TRANSMISSION MEDIA. Factors that directly influences the choice of correct media type; Transmission rate Distance covered Cost & ease of installation.

TRANSMISSION MEDIA

Factors that directly influences the choice of correct media type;

Transmission rate Distance covered Cost & ease of installation Resistance to environmental conditions

Transmission media can be categorized into two;

Guided transmission media Unguided transmission media

Uses cabling system that guides the data signals along a specified path.

Also known as bounded media Cable can be any physical or

conductive media like wires(twisted pair cables), coaxial cables or fiber optics.

Twisted pair consists of color coded pairs of insulated copper wires twisted around one another.

Each wire has a diameter of 0.4 to 0.8mm. Wires are twisted in order to reduce

crosstalk & noise susceptibility. The number of twists per meter/foot is

known as twist ratio (usually 1 to 3 twists) Data is transmitted via electric signal. Twisted pair can be categorized into 6

categories (CAT 1 – 6)

2 types of twisted pair cables; Unshielded Twisted Pairs (UTP) Shielded Twisted Pairs (STP)

Contains no shielded . Usually 4 pair of wires enclosed in same common sheath.

Have resistance rating of 100 ohm Advantages;

Flexible & low cost Can be used for voice / data communication Easy to install & maintain Widely used for cabling LAN

Includes metal shielding over each individual copper wires.

Protects cables from external electromagnetic interferences (EMI)

Therefore can be used in noisy area.

Type description use

Category 1 Telephone wire Used for voice only

Category 2 UTP cable that contains 4 wire pairs

Used for carrying data at 4Mbps for Local Talk

Category 3 UTP cable with 4 pair of wires. Max bandwidth of 16Mbps

Used for 10Mbps Ethernet & 4Mbps token ring

Category 4 UTP cable with 4 pairs of wires. More protection towards crosstalk

Used for 10Mbps Ethernet & 16Mbps token ring

Category 5 UTP cable with 4 pairs of wires. Cat 5E better protection on crosstalk

Used for 100Mbps Ethernet

Category 6 UTP cable with 4 pairs of wires. Can carry data at 1Gbps

Used for Gigabit Ethernet & can carry data up to 1000Mbps

Basically a copper wire used by cable TV companies.

Commonly called coax & carries a signal at much higher frequencies than twisted pair.

Has single copper conductor at its center as medium for transferring an electrical signal.

The copper mesh helps to block any outside interference (electromagnetic).

Thicknet Original ethernet medium and

approximately 1cm thick with solid copper core.

IEEE designates Thicknet as 10BASE-5 (10 represents the speed;10Mbps, Base = baseline transmission & 5 represents maximum segment length;500meters)

Thinnet Uses RG-58A/U coaxial cables & has

diameter of 0.64cm (making it more flexibel & easier to install)

IEEE has designated thinnet as 10BASE-2.

BNC cable connector BNC T connector BNC barrel connector BNC terminator

THICKNET THINNET

Was the original Ethernet wiring

Replaces early thicknet

Also called as thickwire Also called as thinwire

0.4 inches in diameter 0.64cm

Uses vampire taps & transceiver cable as connectors

Uses different BNC connectors to connect cable

Heavy & difficult to bend and install

Light, easy to bend & install

Consists of a center glass core surrounded by several layers of protective materials.

Transfers data in the form of light hence no electrical /electromagnetic interference

Immune to the effects of moisture & lightning Able to support longer distances than coaxial &

twisted pair. Carries information at vastly greater speed

allowing for video conferencing & interactive services.

Costly & difficult to install. 2 categories: single mode & multimode fiber

Can transfer data for longer distance without a repeater

High bandwidth with small diameter of 10micron.

Laser light travels over single path with little reflection.

Since light do not disperse, it can travel longer distance without a repeater.

Contains a core with a large diameter than a single-mode fiber (50 – 115microns)

Due to large diameter, many pulses of light can travel at different angles .

MEDIA TYPE ADVANTAGES DISADVANTAGES

Twisted Pair Cable

InexpensiveWell UnderstoodEasy to add computers

Sensitive to noiseShort distanceLimited bandwidthSecurity; easily trapped

Coaxial Cable

High bandwidthLong distancesNose immunity

Physical dimensionsSecurity; easily tapped

Optical Fiber Cable

Very high bandwidthNoise immunityLong distancesHigh securitySmall size

ConnectionsT splittersExpensiveHigh installation cost

Consists of means (eg. air, space) for the data signals to travel, however there is nothing to guide them along the path.

Not bounded to a cabling media. Electromagnetic waves in the form of

radio, microwave, infrared or others. Used where cables are difficult to use

or install.

Satellite communication Terrestrial Microwave Radio Communication Infrared

Man made object placed into orbit around the earth for the purpose of communication & scientific research.

Consists of radio transmitter & receiver, called transponders & about 22300 miles above earth.

Transponders receive incoming radio signal, amplifies it & retransmits it back.

Provides communication over longer distance. A ground station on one side of the ocean transmits a

signal to the satellite, satellite receives it & transmits it to another station on the other side.

Satellite is costly, hence shared by many organizations Most common satellite are Geosynchronous satellites.

Used for following purpose; Air navigation Television & radio transmission Video-conferencing Global positioning system (GPS)

Used in physical transmission media is impractical / difficult to install. Ex; high buildings, across rivers, mountains, jungles & remote areas.

Transmitted via atmosphere between 2 stations.

Covers distance up to 50km, use repeater station if more than 50km

Uses line of light transmission, the receiver station must be visible to the transmit station.

Can be affected by weather.

Apart from radio & television transmission, radio communication is also used for wireless communication.

Used for private communication with device like portable phones.

Also used for sending & receiving computer data. Consists of transmitter & receiver called base

stations. Radio communication uses electromagnetic

waves but operate at radio frequency range. Area covered depends on the power of

transmitter.

Allows communication via short-range wireless signals

Files & other digital data can be transferred between 2 computers.

Requires line of sight transmissions & used over short distance.

Devices come up with built-in infrared ports – PDA, handphones, laptops etc