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Transmission Medium
- 2. TRANSMISSION MEDIA Transmission media are located below the physical layer Computers use signals to represent data. Signals are ransmitted in form of electromagnetic energy.
- 3. TRANSMISSION MEDIA Transmission Media and Physical Layer
- 4. Classes of transmission media
- 5. FACTORS TO BE CONSIDERED WHILE CHOOSING TRANSMISSION MEDIUM Transmission Rate Cost and Ease of Installation Resistance to Environmental Conditions Distances
- 6. GUIDED MEDIAGUIDED MEDIA Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable.
- 7. TWISTED PAIR CABLE This cable is the most commonly used and is cheaper than others. It is lightweight, cheap, can be installed easily, and they support many different types of network Twisted Pair is of two types : Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP)
- 10. UNSHIELDED VERSUS SHIELDED TWISTED- PAIR CABLE UTP and STP cables
- 11. UNSHIELDED TWISTED PAIR (UTP) Adv: • Ordinary telephone wire • Cheapest • Easiest to install • It has high speed capacity • 100 meter limit Dis adv: • Bandwidth is low when compared with Coaxial Cable • Provides less protection from interference.
- 13. SHIELDED TWISTED PAIR (STP) Adv: • Metal braid or sheathing that reduces interference • Easy to install • Eliminates crosstalk • Higher capacity than unshielded twisted pair • Increases the signaling rate Disadv: • More expensive • Harder to handle (thick, heavy) • Difficult to manufacture
- 14. GUIDED MEDIA - UTP Applications: Telephone lines connecting subscribers to the central office DSL lines LAN – 10Base-T and 100Base-T
- 15. TWISTED PAIR - APPLICATIONS Most common medium Telephone network Within buildings For local area networks (LAN)
- 16. TWISTED PAIR - PROS AND CONS Cheap Easy to work with Low data rate Short range
- 17. GUIDED MEDIA – COAXIAL CABLE Coaxial Cable
- 19. COAXIAL CABLE
- 20. COAXIAL CABLE Inner conductor is a solid wire outer conductor serves both as a shield against noise and a second conductor
- 21. TYPES OF COAXIAL CABLES Baseband : Which is used for digital transmission. It is mostly used for LAN’s. Baseband transmits a single signal at a time with very high speed. Broadband : This uses analog transmission on standard cable television cabling. It transmits several simultaneous signal using different frequencies.
- 22. COAXIAL CABLE PROS Bandwidth is high Used in long distance telephone lines. Television distribution Can carry 10,000 voice calls simultaneously Short distance computer systems links Local area networks Data transmission without distortion.
- 23. CONS Single cable failure can fail the entire network. Difficult to install and expensive when compared with twisted pair.
- 24. GUIDED MEDIA – COAXIAL CABLE Applications: Analog telephone networks Cable TV networks Traditional Ethernet LAN – 10Base2, 10Base5
- 25. FIBER OPTICS • Higher bandwidth • Less expensive • Immune to electrical noise • More secure – easy to notice an attempt to intercept signal • Physical characterizes – Glass or plastic fibers – Very thin (thinner than human hair) – Material is light
- 27. OPTICAL FIBER - PROS • greater capacity – data rates of hundreds of Gbps • smaller size & weight • lower attenuation(Reduction in signal) • Used for both analog and digital signals.
- 28. CONS It is expensive. Difficult to install. Maintenance is expensive and difficult
- 29. GUIDED MEDIA – OPTICAL FIBER CABLE Applications: Backbone networks – SONET Cable TV – backbone LAN 100Base-FX network (Fast Ethernet) 100Base-X
- 30. UNGUIDED MEDIA Wireless transmission waves
- 31. BROADCAST RADIO Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation. FM radio UHF and VHF television still need line of sight suffers from multipath interference reflections from land, water, other objects
- 32. UNGUIDED MEDIA – INFRARED Frequencies between 300 GHz to 400 THz. Can not penetrate walls. Used for short-range communication in a closed area using line-of-sight propagation.
- 33. INFRARED are blocked by walls no licenses required typical uses TV remote control IRD port
- 34. MICROWAVE TRANSMISSION Line-of-site High speed Cost effective Easy to implement Weather can cause interference
- 35. STRAIGHT THROUGH AND CROSSOVER WIRING 35 Wiring within a twisted pair cable is configured as either Straight through, where each wire (or pin) is attached to the same contact point at each end Crossover, where transmit contacts on each end of the cable are connected to the receive contact at the other end
- 38. UTP STRAIGHT-THROUGH CABLE The cable that connects from the switch port to the computer NIC port is called a straight-through cable. 38 Host or RouterHub or Switch
- 39. UTP STRAIGHT-THROUGH CABLE Host or RouterHub or Switch
- 40. UTP CROSS-OVER CABLE The cable that connects from one switch port to another switch port is called a crossover cable. 40
- 42. UTP ROLLOVER CABLE The cable that connects the RJ-45 adapter on the com port of the computer to the console port of the router or switch is called a rollover cable. 42
Editor's Notes
- Coaxial cable, like twisted pair, consists of two conductors, but is constructed differently to permit it to operate over a wider range of frequencies. It consists of a hollow outer cylindrical conductor that surrounds a single inner wire conductor (Stallings DCC8e Figure 4.2b). The inner conductor is held in place by either regularly spaced insulating rings or a solid dielectric material. The outer conductor is covered with a jacket or shield. A single coaxial cable has a diameter of from 1 to 2.5 cm. Coaxial cable can be used over longer distances and support more stations on a shared line than twisted pair. Coaxial cable is a versatile transmission medium, used in a wide variety of applications, including: •Television distribution - aerial to TV & CATV systems •Long-distance telephone transmission - traditionally used for inter-exchange links, now being replaced by optical fiber/microwave/satellite •Short-run computer system links •Local area networks
- The following characteristics distinguish optical fiber from twisted pair or coaxial cable: •Greater capacity: The potential bandwidth, and hence data rate, of optical fiber is immense; data rates of hundreds of Gbps over tens of kilometers have been demonstrated. Compare this to the practical maximum of hundreds of Mbps over about 1 km for coaxial cable and just a few Mbps over 1 km or up to 100 Mbps to 10 Gbps over a few tens of meters for twisted pair. •Smaller size and lighter weight: Optical fibers are considerably thinner than coaxial cable or bundled twisted-pair cable. For cramped conduits in buildings and underground along public rights-of-way, the advantage of small size is considerable. The corresponding reduction in weight reduces structural support requirements. •Lower attenuation: Attenuation is significantly lower for optical fiber than for coaxial cable or twisted pair, and is constant over a wide range. •Electromagnetic isolation: Optical fiber systems are not affected by external electromagnetic fields. Thus the system is not vulnerable to interference, impulse noise, or crosstalk. By the same token, fibers do not radiate energy, so there is little interference with other equipment and there is a high degree of security from eavesdropping. In addition, fiber is inherently difficult to tap. •Greater repeater spacing: Fewer repeaters mean lower cost and fewer sources of error. The performance of optical fiber systems from this point of view has been steadily improving. Repeater spacing in the tens of kilometers for optical fiber is common, and repeater spacings of hundreds of kilometers have been demonstrated.
- Radio is a general term used to encompass frequencies in the range of 3 kHz to 300 GHz. We are using the informal term broadcast radio to cover the VHF and part of the UHF band: 30 MHz to 1 GHz. This range covers FM radio and UHF and VHF television. This range is also used for a number of data networking applications. The principal difference between broadcast radio and microwave is that the former is omnidirectional and the latter is directional. Thus broadcast radio does not require dish-shaped antennas, and the antennas need not be rigidly mounted to a precise alignment. The range 30 MHz to 1 GHz is an effective one for broadcast communications. Unlike the case for lower-frequency electromagnetic waves, the ionosphere is transparent to radio waves above 30 MHz. Thus transmission is limited to the line of sight, and distant transmitters will not interfere with each other due to reflection from the atmosphere. Unlike the higher frequencies of the microwave region, broadcast radio waves are less sensitive to attenuation from rainfall. A prime source of impairment for broadcast radio waves is multipath interference. Reflection from land, water, and natural or human-made objects can create multiple paths between antennas, eg ghosting on TV pictures.
- Infrared communications is achieved using transmitters/receivers (transceivers) that modulate noncoherent infrared light. Transceivers must be within the line of sight of each other either directly or via reflection from a light-colored surface such as the ceiling of a room. One important difference between infrared and microwave transmission is that the former does not penetrate walls. Thus the security and interference problems encountered in microwave systems are not present. Furthermore, there is no frequency allocation issue with infrared, because no licensing is required.