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.

Typedescriptionuse Category 1Telephone wireUsed for voice only Category 2UTP cable that contains 4 wire pairsUsed for carrying data at 4Mbps for Local Talk Category 3UTP cable with 4 pair of wires. Max bandwidth of 16Mbps Used for 10Mbps Ethernet & 4Mbps token ring Category 4UTP cable with 4 pairs of wires. More protection towards crosstalk Used for 10Mbps Ethernet & 16Mbps token ring Category 5UTP cable with 4 pairs of wires. Cat 5E better protection on crosstalk Used for 100Mbps Ethernet Category 6UTP 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

THICKNETTHINNET Was the original Ethernet wiringReplaces early thicknet Also called as thickwireAlso called as thinwire 0.4 inches in diameter0.64cm 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 TYPEADVANTAGESDISADVANTAGES Twisted Pair Cable Inexpensive Well Understood Easy to add computers Sensitive to noise Short distance Limited bandwidth Security; easily trapped Coaxial CableHigh bandwidth Long distances Nose immunity Physical dimensions Security; easily tapped Optical Fiber Cable Very high bandwidth Noise immunity Long distances High security Small size Connections T splitters Expensive High 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 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