Data TransmissionPresented by:

Kristina Westin

Andy Noll

Jen Stoe

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History of Data Transmission

• Morse Code

• Electric Telegraph

• Cables

• Telephone

• Phonograph & Communication Equipment

• Electrical Numerical Integrator and Computer

(developed by the US. Army and University of Pennsylvania late in World War II)

• Computers (Apple I in 1976)

• Robotics

• Analog Video Disc & Digital CD-Rom Disc

“Presently, the United States is the most technologically advanced country in the area of telecommunications with about;

126 million phone lines, 7.5 million cellular phone users, 5 thousand AM radio broadcast stations, 5 thousand FM radio

stations, 1 thousand television broadcast stations, 9 thousand cable television systems, 530 million radios, 193 million television sets, 24 ocean cables, and scores of satellite

facilities!”

Types of Data Transmission Technologies

• Broadcast (radio & TV)• Cable (TV & modems)• Recording (digital & video)• Wired telephony• Mobile communications systems (PCS, cellular, etc.)• Analog (telephone) networks• Digital (data) networks (ISDN, Ethernet, etc.)• Fiber optics• Satellite

What IS Data Transmission?

…The way data is encoded in order for a network to transmit information from one computer to another.

(computer representation)

Computer Representation

This varies according to the TYPE of data:

• Audio data

• Text data

• Graphical data

• Video data

2 Categories of Data Representation

• Digital: information is encoded as a set of binary values

• Analogue: data will be represented by the variation in a

continuous physical quantity

In order for data transmission to occur, there must be a transmission line (also called transmission channel) between the two machines.

Transmission Channels

• Transmission channels allow data to circulate in the form of electromagnetic, electrical, light, or acoustic waves.

• Encoding must be chosen for the transmission signals (based on the physical medium used to transfer the data).

• Simple (serial) data transmission is when there are only two machines communicating, or if only a single piece of data is sent.

• Multiplexing (parallel) is when it is necessary to install several transmission lines or to share the line among several different communications.

What IS a Transmission Channel?

…a connection between 2 machines 1. transmitter - the machine that sends the

data

2. receiver - the machine that receives the data

Machines can sometimes be both receivers and transmitters (for instance, computers connected to a network).

Asynchronous and Synchronous Data Transmission

• Asynchronous transmission uses start and stop bits to signify the beginning and end of a transmission.

• Synchronous transmission uses no start and stop bits. A continual stream of data is sent between the two nodes.

Physical Media

Physical transmission media are the elements that allow information to flow between

transmission devices.

3 Categories of Physical Media• Wire media allow an electrical quantity to circulate

on a cable that is generally metallic • Aerial media refers to the air which allow the

circulation of electromagnetic waves and various types of radio-electric waves

• Optical media allow information to be sent in the form of light

More Transmission Terminology• Guided media - Waves are guided along a physical

path; twisted pair, optical fiber, coaxial cable

• Unguided media - Waves are not guided; air waves, radio

• Direct link- Signal goes from transmitter to receiver with no intermediate devices

• Point-to-point link - Guided media with direct link between two devices

• Multipoint guided configuration -More than two devices sharing the same

medium

Protocols and Handshaking

• Protocol – the agreed-upon format for transmitting data between two devices

(ex. computer and printer)

• Handshaking- the process by which two devices initiate communications - must occur before data transmission as it allows the protocol to be agreed

Analog vs. Digital

Analog Transmission

• 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 strength 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)

Local Area vs. Wide Area

Local Area Transmission• Describes the computers

within our schools• Works well over short

distances• Greater reliability• Ethernet cables are the

main source of connection within school buildings

Wide Area Transmission• Connected computers

can be several miles away

• The major problem is speed of transmission which decreases over distance

• Fiber optic cable is most reliable and the preferred method of data delivery

LAN Tools of Data TransmissionComputer Switch & Ethernet Cables

Advantages of Optical Fiber Cable

• Light-weight • Immune to noise • Low attenuation • Tolerates data rates on the order of 100 Mbps • Bandwidth from tens of megahertz to several gigahertz

• Fiber optic cabling is particularly suited to links between distributors (central link between several buildings, known as backbone) as it allows connections over long distances.

• Furthermore, this type of cable is very secure as it is extremely difficult to tap in to such a cable.

• However, this cable type is not suitable for local network connections. For this reason, twisted pair or coaxial cable are preferred for shorter links.

Wide Area Tools of Data Transmission

Types of cable used for transmission of data

• Coaxial cable

• Fiber Optic Cable

Popular Choices Of

Data Transmission

Fire Wire

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 itself 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

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 which allow devices to utilize the power of the CPU to run the device. USB 2.0 transmits 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.

Universal Serial Bus(USB)

USB Connections

Uploads and Downloads

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!

Data Transmission Speeds

Wireless Data Transmission

For wireless data transmission to occur you need three things

• A transmitter

• A receiver

• A wireless channel– The higher the frequency of the channel the

more information it can transfer.

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Short Range Data Transmissions

Bluetooth Wifi

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Bluetooth

• Range is up to 10 feet and in some cases reach up to 100 meters

• Small Bluetooth chip inserted into the device along with software to run it.

• Invented in 1994 by engineers at Ericsson• In 1998 a group of companies joined forces to add it into

their technology so no company ‘owns’ the rights to it. The group is called SIG (special interest group)

• Meant to be a collaborative tool between various types of technology.

Wi-Fi

• Wireless fidelity• Small Hotspots

– Accessible with a router.

• Transmit at frequencies of 2.4 GHz or 5 GHz

• WiFi radios can transmit on any of three frequency bands – They can also hop between the frequencies

so that more devices can be in the network.

Types of Wifi Networks

Open Open for anyone to use. Anyone can connect.

WEP Wired Equivalent Privacy Can be accessed with a password64 Bit

WPA Wi-Fi Protected Access Uses TKIP, Provides more security

WPA2

Wi-Fi Protected Access 2 Uses a pre-shared key. Most secure

Long Range Data Transmissions

WiMAX

• Worldwide Interoperability for Microwave Access

• Range - 30-mile (50-km) radius from base station

• Speed - 70 megabits per second • Line-of-sight not needed between user

and base station • Frequency bands - 2 to 11 GHz and 10 to

66 GHz (licensed and unlicensed bands)

Satelitte

• Satellite– receive (download) at a speed of about 1

Mbps – send (upload) at a speed of about 200 kbps.

• Cell Phone 3G and 4G Services– Slower than Broadband but accessible

anywhere there is cell phone service.

Network Standards802.11a IEEE wireless

networking standard 54Mbps 5 GHz

802.11b IEEE wireless networking standard 11Mbps 2.4 GHz

802.11g IEEE wireless networking standard 54Mbps

g+ up to 125Mbps

2.4 GHz

802.11n MIMO (multiple-input multiple-output) technology

540Mbps 2.4 GHz

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