Unit 3 communication media

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