Presentation on theme: "Computer Communication & Networks"— Presentation transcript:
1Computer Communication & Networks Lecture # 07Physical Layer: Transmission MediaCourse Instructor:Engr. Sana Ziafat
2Physical Layer Topics to Cover SignalsDigital TransmissionAnalog TransmissionMultiplexingTransmission Media
3Transmission MediaAnything that carry information from source to destination.Physical path between transmitter and receiver in data communication .
4Media Issues Frequency range Some media support higher frequencies than othersImpairmentsDifferent media deform signals differentlySome are more susceptible to noise and distortionCostWe’re in the real world…Number of receiversBroadcast vs. point-to-point
6Types of transmission media Transmission media is divided in to two: Wired or WirelessWired Media (Guided Media) , Is most common and is further divided in to three different types of cabling: Coaxial, Twisted pairs and fiber optic cables.Wireless Media (Unguided Media), which is , in a sense, no media at all, is gaining popularity. Wireless transmission use radio waves or infrared light to transmit data
8Guided Media Waves are guided along solid medium. Guided media is also known as bounded media, since the data signals are bounded system.Cabling technology is not limited to copper wire only. Cables can be any physical or conductive media like wires, coaxial cables or fiber optics.
16Twisted Pair Cable (Pros & Cons) easy to understandmass production - low costmost widely used mediumCons:prone to electromagnetic interferencein power plants, airport buildings, military facilities, cars…Note:In-building networks at our university are almost all twisted pair
17Coaxial CableIt carries high frequency signals than in twisted pair cable.Less susceptible to interference or crosstalk.
22Optical FiberMade of glass or plastic and transmits signal in form of light.Signal is sent using internal reflection.Relies on total internal reflectionLight waves bounce of edge of fiberChannels waves to destinationA glass or plastic core is surrounded by a cladding of less dense glass or plastic.
33Comparing optical fiber to UTP Pros:Immune to electro-magnetic interferenceno crosstalkReduced need for error detection and correctionEnables longer link distancesAttenuation unaffected by transmission rateEasier network upgradeCan combine different services: telephony, TV, internet…Lighter than copper cablesCorrosion resistantCons:Optical components have higher costExpensive deploying protocols
34Unguided Media: Wireless Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication.
35WirelessModern wireless digital communication began in the Hawaiian IslandsWhat is “the best” frequency to use for communication?
39Radio WavesElectromagnetic waves ranging in frequencies between 3 kHz and 1 GHz are normally called radio waves.They are omnidirectional (sends signal in all directions).Radio waves are used for multicast communications, such as radio and television, and paging systems.
41Microwaves Having range from 1 to 300 GHz. They are unidirectional. Microwave propagation is line-of-sight.Very high frequency microwaves can not penetrate walls.Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs.