Presentation on theme: "What is Cable? Transmission Media"— Presentation transcript:
1 What is Cable? Transmission Media Transmission medium is the physical path between the transmitter and receiver.It is the Transmission medium through which information usually moves from one network device to another.In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types.Understanding the characteristics of different types of transmission media and how they relate to other aspects of a network is necessary for the development of a successful network.
3 Factors to Select Transmission Media Data Rate and Bandwidth (BPS and Hz)Distance and Attenuation (meters, dB/km)Interference CharacteristicsNumber of receivers (broadcast vs. point to point)Cost - Remember cabling is a long term investment!
4 Transmission Impairments Impairments exist in all forms of data transmission mediaAnalog signal impairments result in random modifications that impair signal qualityDigital signal impairments result in bit errors (1s and 0s transposed)
5 Types of Media Two major classes Conducted or guided media use a conductor such as a wire or a fiber optic cable to move the signal from sender to receiver.Energy is confined to the medium and guided by itWireless or unguided mediause radio waves of different frequencies and do not need a wire or cable conductor to transmit signalsEnergy spreads out and is not confined
6 Media Sub-types Guided Media Unguided Media Unshielded Twisted Pair (UTP) CableShielded Twisted Pair (STP) CableCoaxial CableFiber Optic CableUnguided MediaTerrestrial microwave transmissionSatellite transmissionBroadcast radioInfrared
7 Twisted Pair WiresConsists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairsOften used at customer facilities and also over distances to carry voice as well as data communicationsLow frequency transmission mediumTwo varietiesSTP (shielded twisted pair)the pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interferenceUTP (unshielded twisted pair)each wire is insulated with plastic wrap, but the pair is encased in an outer covering
8 Twisted PairOne difference between the different categories of UTP is the tightness of the twisting of the copper pairs. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot.Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.
9 Categories of Unshielded Twisted Pair The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated five categories of wire.Type UseCategory 1 Voice Only (Telephone Wire)Category 2 Data to 4 Mbps (LocalTalk)Category 3 Data to 10 Mbps (Ethernet)Category 4 Data to 20 Mbps (16 Mbps Token Ring)Category 5 Data to 100 Mbps (Fast Ethernet)Category 5e Data to 1000 Mbps (Gigabit Ethernet)Category 6 Data to 1000 Mbps (Gigabit Ethernet)Category 7 ?
10 Pros and Cons Benefits of UTP Disadvantages of UTP Inexpensive and readily availableFlexible and light weightEasy to work with and installDisadvantages of UTPSusceptibility to interference and noiseAttenuation problem
11 Twisted Pair - Applications Telephone networkBetween house and local exchange (subscriber loop/local loop)Within buildingsTo private branch exchange (PBX)For local area networks (LAN)10Mbps or 100Mbps or 1000 Mbps
12 Unshielded Twisted Pair Connector The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector (See figure).A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.
14 Shielded Twisted Pair (STP) Cable A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference (RFI, EFI).Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky.Shielded twisted pair is often used on networks using Token Ring topology.More expensive, harder to work with.
16 Coaxial CableCoaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield (See figure). The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.Both conductors share a common center axis, hence the term “co- axial”
18 Pros and Cons Coax Advantages Coax Disadvantages Higher bandwidth Can be tapped easily (pros and cons)Much less susceptible to interference than twisted pairCoax DisadvantagesHigh attenuation rate makes it expensive over long distanceBulky - coaxial cabling is difficult to install
19 Coaxial Cable Applications Most versatile mediumTelevision distributionAriel to TVCable TVLong distance telephone transmissionBeing replaced by fiber opticShort distance computer systems linksLocal area networks
20 Types of Coaxial Cable Thin Coax Thick Coax Thin coaxial cable is also referred to as thinnet. Thin coaxial cable is popular in linear bus networks.Thick CoaxThick coaxial cable is also referred to as thicknet.Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network.One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
21 Coaxial Cable Connectors The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector (See figure). Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather than screw, onto the cable.
22 Fiber Optic CableRelatively new transmission medium used by telephone companies in place of long-distance trunk linesAlso used by private companies in implementing local data communications networksRequire a light source with injection laser diode (ILD) or light-emitting diodes (LED)
23 Fiber Optic CableFiber optic cabling consists of a center glass core surrounded by several layers of protective materials.It transmits light rather than electronic signals, eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference.It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.
24 Fiber Optic Layers consists of three concentric sections plastic jacketglass or plasticcladdingfiber core24
27 Facts About Fiber Optic Cables Outer insulating jacket is made of Teflon or PVC.Kevlar fiber helps to strengthen the cable and prevent breakage.A plastic coating is used to cushion the fiber center.Center (core) is made of glass or plastic fibers.
28 Fiber Optic CableFiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair.It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services.The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify.
29 Optical Fiber - Transmission Characteristics Act as wave guide for 1014 to 1015 HzPortions of infrared and visible spectrumLight Emitting Diode (LED)CheaperWider operating temp rangeLast longerInjection Laser Diode (ILD)More efficientGreater data rate
30 Fiber Optic Types Multimode step-index fiber the reflective walls of the fiber move the light pulses to the receiverMultimode graded-index fiberacts to refract the light toward the center of the fiber by variations in the densitySingle mode fiberthe light is guided down the center of an extremely narrow core30
32 Pros and Cons Fiber Optic Advantages Fiber Optic Disadvantages Greater capacity - data rates of hundreds of GbpsSmaller size and lighter weightLower attenuationElectromagnetic isolation - immunity to environmental interference and highly secure due to tap difficulty and lack of signal radiationGreater repeater spacing - 10s of km at leastFiber Optic DisadvantagesExpensive over short distanceRequires highly skilled installersAdding additional nodes is difficult
33 Fiber Optic ConnectorThe most common connector used with fiber optic cable is an ST connector. It is barrel shaped, similar to a BNC connector. A newer connector, the SC, is becoming more popular. It has a squared face and is easier to connect in a confined space.
34 Comparison of the Three Guided Media Types 1000 THz1 THz1 GHz1 MHzOptical Fiber1 kHz0.13/8” Coaxial Cable22-gauge Twisted PairFrequencydB/km110100
35 Wireless (Unguided Media) TransmissionTransmission and reception are achieved by means of an antennaDirectionaltransmitting antenna puts out focused beamtransmitter and receiver must be alignedOmnidirectionalsignal spreads out in all directionscan be received by many antennas
36 Wireless (Unguided Media) Frequencies Three general ranges of frequencies30MHz to 1GHzBroadcast radioOmnidirectional2GHz to 40GHz microwave frequenciesMicrowaveHighly directionalPoint to pointSatellite3 x 1011 to 2 x 1014Infrared
39 Terrestrial Microwave Transmission Uses the radio frequency spectrum, commonly from 2 to 40 GHzTransmitter is a parabolic dish, mounted as high as possibleUsed by common carriers as well as by private networksRequires unobstructed line of sight between source and receiverCurvature of the earth requires stations (called repeaters) to be ~30 miles apart39
40 Terrestrial Microwave Applications Long-haul telecommunications service for both voice and television transmissionShort point-to-point links between buildings for closed-circuit TV or a data link between LANs
42 Pros and Cons Microwave Transmission Advantages No cabling needed between sitesWide bandwidthMulti-channel transmissionsUsed for long haul or high capacity short haulRequires fewer amplifiers and repeatersMicrowave Transmission DisadvantagesLine of sight requirementExpensive towers and repeatersSubject to interference such as passing airplanes and rainFrequency bands are regulated42
43 Satellite Microwave Transmission Satellite is a microwave relay station in spaceCan relay signals over long distancesGeostationary satellitesremain above the equator at a height of 22,300 miles (geosynchronous orbit)travel around the earth in exactly the time the earth takes to rotateEarth stations communicate by sending signals to the satellite on an uplinkThe satellite then repeats those signals on a downlinkThe broadcast nature of the downlink makes it attractive for services such as the distribution of television programming43
45 Satellite Transmission Process transponderdishdish22,300 milesuplink stationdownlink station45
46 Satellite Transmission Applications Television distributiona network provides programming from a central locationdirect broadcast satellite (DBS)Long-distance telephone transmissionhigh-usage international trunksPrivate business networks
47 Pros and Cons Satellite Advantages Satellite Disadvantages Can reach a large geographical areaHigh bandwidthCheaper over long distancesSatellite DisadvantagesHigh initial costSusceptible to noise and interferencePropagation delay (0.25 sec) - requires sophisticated flow control
50 Broadcast Radio Broadcast radio is omnidirectional Covers 30MHz to 1 GHz (FM, UHF, VHF)Need line of sight. Ionosphere is transparent above 30MHz, hence no atmospheric reflectionAdvantagesLess sensitive to attenuation from rainfallDisadvantagesMultipath interference is significant
51 InfraredTransceivers operate with line of sight or reflection from light-colored surfaceModulate noncoherent infrared lighte.g. TV remote control, IRD portAdvantagesDoes not penetrate walls - enhanced securityNo licensing of frequenciesDisadvantagesOperate on limited distances
53 RJ-45 ConnectorThe RJ-45 connector is commonly used for network cabling and for telephony applications. It's also used for serial connections in special cases.
54 RJ-45 Connector for LANAlso, please note that it is very important that a single pair be used for pins 3 and 6. If one conductor from one pair is used for pin 3 and a conductor from another pair is used for pin 6, performance will degrade. See the following figure.