All the Lectures of Computer communication & Network
|Subject Title: Computer communication & Network|
|Class No: 1|
The Transmitted is a collection of electronic components,
& circuits designed to convert the information into a signal suitable
for transmission over a given communication medium.
It be a simple a microphone or as a microwave radio transmission.
|Class No: 2|
Communication channel is the medium by which the electronic signal is sent
from one place to another.
In it's simplest form medium may be a pair of wire that carry a voice signal
be an optical fiber cable medium.
the receiver is an other collection of electronic components & circuits that accepts the
transmitted message, from the channel & convert it back into a form
understandable by human.
It may be an earphone or a complex electronic receiver.
Regardless whether the original information signals are analog digital, they all are reffered as baseban signals.
in a communication system when putting information or original signal
(voice , video, signals) Directly into the medium is known as base band transmission.
|Class No: 3|
In a Communication System when Putting information or Original signals into the medium after the modulation than signals are known as Broadband Signals.
Base Band Signals VS Broad Band Signals
(1) Base Band Signals: Transmitted without modulations.
(2) Broad Band Signals: Transmitted after the modulations.
Models of Commnuication:
(2) Half duplex
(3) Full duplex
faster than Router minimize the load of signals.
(1) Passive Hub => Bus topologies
(2) Active Hub => Ring topologies
Passive Hub: Dosenot have generate the signal.
Active Hub: Has ability to regenerate the signal.
Repeater and Regenerator.
Repeater sending the same data.
Regenrator to distribute Noice, reduce noice and to given the result.
Amplifier: To increase the ability of signal. and also increase the signals.
Disadvantage: if the noice is meet with them it will taken in the signal.
Discard: Means to stop signals to reduce the signal.
|Class No: 4|
Noice: (un wanted energy or un wanted signals)
Noice: has a gread importance in every type of communication.
Def: Noice, is a random energy that inter with important information signals.
any un-wanted introduction of energy tending to interface with the proper reception and reproduction of transmitteed signals.
Source of Signals.
There are two major source of Noice:
(1) External Noice:
(2) Internal Noice:
External Noice is further devided into
(3)Extra terrestial Noice
(1) The Industerial Noice that manufacturing company or equipment
production such as
Auto Mobile, ignition systems, Electronic motors egenerators.
Any kind of electric equipment have high voltage and current can produce Noice.
Exa: Tube light, high vltage wires etc.
Earth: it is less effected to the signals.
15 HZ <-----> more than 150 MHZ
|Class No: 5|
Conclusion of External Noice:
Continous of external Noice:
External Noice is the fact of life, that must be considerd Atmospheric and space
noice simply can not eliminated.
In general b/c there are so many source of Industerial noice, there is no any way to countrol it.
The key to reliable communication is simply to generate the signal at high power
so that they over come noice.
Internal Noice is generally associated the noice which is generated inside the receiver
electronic components such as, diode.
Transister are major source of internal Noice,
Although this noice is a low level noice.
it's mostly effected the weak signal.
However the sources of internal noice are well known sa, the designer can countrol this type of noice.
Mostly internal noice is caused by the thermal agitation.
Thermalagitation refers to the random motion of atoms & electronics components,
caused by the heat,
It is also known as white or thonson noice.
Noice Figure F:
A variety of methods are used to express the noice quatity of reciever , one of these
methods is known as noice figure which is the ratio of the S/N.
Power at the input to the S/N power at the output,
the device under consideraton can be the entire receiver or a signle amplifier stage
the noice figure F also called the noice factor can be computed with the expression.
F= S/N Input
|Class No: 6|
Signal to Noice Ration:
=> S/N Ration is simply a numbers that indicates the relative strength
of signal and noice.
=> (Ratio) Stronger the signal the weak will be the noice the higher the S/N ratio,
if the signal is weak the stronger, the noice, the lower the S/N ratio and
reception will be less reliable.
=> The Design of communication (equation) equipment has it's "Objective" to produce
the higher S/N Ratio possible.