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Chapter 18 Wireless Multimedia

Chapter 18 Wireless Multimedia. Information Technology in Theory By Pelin Aksoy and Laura DeNardis. Objectives.

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Chapter 18 Wireless Multimedia

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  1. Chapter 18Wireless Multimedia Information Technology in Theory By Pelin Aksoy and Laura DeNardis

  2. Objectives • Understand the role of multimedia access devices such as cell phones and how they have integrated previously separate applications such as voice, Internet applications, electronic commerce, and entertainment • Understand how Bluetooth and spread spectrum technologies work • Examine the concepts of cells, frequency reuse, and handoff in cellular networks Information Technology in Theory

  3. Objectives (continued) • Become familiar with the main architectural components of a cellular network • Understand the role of cellular standards such as GSM and differentiate between 1G, 2G, and 3G systems • Examine emerging wireless broadband technologies such as WiMAX and how they might transform information access Information Technology in Theory

  4. Wireless Multimedia Devices • A major transition in IT has been the integration of previously disparate functions into a more unified and mobile multimedia environment • Mobile telephony • Web browsing • Electronic mail • Camera • GPS • Video player • Text messaging (also known as SMS) • Music player • Organizer • Calendar • Office applications and presentation software Information Technology in Theory

  5. Wireless Multimedia Devices (continued) Information Technology in Theory

  6. The Bluetooth Standard • Bluetooth technology is a short-range wireless communication standard designed for geographically limited transmissions • Also known as the IEEE 802.15.1 standard, Bluetooth is an industry specification for encrypted radio communications • It uses an unlicensed (2.4 to 2.485 GHz) frequency band of the radio spectrum, similar to Wi-Fi frequencies Information Technology in Theory

  7. The Bluetooth Standard (continued) • The Bluetooth standard specifies three classes of devices that operate at different ranges: • Class 1 radio, which operates at up to 100 meters • Class 2 radio, which operates in a range of approximately 10 meters • Class 3 radio, which operates in an extremely short range of up to 1 meter • Bluetooth uses a wireless transmission approach called frequency hopping spread spectrum (FHSS), which divides the allocated frequency band into smaller bands and rapidly hops between 79 frequencies at a rate of 1600 hops per second Information Technology in Theory

  8. The Bluetooth Standard (continued) • Another type of spread spectrum is direct sequence spread spectrum (DSSS) • The Bluetooth standard uses FHSS, the technique that transmits the signal across a transmission channel using various frequencies • The duration in which each frequency is used is extremely brief, considering that more than 1000 frequencies are used per second • DSSS techniques do not hop from one frequency to the next, but instead rely on spreading the energy of the transmission onto a large range of frequencies at any given time Information Technology in Theory

  9. The Bluetooth Standard (continued) • It is inherently difficult to jam spread spectrum transmission because transmissions are distributed across a range of frequencies rather than a single frequency • The sequence of frequencies that the transmitter hops in FHSS is based on a “pseudorandom” code—because the code is a binary number that is actually generated with an algorithm, it is called pseudo-random Information Technology in Theory

  10. The Bluetooth Standard (continued) Information Technology in Theory

  11. The Bluetooth Standard (continued) • Another fundamental technical property of Bluetooth technology is that a group of Bluetooth devices, usually called a piconet, is synchronized both by time and by a common pattern of frequency hopping • A “master” device provides the definitive clock and hop pattern information to which the other “slave” devices synchronize Information Technology in Theory

  12. The Bluetooth Standard (continued) Information Technology in Theory

  13. Cellular Technology • Cell phones and most other wireless multimedia devices connect to cellular networks • Throughout the world, the frequency spectrum allocated for cellular transmission systems ranges from hundreds of megahertz to a few gigahertz • Unlike the unlicensed band used with Bluetooth, cellular technologies use licensed frequency bands within the radio spectrum Information Technology in Theory

  14. Frequency Reuse • One option for providing radio coverage in a metropolitan area is to install a single, high-powered, large antenna • The coverage area, or reach of the signal, depends on the size, shape, and height of the antenna; the topography of the surrounding area; the transmission power of the antenna; the frequency being used; and any ambient atmospheric conditions such as weather Information Technology in Theory

  15. Frequency Reuse (continued) • Because only a limited number of radio frequencies are made available to a service that provides wireless access, conserving frequency is a key requirement of the system design • One solution to conserving a limited number of available frequencies within a large geographical area is to split the area into smaller areas called cells and place an individual antenna called a base station within each smaller area Information Technology in Theory

  16. Frequency Reuse (continued) Information Technology in Theory

  17. Frequency Reuse (continued) • Each base station transmits at a much lower power than a single antenna that could cover an entire region • A cell may therefore be defined as a geographical area covered by a base station • Although the shape of a cell is actually more circular, the theoretical shape of the cell is traditionally depicted as hexagonal Information Technology in Theory

  18. Frequency Reuse (continued) Information Technology in Theory

  19. Frequency Reuse (continued) • The same radio frequencies can be used in multiple cells as long as the base station transmitters are far enough apart and if the level of transmission power is low enough not to interfere with other cells that use the same frequency • Each 7-cell group, or cluster, uses the same set of frequencies, which allows the system to support many more users than a single antenna • Cellular networks can handle a large number of calls with a relatively small number of channels because of this frequency reuse—a single frequency can be used simultaneously in different nonadjacent cells Information Technology in Theory

  20. Frequency Reuse (continued) • The number of cells into which a larger geographical area would be divided mainly depends on the subscriber density, the number of users who require service in the area • One of the most common approaches for handling increases in subscriber density is cell splitting • Another technique to increase system capacity is cell sectoring • Additionally, access mechanisms enable numerous users to share each channel, improving the capacity of cellular systems Information Technology in Theory

  21. Frequency Reuse (continued) Information Technology in Theory

  22. Frequency Reuse (continued) • One base station can communicate with many mobile devices • Traditionally, each of these communications actually uses two frequencies in any given instant • The distinction between walkie-talkie service on cell phones and real-time, two-way communications illustrates the difference between full duplex and half duplex transmission Information Technology in Theory

  23. Frequency Reuse (continued) Information Technology in Theory

  24. Frequency Reuse (continued) • As a caller moves away from a base station, the signal becomes increasingly weak • The base stations coordinate this signal strength detection through a switching center called a mobile telephone switching office (MTSO) • There is a transparent transfer from the base station of one cell to the base station of another, and an associated change in the frequency channel that carries the transmission • This process is called a handoff Information Technology in Theory

  25. Frequency Reuse (continued) Information Technology in Theory

  26. Frequency Reuse (continued) • The main components of a cellular system are the base station antenna and control unit in each cell, the mobile devices that communicate with each base station, and an MTSO • The three main functions of the MTSO are to: • Interconnect surrounding base stations • Perform control functions such as handoffs and channel assignment • Serve as the interface between the base station and PSTN Information Technology in Theory

  27. Frequency Reuse (continued) Information Technology in Theory

  28. Frequency Reuse (continued) • A base station tower usually has two or more sets of antennas and base station equipment, because competing cell phone providers often share the same antenna structure • When a user turns on a cell phone or other wireless device, it scans for the strongest control channel • When a wireless device detects the strongest control channel of a nearby base station, it exchanges control information with the base station to make the network aware of its position Information Technology in Theory

  29. Multiple Access Methods • One important design characteristic of a cellular network is its access method, the approach that allows numerous mobile users to share a transmission medium within the same cell • In the case of wireless, the access method determines how numerous devices share the finite resource of a radio spectrum for transmission Information Technology in Theory

  30. FDMA • FDMA divides the available spectrum into smaller frequency channels • Each device that uses the system occupies one frequency channel for transmitting information and another frequency channel for receiving information • In FDMA, each user within a particular cell is assigned a frequency from the designated frequencies for that cell, and all users may transmit simultaneously to the base station Information Technology in Theory

  31. FDMA (continued) Information Technology in Theory

  32. TDMA • One example of a more efficient multiple access method is called Time Division Multiple Access (TDMA) • Cellular systems that use TDMA divide each frequency band into time slots • In this way, multiple devices can share a single frequency by being allocated their own time slots within the band Information Technology in Theory

  33. TDMA (continued) Information Technology in Theory

  34. CDMA • While FDMA assigns a certain frequency to wireless devices and TDMA assigns each device time slots within a given frequency, Code Division Multiple Access (CDMA) assigns each transmitting device a unique digital code • Each user has a unique pseudo-random code for spreading transmissions across the frequency band • CDMA supports more users within the same cell and provides higher data rates than FDMA and TDMA Information Technology in Theory

  35. CDMA (continued) Information Technology in Theory

  36. Generational Evolution of Cellular Standards • The first widespread cellular service was an analog standard called Advanced Mobile Phone Service (AMPS), which predominated in the United States for years • This generation of analog cellular telephony is usually called 1G (first generation) • AMPS used FDMA as its access method and required considerable bandwidth to accommodate areas of high subscriber density Information Technology in Theory

  37. Generational Evolution of Cellular Standards (continued) • Second-generation cellular, or 2G, refers loosely to the first generation of digital cellular approaches • A digital version of AMPS, called D-AMPS, uses TDMA as its multiple access scheme • Another example of a 2G standard is GSM (global system for mobile communications) • GSM is a popular standard (especially in Europe) for voice and data over cellular using TDMA • Yet another example is IS-95 (Interim standard 95), which is used in the United States and is based on CDMA Information Technology in Theory

  38. Generational Evolution of Cellular Standards (continued) • 3G systems usually refer to digital approaches that have high data rates • They are optimized for today’s multimedia wireless requirements to access Web applications and text messaging; download audio, video, and images; and transmit voice communications • One 3G cellular standard that uses the CDMA access method is CDMA2000 • Another example is Universal Mobile Telecommunications System (UMTS), which is also primarily based on CDMA technology Information Technology in Theory

  39. Wi-FI, WiMAX, and Cellular Integration • Manufacturers of cell phones and other handheld multimedia devices sometimes offer both Wi-Fi and cellular access from a single device, which is sometimes called a dual mode GSM/Wi-Fi device • Most of these devices integrate VoIP technology as well • Devices that support both cellular and Wi-Fi can use Wi-Fi connectivity when users are in proximity with a Wi-Fi network (using VoIP) or connect to a GSM network when the user is outside the range of the wireless local area network Information Technology in Theory

  40. Wi-FI, WiMAX, and Cellular Integration (continued) • Businesses use this capability to reduce cell phone expenses because employees can use existing wireless LAN access at little extra cost when in the office and only use cellular service when away from the office or other Wi-Fi network • Other manufacturers are introducing GSM/Wi-Fi base stations designed for homes, which connect a user’s wireless device to a broadband connection such as DSL or a cable modem Information Technology in Theory

  41. Wi-FI, WiMAX, and Cellular Integration (continued) • Another network standard that could enable further network convergence is the emerging broadband wireless technology known as WiMAX (Worldwide Interoperability for Microwave Access) • WiMAX is actually another name for the formal networking standard known as IEEE 802.16 Information Technology in Theory

  42. Wi-FI, WiMAX, and Cellular Integration (continued) • WiMAX would provide wireless access at high transmission rates, like Wi-Fi, but over much greater geographical ranges • The range could span several miles depending on whether the user is mobile or stationary; stationary users can connect across much greater distances than mobile users • Some areas of the developing world do not have an extensive telecommunications infrastructure, so a technology such as WiMAX has been cited as a possible way to efficiently deliver broadband access Information Technology in Theory

  43. Wi-FI, WiMAX, and Cellular Integration (continued) • WiMAX is different from Wi-Fi in many ways: it is designed for much greater distances, it uses a different channel access method, and it uses a licensed part of the radio frequency spectrum • WiMAX is sometimes called a 4G wireless system • This loose category usually indicates that the service is completely IP-based, will operate consistently at high speeds from 100 Mbps into the Gbps range, and will be oriented toward further convergence and seamless integration of previously disparate networks Information Technology in Theory

  44. Wi-FI, WiMAX, and Cellular Integration (continued) Information Technology in Theory

  45. Wireless multimedia devices are mobile communication and information platforms that provide mobile voice calls, e-mail, text messaging, GPS, Web browsing, calendar applications, office applications, cameras, and media players Wireless multimedia devices often have built-in capabilities to interface with multiple wireless network technologies, including cellular systems, Bluetooth technology, GPS systems, and Wi-Fi Bluetooth is a short-range digital wireless standard It operates at an unlicensed radio frequency band and uses a transmission approach called spread spectrum technology Summary Information Technology in Theory

  46. Summary (continued) • FHSS divides a frequency band into small channels, with transmissions rapidly hopping between frequencies at rates of more than 1000 hops per second • This approach enables efficient spectrum usage, provides significant security, and reduces interference with nearby radio transmissions • DSSS spreads the transmission across a range of frequencies using a pseudo-random code • Cellular systems are divided into smaller areas called cells, each with their own base station antenna that transmits an RF signal Information Technology in Theory

  47. Summary (continued) • Frequency reuse in cellular systems maximizes available frequencies by reusing them in nonadjacent cells • Most cellular networks use either Time Division Multiple Access or Code Division Multiple Access methods to facilitate channel access among numerous devices • The cellular industry categorizes networks into generations known as 1G (such as AMPS), 2G (such as GSM), and 3G, which includes CDMA2000 and UMTS • Some people refer to a fourth generation of wireless, 4G, and cite WiMAX as an example • WiMAX, also known as IEEE 802.16, is a formal networking standard developed by the IEEE for metropolitan area high-speed wireless service Information Technology in Theory

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