This document provides an overview of wireless networks and protocols. It discusses wireless personal area networks (WPANs) such as Bluetooth and infrared, wireless local area networks (WLANs) using IEEE 802.11 standards, and wireless metropolitan area networks (WMANs) such as WiMAX. For WLANs, it describes wireless access points, common network architectures, and media access control protocols including carrier sense multiple access with collision avoidance (CSMA/CA) and carrier sense multiple access with collision detection (CSMA/CD).

1. CSC 4315
(WIRELESS NETWORKS AND
PROTOCOLS)
LECTURE 5
Department of Maths and Computer-
Science
Faculty of Natural and Applied Science
BY
DR. BABANGIDA ALBABA
AND
UMAR DANJUMA MAIWADA

2. WIRELESS NETWORKS
 Wireless network is a network set up by using
radio signal frequency to communicate among
computers and other network devices. Sometimes
it's also referred to as WiFi network or WLAN. This
network is getting popular nowadays due to easy
to setup feature and no cabling involved.
 A wireless network is a computer network that
uses wireless data connections between network
nodes. Wireless networking is a method by which
homes, telecommunications networks and business
installations avoid the costly process of introducing
cables into a building, or as a connection between
various equipment locations. Wireless
telecommunications networks are generally
implemented and administered using radio
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4. WIRELESS STANDARDS FOR DIFFERENT
NETWORK TYPES
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5. WIRELESS PERSONAL AREA NETWORK
 Wireless Personal Area Network (WPAN) is a
computer network used for communication among
computer devices close to one person, typically a few
meters. PAN’s can be used for communication among
the personal devices themselves (intrapersonal
communication), or for connecting to a higher level
network and the Internet. PANs may be wired with
computer buses such as USB and FireWire.
 Common Wireless PAN technology standards include.
 Bluetooth (an industrial specification known as IEEE
802.15.1).
 HomeRF (developed by the Home Radio Frequency
Working Group)
 Infrared (developed by the Infrared Data Association
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7. COMPARISON OF WPAN TECHNOLOGY
STANDARDS
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8. WIRELESS LOCAL AREA NETWORK
 Wireless Local Area Network (WLAN) uses radio
communication to accomplish the same functionality as
a wired LAN i.e. connecting two or more computer
devices within a single room, building or site. WLANs
can have one of 3 architectures: Ad-hoc, Infrastructure
based, or Mesh network.
 An ad-hoc wireless network is a casual network in which
wireless devices talk directly to each other without the use
of an access point. An ad-hoc network can spring up
between two laptops in a coffee shop.
 In an infrastructure-mode wireless network, access
points connected to the wired network act as a bridge to
wireless clients. All wireless access points are connected to
the wired network and all wireless traffic travels to the wired
network on the way to its destination.
 Mesh networks use “smart” access points, which act as
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10. ACCESS POINT
 An access point is a station that transmits and
receives data (sometimes referred to as a
transceiver).
 An access point connects users to other users
within the network and also can serve as the point
of interconnection between the WLAN and a fixed
wire network.
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11. WIRELESS ACCESS POINT
 a wireless access point (WAP), or more generally just
access point (AP), is a networking hardware device
that allows other Wi-Fi devices to connect to a wired
network.
 Wireless Access Point (WAP) is a networking
hardware device that allows a Wi-Fi compliant device to
either:
 connect via Ethernet to a non wireless router and 'turn it into'
a wireless signal.
 connect via Ethernet to a wireless router, to provide a brand
new wireless signal.
 The WAP can also be an integral component of the
router itself i.e. a router can be a access point but an
access point cannot be a router.
 When an infrastructure-based WLAN expands to consist
of multiple access points on one logical network, it is
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13. IEEE 802.11 WLAN STANDARDS
 These standards come from the Institute of
Electrical and Electronics Engineers (IEEE), which
only sets the specifications for the standards—it
doesn’t test individual wireless products for
compliance to these standards. That is normally
done by an organization called the Wi-Fi Alliance.
 The 2.4-GHz frequency band is appealing it is free.
But this also means there’s no central entity to
coordinate frequency use. Interference with other
2.4-GHz devices (e.g. baby monitor, and medical
equipment) can be a problem especially in urban
environments and apartment buildings. 13

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15. WLAN PERFORMANCE
The problem of interference with nearby devices is extremely
variable. One network can experience serious slowdowns in an
environment that seems very similar to another wireless network
that’s operating perfectly.
 Most wireless vendors offer a software program that allows you
to monitor signal strength and connection speed. One way to
test for interference is to place an access point in your office,
insert a wireless card in your laptop, and then roam around to
evaluate the strength of the signal. This can reveal areas for
access points that offer strongest signal and fastest connection.
 Another way to minimize interference is to simply remove or
reposition the devices that cause it. Keep devices such as
microwave ovens at least six feet from access points. If you’re
having significant interference problems with the 2.4-GHz band,
it may be worthwhile to switch to 5-GHz.
 Some buildings provide special obstacles to wireless
transmission. For example solid stone walls or brick buildings
can interfere with wireless transmission. For this reason, a
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16. CARRIER SENSE MULTIPLE ACCESS (CSMA)
 Carrier Sense Multiple Access (CSMA) is a
network protocol that listens to or senses network
signals on the carrier/medium before transmitting
any data.
 In order to avoid (or reduce) the possibility of
interference, the carrier sense multiple access
(CSMA) protocol was originally implemented is
used in WLAN network interface cards.
 With CSMA, a transmitter attempts to detect the
presence of a carrier signal from another node
before attempting to transmit. If a carrier is sensed,
the node waits for the transmission in progress to
end before initiating its own transmission.
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19. CARRIER SENSE MULTIPLE ACCESS
COLLISION AVOIDANCE (CSMA/CA)
 Carrier-sense multiple access with collision
avoidance (CSMA/CA) in computer networking, is
a network multiple access method in which carrier
sensing is used, but nodes attempt to avoid
collisions by beginning transmission only after the
channel is sensed to be "idle".
 Carrier Sense Multiple Access/with Collision
Avoidance (CSMA/CA) is a network contention
protocol used for carrier transmission in networks
using the 802.11 standard. CSMA/CA increases
network traffic as it requires sending out a signal to
the network even before transmitting any real data.
 CSMA/CA has been used in a variety of wired
communication systems, it is particularly beneficial
in a wireless LAN due to a common problem of
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20. LIMITATIONS OF CSMA/CA
 With CSMA alone, WLAN’s still experience two
major problems termed the Hidden Node and
Exposed Node Problems.
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21. CSMA WITH COLLISION AVOIDANCE
(CSMA/CA)
 CSMA/CA uses control packets to improve network
performance
 As usual, all nodes sense carrier (physically) before
transmission. If channel is idle, a node uses control
packets (RTS and CTS) to set up communication
 All other nodes that hear the CTS broadcast know
that the sender will be busy for the indicated duration
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23. CARRIER SENSE MULTIPLE ACCESS
COLLISION DETECTION (CSMA/CD)
 Carrier sense multiple access with collision detection or
CSMA/CD is a protocol (or rule) used by computer ethernet
networks. ... When this collision occurs, the computers
stop sending information, wait for a random amount of time,
and then check before resending the information.
 This is used in combination with collision detection in which
a transmitting station detects collisions by sensing
transmissions from other stations while it is transmitting a
frame.
 When this collision condition is detected, the station stops
transmitting that frame, transmits a jam signal, and then
waits for a random time interval before trying to resend the
frame.
 CSMA/CD is a modification of pure carrier-sense multiple
access (CSMA). CSMA/CD is used to improve CSMA
performance by terminating transmission as soon as a
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24. WIRELESS METROPOLITAN AREA NETWORK
 Wireless metropolitan area networks (WMANs)
enable users to establish wireless connections
between multiple locations within a metropolitan
area (e.g., between multiple office buildings in a city
or on a university campus), without the high cost of
laying fiber or copper cabling and leasing lines.
 WMANs can also serve as backups for wired
networks, should the primary leased lines for wired
networks become unavailable. WMANs use either
radio waves or infrared light to transmit data.
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26. WIMAX
 WiMAX (Worldwide Interoperability for Microwave
Access) is a family of wireless broadband
communication standards based on the IEEE 802.16 set
of standards, which provide multiple physical layer
(PHY) and Media Access Control (MAC) options.
 WiMAX is a family of wireless broadband
communication standards based on the IEEE 802.16 set
of standards, which provide multiple physical layer and
Media Access Control options.
 WiMAX refers to interoperable implementations of the
IEEE 802.16 family of wireless-networks standards
ratified by the WiMAX Forum. (Similarly, Wi-Fi refers to
interoperable implementations of the IEEE 802.11
Wireless LAN standards certified by the Wi-Fi Alliance.)
WiMAX Forum certification allows vendors to sell fixed
or mobile products as WiMAX certified, thus ensuring a
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27. WMAN STANDARDS
 The major WMAN standards are: HiperMAN,
HiperACCESS, and 802.16 (more commonly known as
WiMAX). In practical terms, WiMAX would operate similar to
WiFi but at higher speeds, over greater distances and for a
greater number of users.
 A WiMAX system consists of two parts:
o A WiMAX tower, which is similar in concept to a cell-phone tower.
A single WiMAX tower can provide coverage to a very large area -
- as big as 3,000 square miles (~8,000 square km).
o A WiMAX receiver, which could be a small box or PCMCIA card,
or they could be built into a laptop the way WiFi access is today.
 A WiMAX tower station can connect directly to the Internet
using a highbandwidth, wired connection (for example, a T3
line). It can also connect to another WiMAX tower using a
line-of-sight, microwave link. This connection to a second
tower (often referred to as a backhaul), along with the
ability of a single tower to cover up to 3,000 square miles, is
what allows WiMAX to provide coverage to remote rural
areas.
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28. TYPES OF WMAN
 There are two basic types of WMANs: Back haul
and Last mile.
 Back haul is an option for enterprises that can't afford
to install or lease fiber to connect their facilities over a
large campus or city.
 Last mile is used as an alternative to residential
broadband DSL/cable modem or Fibre. It is also handy
for temporary networks, such as large construction sites
or areas where network service is disrupted.
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30. QUESTIONS
THANK YOU FOR YOUR ATTENTION !!!
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