UNIT II (PHYSICAL LAYER).pptx
- 1. U N I T I I PHYSICAL LAYER
- 2. SYLABUS GUIDED TRANSMISSION MEDIA: MAGNETIC MEDIA – TWISTED PAIR – COAXIAL CABLE – FIBER OPTICS. WIRELESS TRANSMISSION: ELECTROMAGNETIC SPECTRUM– RADIO TRANSMISSION – MICROWAVE TRANSMISSION – INFRARED AND MILLIMETER WAVES – LIGHT WAVES. COMMUNICATION SATTELLITES: GEOSTATIONARY, MEDIUM – EARTH ORBIT, LOW EARTH – ORBIT SATELLITIES – SATELLITES VERSUS FIBER.
- 3. WHAT IS TRANSMISSION MEDIA? • Sending of data from one device to another is called Transmission of data. • Medium used to transmit the data is called Media. • Transmission of data through Medium is called Transmission Media.
- 4. GUIDED TRANSMISSION MEDIA • It is defined as the physical medium through which the signals are transmitted. • It is also known as Bounded media. • Guided transmission media means the data signals are guided along with the path like cabling system. • They don’t have any other way to go they have to pass through the given cable or wire. • In guided media, transmitted data travels through cabling system that has a fixed path. For example, copper wires, fibre optic wires, etc.
- 6. TWISTED PAIR • A twisted pair consists of two insulated copper wires arranged in a regular spiral pattern. • Twisted pair may be used to transmit both analog and digital transmission. • Twisted pair is limited in distance, bandwidth, and data rate. • The attenuation for twisted pair is a very strong function of frequency.
- 7. Unshielded Twisted Pair(UTP) • An unshielded twisted pair is widely used in telecommunication. • Cheapest • Easiest to install • Suffers from external EM interference Shielded Twisted Pair(STP) • A shielded twisted pair is a cable that contains the mesh surrounding the wire that allows the higher transmission rate. • Metal braid or sheathing that reduces inferences • More expensive • Easiest to install • Harder to handle (thick, heavy)
- 8. COAXIAL CABLE • Coaxial cable consist the followings layers in its construction The copper conductor Insulation layer of plastic foam Second conductor or shield of wire mesh tube or metallic foam Outer jacket of tough plastic • Coaxial cable can be used over longer distances and support more stations on a shared line than twisted pair. • Coaxial cable is used in a wide variety of applications including: Television distribution- Aerial to TV systems.
- 9. FIBER OPTICS • Fibre optic cable is a cable that uses electrical signals for communication. • Fibre optic is a cable that holds the optical fibres coated in plastic that are used to send the data by pulses of light. • The plastic coating protects the optical fibres from heat, cold, electromagnetic interference from other types of wiring. • Fibre optics provide faster data transmission than copper wires.
- 10. MAGNETIC MEDIA Any storage medium that utilizes magnetic patterns to represent information is considered magnetic media. Good examples of a magnetic media and magnetic storage is a tape drive, floppy diskette, and hard drive.
- 11. WIRELESS TRANSMISSION • Wireless transmission is a form of unguided media. Wireless communication involves no physical link established between two or more devices, communicating wirelessly. Wireless signals are spread over in the air and are received and interpreted by appropriate antennas.
- 12. ELECTROMAGNETIC SPECTRUM • The electromagnetic spectrum is a collection of frequencies, wavelengths, and photon energies of electromagnetic waves spanning from 1Hz to 1025Hz, equivalent to wavelengths ranging from a few hundred kilometres to a size smaller than the size of an atomic nucleus. The electromagnetic spectrum can thus be described as the range of all types of electromagnetic radiation in basic terms. In a vacuum, all electromagnetic waves travel at the same speed as light. For different forms of electromagnetic waves, however, the wavelengths, frequencies, and photon energy will vary.
- 13. • A little part of electromagnetic spectrum can be used for wireless transmission. The electromagnetic spectrum is the entire range of electromagnetic radiation according to the wavelength or frequencies. • The waves in order of increasing frequencies are radio waves, microwaves, • infrared rays, visible light, UV rays, X-rays and gamma rays • The section of the spectrum in the range of radio waves and microwaves has been divided into a number of frequency bands as officially referred by ITU (International Telecommunication Union). These bands are rated from VLF (Very Low Frequency) to EHF (Extremely High Frequency).
- 15. UNGUIDED TRANSMISSIOM MEDIA • An unguided transmission transmits the electromagnetic waves without using any physical medium. Therefore, it is also known as wireless transmission. • In unguided media, air is the media through which the electromagnetic energy can flow easily.
- 16. RADIO TRANSMISSION • In the electromagnetic spectrum, all omnidirectional waves in the frequencies 3KHz to 1GHz are called radio waves. They are widely used for communications since they are easy to generate, can travel long distances and can penetrate buildings. Radio waves have omnidirectional antennas, i.e., antennas that can send signals in all directions. • The properties of radios waves vary according to their frequencies. However, radio waves at all frequencies are prone to interference from electrical equipments like motors etc.
- 17. • Radio waves are easy to generate, can travel long distances, and can penetrate buildings easily, so they are widely used for communication, both indoors and outdoors. • Radio waves also are omnidirectional, meaning that they travel in all directions from the source, so the transmitter and receiver do not have to be carefully aligned physically. • Frequency ranging from 3 Hz (Extremely Low Frequency) to 300 GHz (Extremely High Frequency). • Radio waves at lower frequencies can travel through walls whereas higher RF can travel in straight line and bounce back. • The power of low frequency waves decreases sharply as they cover long distance. High frequency radio waves have more power.
- 18. HIGH FREQUENCY RADIO WAVES • Radio waves of high frequencies are prone to be absorbed by rain and other obstacles. • They use Ionosphere of earth atmosphere. • High frequency radio waves such as HF and VHF bands are spread upwards. • When they reach Ionosphere, they are refracted back to the earth. • The military communicates in the HF and VHF bands • They are also used for long distance • broadcasting and FM radio.
- 19. MICRO TRANSMISSION • In the electromagnetic spectrum, waves within the frequencies 1GHz to 300GHz are called microwaves.
- 21. INFRARED AND MILLIMETER WAVES
- 22. • Infrared Data Transmission. IrDA (Infrared Data Association) is an industry standard for wireless communication with infrared light. Many laptops sold today are equipped with an IrDA-compatible transceiver that enables communication with other devices, such as printers, modems, LANs, or other laptops.
- 26. MILLIMETER WAVES • Millimeter wave (MM wave), also known as millimeter band, is the band of spectrum with wavelengths between 10 millimeters (30 GHz) and 1 millimeter (300 GHz). It is also known as the extremely high frequency (EHF) band by the International Telecommunication Union (ITU). • Millimeter waves allow for the possibility of 5G networks that provide vastly improved speed and reliability. Data traveling over mobile networks at incredible speed with imperceptible latency could be the norm, paving the way for innovations in mobile data applications.
- 28. LIGHT WAVES • Electromagnetic waves within the frequency range of 400 THz – 790 THz are detected by the human eye. Light transmission is line of sight propagation and is blocked by obstacles.
- 29. COMMUNICATION SATELLITES • A communication satellite is an artificial satellite that acts as a large repeater in the sky. It receives signals from the source transmitter, amplifies using transponders, and relays them to the receiver.
- 30. • Geostationary Satellite (GEO) − They are at 36,000 km (about 22369.36 mi) from the earth’s surface. They have same orbital period as earth’s rotation. So, they appear to be still in the sky. At least 3 GEOs are needed for global coverage. • Medium Earth Orbit Satellite (MEO) − They are placed between the two Van Allen belts, at a distance between 2,000 km to 36,000 km from the earth’s surface. At least 10 MEOs are needed for global coverage. • Low Earth Orbit Satellite (LEO) − They are situated below the Lower Van Allen belt. Their orbital altitude is 160 km to 2000 km. For global coverage, as high as 50 LEOs are required.
- 35. This Photo by Unknown Author is licensed under CC BY