unit 3 communication media
TRANSCRIPT
UNIT - 3
COMMUNICATION MEDIA
COMMUNICATION MEDIA OR
TRANSMISSION MEDIA
CLASSES OF TRANSMISSION MEDIA
Twisted-Pair Cable
UTP and STP cables
CATEGORIES OF UTP
UTP Connector
UTP Performance
ApplicationsTwisted-pair cables are used in telephone lines toprovide voice and data channels. The
local loop-the line that connects subscribers to thecentral telephone office---commonly
consists of unshielded twisted-pair cables.
The DSL lines that are used by the telephonecompanies to provide high-data-rate
connections also use the high-bandwidth capabilityof unshielded twisted-pair cables.
Local-area networks such as 10Base-T and 100Base-T,also use twisted-pair cables.
Coaxial Cable
Coaxial Cable Standards
Coaxial Cable Connectors
Coaxial cable performance
ApplicationsCoaxial cable was widely used in analog telephone networks where a
single coaxial network could carry 10,000 voice signals. Later it was used in digitaltelephone networks where a single coaxial cable could carry digital data up to600 Mbps. However, coaxial cable in telephone networks has largely beenreplaced today with fiber-optic cable.
Cable TV networks also use coaxial cables. In the traditional cable TVnetwork, the entire network used coaxial cable. Later, however, cable TVproviders replaced most of the media with fiber-optic cable; hybrid networks usecoaxial cable only at the network boundaries, near the consumer premises. CableTV uses RG-59 coaxial cable.
Another common application of coaxial cable is in traditional EthernetLANs. Because of its high bandwidth, and consequently high data rate, coaxialcable was chosen for digital transmission in early Ethernet LANs. The 10Base-2, orThin Ethernet, uses RG-58 coaxial cable with BNe connectors to transmit data at10 Mbps with a range of 185 m. The 10Base5, or Thick Ethernet, uses RG-11(thick coaxial cable) to transmit 10 Mbps with a range of 5000 m. Thick Ethernethas specialized connectors.
Fiber-Optic Cable
Optical fiber
Propagation Modes
Propagation Modes...
FIBER TYPES
Fiber Construction
Fiber Optic Cable Connectors
Optical fiber performance
Advantages of Optical Fiber
Higher bandwidth
Less signal attenuation
Immunity to electromagnetic interference
Resistance to corrosive materials.
Light weight
Greater immunity to tapping
Disadvantages of Optical Fiber
Installation and maintenance
Unidirectional light propagation
Cost
UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic waves without using a physical conductor.
This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and
thus are available to anyone who has a device capable of receiving them.
Electromagnetic spectrum for wireless communication
Propagation methods
Bands (Radio frequency allocation)
Wireless transmission waves
Radio WavesElectromagnetic waves ranging in frequencies
between 3 kHz and 1 GHz are called radio waves
Terrestrial Microwaves
Electromagnetic waves having frequencies between I and 300 GHz are called microwaves.
SATELLITE COMMUNICATION
Satellite orbits
Three Categories of Satellites
GEO Satellites
MEO Satellites
GPS
Trilateration on a plane
LEO Satellites
Iridium Teledesic
The Iridium system has 66 satellites in 6
LEO orbits, each at an altitude of 750 km
Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km.
CELLULAR TELEPHONY
FREQUENCY-REUSE PRINCIPLE
1. Transmitting
2. Receiving
3. Handoff
4. Roaming
First Generation (1G)
Second Generation (2G)
Second Generation (2G) …
D-AMPS
GSM
Third Generation