1. Assignment on
Course title:Data communication
Course code: 313
Submitted to Submitted by
Pranab Bandhu Nath Fatema Yesmin Aka
Lecturer of CSE ID: 1834902155
City university Sec: 49th (B)
2. Signal
When data is sent over physical medium, it
needs to be first converted into electromagnetic
signals. Data itself can be analog such as human
voice, or digital such as file on the disk.Both
analog and digital data can be represented in
digital or analog signals.
• Analog Signal
• Digital Signal
3. Analog Signal
An analog signal is any continuous signal for
which the time-varying feature of the signal is a
representation of some other time-varying
quantity, i.e., analogous to another time-varying
signal. For example, in an analog audio signal,
the instantaneous voltage of the signal varies
continuously with the pressure of the sound
waves.
ANALOG: Human voice.
4. Digital Signal
A digital signal is a signal that is being used to
represent data as a sequence of discrete values;
at any given time it can only take on, at most,
one of a finite number of values.This contrasts
with an analog signal, which represents
continuous values; at any given time it
represents a real number within a continuous
range of values.
DIGITAL: Document on a disk.
5. Digital Modulation
The term DM stands for digital modulation, and it is
a common term for the techniques of modulation.
This modulation uses discrete signals for
modulating a carrier wave. Indifference, both the
amplitude modulation and frequency modulation
techniques are analog. Digital modulation removes
communication noise as well as provides enhanced
strength for the signal intrusion. But, it is not rare to
digital modulation schemes for introducing time
delay because of the required process. To avoid
this, a comfort SST (Secure Stream Technology)
audio is designed.
6. Types of Digital Modulation
There are several kinds of digital modulation
techniques are available based on the requirement
which includes the following.
1) ASK (Amplitude Shift Keying): In amplitude shift
keying, once the instant amplitude of the carrier
signal is changed in quantity toward m(t)
message signal. The applications of ASK mainly
include IR remote controls and fiber optic
transmitter & receiver.
If signal on-1
If signal off-0
7. Types of Digital Modulation
2) FSK (Frequency Shift Keying): In frequency
shift keying, when the immediate frequency of
the carrier signal is changed then the
information will be transmitted. The applications
of frequency shift keying mainly include several
modems in telemetry systems,telephone line
and phase shift keying.
1-High Frequency
0-Low Frequency
8. Types of Digital Modulation
3) PSK Digital Modulation(Phase Shift Keying):
In phase shift keying, the instant phase of the
carrier signal is moved for this modulation. If the
m(t) baseband signal is =1 then the carrier signal
within phase will be transmitted.The
applications of phase shift keying include a
broadband modem (ADSL), satellite
communications, mobile phones, etc.
9. Types of PSK Modulation
1. Binary Phase Shift Keying: This is also called as 2-
phase PSK or Phase Reversal Keying. In this technique,
the sine wave carrier takes two phase reversals such
as 0° and 180°.BPSK is basically a Double Side Band
Suppressed Carrier modulation scheme, for message
being the digital information.
2. Quadrature Phase Shift Keying: This is the phase shift
keying technique, in which the sine wave carrier takes
four phase reversals such as 0°, 90°, 180°, and 270°.If
this kind of techniques are further extended, PSK can
be done by eight or sixteen values also, depending
upon the requirement.
