1. CWNA Guide to Wireless LANs, Second Edition Chapter Twelve Personal, Metropolitan, and Wide Area Wireless Networks

2. CWNA Guide to Wireless LANs, Second Edition2 WPANs: Radio Frequency ID (RFID) Figure 12-8: RFID tag

3. CWNA Guide to Wireless LANs, Second Edition3 WPANs: Radio Frequency ID (continued) Passive RFID tags: No power supply –Can be very small –Limited amount of information transmitted Active RFID tags: Must have power source –Longer ranges/larger memories than passive tags Table 12-4: RFID tags

4. CWNA Guide to Wireless LANs, Second Edition4 WPANs: IrDA Infrared Data Association IrDA specifications include standards for physical devices and network protocols they use to communicate Devices communicate using infrared light-emitting diodes –Recessed into device –Many design considerations affect IrDA performance

5. CWNA Guide to Wireless LANs, Second Edition5 WPANs: IrDA (continued) Figure 12-9: IrDA diodes in device

6. CWNA Guide to Wireless LANs, Second Edition6 WPANs: IrDA (continued) IrDA drawbacks: –Designed to work like standard serial port on a personal computer, which is seldom used today –Cannot send and receive simultaneously –Strong ambient light can negatively impact transmissions –Angle and distance limitation between communicating devices

7. CWNA Guide to Wireless LANs, Second Edition7 Infrared Many wireless devices, such as PDAs, use infrared (IR) technology Two common uses of infrared wireless technology are IrDA and wireless local area networks (WLANs)

8. CWNA Guide to Wireless LANs, Second Edition8 Communications Models and Standards International Organization for Standardization (ISO) began work in 1970s to develop specifications for communication by computer-based networks Goal was to create an abstract model of networking rather than official physical standard Completed in 1983, these conceptual specifications are known as Open System Interconnect (OSI) model

9. CWNA Guide to Wireless LANs, Second Edition9 Communications Model: OSI Breaks complex functions into seven basic layers Each layer performs specific function that involves different tasks See Table 4-1

10. CWNA Guide to Wireless LANs, Second Edition10 OSI Layers and Functions

11. CWNA Guide to Wireless LANs, Second Edition11 OSI Model Tasks may be performed using hardware and software Each layer must cooperate with layer immediately above and immediately below it Data travels down layers from sending device, and then up layers to receiving device See Figure 4-2

12. CWNA Guide to Wireless LANs, Second Edition12 OSI Data Flow

13. CWNA Guide to Wireless LANs, Second Edition13 Communications Standards: IEEE 803 Institute of Electrical and Electronics Engineers (IEEE) began Project 802 to create standards that would ensure interoperability among data networks While OSI model is theoretical, Project 802 created standards for actual practice Several standards emerged from Project 802 including 802.3 (Ethernet) and 802.5 (Token Ring)

14. CWNA Guide to Wireless LANs, Second Edition14 Project 802 Project 802 subdivided OSI model Layer 2, Data Link, into two sublayers –Logical Link Control (LLC) –Media Access Control (MAC) For wireless networks, defined by 802.11, IEEE also subdivided Physical layer into two parts –Physical Medium Dependent (PMD) –Physical Layer Convergence Procedure (PLCD) See Figure 4-3

15. CWNA Guide to Wireless LANs, Second Edition15 OSI Model versus IEEE Project 802

16. CWNA Guide to Wireless LANs, Second Edition16 PLCP Sublayer PMD sublayer –Includes standards for wireless medium such as IR and RF –Defines how medium transmits and receives data PLCD sublayer –Reformats data received from MAC layer into packet or frame that PMD sublayer can transmit, as shown in Figure 4-4 –Listens to medium to determine when data can be sent

17. CWNA Guide to Wireless LANs, Second Edition17 PLCD Sublayer Reformats MAC Data

18. CWNA Guide to Wireless LANs, Second Edition18 Summary of PMD and PLCD Sublayers

19. CWNA Guide to Wireless LANs, Second Edition19 Network Protocol Stacks Protocols are rules network must follow for communications to pass between devices –Protocols are also divided into layers, generally corresponding to the OSI model Variety of network protocol stacks –Transmission Control Protocol/Internet Protocol (TCP/IP)—a standard protocol for the Internet –Internet Packet eXchange/Sequenced Packet eXchange (IPX/SPX)—an older Novell NetWare protocol –AppleTalk—used by Apple Macintosh computers

20. CWNA Guide to Wireless LANs, Second Edition20 Infrared WLANs Several different IR WLANs have been developed during past 20 years Infrared WLANs use part of electromagnetic spectrum just below visible light IR shares these characteristics –Operates at high frequencies –Travels in straight lines –Does not penetrate physical objects

21. CWNA Guide to Wireless LANs, Second Edition21 Other IR Characteristics Has an abundance of available bandwidth that is unregulated Operates at high data rates Is more secure than radio frequency transmissions Avoids many kinds of interference that affect RF signals Components are small and consume little power

22. CWNA Guide to Wireless LANs, Second Edition22 Other IR Characteristics IR transmissions can be directed or diffused Directed transmission uses a narrow beam and line of sight –Both emitter and detector must be aimed directly at one another Diffused transmission uses a wide beam and reflected light –Both emitter and detector point at a reflection point on the ceiling –Limited to 4 Mbps with a range of 30 to 50 feet

23. CWNA Guide to Wireless LANs, Second Edition23 IEEE 802.11 Infrared WLANs IEEE 802.11 outlines specifications for infrared WLANs Uses diffused transmission PHY layer both reformats data from PLCP layer and transmits light impulses (PMD)

24. CWNA Guide to Wireless LANs, Second Edition24 Diffused Infrared Physical Layer Convergence Procedure Standards Frame size is measured in time slots rather than bits

25. CWNA Guide to Wireless LANs, Second Edition25 Parts of the Infrared PLCP Frame Synchronization field allows emitter and receiver to synchronize Start Frame Delimiter defines beginning of frame by transmitting 1001 Data Rate value sets transmission speed

26. CWNA Guide to Wireless LANs, Second Edition26 Parts of the Infrared PLCP Frame Direct Current Level Adjustment lets receiving device determine signal level

27. CWNA Guide to Wireless LANs, Second Edition27 Parts of the Infrared PLCP Frame Length field indicates time to transmit entire frame Header Error Check has value to determine if data was transmitted correctly Data field can be from 1 to 20,000 time slots Although the current IEEE 802.11 standard allows data transmission rates of 1 or 2 Mbps, the preamble and header are always transmitted at 1 Mbps to accommodate slower devices

28. CWNA Guide to Wireless LANs, Second Edition28 Diffused Infrared Physical Medium Dependent Standards PMD layer translates 1s and 0s into light pulses for transmission –A 1 bit has a higher intensity signal than a 0 bit Transmissions at 1 Mbps use a 16-pulse position modulation (16-PPM), as shown in Table 4-4 Transmissions at 2 Mbps use a 4-pulse modulation (4-PPM), as shown in Table 4-5

29. CWNA Guide to Wireless LANs, Second Edition29 16-PPM Values

30. CWNA Guide to Wireless LANs, Second Edition30 4-PPM Values A time slot is always one nanosecond (ns) or a billionth of a second, but a 4-PPM transmission contains four times as much data as a 16-PPM transmission

31. CWNA Guide to Wireless LANs, Second Edition31 IrDA Infrared Data Association (IrDA) is the most common infrared connection today It links notebook computers, Personal Digital Assistants (PDA) handheld devices, cameras, watches, pagers, and kiosks IrDA specifications include both physical devices and network protocols used for communication

32. CWNA Guide to Wireless LANs, Second Edition32 Overview IrDA devices have common characteristics –Communicate with minimal preconfiguration –Provide point-to-point data transfer between only two devices at a time –Devices include broad range of computing and communicating technology –Inexpensive technology Three versions of IrDA specifications are shown in Table 4-6

33. CWNA Guide to Wireless LANs, Second Edition33 Three Versions of IrDA Specifications

34. CWNA Guide to Wireless LANs, Second Edition34 Multiple Infrared Connections Single IrDA link can establish multiple simultaneous connections –Two IrDA devices can simultaneously send and receive mail, update calendar and contact information, and print documents –A separate program controls each activity IrDA devices use infrared light emitting diodes (LEDs) to send and photodiodes to receive signals –See Figure 4-6

35. CWNA Guide to Wireless LANs, Second Edition35 Infrared LEDs and Photodiodes

36. CWNA Guide to Wireless LANs, Second Edition36 Diodes in Device

37. CWNA Guide to Wireless LANs, Second Edition37 Design Factors Improve IrDA Communication Transparent window in front of IR module should be flat instead of curved Window should be violet to minimize loss of signal Module should be recessed several millimeters into device case to minimize interference from ambient light

38. CWNA Guide to Wireless LANs, Second Edition38 IrDA Protocol Stack IrDA Protocol stack has several layers

39. CWNA Guide to Wireless LANs, Second Edition39 Functions of the Layers of the IrDA Protocol Stack IrDA Physical Layer Protocol (IrPHY) controls hardware IrDA Link Access Protocol (IrLAP) encapsulates frames and defines how connections are established IrDA Link Management Protocol (IrLMP) allows devices to detect other devices IrDA Transport Protocol (Tiny TP) manages channels, corrects errors, divides data into packets, and reassembles original data

40. CWNA Guide to Wireless LANs, Second Edition40 IrDA Physical Layer Protocol (IrPHY) IrPHY controls hardware Function depends on which one of two standard is used –Serial Infrared (Version 1.0) –Fast Infrared (Version 1.1)

41. CWNA Guide to Wireless LANs, Second Edition41 Serial Infrared (Version 1.0) SIR transmitter works like standard serial port on a PC –Figure 4-9 shows block diagram of SIR transmitter Uses UART (Universal Asynchronous Receiver/Transmitter) chip on PC Serial port transmits bits one after another Parallel port transmits all eight bits as a byte See Figure 4-10

42. CWNA Guide to Wireless LANs, Second Edition42 SIR Transmitter Block Diagram

43. CWNA Guide to Wireless LANs, Second Edition43 Parallel and Serial Transmission

44. CWNA Guide to Wireless LANs, Second Edition44 Functions of the UART Converts bytes into a single serial bit stream for outbound transmission Converts serial bit stream into parallel bytes for incoming transmission Can add an optional parity bit for error checking Adds and removes optional start and stop delineators called start and stop bits

45. CWNA Guide to Wireless LANs, Second Edition45 Functions of the UART Provides some buffering of data to keep computer and the serial device coordinated May handle other interrupt and device management to coordinate speed of computer and device

46. CWNA Guide to Wireless LANs, Second Edition46 UART Frame

47. CWNA Guide to Wireless LANs, Second Edition47 NRZ with Same Bit Transmitted Standard RS-232 serial ports can use NRZ (non-return- to-zero) techniques that keep output level the same for the entire bit period

48. CWNA Guide to Wireless LANs, Second Edition48 Return-to-Zero, Inverted (RZI) IrDA devices cannot use NRZ technology They use RZI that uses the inverse of RZ –RZI increases voltage for a 0 bit and no voltage for a 1 bit UARTS have a 16x clock cycle, as shown in Figure 4-13

49. CWNA Guide to Wireless LANs, Second Edition49 IrDA SIR Transmission

50. CWNA Guide to Wireless LANs, Second Edition50 Fast Infrared (Version 1.1) Specifies data transfer at 4 Mbps Retains backward compatibility with SIR devices Figure 4-14 shows block diagram of FIR transmission

51. CWNA Guide to Wireless LANs, Second Edition51 FIR Transmitter Block Diagram

52. CWNA Guide to Wireless LANs, Second Edition52 IrDA FIR Transmission FIR uses 4 PPM Only two bits are transmitted Receiving device determines transmitted bit by locating pulse within time slot

53. CWNA Guide to Wireless LANs, Second Edition53 Other Considerations Several other factors influence infrared transmission, including –Latency –Ambient light –Deflection angle

54. CWNA Guide to Wireless LANs, Second Edition54 Half-Duplex and Latency IrDA devices cannot send and receive at same time –Their communication mode is half-duplex A time delay is required for device to stop transmitting and get ready to receive –This delay is called latency or receiver set-up time –IrDA specifications allow 10 ms latency

55. CWNA Guide to Wireless LANs, Second Edition55 Ambient Light IrDA specifies test methods for measuring data integrity of an IrDA connection under electromagnetic fields, sunlight, incandescent light, and fluorescent light Lux is a photometric measurement of light intensity If lux values exceed standard, devices may still communicate, but they must be placed closer to each other

56. CWNA Guide to Wireless LANs, Second Edition56 Deflection Angle How sending and receiving IrDA devices align is important Devices with a deflection angle up to 15 degrees can be 3 feet apart, as shown in Figure 4-16 With deflection angle between 15 and 30 degrees, devices must be closer together With a deflection angle over 30 degrees, infrared transmission will be impossible

57. CWNA Guide to Wireless LANs, Second Edition57 Deflection Angle

58. CWNA Guide to Wireless LANs, Second Edition58 Wireless Metropolitan Area Networks Cover an area of up to 50 kilometers (31 miles) Used for two primary reasons: –Alternative to an organization’s wired backhaul connection i.e., T1, T3, T4 lines –Fiber Optics Very expensive to install backhaul connections Often less expensive to use a WMAN to link remote sites

59. CWNA Guide to Wireless LANs, Second Edition59 Wireless Metropolitan Area Networks (continued) Used for two primary reasons (continued): –Overcome last mile connection Connection that begins at a fast Internet service provider, goes through local neighborhood, and ends at the home or office Slower-speed connection –Bottleneck

60. CWNA Guide to Wireless LANs, Second Edition60 Wireless Metropolitan Area Networks: Free Space Optics Optical, wireless, point-to-point, line-of-sight wireless technology –Able to transmit at speed comparable to Fiber Optics –Transmissions sent by low-powered IR beams Advantages compared to fiber optic and RF: –Lower installation costs –Faster installation –Scaling transmission speed –Good security Atmospheric conditions can affect transmission

61. CWNA Guide to Wireless LANs, Second Edition61 Wireless Metropolitan Area Networks: Local Multipoint Distribution Service (LMDS) LMDS provides wide variety of wireless services –High-frequency, low-powered RF waves have limited range –Point-to-multipoint signal transmission Signals transmitted back are point-to-point –Voice, data, Internet, and video traffic –Local carrier determines services offered LMDS network is composed of cells –Cell size affected by line of site, antenna height, overlapping cells, and rainfall

62. CWNA Guide to Wireless LANs, Second Edition62 Wireless Metropolitan Area Networks: LMDS (continued) Figure 12-11: LMDS cell

63. CWNA Guide to Wireless LANs, Second Edition63 Wireless Metropolitan Area Networks: Multichannel Multipoint Distribution Service (MMDS) Many similarities to LMDS –Differs in area of transmission –Higher downstream transmission, lower upstream transmission, greater range In homes, alternative to cable modems and DSL service For businesses, alternative to T1 or fiber optic connections MMDS hub typically located at a very high point –On top of building, towers, mountains

64. CWNA Guide to Wireless LANs, Second Edition64 Wireless Metropolitan Area Networks: MMDS (continued) Hub uses point-to-multipoint architecture –Multiplexes communications to multiple users –Tower has backhaul connection MMDS uses cells –Single MMDS cell as large as 100 LDMS cells Receiving end uses pizza box antenna Advantages: –Transmission range, cell size, low vulnerability to poor weather conditions Still requires line-of-site, not encrypted

65. CWNA Guide to Wireless LANs, Second Edition65 Wireless Metropolitan Area Networks: IEEE 802.16 (WiMAX) High potential –Can connect IEEE 802.11 hotspots to Internet –Can provide alternative to cable and DSL for last mile connection –Up to 50 kilometers of linear service area range –Does not require direct line of sight –Provides shared data rates up to 70 Mbps Uses scheduling system –Device competes once for initial network entry

66. CWNA Guide to Wireless LANs, Second Edition66 Wireless Metropolitan Area Networks: IEEE 802.16 (continued) Currently addresses only devices in fixed positions –802.16e will add mobile devices to the standard IEEE 802.20 standard: Sets standards for mobility over large areas –Will permit users to roam at high speeds WiMAX base stations installed by a wireless Internet service provider (wireless ISP) can send high-speed Internet connections to homes and businesses in a radius of up to 50 km (31 miles)

67. CWNA Guide to Wireless LANs, Second Edition67 Wireless Wide Area Networks (WWANS) Wireless networks extending beyond 50 kilometers (31 miles) Two primary technologies: –Digital cellular telephony –Satellites

68. CWNA Guide to Wireless LANs, Second Edition68 Digital Cellular Telephony Two keys to cellular telephone networks: –Coverage area divided into cells Cell transmitter at center Mobile devices communicate with cell center via RF Transmitters connected to base station, Each base station connected to a mobile telecommunications switching office (MTSO) –Link between cellular and wired telephone network –All transmitters and cell phones operate at low power Enables frequency reuse

69. CWNA Guide to Wireless LANs, Second Edition69 Digital Cellular Telephony (continued) Figure 12-13: Frequency reuse

70. CWNA Guide to Wireless LANs, Second Edition70 Satellites Satellite use falls into three broad categories: –Acquire scientific data, perform research –Examine Earth Military and weather satellites –“Reflectors” Relay signals Communications, navigation, broadcast

71. CWNA Guide to Wireless LANs, Second Edition71 Satellites (continued) Satellite systems classified by type of orbit: –Low earth orbiting (LEO): Small area of earth coverage Over 225 satellites needed for total coverage of earth Must travel very fast –Medium earth orbiting (MEO): Larger area of coverage than LEO Do not need to travel as fast –Geosynchronous earth orbiting (GEO): orbit matches earth’s rotation “Fixed” position Very large coverage area

72. CWNA Guide to Wireless LANs, Second Edition72 Satellites (continued) Figure 12-14: LEO coverage area

73. CWNA Guide to Wireless LANs, Second Edition73 The Future of Wireless Networks IEEE 802.11 subcommittees currently at work: –802.11d: Supplementary to 802.11 MAC layer Promote worldwide use of 802.11 WLANs –802.11f: Inter-Access Point Protocol (IAPP) Will assist with faster handoff from one AP to another –802.11h: Supplement to MAC layer to comply with European regulations for 5 GHz WLANs –802.11j: Incorporates Japanese regulatory extensions to 802.11a standard –802.11s: Defines a mesh wireless network Devices configure themselves and are intelligent

74. CWNA Guide to Wireless LANs, Second Edition74 Summary WPANs encompass technology that is designed for portable devices, typically PDAs, cell phones, and tablet or laptop computers at transmission speeds lower than the other types of networks The IEEE 802.15 standards address wireless personal area networks RFID is not a standard but is a technology that uses RF tags to transmit information IrDA technology uses infrared transmissions to transmit data at speeds from 9,600 bps to 16 Mbps

75. CWNA Guide to Wireless LANs, Second Edition75 Summary (continued) FSO is an optical, wireless, point-to-point wireless metropolitan area network technology LMDS can provide a wide variety of wireless services, including high-speed Internet access, real-time multimedia file transfer, remote access to local area networks, interactive video, video-on- demand, video conferencing, and telephone MMDS has many of similarities to LMDS, yet has a longer distance range

76. CWNA Guide to Wireless LANs, Second Edition76 Summary (continued) The IEEE 802.16 (WiMAX) standard holds great promise for providing higher throughput rates for fixed location and mobile users Wireless wide area network (WWAN) technology encompasses digital cellular telephony and satellite The future of wireless networks is hard to predict, but most experts agree that wireless networks will be faster, more global, and easier to use in the years ahead