Wireless Data Networks
Dr Chandimal Jayawardena

Contents
Wireless Communication Basics
Wireless Local Area Networks
Fundamentals of Wireless Mesh Networks
Wireless Personal Area Networks
Wireless Metropolitan Area Networks
Wireless Sensor Networks
Introduction to Digital Cellular Systems

Wireless Systems
Wireless PANs
Wireless LANs
Wireless MANs
Mobile Communication Systems
bl

Wireless Technologies

Wireless Data Networks
50 Mbps
Spread
10 Mbps
Spectrum
Infrared Wireless
2 Mbps
LANs
Wireless
Data Rates
s
LANs
1 Mbps
2.5 GHz
Service
D
Broadband PCS
56 Kbps
Circuit and Packet Data
19.6 Kbps Cellular, CDPD, Mobitex, DataTac
Narrow Band
9.6 Kbps Satellite
Wireless LANs Narrowband PCS
Local Wide
Coverage Area

Wireless Technologies
WAN
(Wide Area Network)
MAN
(Metropolitan Area Network)
LAN
(Local Area Network)
PAN
(Personal Area
Network)
PAN LAN MAN WAN
802.11a, 11b, 11g 802.11 GSM, GPRS,
Standards Bluetooth HiperLAN2 MMDS, LMDS CDMA, 2.5–3G
Speed <1 Mbps 2–54+ Mbps 22+ Mbps 10–384 Kbps
Range Short Medium Medium–Long Long
PDAs, M bil
PDA Mobile
Peer-to-Peer Enterprise Fixed, Last
Applications Phones, Cellular
Device-to-Device Networks Mile Access
Access

What is a wireless LAN?
It provides all the features and benefits of
traditional LAN technologies such as Ethernet,
but without the limitations of wires or cables
Instead of using twisted-pair or fiber-optic
cable, WLANs use infrared light (IR) or radio
, g()
frequencies (RFs).
The use of RF is far more popular for its
longer range higher bandwidth, and wider
range, bandwidth
coverage.

Unlicensed Frequency Bands

No more wires?
Wireless systems are not completely
wireless.
Wireless systems are connected to
traditional wired LAN systems.
Furthermore, wireless devices must be
powered to provide energy to encode,
decode, compress, decompress,
decode compress decompress
transmit, and receive wireless signals.

Wireless standards and
certifications for WLANs

WiFi

Momentum is Building in
Wireless LANs
• Wireless LAN is an “addictive” technology
• Strong commitment to Wireless LANs by
technology heavy-weights
–Cisco, IBM, Intel, Microsoft
• Embedded market is growing
–Laptop PC’s with “wireless inside”
–PDA’s are next
• The WLAN market is expanding
from I d t S
f Industry-Specific Applications,
ifi A li ti
to Universities, Homes, & Offices

Wireless LANs Are Taking Off
Wi l LAN A T ki
Future Growth
Worldwide WLAN Market
*includes embedded clients, add-on client
includes add on
Due To:
DT
cards, & infrastructure equipment for both
the business and consumer segments
Standards
($ Billions) High Bandwidth Needs
CAGR = 43%
$11.0 Low Cost
$10.3
$10.0 $9.0
Embedded in Laptops
$9.0
$8.0
$8 0 Variety of Devices
$7.0 $6.0
Voice + Data
$6.0
$5.0 Multiple Applications
$4.0 $3.3
Security Issues Solved
S it I Sl d
$2.6
$
$3.0
$1.7
$2.0 Ease of Deployment
$1.0
Network Mgmt. Tools
$0.0
2001 2002 2003 2004 2005 2006
Enterprise Adoption
Source: Forward Concepts, 2003

Benefits of WLANs

WLAN Evolution: 2000–
Present
Warehousing
Retail
Healthcare
Education
• Businesses
• Home
11 Mbps 54 Mbps
Speed 860 Kbps 1 and 2 Mbps
1 and 2 Mbps
Standards-based
Network Proprietary
5 GHz
Radio 900 MHz 2.4 GHz 2.4 GHz
802.11 802.11a,b 802.11g
IEEE 802 11Begins
802.11Begins
Ratified Ratified Drafted
Drafting
1986 1998 2000 2002
1988 1990 1992 1994 1996

Wireless Communication Basics
Radio Transmission Fundamentals
Dr. Chandimal Jayawardena

Networking Media
Different types of networking media that are used
at the physical layer
Shielded twisted pair
Unshielded twisted pair
Coaxial cable
C i l bl
Fiber-optic cable
Radio waves – Medium used for wireless technologies

Wave

Sine Wave

Amplitude — The distance from zero to the maximum value of each
alternation is called the amplitude. The amplitude of the positive alternation
and the amplitude of the negative alternation are the same.
Period — The time it takes for a sine wave to complete one cycle is defined as
the period of the waveform. The distance traveled by the sine wave during this
period is referred to as its wavelength.
Wavelength — Wavelength, indicated by the Greek lambda symbol λ, is the
distance along the waveform from one point to the same point on the next
cycle.
Frequency — The number of repetitions or cycles per unit time is the
frequency, typically expressed in cycles per second, or Hz

Frequency vs. Time
Calculation
The inverse relationship between time (t),
the period in seconds, and frequency (f),
in Hz, is indicated by the following
formulas:
t = 1/f
f = 1/t

Frequency vs. Wavelength

EM Spectrum

Radio frequencies

Watt
A watt is the basic unit of power, and power is related to energy.
However, power is a rate, and energy is a quantity. The formula
for power is
P = ∆E / ∆t
∆E is the amount of energy transferred (in Joules)
∆t is the time interval over which that energy is transferred.
Example: One Joule of energy is transferred in one second, this is
second
one watt (W) of power

Calculating dB
The formula for calculating dB is as follows:
dB = 10 log10 (Pfi l/Pref)
final f
dB = The amount of decibels. This usually represents a
loss in power, as the wave travels or interacts with matter
power matter,
but it can also represent a gain, as when traveling through
an amplifier.
Pfinal = The final power. This is the delivered power after
some process has occurred.
Pref = The reference power. This is the original power.

Decibel Reference
dB milliWatt (dBm) —unit of measurement for signal strength or power level.
( ) g g p
dB dipole (dBd) —the gain an antenna has, as compared to a dipole antenna
at the same frequency. A dipole antenna is the smallest, least gain practical
antenna that can be made.
dB isotropic (dBi) —the gain a given antenna has, as compared to a
theoretical isotropic, or point source, antenna.
Effective Isotropic Radiated Power (EIRP) —the effective power found in the
main lobe of a transmitter antenna It is equal to the sum of the antenna gain,
antenna. gain
in dBi, plus the power level, in dBm, into that antenna.
Gain —the amount of increase in energy that an antenna appears to add to
an RF signal. Cisco Aironet wireless is standardized on dBi to specify gain
measurements. Some antennas are rated in dBd. To convert any number from
dBd to dBi, simply add 2.14 to the dBd number.

Fourier Synthesis
When two EM waves occupy the same space, their
effects combine to form a new wave of a different
s ape
shape.
A special sum of sine waves, of harmonically related
frequencies,
frequencies could be added together to create any
wave pattern. Harmonically related frequencies are
simply frequencies that are multiples of some basic
frequency.
frequency Complex waves can be built out of simple
waves.
The sum is called a Fourier Series

Signals

Viewing signals in time

Viewing signals in frequency

Digital Signals in Time