Computers Are Your FutureSlide 2What You Will Learn . . .Slide 4ConnectivityMoving Data: Bandwidth and ModemsSlide 7Slide 8Wireless Transmission MediaWireless Transmission Media: Twisted PairWireless Transmission Media: Coaxial CableWireless Transmission Media: Fiber OpticWireless Transmission Media: InfraredWireless Transmission Media: RadioWireless Transmission Media: BluetoothWireless Transmission Media: MicrowavesWireless Transmission Media: SatellitesWired Communication via the PSTNMultiplexingLast Mile TechnologiesSlide 21Convergence: Is it a Phone or a Computer?Cellular TelephonesPersonal Communication Service (PCS)Web-Enabled DevicesWired and Wireless ApplicationsSlide 27Facsimile (Fax) TransmissionSatellite Radio, GPSText, Picture, and Video MessagingChapter 3 SummarySlide 32Computers Are Your Future© 2006 Prentice-Hall, Inc.© 2006 Prentice-Hall, Inc Slide 2Computers Are Your Future Chapter 3Computers Are Your FutureChapter 3Wired and Wireless Communication© 2006 Prentice-Hall, Inc Slide 3Computers Are Your Future Chapter 3What You Will Learn . . .The definition of bandwidthThe bandwidth needs of a typical userHow modems change digital signals into analog Transmission media and methodsLimitations of public switched telephone network (PTSN) for sending and receiving data© 2006 Prentice-Hall, Inc Slide 4Computers Are Your Future Chapter 3What You Will Learn . . .Multiplexing and digital telephony and their impact on line usageExamples of how digitization and convergence are blurring the boundaries between popular communication devicesVarious wired and wireless applications© 2006 Prentice-Hall, Inc Slide 5Computers Are Your Future Chapter 3Connectivitythe ability to link various media and devices© 2006 Prentice-Hall, Inc Slide 6Computers Are Your Future Chapter 3Moving Data: Bandwidth and ModemsCommunications – sending and receiving messagesCommunications channels – paths through which messages are passedSignals can be:Analog – data is in continuous waveformsDigital – data is in discontinuous pulses (0’s & 1’s)digitalanalog© 2006 Prentice-Hall, Inc Slide 7Computers Are Your Future Chapter 3Moving Data: Bandwidth and ModemsBandwidth – the amount of data that can be transmitted through a given communications channelAnalog measured in cycles per second (Hz)Digital measured in bits per second (bps)Broadband – any transmission medium that transports high volumes of data at high speeds© 2006 Prentice-Hall, Inc Slide 8Computers Are Your Future Chapter 3Moving Data: Bandwidth and ModemsModemsTransmit data over telephone linesModulation – converts digital (from computer) to analog to cross telephone linesDemodulation – converts analog (phone lines) to digital for computer© 2006 Prentice-Hall, Inc Slide 9Computers Are Your Future Chapter 3Wireless Transmission MediaWireless transmission media refers to the methods of carrying data through the air or space using infrared, radio, or microwave signals© 2006 Prentice-Hall, Inc Slide 10Computers Are Your Future Chapter 3Wireless Transmission Media: Twisted PairTwisted Pair – two insulated wires twisted around each other – used for telephone wires© 2006 Prentice-Hall, Inc Slide 11Computers Are Your Future Chapter 3Wireless Transmission Media: Coaxial CableCoaxial Cable – center copper wire surrounded by insulation, surrounding a layer of braded wire© 2006 Prentice-Hall, Inc Slide 12Computers Are Your Future Chapter 3Wireless Transmission Media: Fiber OpticFiber-optic cable – thin strands of glass that carry data by light pulses© 2006 Prentice-Hall, Inc Slide 13Computers Are Your Future Chapter 3Wireless Transmission Media: InfraredInfrared is a wireless transmission medium that carries data via light beamsTransmitter and receiver must be in line of sightAn IrDa port is needed to use infrared with a computer© 2006 Prentice-Hall, Inc Slide 14Computers Are Your Future Chapter 3Wireless Transmission Media: RadioRadio is a wireless transmission medium that carries data via radio frequency signalsWireless LANs in a home or business are one type of radio technologyRadio signals can be long range (between cities or regions) and short range (within a building)Radio signals are susceptible to noise and electrical interference© 2006 Prentice-Hall, Inc Slide 15Computers Are Your Future Chapter 3Wireless Transmission Media: BluetoothShort-range radio transmission technologyDevices identify each other by identification numberConnection is confirmed before it is made finalDoes not require a line of site© 2006 Prentice-Hall, Inc Slide 16Computers Are Your Future Chapter 3Wireless Transmission Media: MicrowavesMicrowaves are high-frequency radio wavesMuch of long-distance telephone service is carried by microwavesMicrowaves travel in a straight lineMicrowave relay stations are built about 30 miles apart© 2006 Prentice-Hall, Inc Slide 17Computers Are Your Future Chapter 3Wireless Transmission Media: SatellitesSatellites are microwave relay stations suspended in spaceThey are positioned in geosynchronous orbitsSatellites use microwave signals to transmit data to and from earth-based microwave relay stations© 2006 Prentice-Hall, Inc Slide 18Computers Are Your Future Chapter 3Wired Communication via the PSTNThe public switched telephone network (PSTN) is the world telephone systemIt is used for data as well as voice communicationsTwisted-pair wire and fiber-optic cable provide the connections for the systemHome and business phones are connected to subscriber loop carriers (SLCs)The area serviced by SLCs is called the local loop© 2006 Prentice-Hall, Inc Slide 19Computers Are Your Future Chapter 3MultiplexingMultiplexing technology enables simultaneous multi-use of transmission linesCopper wire allows up to 24 simultaneous calls per wireFiber-optic cable permits up to 43,384 calls per strand© 2006 Prentice-Hall, Inc Slide 20Computers Are Your Future Chapter 3Last Mile TechnologiesThe “last mile” refers to the phone lines that connect homes and businesses to the local loopThe inability of users to access the high-speed fiber-optic cable creates a bottleneck of data called the last mile problem© 2006 Prentice-Hall, Inc Slide 21Computers Are Your Future Chapter 3Last Mile TechnologiesDigital telephony technologies that use twisted-pair wire