0 lecture 1 wp wireless protocol

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

OBJECTIVES
 Fundamental Aspects of Wireless Networks
o Electromagnetic Waves
o Radio Spectrum
o Radio Transmitter and Receiver
o Antennas
 Wireless Networks
o Wireless Personal Area Network (WPAN)
o Wireless Local Area Network (WLAN)
o Wireless Metropolitan Area Network (WMAN)
 Mobile Cellular Networks
o Basic Concepts (from the 1st Generation)
o The Evolution of Mobile Networks from 1G to 4G
2

ELECTROMAGNETIC WAVES
 Electromagnetism is a branch of physics involving
the study of the electromagnetic force, a type of
physical interaction that occurs between electrically
charged particles.
 An electromagnetic field is a physical field produced
by electrically charged objects. It affects the
behavior of charged objects in the vicinity of the
field.
 Electromagnetic waves or EM waves are waves
that are created as a result of vibrations between
an electric field and a magnetic field. In other
words, EM waves are composed of oscillating
magnetic and electric fields.
3

WHAT ARE ELECTROMAGNETIC WAVES?
 As has been observed from nature,
Electromagnetic (EM) waves are oscillations
formed when an electric field couples with a
magnetic field and which can travel through any
physical media (e.g. air, water, rock) or through
a vacuum (e.g. space).
 In a vacuum, the waves travel at the speed of
light (3 x 108m/s), but through physical media
they travel a bit slower.
 The magnetic and electric fields of an EM wave
are perpendicular to each other and to the
direction of travel of the wave.
4

WHAT ARE THE NATURAL SOURCES OF EM
WAVES?
 The Sun is the earth's primary source of EM waves (or
radiation). It is radiation from the Sun which sustains all
life on the planet.
 Radioactive materials (e.g. uranium) are emitters of
particle radiation and EM radiation. The particles emitted
are either alpha particles or electrons. Every particle
emission is accompanied by a tiny pulse of EM radiation
which has a gamma ray signature.
 Stars and Lightning are also natural sources of EM
waves.
o In general, all hot objects emit radiation over a wide
range of wavelengths.
6

WAVELENGTH AND FREQUENCY
 EM waves are described by Wavelength, Frequency and
Amplitude.
 Wavelength (λ) is the distance between two consecutive
peaks of a wave, measured in meters (m). The range of
wavelengths varies from as long as 100,000 Km to smaller
than 1 pm (i.e. 10-12 m).
 Frequency (f) is the number of wave cycles that would pass
through a point in one second (measured in Hertz (Hz)).
Since all EM waves travel at the same speed, the frequency
of an EM wave is inversely proportional to wavelength and
are defined by the relation C = λf (C = speed of light)
 The lowest EM wave frequency (3 Hz) is generated by
lightning and other natural disturbances. The frequency of
alternating current flowing in electric power grids is 50 or 60
Hz, making power grids an unintentional source of EM
8

THE ELECTROMAGNETIC SPECTRUM
 EM Spectrum is the range of all types of EM waves.
10
The higher the
Frequency of an
EM
wave, the more
energy it has.

11
Gamma Rays
(> 3x1019 Hz)
X-Rays
(3x1017-3x1019 Hz)
Ultraviolet Light
(800THz-30 PHz)
Visible Light
(430THz –
800THz)Infrared
(300GHz –
430THz)
Microwaves
(300MHz –
300GHZ)Radio Waves
(3 kHz –
300GHz)

SO WHERE EXACTLY ARE THESE EM WAVES?
 Can we see them? - Only a small portion of the EM
spectrum can be seen by the human eye. This portion is
called the White Light (or Visible Light), which contains all
the colors of the rainbow, from red to violet.
 Can we hear them? - There are 2 types of waves;
Longitudinal waves are waves that can only pass through
a medium e.g. Ocean and Sound waves. EM radiation travel
as Transverse waves, which don’t need a medium.
Humans can’t hear EM waves because our eardrum only
senses longitudinal waves.
 Are they harmful? - Over-exposure to certain types of
electromagnetic radiation can be harmful. The higher the
frequency of the radiation, the more damage it is likely to
cause to the body:
o Microwaves cause internal heating of body tissues. Infrared
radiation is felt as
heat and causes skin burns. X-rays and Gamma rays can
damage cells, causing
12

AMPLITUDE (INTENSITY OR POWER DENSITY) OF AN
EM WAVE
 The amplitude (normally called intensity or power density) of
EM waves obeys the inverse square law, which states that
the intensity of a wave in free space decreases in proportion to
the square of the distance from source i.e. P α 1/d2.
Attenuation is the term used to describe when a signal's
intensity is reduced.
 Intensity at different distances is calculated as P1/P2 = d2
2/d12
 P1 = signal intensity at distance 1
 P2 = signal intensity at distance 2
 d1 = distance 1 from light source (m)
 d2 = distance 2 from light source (m)
 If a travelling EM wave hits an obstacle, some of its energy is
absorbed, causing even faster attenuation.
 A t t e n u a t i o n i s m e a s u r e d i n Decibels (dB) and is
calculated as 10Log10 (Pin/Pout)
14

PROPAGATION CHARACTERISTICS OF EM
WAVES
 Once an EM wave has been transmitted, it has certain propagation
characteristics associated with its frequency.
 Specific waves have distinct abilities to hop, spread and penetrate.
Certain waves can go through or bounce off walls or curve around
corners better than others. For example, your mobile phone works
inside a building because its wave signal goes through windows
and walls, but you will generally need a rooftop aerial for your TV
set to achieve good reception.
 The characteristics of EM waves vary, but there are few general
rules;
o Gamma rays and ELF waves will penetrate almost
anything.
o In free space, low frequency signals travel longer because
the wave is either diffracted by the ground obstacles or
reflected/refracted by the upper atmospheric layers.
o Higher frequency waves can better penetrate through the
human body. For example, infrared and visible light waves are
15

REFLECTION, REFRACTION AND DIFFRACTION
OF EM WAVES
 Reflection is the change in direction of a wave at
an interface between two different media such that
the wave returns from where it originated. With
reflection, angle of incidence is equal to the angle
of reflection.
 Refraction occurs when the direction of an EM
wave changes as it moves from an area of one
refractive index to another. With refraction, angle of
incidence is not equal to the angle of reflection.
 Diffraction occurs when EM waves encounter an
obstacle and they tend to travel around them.
16

QUESTIONS???
THANK YOU FOR YOUR ATTENTION
18

0 lecture 1 wp wireless protocol

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