{{Transmission Transmission MediaMedia

Information can be transmitted through a medium by varying Information can be transmitted through a medium by varying some physical property.some physical property.

The physics of the universe places some limits on what can be The physics of the universe places some limits on what can be

sent over a channel. sent over a channel.

Purpose of the physical layer -- to transport a raw bit stream from Purpose of the physical layer -- to transport a raw bit stream from one machine to another one machine to another

Guided and Unguided mediaGuided and Unguided media

Theoretical Theoretical

The protocol determines the following:The protocol determines the following:

Type of error checking to be used if any Type of error checking to be used if any

Data compression method.Data compression method.

Method for sending device to indicate that it has finished Method for sending device to indicate that it has finished sending a message.sending a message.

Method for receiving device to indicate that it has Method for receiving device to indicate that it has received a message received a message

Whether transmission is to be synchronous or Whether transmission is to be synchronous or asynchronous asynchronous

ProtocolsProtocols

Coaxial Cable consists of 2 conductors. The inner Coaxial Cable consists of 2 conductors. The inner conductor is held inside an insulator with the conductor is held inside an insulator with the other conductor woven around it providing a other conductor woven around it providing a shield.shield.

An insulating protective coating called a jacket An insulating protective coating called a jacket covers the outer conductor.covers the outer conductor.

The outer shield protects the inner conductor from The outer shield protects the inner conductor from outside electrical signals. outside electrical signals.

The distance between the outer conductor The distance between the outer conductor (shield) and inner conductor plus the type of (shield) and inner conductor plus the type of material used for insulating the inner conductor material used for insulating the inner conductor determine the cable properties or determine the cable properties or impedance.impedance.

Coaxial CableCoaxial Cable

Advantages:Advantages:

Not susceptible to interferenceNot susceptible to interference

Transmits fasterTransmits faster

With FDM it can carry 10,000 voice channelsWith FDM it can carry 10,000 voice channels

Disadvantages:Disadvantages:

Heavy & bulky Heavy & bulky

Needs booster over distance. Like repeaters or amplifiers Needs booster over distance. Like repeaters or amplifiers are needed every few Km.are needed every few Km.

Optical Fiber consists of thin glass fibers that can carry Optical Fiber consists of thin glass fibers that can carry information at frequencies in the visible light spectrum information at frequencies in the visible light spectrum and beyond. and beyond.

The typical optical fiber consists of a very narrow strand The typical optical fiber consists of a very narrow strand of glass called the Core. of glass called the Core.

Around the Core is a concentric layer of glass called the Around the Core is a concentric layer of glass called the Cladding. Cladding.

A typical Core diameter is 62.5 microns (1 micron = 10-6 A typical Core diameter is 62.5 microns (1 micron = 10-6 meters). Typically Cladding has a diameter of 125 meters). Typically Cladding has a diameter of 125 microns. microns.

Optical FiberOptical Fiber

Advantages:Advantages:Security: cannot tap into cable. Security: cannot tap into cable. Large Capacity due to BW (bandwidth) Large Capacity due to BW (bandwidth) No corrosion No corrosion Longer distances than copper wire Longer distances than copper wire Smaller and lighter than copper wire Smaller and lighter than copper wire Faster transmission rate Faster transmission rate Disadvantages :Disadvantages : Physical vibration will show up as signal noise. Physical vibration will show up as signal noise. Limited physical arc of cable. Bend it too much & it will Limited physical arc of cable. Bend it too much & it will

break.break.Difficult to split.Difficult to split.

Twisted pair cable consists of a pair of Twisted pair cable consists of a pair of insulated wires twisted together. It is a cable insulated wires twisted together. It is a cable type used in telecommunication for very long type used in telecommunication for very long time. Cable twisting helps to reduce noise time. Cable twisting helps to reduce noise pickup from outside sources and crosstalk on pickup from outside sources and crosstalk on multi-pair cables. multi-pair cables.

Twisted pair cable is good for transferring Twisted pair cable is good for transferring balanced differential signals. The practice of balanced differential signals. The practice of transmitting signals differentially dates back transmitting signals differentially dates back to the early days of telegraph and radio. to the early days of telegraph and radio. Twisted pair Twisted pair

cablecable

Advantage:Advantage:

Improved signal-to-noise ratio, crosstalk, and ground Improved signal-to-noise ratio, crosstalk, and ground bounce that balanced signal transmission bring are bounce that balanced signal transmission bring are particularly valuable in wide bandwidth and high fidelity particularly valuable in wide bandwidth and high fidelity systemssystems

Disadvantage:Disadvantage:

The application originally designed for some other type of The application originally designed for some other type of cabling need usually special adapters which cost money cabling need usually special adapters which cost money

What is Bluetooth?What is Bluetooth?

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)

{{ {{Bluetooth vs Wi-FiBluetooth vs Wi-Fi

Bluetooth Wi-Fi

Range: 10 meters 100 meters

Bandwidth: Low ( 800Kbps )

High (11Mbps )

Cost: Low High

Power Consumption:

Low High

Bluetooth vs Infar-RedBluetooth vs Infar-Red

Bluetooth Infar-red

Range: 10 meters 1 meters

Versatility: Every devices could work together

Need specific devices.

Orientation: Does not require a direct line of sight

Requires a direct line of sight

Connectivity: Many To Many One to one

Comparison with other wireless Comparison with other wireless technologiestechnologies

3G has dominated the modern world in 3G has dominated the modern world in just a few years. just a few years.

//////////////////////////WHAT IS 3GWHAT IS 3G----------3G is the third generation of wireless technologies. It comes 3G is the third generation of wireless technologies. It comes with enhancements over previous wireless technologies, like with enhancements over previous wireless technologies, like high-speed transmission, advanced multimedia access and high-speed transmission, advanced multimedia access and global roaming. 3G is mostly used with mobile phones and global roaming. 3G is mostly used with mobile phones and handsets as a means to connect the phone to the Internet or handsets as a means to connect the phone to the Internet or other IP networks in order to make voice and video calls, to other IP networks in order to make voice and video calls, to download and upload data and to surf the net.download and upload data and to surf the net.1G---transmitted analog data only1G---transmitted analog data only2G---transmitted digital data at speeds of 9.6-19.2 kbps2G---transmitted digital data at speeds of 9.6-19.2 kbps3G---transmitted digital data at speeds from 144kbps to 2.4 Mbps3G---transmitted digital data at speeds from 144kbps to 2.4 Mbps