Transcript Network Hardware

{ Transmission
Media
Theoretical

Information can be transmitted through a medium by varying
some physical property.

The physics of the universe places some limits on what can be
sent over a channel.

Purpose of the physical layer -- to transport a raw bit stream from
one machine to another

Guided and Unguided media
Protocols
The protocol determines the following:

Type of error checking to be used if any

Data compression method.

Method for sending device to indicate that it has finished
sending a message.

Method for receiving device to indicate that it has
received a message

Whether transmission is to be synchronous or
asynchronous

Coaxial Cable consists of 2 conductors. The inner
conductor is held inside an insulator with the other
conductor woven around it providing a shield.

An insulating protective coating called a jacket
covers the outer conductor.

The outer shield protects the inner conductor from
outside electrical signals.

The distance between the outer conductor
(shield) and inner conductor plus the type of
material used for insulating the inner conductor
determine the cable properties or impedance.
Coaxial Cable
Advantages:
Not susceptible to interference
Transmits faster
With FDM it can carry 10,000 voice channels
Disadvantages:
Heavy & bulky
Needs booster over distance. Like repeaters or amplifiers
are needed every few Km.
Optical Fiber

Optical Fiber consists of thin glass fibers that can carry
information at frequencies in the visible light spectrum
and beyond.

The typical optical fiber consists of a very narrow strand
of glass called the Core.

Around the Core is a concentric layer of glass called the
Cladding.

A typical Core diameter is 62.5 microns (1 micron = 10-6
meters). Typically Cladding has a diameter of 125
microns.
Advantages:
Security: cannot tap into cable.
Large Capacity due to BW (bandwidth)
No corrosion
Longer distances than copper wire
Smaller and lighter than copper wire
Faster transmission rate
Disadvantages :
Physical vibration will show up as signal noise.
Limited physical arc of cable. Bend it too much & it will
break.
Difficult to split.


Twisted pair cable consists of a pair of
insulated wires twisted together. It is a cable
type used in telecommunication for very long
time. Cable twisting helps to reduce noise
pickup from outside sources and crosstalk on
multi-pair cables.
Twisted pair cable is good for transferring
balanced differential signals. The practice of
transmitting signals differentially dates back
to the early days of telegraph and radio.
Twisted pair cable
Advantage:
Improved signal-to-noise ratio, crosstalk, and ground
bounce that balanced signal transmission bring are
particularly valuable in wide bandwidth and high fidelity
systems
Disadvantage:
The application originally designed for some other type of
cabling need usually special adapters which cost money
Bluetooth is a short-range wireless technology used for connecting and
transferring information between devices such as mobile phones,
laptops, PCs, PDAs, printers, digital cameras, mice and keyboards.
Bluetooth makes it easy to connect two devices wirelessly when it would
be otherwise impossible to connect them with cables.
Bluetooth Logo
A master Bluetooth device
can communicate with a
maximum of seven devices in
a network.
(the picture right is the
diagrammatic sketch of the
Bluetooth network)
What is Bluetooth?
{
Bluetooth vs Wi-Fi
Bluetooth
Wi-Fi
Range:
10 meters
100 meters
Bandwidth:
Low ( 800Kbps )
Cost:
Power
Consumption:
{
Bluetooth vs Infar-Red
Bluetooth
Infar-red
Range:
10 meters
1 meters
High (11Mbps )
Versatility:
Every devices
could work
together
Need specific
devices.
Low
High
Orientation:
Does not
require a direct
line of sight
Requires a
direct line of
sight
Low
High
Connectivity:
Many To Many
One to one
Comparison with other wireless technologies
3G has dominated the modern world in just a few years.
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WHAT IS 3G
-----3G is the third generation of wireless technologies. It comes
with enhancements over previous wireless technologies, like highspeed transmission, advanced multimedia access and global roaming.
3G is mostly used with mobile phones and handsets as a means to
connect the phone to the Internet or other IP networks in order
to make voice and video calls, to download and upload data and to
surf the net.
1G---transmitted analog data only
2G---transmitted digital data at speeds of 9.6-19.2 kbps
3G---transmitted digital data at speeds from 144kbps to 2.4 Mbps