrial microwave
telecommunication system, is installed to support 2400
telephone circuits.
In 965 INTELSAT launches the Early Bird geostationary
satellite.
1964 AT&T’s Improved Mobile Telephone Service (IMTS)
eliminates the need for push-to-talk operation and offers
automatic dialing
In January, 1983 , TCP/IP is selected as the official protocol for
the ARPANET
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HISTORY OF WIRELESS COMMUNICATIONS
In 1983, Motorola introduces the DynaTAC mobile telephone
unit, the first truly “mobile” radiotelephone.
In1983, On October 13, the first commercial cellular system
begins operating in Chicago. In December 1983, the second
system is activated in the Baltimore/Washington, D.C.
In1984 the Cellular Telecommunications Industry Association
is founded in May.
In1985 , At year's end, there are 340,213 cell phone
subscribers.
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HISTORY OF WIRELESS COMMUNICATIONS
In1990, Cellular subscribership surpasses 5 million.
In1992 , World’s first commercial text message is sent by
employees of Logica CMG.
In1993, the first smart phone (IBM’s Simon) is released to the
public and offers consumers a calendar, address book,
calculator, email, faxing services and games.
In1993, Internet Protocol version 4 (IPv4) established for
reliable transmission over the Internet in conjunction with the
Transport Control Protocol (TCP)
.
HISTORY OF WIRELESS COMMUNICATIONS
In1997 Original version of the standard IEEE 802.11 for
wireless local area networking is released.
In 1998 , Ericsson, IBM, Intel, Nokia, and Toshiba develop
Bluetooth for wireless data exchange between handheld
computers or cellular phones and stationary computers
In1999 , Wi-Fi® brand adopted for technology based upon
IEEE 802.11 specifications for wireless local area networking.
