Transcript resources - jhu-bcps-hos

resources
http://en.kioskea.net/contents/transmission/transintro.php3
http://www.everythingusb.com/
http://library.thinkquest.org/27887/gather/fundamentals/analog_and_digital.shtml
http://mindprod.com/jgloss/transmissionspeed.html
http://www.usb-ware.com/firewire-vs-usb.htm
http://kbserver.netgear.com/images/1561_straight_ethernet.jpg
http://www.techiesouls.com/wp-content/uploads/2008/12/usb_firewire.jpg
http://www.arconlab.com/computerlab/images/FireWire.jpg
http://gadgethim.com/wp-content/uploads/2009/09/star-wars-darth-vaders-usb-hub.jpg
http://www.mcmcomputers.co.uk/images/USB-2.0.jpg
http://www.global-b2bnetwork.com/direct/dbimage/50135408/8_Port_Mini_Ethernet_Hub.jpg
http://www.google.com/imgres?imgurl=http://static.howstuffworks.com/
gif/ethernet3.gif&imgrefurl=http://computer.howstuffworks.com/etherne
t.htm/printable&usg=__srQvmjtUS4KbXazvIjOh4WgWeGA=&h=342&
w=396&sz=18&hl=en&start=1&um=1&itbs=1&tbnid=sdtdjBS3CDvx2M
:&tbnh=107&tbnw=124&prev=/images%3Fq%3Dethernet%26um%3D
1%26hl%3Den%26safe%3Dactive%26ndsp%3D20%26tbs%3Disch:1
Types of Data
Audio data
Text data
Graphical data
Video data
Data that is sent from one computer to another is simple, but if several
machines are involved, this requires several transmission lines. This
process is called multi-plexing
In order for data transmission to occur, there
must be a transmission line,
also called transmission channel or channel,
between the two machines.
Local Area vs. Wide Area
Computers in our schools are connected in what would be called a
local area. This works well because of the short distances. Wide
areas would cover computers that were several miles apart. The
major problem with this situation is that over distance data
transmission speed decreases and shorter distances tend to have
greater reliabilty. Fiber optic cables have helped increase not only
speed but also reliabilty.
Introduction to digital transmission
Digital transmission is the sending of information over a physical
communications media in the form of digital signals. Analogue signals must
therefore be digitised first before being transmitted.
However, as digital information cannot be sent directly in the form of 0s and 1s,
it must be encoded in the form of a signal with two states, for example:
Analog Transmission
Data transmission takes two distinct forms, Analog vs Digital.
Analog uses signals that carry sound waves or pictures. These forms of
information are then carried via either wires or wireless tools to receiving
units. The signal strenght varies based on frequency or amplitude.
Digital Transmission
The first form of digital transmission of information was the Morse code.
Digital transmission of information utilizes binary code to transmit data (1/0)
Popular Choices
Of
Data Transmission
Fire Wire
FireWire, uses a "Peer-to-Peer" architecture in which the peripherals
determine the most effective device for the transfer of information. This
will enable a smooth and efficient dissemination of information.
Hi-Speed USB 2.0 uses a "Master-Slave" architecture in which the
computer itselft determines the best means of data transmission. The
CPU selects from the peripherals that are attached to the machine. This
tends to slow the transmission of data and further impacts the CPU
Fire Wire
Universal Serial Bus
(USB)
This style of connection has been the industry standard for 13
years and serves as one of the most vital data transmission
devices. USB offers internal power options wich allow devices
to utilize the power of the CPU to run the device. USB 2.0
transmitts data at 480 Mbps. USB connections now face stiff
competition from wireless connections, but as things stand, its
effects are still being felt through out the world.
Computer Switch
Ethernet Hub
USB Connections
Upload and download
Download refers to data transfer from the server to your
computer and upload refers to data transfer from your
computer to the server. It is of interest to know that upload and
download occur on separate transmission channels (whether
this be on a modem or on a special-purpose line). So, when
you are sending (uploading) a document you are not losing
any download bandwidth!
The principles of analogue transmission
Analogue data transmission consists of sending information over a
physical transmission medium in the form of a wave. Data is transmitted
via a carrier wave, a simple wave whose only purpose is to transport data
by modification of one of its characteristics (amplitude, frequency or
phase), and for this reason analogue transmission is generally called
carrier wave modulation transmission. Three types of analogue
transmission are defined depending on which parameter of the carrier
wave is being varied:
Data Transmission Rates
Per/Sec
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
3-D Column 1
Downstream
Receive
Cabling types
Several physical data-transmission media are available to connect together
the various devices on a network. One possibility is to use cables. There
are many types of cables, but the most common are:
Coaxial cable
Double twisted pair
Optical fibre
Coaxial cable
Coaxial cable has long been the preferred form of cabling, for the
simple reason that it is inexpensive and easily handled (weight,
flexibility, ...).
Optical fiber is a cable with numerous advantages:
Light-weight
Immune to noise
Low attenuation
Tolerates data rates on the order of 100 Mbps
Bandwidth from tens of megahertz to several gigahertz (monomode
fibre)
Fibre optic cabling is particularly suited to links between distributors
(central link between several buildings, known as backbone) as it allows
connections over long distances (from several kilometres to 60 km in the
case of single-mode fibre) without requiring earthing. Furthermore, this
type of cable is very secure as it is extremely difficult to tap in to such a
cable.
However, despite its mechanical flexibility, this cable type is not suitable
for local network connections as it is difficult to install and is very
expensive. For this reason, twisted pair or coaxial cable are preferred for
short links.