0 lecture 3 wp wireless protocol

CSC 4315
(WIRELESS NETWORKS AND
PROTOCOLS)
LECTURE 3
Department of Maths and Computer-
Science
Faculty of Natural and Applied Science
BY
DR. BABANGIDA ALBABA
AND
UMAR DANJUMA MAIWADA

RADIO TRANSMITTER AND RECEIVER
 Radio is the technology of signaling or communicating
using radio waves. Radio waves are electromagnetic
waves of frequency between 30 hertz (Hz) and
300 gigahertz (GHz). They are generated by an
electronic device called a transmitter connected to an
antenna which radiates the waves, and received by a
radio receiver connected to another antenna.
 Transmitter is a set of equipment used to generate and
transmit electromagnetic waves carrying messages or
signals, especially those of radio or television.
 Receiver is a device, as in a radio or telephone, that
converts incoming radio, microwave, or electrical
signals to a form, such as sound or light, that can be
perceived by humans.
2

 Radio Transmitter is an electronic device which
produces radio waves with an antenna. The
transmitter itself generates a radio frequency
alternating current, which is applied to the antenna.
When excited by this alternating current, the
antenna radiates radio waves.
 Radio Receiver, also known as a receiver,
wireless or simply radio is an electronic device
that receives radio waves and converts the
information carried by them to a usable form. It is
used with an antenna. The antenna intercepts radio
waves (electromagnetic waves) and converts them
to tiny alternating currents which are applied to the
receiver, and the receiver extracts the desired
3

MAXWELL’S LAWS
 Maxwell's equations are a set of coupled partial
differential equations that, together with the Lorentz
force law, form the foundation of classical
electromagnetism, classical optics, and electric
circuits. The equations provide a mathematical
model for electric, optical, and radio technologies,
such as power generation, electric motors, wireless
communication, lenses, radar etc.
 Maxwell's equations describe how electric and
magnetic fields are generated by charges, currents,
and changes of the fields.
 The changing magnetic field creates a changing
electric field through Faraday's law. In turn, that
electric field creates a changing magnetic field
through Maxwell's addition to Ampère's law.
4

APPLICATION OF MAXWELL’S LAWS IN
PRACTICE
 In the later part of the 19th century, scientists
figured out how to electronically generate radio
waves using electric currents. The basic physical
laws that govern EM waves are described by
Maxwell’s equations.
 From Maxwell’s laws, it is understood that when
alternating current (AC) moves through a wire (or
other physical conductor), some of that energy
escapes into the surrounding space as an
alternating magnetic field. That magnetic field
creates an alternating electric field in space
(having the same frequency as the original AC),
which in turn creates another magnetic field and so
forth until the original current is interrupted.
5

6
In practice, two components
are required for radio
c o m m u n i c a t i o n : a
T r a n smi t t e r and a
Receiver.

RADIO TRANSMITTER
 A radio transmitter is a device that generates radio
waves that carry useful information such as audio,
video, or digital data.
 Power supply provides the necessary electrical power
for operation.
 Oscillator creates alternating current (AC), referred to
as the Carrier Wave, at the frequency on which the
transmitter will transmit.
 Modulator adds actual information (e.g. audio or video)
to the carrier wave.
 Amplifier amplifies the modulated carrier wave to
increase its power. The more powerful the amplifier, the
more powerful the broadcast.
 Antenna converts the amplified signal to radio waves.
7

HOW DOES THE OSCILLATOR WORK?
 An Oscillator has three basic parts; Oscillatory
Circuit, Amplifier and a Feedback Network.
 The Oscillatory Circuit consists of passive
components such as filter circuits that are responsible
for shape and frequency of the wave produced.
 The Amplifier increases the voltage level (power) of
the input wave signal.
 The Feedback Network sends back part of the output
signal to the amplifier input in such a way that it is
regenerated, re-amplified and fed back again to
maintain a constant output signal.
9

THE OSCILLATORY CIRCUIT
 As previously stated, the wave shape and amplitude of
the output signal are determined by the design of the
oscillatory circuit and choice of component values.
The frequency of the output wave may be fixed or
variable, depending on the oscillator design.
 o RF oscillators working at frequencies above 30 to 50kHz
use LC (inductors and capacitors) or Crystals to control their
frequency. These may also be classified as HF, VHF, and
UHF oscillators, depending on their frequency.
 o LF oscillators are generally used for generating
frequencies below 30kHz and are usually RC oscillators i.e.
they use resistors and capacitors to control their frequency.
11

EXAMPLE OF A BASIC RC OSCILLATORY
CIRCUIT
 If all the resistors, R and the capacitors, C in the
phase shift network are equal in value, then the
frequency of oscillations produced by the RC
oscillator is given as: fr = 1/2πRC√2N, where
 u ƒr = Output Frequency in Hertz
 u R = Resistance in Ohms
 u C = Capacitance in Farads
 u N = number of RC stages.
 For an LC oscillator
fr = 1/2πLC
13

WHAT IS MODULATION?
 Modulation is a process of mixing a signal with a
sinusoid to produce a new signal. This new signal,
conceivably, will have certain benefits over an un-
modulated signal. Mixing of low frequency signal with
high frequency carrier signal is called modulation.
 modulation is the process of varying one or more
properties of a periodic waveform, called the carrier
signal, with a modulating signal that typically contains
information to be transmitted. Most radio systems in
the 20th century used frequency modulation (FM) or
amplitude modulation (AM) for radio broadcast.
 A modulator is a device that performs modulation. A
demodulator (sometimes detector or demod) is a
device that performs demodulation, the inverse of
modulation. A modem (from modulator–demodulator)
15

16
 A carrier wave by itself doesn't carry information
that we can relate to (such as speech or data). To
include useful information, another wave needs to
be imposed, called an input signal, on top of the
carrier wave. This process of imposing an input
signal onto a carrier wave is called modulation.
 Modulation changes the shape of a carrier wave to
somehow encode the speech or data information
that we were interested in carrying. Modulation is
like hiding a code inside the carrier wave.

SOME MODULATION SCHEMES
 If an input signal's amplitude varies with the
loudness of a user's voice and adds this to the
carrier, the carrier's amplitude will change
according to the input signal that's been fed into it.
 If the input signal is added to the carrier wave, it will
change the frequency of the carrier wave according
to input signal.
 In digital modulation, voice is sampled at some rate
and then compressed and turned into a bit stream –
a stream of zeros and ones – and this in turn is
created into a particular kind of wave which is then
superimposed on the carrier. 18

WHY THE NEED FOR CARRIER WAVES?
 An interesting question is, why have carrier waves in
modulation at all? Why not simply use the input signal
directly? After all, it is carrying all the information that
we're interested in and it only occupies a few kilohertz
and bandwidth. So why not use it directly? Why are
carriers and modulation needed at all?
 The input signals themselves do not have much power
and need a fairly large antenna in order to transmit the
information. Also the very low frequency of the waves
means they will need massive amplification in order to
transmit those very low frequencies.
 In order to keep communication cheap and convenient
and require less power to carry as much information as
possible, carrier systems with modulated carriers are
20

MODULATION AND BANDWIDTH
 One key element of any signal is the bandwidth it
occupies. This is important because it defines the
channel bandwidth required, and hence the number of
channels that can be accommodated within a given
segment of radio spectrum. With pressure on the radio
spectrum increasing, the radio signal bandwidth is an
important feature of any type of radio emission or
transmission.
 The bandwidth (energy/capacity) is governed by two
major features:
 o The type of modulation - Some forms of modulation use
their bandwidth more effectively than others. Accordingly
where spectrum usage is of importance, this alone may dictate
the choice of modulation.
21

RADIO RECEIVER
 A radio receiver uses an antenna to capture radio waves
and extracts only those waves that are vibrating at the
desired frequency. It then extracts the data signals that
were added to those waves, amplifies the signals, and
finally plays them (e.g. on a speaker for audio data).
 Antenna captures the radio waves e.g. a length of wire.
 RF amplifier amplifies the very weak radio frequency (RF)
signal received from the antenna so that the signal can be
processed by the tuner.
 Tuner extracts signals of a particular frequency from a mix
of signals of different frequencies.
 Detector separates the audio information from the carrier
wave.
 Audio amplifier amplifies the weak signal that comes
22

QUESTIONS
THANK YOU FOR YOUR ATTENTION !!!
24

0 lecture 3 wp wireless protocol

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0 lecture 3 wp wireless protocol