COTN 1220 Data Communication Guided and Wireless Media PDF

COTN 1220 – Data Communication Guided and Wireless Media INTRODUCTION The world of computer networks would not exist if there were no medium by which to transfer data The two major categories of media include: Conducted media Wireless media TWISTED PAIR WIRE One or more pairs of single...

COTN 1220 – Data Communication Guided and Wireless Media INTRODUCTION The world of computer networks would not exist if there were no medium by which to transfer data The two major categories of media include: Conducted media Wireless media TWISTED PAIR WIRE One or more pairs of single conductor wires that have been twisted around each other Twisted pair wire is classified by category. Twisted pair is currently Category 1 through Category 7, although Categories 1, 2, 3, 4 and 5 are nearly obsolete Twisting the wires helps to eliminate electromagnetic interference between the two wires Shielding can further help to eliminate interference TWISTED PAIR WIRE TWISTED PAIR WIRE TWISTED PAIR WIRE TWISTED PAIR WIRE (CONT.) UTP Category Typical Use Max Data Transfer Rate Max Transmission Range Category 5e LANs 1000Mbps 100 m (328 ft) Category 6 LANs 1000Mbps 100 m (328 ft) Category 7 LANs 10Gbps 100 m (328 ft) TWISTED PAIR SUMMARY Most common form of wire Relatively inexpensive Easy to install Carries high data rates (but not the highest) Can suffer from electromagnetic noise Can be easily wire-tapped Comes in shielded and unshielded forms COAXIAL CABLE A single wire wrapped in a foam insulation surrounded by a braided metal shield, then covered in a plastic jacket. Cable comes in various thicknesses Baseband coaxial technology uses digital signaling in which the cable carries only one channel of digital data Broadband coaxial technology transmits analog signals and can support multiple channels COAXIAL CABLE COAXIAL CABLE RG-8/U Cable RG-58/AU Cable COAXIAL CABLE SUMMARY A single wire surrounded by a braided shield Because of shielding, can carry a wide bandwidth of frequencies Thus is good with applications such as cable television Not as easy to install as twisted pair More expensive than twisted pair FIBER-OPTIC CABLE A thin glass cable approximately a little thicker than a human hair surrounded by a plastic coating and packaged into an insulated cable A photo diode or laser generates pulses of light which travel down the fiber optic cable and are received by a photo receptor FIBER-OPTIC CABLE FIBER-OPTIC CABLE FIBER-OPTIC CABLE FIBER-OPTIC CABLE (HTTPS://YOUTU.BE/JZOG39V73C4) FIBER-OPTIC CABLE Fiber-optic cable is capable of supporting millions of bits per second for 1000s of meters Thick cable (62.5/125 microns) causes more ray collisions, so you must transmit slower. This is step index multimode fiber. Typically use LED for light source, shorter distance transmissions Thin cable (8.3/125 microns) – very little reflection, fast transmission, typically uses a laser, longer transmission distances; known as single mode fiber FIBER-OPTIC CABLE Fiber-optic cable is susceptible to reflection (where the light source bounces around inside the cable) and refraction (where the light source passes out of the core and into the surrounding cladding) Thus, fiber-optic cable is not perfect either. Noise is still a potential problem FIBER-OPTIC CABLE FIBER-OPTIC CABLE FIBER-OPTIC CABLE SUMMARY Fiber optic cable can carry the highest data rate for the longest distances Initial cost-wise, more expensive than twisted pair, but less than coaxial cable But when you consider the superiority of fiber, initial costs outweighed by capacities Need to fibers for a round-trip connection Not affected by electromagnetic noise and cannot be easily wiretapped, but still noise WIRELESS WIRELESS MEDIA Radio, satellite transmissions, and infrared light are all different forms of electromagnetic waves that are used to transmit data Technically speaking – in wireless transmissions, space is the medium Note in the following figure how each source occupies a different set of frequencies WIRELESS MEDIA TERRESTRIAL MICROWAVE TRANSMISSION Land-based, line-of-sight transmission Approximately 20-30 miles between towers Transmits data at hundreds of millions of bits per second Signals will not pass through solid objects Popular with telephone companies and business to business transmissions TERRESTRIAL MICROWAVE TRANSMISSION TERRESTRIAL MICROWAVE TRANSMISSION SATELLITE MICROWAVE TRANSMISSION Similar to terrestrial microwave except the signal travels from a ground station on earth to a satellite and back to another ground station Can also transmit signals from one satellite to another Satellites can be classified by how far out into orbit each one is (LEO, MEO, GEO, and HEO) SATELLITE MICROWAVE TRANSMISSION LEO (Low-Earth-Orbit) – 100 to 1000 miles out Used for wireless e-mail, special mobile telephones, pagers, spying, videoconferencing MEO (Middle-Earth-Orbit) – 1000 to 22,300 miles Used for GPS (global positioning systems) and government GEO (Geosynchronous/geostationary-Earth-Orbit) – 22,300 miles Geosynchronous - always over the same position on earth at the same time of day Orbit = earth’s rotation time = 23 hours, 56 minutes and 4 seconds Geostationary – located over the equator Used for weather, television, government operations SATELLITE MICROWAVE TRANSMISSION HEO (Highly Elliptical Earth orbit) – satellite follows an elliptical orbit Used by the military for spying and by scientific organizations for photographing celestial bodies SATELLITE MICROWAVE TRANSMISSION SATELLITE MICROWAVE TRANSMISSION Satellite microwave can also be classified by its configuration (see next figure): Bulk carrier configuration Multiplexed configuration Single-user earth station configuration (e.g. VSAT) SATELLITE MICROWAVE TRANSMISSION CELLULAR TELEPHONES Wireless telephone service, also called mobile telephone, cell phone, and PCS To support multiple users in a metropolitan area (market), the market is broken into cells Each cell has its own transmission tower and set of assignable channels CELLULAR TELEPHONES CELLULAR TELEPHONES CELLULAR TELEPHONES CELLULAR TELEPHONES Placing a call on a cell phone You enter a phone number on your cell phone and press Send. Your cell phone contacts the nearest cell tower and grabs a set-up channel. Your mobile identification information is exchanged to make sure you are a current subscriber. If you are current, you are dynamically assigned two channels: one for talking, and one for listening. The telephone call is placed. You talk. CELLULAR TELEPHONES Receiving a call on a cell phone Whenever a cell phone is on, it “pings” the nearest cell tower every several seconds, exchanging mobile ID information. This way, the cell phone system knows where each cell phone is. When someone calls your cell phone number, since the cell phone system knows what cell you are in, the tower “calls” your cell phone. BLUETOOTH Bluetooth is a specification for short-range, point-to-point or point- to-multipoint voice and data transfer Bluetooth can transmit through solid, non-metal objects Its typical link range is from 10 cm to 10 m, but can be extended to 100 m by increasing the power Bluetooth enable users to connect to a wide range of computing and telecommunication devices without the need of connecting cables Typical uses include phones, modems, LAN access devices, headsets, notebooks, and desktop computers WIRELESS LOCAL AREA NETWORKS (IEEE 802.11) This technology transmits data between workstations and local area networks using high-speed radio frequencies Current technologies allow up to 100 Mbps (theoretical) data transfer at distances up to hundreds of feet Four popular standards: IEEE 802.11b, a, g, n, ac, ax More on this later in the course INFRARED TRANSMISSIONS Transmissions that use a focused ray of light in the infrared frequency range Very common with remote control devices, but can also be used for device-to-device transfers, such as PDA to computer MEDIA SELECTION CRITERIA Cost Speed Distance and expandability Environment Security COST Different types of costs Initial cost – what does a particular type of medium cost to purchase? To install? Maintenance / support cost ROI (return on investment) – if one medium is cheaper to purchase and install but is not cost effective, where are the savings? SPEED Two different forms of speed: Propagation speed – the time to send the first bit across the medium This speed depends upon the medium Airwaves and fiber are speed of light Copper wire is two thirds the speed of light Data transfer speed – the time to transmit the rest of the bits in the message This speed is measured in bits per second EXPANDABILITY AND DISTANCE Certain media lend themselves more easily to expansion Don’t forget right-of-way issue for conducted media and line-of-sight for certain wireless media ENVIRONMENT Many types of environments are hazardous to certain media Electromagnetic noise Scintillation and movement Extreme environmental conditions SECURITY If data must be secure during transmission, it is important that the medium not be easy to tap Make the wire impervious to electromagnetic wiretapping Encrypt the signal going over the medium SUMMARY All data communication media can be divided into two basic categories: (1) physical or conducted media, and (2) radiated or wireless media, such as satellite systems The three types of conducted media are twisted pair, coaxial cable, and fiber-optic cable Twisted pair and coaxial cable are both metal wires and are subject to electromagnetic interference SUMMARY Fiber-optic cable is a glass wire and is impervious to electromagnetic interference Experiences a lower noise level Has best transmission speeds and long-distance performance of all conducted media Several basic groups of wireless media exist: terrestrial microwave transmissions, satellite transmissions, cellular telephone systems, infrared transmissions, WiMAX, and Bluetooth SUMMARY Each of the wireless technologies is designed for specific applications When trying to select particular medium for an application, it helps to compare the different media using these six criteria: cost, speed, expandability and distance, right-of-way, environment, and security Videos https://youtu.be/_NX99ad2FUA https://youtu.be/rrUHjb3hfjM https://youtu.be/KTXWO3cbfyQ