Transmission mediums in computer networks
- 1. Transmission Mediums in Computer Networks
- 2. Transmission Medium Transmission media is a pathway that carries the information from sender to receiver. We use different types of cables or waves to transmit data. Data is transmitted normally through electrical or electromagnetic signals. An electrical signal is in the form of current. An electromagnetic signal is series of electromagnetic energy pulses at various frequencies. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 3. These signals can be transmitted through copper wires, optical fibers, atmosphere, water and vacuum Different Medias have different properties like bandwidth, delay, cost and ease of installation and maintenance. Transmission media is also called Communication channel. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 4. The data transmission capabilities of various Medias vary differently depending upon the various factors. These factors are: 1. Bandwidth. It refers to the data carrying capacity of a channel or medium. Higher bandwidth communication channels support higher data rates. 2. Radiation. It refers to the leakage of signal from the medium due to undesirable electrical characteristics of the medium. 3. Noise Absorption. It refers to the susceptibility of the media to external electrical noise that can cause distortion of data signal. 4. Attenuation. It refers to loss of energy as signal propagates outwards. The amount of energy lost depends on frequency. Radiations and physical characteristics of media contribute to attenuation. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 5. Types of Transmission Media Transmission media is broadly classified into two groups. 1. Wired or Guided Media or Bound Transmission Media 2. Wireless or Unguided Media or Unbound Transmission Media BY LECTURER SURAJ PANDEY CCT COLLEGE
- 7. Factors to be considered while choosing Transmission Medium Transmission Rate Cost and Ease of Installation Resistance to Environmental Conditions Distances
- 8. Bounded/Guided Transmission Media It is the transmission media in which signals are confined to a specific path using wire or cable. The types of Bounded/ Guided are discussed below.
- 9. 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. Some important points : Its frequency range is 0 to 3.5 kHz. Typical attenuation is 0.2 dB/Km @ 1kHz. Typical delay is 50 µs/km. Repeater spacing is 2km. Twisted Pair is of two types : 1. Unshielded Twisted Pair (UTP) 2. Shielded Twisted Pair (STP)
- 10. Unshielded Twisted Pair Cable It is the most common type of telecommunication when compared with Shielded Twisted Pair Cable which consists of two conductors usually copper, each with its own colour plastic insulator. Identification is the reason behind coloured plastic insulation. UTP cables consist of 2 or 4 pairs of twisted cable. Cable with 2 pair use RJ-11 connector and 4 pair cable use RJ- 45 connector.
- 11. Advantages : Installation is easy Flexible Cheap It has high speed capacity, 100 meter limit Higher grades of UTP are used in LAN technologies like Ethernet. It consists of two insulating copper wires (1mm thick). The wires are twisted together in a helical form to reduce electrical interference from similar pair.
- 12. Disadvantages : Bandwidth is low when compared with Coaxial Cable Provides less protection from interference.
- 13. Shielded Twisted Pair Cable This cable has a metal foil or braided-mesh covering which encases each pair of insulated conductors. Electromagnetic noise penetration is prevented by metal casing. Shielding also eliminates crosstalk (explained in KEY TERMS Chapter). It has same attenuation as unshielded twisted pair. It is faster the unshielded and coaxial cable. It is more expensive than coaxial and unshielded twisted pair.
- 14. Advantages : Easy to install Performance is adequate Can be used for Analog or Digital transmission Increases the signalling rate Higher capacity than unshielded twisted pair Eliminates crosstalk Disadvantages : Difficult to manufacture Heavy
- 15. Coaxial Cable Coaxial is called by this name because it contains two conductors that are parallel to each other. Copper is used in this as centre conductor which can be a solid wire or a standard one. Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit. The outer conductor is also encased in an insulating sheath. The outermost part is the plastic cover which protects the whole cable.
- 17. There are two types of Coaxial cables : BaseBand This is a 50 ohm (Ω) coaxial cable 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. The major drawback is that it needs amplification after every 1000 feet. BroadBand This uses analog transmission on standard cable television cabling. It transmits several simultaneous signal using different frequencies. It covers large area when compared with Baseband Coaxial Cable.
- 18. Advantages : Bandwidth is high Used in long distance telephone lines. Transmits digital signals at a very high rate of 10Mbps. Much higher noise immunity Data transmission without distortion. The can span to longer distance at higher speeds as they have better shielding when compared to twisted pair cable Disadvantages : Single cable failure can fail the entire network. Difficult to install and expensive when compared with twisted pair. If the shield is imperfect, it can lead to grounded loop.
- 19. Fiber-Optics Cable Optical fiber consists of thin glass fibers or plastic that can carry information at frequencies in the visible light spectrum and beyond. The typical optical fiber consists of a very narrow strand of glass called the core. Around the core is a concentric layer of glass called the cladding? An optical transmission system has three basic components (a) Light source (b) Transmission medium (fiber optics) (c) Detector Light source: In such a system a pulse of light indicates bit 1 and the absence of light indicates bit 0. Light source can be an LED or a laser beam. Transmission medium: Transmission medium is the ultra-thin fiber of glass. Detector: A detector generates an electrical pulse when the light falls on it, BY LECTURER SURAJ PANDEY CCT COLLEGE
- 20. The core in fiber optic cable is surrounded by glass cladding with lower index of refraction as compared to core to keep all the light in core. This is covered with a thin plastic jacket to protect the cladding. The fibers are grouped together in bundles protected by an outer shield. Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second)
- 22. Types of Optical Fibers BY LECTURER SURAJ PANDEY CCT COLLEGE
- 23. Single Mode Fiber The various characteristics of Single mode fiber are:- 1. The diameter of glass core in single mode fiber is very small ranging from 8 to 10 microns. 2. In this mode, light can propagate only in a straight line, without bouncing. 5. Single mode fibers are more expensive and are widely used for long distance communication. 6. These types of fibers can transmit data at 50 Gbps for 100 kilometers without amplification. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 24. Multimode Fiber 1. In multimode fiber, multiple beams travel in the core in different paths. 2. In multimode fiber, the diameter of core is about 50 microns. 3. Multimode fibers are further categorized into Step index fibers and Graded index fibers. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 25. Advantages of Optical Fiber 1. They are not affected by electrical and magnetic interference as the data travel in form of light. 2. Optical fiber offers higher bandwidth than twisted pair or coaxial cable. 3. Optical fibers are thin, lighter in weight and small in size as compared to other wired Medias. It is easier to group several optical fibers in one bundle. 4. Glass is more resistant to corrosive materials as compared to copper. Hence can be laid in different environments. 5. In optical fibers, attenuation (loss of signal) is very low. Therefore these fibers can run several kilometers without amplification. 6. Fibers do not leak light and are quite difficult to tap. So they provide security against potential wiretappers. 7. There is no cross-talk problem in optical fibers. 8. They are highly suitable for environments where speed is needed with full accuracy. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 26. Disadvantages of Optical Fiber 1. Fiber optics cables are fragile i.e. more easily broken than wires. 2. Being fragile, optical fibers need to be put deep into the land. This causes a lot of installation cost. Also the interface used for these fibers are expensive. 3. Optical fibers are unidirectional for two-way communication, two fibers are required. 4. It is a newer technology and requires skilled people to administer and maintain them. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 27. Characteristics of Optical Fiber Cables: Fiber optic cables have the following characteristics: 1. Fiber optic cabling can provide extremely high bandwidths in the range from 100 mbps to 2 gigabits because light has a much higher frequency than electricity. 2. The number of nodes which a fiber optic can support does not depend on its length but on the hub or hubs that connect cables together. 3. Fiber optic cable has much lower attenuation and can carry signal to longer distances without using amplifiers and repeaters in between. 4. The cost of tiber optic cable is more compared to twisted pair and co- axial. 5. The installation of fiber optic cables is difficult and tedious. BY LECTURER SURAJ PANDEY CCT COLLEGE
- 28. UnBounded/UnGuided Transmission Media Unguided or wireless media sends the data through air (or water), which is available to anyone who has a device capable of receiving them. Types of unguided/ unbounded media are discussed below : Radio Transmission MicroWave Transmission
- 29. Radio Transmission Radiowaves are omni directional i.e. they travel in all the directions from the source. Because of this property, transmitter and receiver need not to be aligned. Radiowaves can penetrate buildings easily, so they are widely use for communication both indoors outdoors. At high frequencies, radiowaves tends to travel in straight line and bounce off the obstacles. They are also absorbed by rain. Radiowaves me widely used for AM and FM radio, television, cordless telephone, cellular phones, paging and wireless LAN. Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation. These waves are used for multicast communications.
- 30. Microwave Transmission Microwaves have been used in data communications for a long time. They have a higher frequency than radio waves and therefore can handle larger amounts of data. Microwave transmission is line of sight transmission. The transmit station must be in visible contact with the receive station. Microwaves operate at high operating frequencies of 3 to 10 GHz. This allows them to carry large quantities of data due to their large bandwidth. There are 2 types of Microwave Transmission : 1. Terrestrial Microwave 2. Satellite Microwave Advantages of Microwave Transmission Used for long distance telephone communication Carries 1000’s of voice channels at the same time High frequency/short wavelength signals require small antennae. Disadvantages of Microwave Transmission It is Very costly Attenuation by solid objects: birds, rain, snow and fog.
- 31. Terrestrial Microwave For increasing the distance served by terrestrial microwave, repeaters can be installed with each antenna .The signal received by an antenna can be converted into transmittable form and relayed to next antenna. There are two types of antennas used for terrestrial microwave communication : 1. Parabolic Dish Antenna In this every line parallel to the line of symmetry reflects off the curve at angles in a way that they intersect at a common point called focus. This antenna is based on geometry of parabola. 2. Horn Antenna It is a like gigantic scoop. The outgoing transmissions are broadcast up a stem and deflected outward in a series of narrow parallel beams by curved head.
- 32. Satellite Microwave This is a microwave relay station which is placed in outer space. The satellites are launched either by rockets or space shuttles carry them. These are positioned 3600KM above the equator with an orbit speed that exactly matches the rotation speed of the earth. As the satellite is positioned in a geo- synchronous orbit, it is stationery relative to earth and always stays over the same point on the ground. This is usually done to allow ground stations to aim antenna at a fixed point in the sky.
- 33. Features of Satellite Microwave : Bandwidth capacity depends on the frequency used. Satellite microwave deployment for orbiting satellite is difficult. Advantages of Satellite Microwave : Transmitting station can receive back its own transmission and check whether the satellite has transmitted information correctly. A single microwave relay station which is visible from any point. Disadvantages of Satellite Microwave : Satellite manufacturing cost is very high Cost of launching satellite is very expensive Transmission highly depends on whether conditions, it can go down in bad weather