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CWNA Guide to Wireless LANs, Second Edition

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Presentation on theme: "CWNA Guide to Wireless LANs, Second Edition"— Presentation transcript:

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

2 Objectives List WLAN devices and describe their basic functions
Explain the different types of communication standards and why standards are important List the three major wireless standards and regulatory agencies and their functions Describe the different IEEE WLAN standards

3 WLAN Devices: Wireless Network Interface Card
Network interface card (NIC): Connects computer to network so that it can send and receive data Wireless NICs perform same function, but without wires When wireless NICs transmit: Change computer’s internal data from parallel to serial transmission Divide data into packets and attach sending and receiving computer’s address Determine when to send packet Transmit packet

4 WLAN Devices: Wireless Network Interface Card (continued)
Network interface card for a wired network

5 WLAN Devices: Wireless Network Interface Card (continued)
Wireless NICs for desktop computers: (a) PCI network interface card, (b) standalone USB device, (c) USB key

6 WLAN Devices: Wireless Network Interface Card (continued)
Wireless NICs for laptop computers: (a) CardBus card; (b) Mini PCI card

7 WLAN Devices: Wireless Network Interface Card (continued)
For smaller devices, several options: CardBus or Type II PC Card May require a sled CompactFlash (CF) card: Consists of small circuit board containing flash memory chips and dedicated controller chip Small and consume little power SDIO (Secure Digital I/O) or SDIO NOW! Card: Provides high-speed data input/output with low power consumption

8 WLAN Devices: Wireless Network Interface Card (continued)
A movement towards integrating wireless NICs Would eliminate need for external wireless NICs Software drivers necessary to allow wireless NIC and operating system (OS) to interface Windows XP and PDA OSs have built-in drivers

9 WLAN Devices: Access Point
Three major parts: Antenna and radio transmitter/receiver RJ-45 wired network interface Special bridging software To interface wireless devices to other devices Two basic function: Base station for wireless network Bridge between wireless and wired networks

10 WLAN Devices: Access Point (continued)
An access point acts as a bridge between the wireless network and a wired network

11 WLAN Devices: Access Point (continued)
Range depends on several factors: Type of wireless network supported Walls, doors, and other solid objects 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

12 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

13 WLAN Devices: Remote Wireless Bridge (continued)
Point-to-point remote wireless bridge

14 WLAN Devices: Remote Wireless Bridge (continued)
Point-to-multipoint remote wireless bridge

15 WLAN Devices: Remote Wireless Bridge (continued)
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 Distance between buildings using remote wireless bridges can be up to 18 miles at 11 Mbps or 25 miles transmitting 2 Mbps

16 WLAN Devices: Remote Wireless Bridge (continued)
Root and non-root modes

17 WLAN Devices: Remote Wireless Bridge (continued)
Repeater mode

18 WLAN Devices: Wireless Gateway
Combines wireless management and security in single appliance Authentication Encryption Intrusion detection and malicious program protection Bandwidth management Centralized network management

19 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)

20 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

21 Institute of Electrical and Electronics Engineers (continued)
Current IEEE 802 committees

22 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 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 standards

23 Wi-Fi Alliance (continued)
WECA changed name 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

24 Federal Communications Commission (FCC): Responsibilities
Primary regulatory agency for wireless communications in U.S. and territorial possessions Independent government agency Directly responsible to Congress Broad range of responsibilities Develop and implement regulatory programs Process applications for licenses and other filings Analyze complaints Conduct investigations Take part in congressional hearings

25 FCC: Regulating the Radio Frequency Spectrum
FCC regulates radio frequency spectrum Entire range of all radio frequencies Spectrum divided into 450 different bands U.S. obligated to comply with international spectrum allocations FCC license normally required to send and receive on a specific frequency License-exempt spectrum or unregulated bands: Bands that are available nationwide to all users Created to foster development of new devices

26 FCC: Regulating the Radio Frequency Spectrum (continued)
Common radio frequency bands

27 FCC: Regulating the Radio Frequency Spectrum (continued)
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

28 FCC: Regulating the Radio Frequency Spectrum (continued)
Unlicensed bands

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

30 IEEE 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 Infrared light: Can be used for wireless transmissions Invisible Emitter: Device that transmits a signal Detector: Device that receives a signal

31 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 standard outlining radio wave transmissions has become preferred method for wireless LANs

32 IEEE b standard’s 2 Mbps bandwidth not sufficient for most network applications 802.11b amendment added two higher speeds (5.5 Mbps and 11 Mbps) to original 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

33 IEEE a IEEE a 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 b published at same time 802.11a came to market later due to technical issues and high production cost Range of a is less than that of b

34 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

35 Projected IEEE 802.11n Currently in evaluation stage
Top speed of n 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 pre-N

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