CWNA Guide to Wireless LANs, Second Edition

1. CWNA Guide to Wireless LANs, Second Edition Chapter One It’s a Wireless World

2. A Day in the Life of a Wireless User: Home • Hotspots: Locations where wireless data services are available • Wireless local area network (WLAN): Essentially identical to standard local area network (LAN) • Except devices not connected by wires • Can increase productivity

3. A Day in the Life of a Wireless User: Car • Bluetooth wireless standard: Enables short range wireless communication • Used in many small devices

4. A Day in the Life of a Wireless User: Office • Fixed broadband wireless: Wireless transmissions between immobile devices • Typically between office buildings • Utilizes small, customized antennas • Free space optics (FSO): Alternative to high-speed fiber optic transmissions

5. A Day in the Life of a Wireless User: On Site • Radio frequency identification (RFID) tags: • “Electronic barcodes” • Used to identify items • Can be read if anywhere within range of transmitted radio signal • Depending on device

6. Wireless Local Area Networks (WLANs) • Wi-Fi (Wireless Fidelity): Based on standard that transmits at up to 11 Mbps • Computers on WLAN must have wireless network interface cards (wireless NIC or Wireless adapter) • Performs same basic functions as standard NIC, plus more • Access point (AP): Transfers signals between wireless NICs • Patch cable connects AP to wired LAN or Internet

7. Bluetooth • Low-power wireless data and voice transmission technology • Bluetooth devices communicate via radio modules • Link manager: Software that helps identify other Bluetooth devices, creates links between devices, and sends and receives data • Transmit data at up to 1 Mbps over 10 meters • Bluetooth devices within range of each other automatically connect • Master and slave

8. Telecommunications Links • Integrated Services Digital Networks (ISDN): Transmits at 256 Kbps • T-1 lines: Transmit at 1.544 Mbps • Cable modems: Use television cable connection • Digital subscriber lines (DSL): Use telephone lines • WiMax: Signal transmitted between antennas • Up to 75 Mbps and over up to 35 miles • Fixed Broadband

9. Telecommunications Links (continued) • FSO: Transmit at speeds up to 1.25 Gbps over up to 4 miles • Line-of-site transmission Figure 1-6: Free space optics transceiver

10. Cellular Telephony • Global Systems for Mobile (GSM) a communications technology • Coverage includes most of US and parts of Europe and Japan • Transmission speeds up to 9.6 Kbps • Uses Wireless Application Protocol (WAP) • Standard way to transmit, format, and display data for devices like cell phones and handheld devices

11. Cellular Telephony (continued) Figure 1-8: Browsing the World Wide Web

12. Cellular Telephony (continued) • WAP cell phone runs a microbrowser that uses Wireless Markup Language (WML) instead of HTML • WAP gateway or proxy: Translates between WML and HTML Figure 1-9: WAP communications

13. Radio Frequency Identification (RFID) • Like an electronic barcode: • Can contain larger amounts of updatable information • Information transmitted via radio waves • Range typically about 1 foot at 5 Mbps Figure 1-10: RFID tag

14. Wireless LAN Applications: Business • Wireless LAN technologies have significantly changed how business conducted • Meetings not confined to conference rooms • Easier to connect to network resources and Internet • Can create office in space where traditional infrastructure does not exist

15. Wireless LAN Applications: Healthcare (continued) Figure 1-12: Video pill

16. Wireless Advantages and Disadvantages: Advantages • Mobility is Primary advantage of wireless technology • Easier and Less Expensive Installation: Installing network cabling in older buildings difficult and costly • Increased Reliability • eliminates certain types of cable failures and increases overall network reliability

17. Wireless Advantages and Disadvantages: Advantages • Disaster Recovery: • Hot site:Off-site facility that can run business’s operations if primary site is not available • Generally maintained by third party • Expensive • Cold site:Customer provides and installs equipment • Many businesses use cold sites and WLANs as major piece of disaster recovery plan • No consideration given to network cabling

18. Wireless Advantages and Disadvantages: Disadvantages • Security: Wireless signals broadcast in open air • Security for wireless LANs is prime concern • Unauthorized users might access network • Attackers might view transmitted data • Employees could install rogue access points • Attackers could easily crack existing wireless security • Radio Signal Interference:Signals from other devices can disrupt wireless transmissions • Health Risks: Wireless devices emit RF energy • Not known if or to what extent low levels of RF might cause adverse health effects

19. CWNA Guide to Wireless LANs, Second Edition Chapter Two Wireless LAN Devices and Standards

20. WLAN Devices: Access Point • Threemajor parts: • Antenna and radio transmitter/receiver • RJ-45 wired network interface • Special bridging software • To interface wireless devices to other devices • Two basic functions: • Base station for wireless network • Bridge between wireless and wired networks

21. WLAN Devices: Access Point • Range depends on several factors: • Type of wireless network, walls, doors, and other solid objects (think refrigerator) • Number of wireless clients that single AP can support varies: • Theoretically over 100 clients • No more than 50 for light network use • No more than 20 for heavy network use • Power over Ethernet (PoE):Power delivered to AP through unused wires in standard unshielded twisted pair (UTP) Ethernet cable

22. WLAN Devices: Remote Wireless Bridge • Bridge:Connects two network segments together • Even if they use different types of physical media • Remote wireless bridge:Connects two or more wired or wireless networks together • Transmit at higher power than WLAN APs • Use directional antennas to focus transmission in single direction • Delay spread:Minimize spread of signal so that it can reach farther distances • Have software enabling selection of clearest transmission channel and avoidance of noise and interference

23. WLAN Devices: Remote Wireless Bridge • Four modes: • Access point mode: Functions as standard AP • Root mode: Root bridge can only communicate with other bridges not in root mode • Non-root mode: Can only transmit to another bridge in root mode • Repeater mode: Extend distance between LAN segments • Placed between two other bridges

24. Advantages and Disadvantages of Standards Table 2-1: Advantages and disadvantages of standards

25. 3 Types of Standards • De Facto, De jure and Consortia • De facto standards: Common practicesthat the industry follows for various reasons • Ranging from ease of use to tradition to what majority of users do • Usually established by success in marketplace • De jure standards: Official standards • Controlled by organization or body that has been entrusted with that task • Process for creating these standards can be very involved

26. Types of Standards (continued) • One complaint against de jure standards is amount of time it takes for a standard to be completed • Consortia: Usually industry-sponsored organizations that want to promote a specific technology • Goal is to develop a standard that promotes organization’s specific technology in little time

27. Enforcing Standards • Marketplace itself enforces some standards • Standards created by consortia often regulated by marketplace • De jure standards often enforced by outside regulatory agency • Ensure that participants adhere to prescribed standards • Must have power to enforce standards and effectively punish those who refuse to abide by them

28. Wireless Standards Organizations and Regulatory Agencies • Three primary standard-setting and regulatory bodies that play major role in wireless LAN technology • Institute of Electrical and Electronics Engineers (IEEE) • Wi-Fi Alliance • U.S. Federal Communications Commission (FCC)

29. Institute of Electrical and Electronics Engineers (IEEE) • Establishes standards for telecommunications • Also covers wide range of IT standards • World’s largest technical professional society • 37 Societies and Councils • Publish technically focused journals, magazines, and proceedings • Work on over 800 standards • Best known for its work in establishing standards for computer networks • Project 802 • February 1980….hence 80+2 = 802

30. Institute of Electrical and Electronics Engineers Table 2-2: Current IEEE 802 committees

31. Wi-Fi Alliance • Wireless Ethernet Compatibility Alliance (WECA): Consortium of wireless equipment manufacturers and software providers formed to promote wireless network technology • Three goals: • Encourage wireless manufacturers to use IEEE 802.11 technologies • Promote and market these technologies to consumers at home, and in small and large organizations • Test and certify that wireless products adhere to the IEEE 802.11 standards

32. Wi-Fi Alliance (continued) • WECA changed to Wi-Fi Alliance in 2002 • Reflected name of certification that it uses (Wi-Fi) to verify that products follow IEEE standards • Only products that pass Wi-Fi Alliance tests may be referred to as Wi-Fi Certified • Wi-Fi Alliance now allows businesses to apply to be registered as a Wi-Fi ZONE • Qualifies them to be placed in online database of wireless hotspot locations • Can be accessed through Alliance’s Web site

33. FCC: Regulating the Radio Frequency Spectrum • Two unregulated bands used for WLANs • Industrial, Scientific, and Medical (ISM) band • Unlicensed National Information Infrastructure (U-NII) band • Intended for devices that provide short-range, high-speed wireless digital communications • Negative features of unregulated bands: • Devices from different vendors may attempt to use same frequency • Can cause interference and unpredictability

34. FCC: Regulating the Radio Frequency Spectrum Table 2-4: Unlicensed bands

35. Types of Wireless LANs • Since late 1990s, IEEE has approved four standards for wireless LANs: • IEEE 802.11 • IEEE 802.11b • IEEE 802.11a • IEEE 802.11g • IEEE 802.11n expected to be approved by 2006

36. IEEE 802.11 • Specified that wireless transmission could take place via infrared (IR) or radio signals • Infrared Transmissions: • Can send data by the intensity of the infrared light wave • Light spectrum: All types of light • Infraredlight: Can be used for wireless transmissions • Invisible • Emitter: Device that transmits a signal • Detector: Device that receives a signal

37. IEEE 802.11 (continued) • Infrared Transmissions (continued): • Advantages: • Does not interfere with other communications signals • Not affected by other signals • Does not penetrate walls • Disadvantages: • Lack of mobility • Limited range • Confined to indoor use • Slow transmission speed

38. IEEE 802.11 (continued) • Radio Wave Transmissions: • Radio waves can penetrate through objects • Provides mobility • Radio waves travel longer distances • Can be used indoors and outdoors • Radio waves can travel at much higher speeds than infrared transmissions • IEEE 802.11 standard outlining radio wave transmissions has become preferred method for wireless LANs

39. IEEE 802.11b • 802.11 standard’s 2 Mbps bandwidth not sufficient for most network applications • 802.11bamendment added two higher speeds (5.5 Mbps and 11 Mbps) to original 802.11 standard • Uses ISM band • Supports wireless devices up to 115 meters (375 feet) apart • Radio waves decrease in power over distance • 802.11b standard specifies that, when devices out of range to transmit at 11 Mbps, devices drop transmission speed to 5.5 Mbps

40. IEEE 802.11a • IEEE 802.11a standard specifies maximum rated speed of 54 Mbps • Also supports 48, 36, 24, 18, 12, 9,and 6 Mbps transmissions using U-NII band • 802.11a and 802.11b published at same time • 802.11a came to market later due to technical issues and high production cost • Range of 802.11a is less than that of 802.11b

41. IEEE 802.11g • Effort to combine best features of 802.11a and 802.11b • Data transfer rates to 54 Mbps • Support devices up to 115 meters apart • 802.11g standard specifies that devices operate entirely in ISM frequency

42. Projected IEEE 802.11n • Currently in evaluation stage • Top speed of 802.11n standard will be anywhere from 100 Mbps to 500 Mbps • Ratification may not occur until 2006 • Devices based on standard may appear prior to that • 802.11 pre-N

43. CWNA Guide to Wireless LANs, Second Edition Chapter Three How Wireless Works

44. Frequency (continued) • Frequency: Rate at which an event occurs • Cycle: Changing event that creates different radio frequencies • When wave completes trip and returns back to starting point it has finished one cycle • Hertz (Hz): Cycles per second • Kilohertz (KHz) = thousand hertz • Megahertz (MHz) = million hertz • Gigahertz (GHz) = billion hertz

45. Frequency (continued) • Frequency of radio wave can be changed by modifying voltage • Radio transmissions send a carrier signal • Increasing voltage will change frequency of carrier signal

46. Analog Modulation • Amplitude: Height of carrier wave • Amplitude modulation (AM): Changes amplitude so that highest peaks of carrier wave represent 1 bit while lower waves represent 0 bit • Frequency modulation (FM): Changes number of waves representing one cycle • Number of waves to represent 1 bit more than number of waves to represent 0 bit • Phase modulation (PM): Changes starting point of cycle • When bits change from 1 to 0 bit or vice versa

47. Antenna Concepts • Radio waves transmitted/received using antennas Figure 3-24: Antennas are required for sending and receiving radio signals

48. Characteristics of RF Antenna Transmissions • Polarization: Orientation of radio waves as they leave the antenna Figure 3-25: Vertical polarization

49. Characteristics of RF Antenna Transmissions (continued) • Wave propagation:Pattern of wave dispersal Figure 3-26: Sky wave propagation

50. Characteristics of RF Antenna Transmissions (continued) Figure 3-27: RF Line of Sight (LOS) propagation