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Wireless Networking. By: Todd Deshane And Ashwin Venkatraman. Introduction. What is a wireless network? A technology that enables two or more entities to communicate without network cabling. Different Wireless Networks. IrDA (Infrared Data Association)

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Wireless Networking


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    1. Wireless Networking By: Todd Deshane And Ashwin Venkatraman

    2. Introduction • What is a wireless network? • A technology that enables two or more entities to communicate without network cabling

    3. Different Wireless Networks • IrDA (Infrared Data Association) • Uses beams in the infrared light spectrum • Bluetooth • Uses 2.45 gigahertz radio waves, but emits weak signals • Limits distance to 10 feet, but travels through walls • HomeRF (SWAP) – developed by businesses • 6 voice channels and 1 data channel • Slow, and limited range, but cheap

    4. Wireless Fidelity (Wi-Fi) • Essentially, this technology is a variation of the IEEE 802.11 specification known as 802.11b • Focuses on Direct-Sequence Spread Spectrum (DSSS) • High data rate (max of 11 Mbps) • In the case of interference, speed drops in halves (11 Mbps to 5.5 Mbps to 2 Mbps to 1 Mbps)

    5. Wi-Fi • Advantages: • Fast (11 Mbps) • Reliable • Long Range (up to 1000 ft outdoors, 400 ft indoors) • Easy integration to wired networks • Compatible with original 802.11 DSSS standard • Disadvantages: • Speed may fluctuate

    6. 802.11a vs. 802.11b • Frequency • 802.11b transfers at 2.4 gigahertz • 802.11a transfers at 5 gigahertz • Coverage Distance • 802.11b goes about 400 feet indoors • 802.11a goes about 60 feet indoors • Need more access points to cover a location • Compatible to each other? • Not yet.

    7. ITL Wireless Equipment • 2 Wireless Access Point Routers (with built in 4 port switch) • Wired Equivalent Privacy (WEP) available • 8 Wireless PCMCIA Cards • 4 ORiNOCO Gold 11 Mbps PC Cards • 4 3Com 11 Mbps PC Cards

    8. Wireless Access Point • LINKSYS • Model No. BEFW11S4 ver. 2 • Supports • IEEE 802.3 (10BaseT) • IEEE 802.3u (100BaseTX) • IEEE 802.11b (Wireless) • Built-in router capability • Obtains a Clarkson IP and uses DHCP • Built-in 4 port switch • Fully-configurable through simple web interface

    9. Wireless Cards • 11Mbs • 802.11b compatible • 4 3Com Cards • Model No. 3CRWE62092A • 4 ORiNOCO (Lucent) Cards • Model No. 012352/G

    10. Performance • Inside Range • anywhere except in bathrooms • Usually 11 Mbps connection • Outside Range • To the SC lecture wing door (closest to ERC) • Covers faculty lot next to ERC • Half way to Rowley • Connection slows as move away from access point

    11. Summer Research • Protocol • Method of Communication • Spoken Language • Networked Programs (AIM) • HTTP, Telnet, FTP

    12. Two Main Protocols (Internet) • UDP (User Datagram Protocol) • Fast, bare-bones, not reliable or friendly • Can lose data at any time • TCP (Transmission Control Protocol) • Slower, many features, very reliable • All data will get to the other side

    13. PCAttcp • Measuring tool for TCP and UDP • Speed, Throughput, Time • Amount of Data Sent vs. Amount Received

    14. Our PCAttcp Controller • Enhanced UDP transfers • Automated the entire process • Created an easy way to compile results and graphs using a spreadsheet for output • Ran tests on various types of connections

    15. The End! • Thoughts or questions?

    16. References • http://www.howstuffworks.com/wireless-network.htm • http://www.80211-planet.com/columns/article/0,4000,1781_961181,00.html • http://www.80211-planet.com/columns/article/0,4000,1781_947661,00.html • http://www.pcausa.com

    17. Same LAN (inside Clarkson) Same Switch (same lab) LAN to LAN (Clarkson to SUNY Potsdam) LAN to Internet (Clarkson to a Roadrunner service) Note: LAN stands for “Local Area Network” Different PCATTCP Trials Same Host (same computer)

    18. Bluetooth (cont) • spread-spectrum frequency hopping – a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis • When two Bluetooth devices come in contact with each other, they automatically conversate and form a personal-area network (PAN)

    19. Spread spectrum • Spread-spectrum – data is sent in small pieces over a number of discrete frequencies available for use at any time in the specified range

    20. Frequency-hopping spread spectrum • send a short burst of data, shift frequencies (hop) and then send another short burst • Since the FHSS devices that are communicating agree on which frequencies to hop to, and use each frequency for a brief period of time (less than 400 milliseconds) before moving on, several independent FHSS networks can exist in the same physical area without interfering with each other

    21. Direct-sequence spread spectrum • splitting each byte of data into several parts and sending them concurrently on different frequencies • DSSS uses a lot of the available bandwidth, about 22 megahertz (MHz).

    22. The Basics • 4 different types of wireless networks • IrDA (Infrared Data Association) • Bluetooth • HomeRF (SWAP) • “Shared Wireless Access Protocol” • WECA (Wi-Fi) • “Wireless Ethernet Compatibility Alliance”

    23. IrDA (Infrared Data Association) • Uses beams of light in the infrared spectrum • Remote controls • Fairly reliable and low-cost • Drawback: It is a “line-of-sight” technology • less interference • Drawback: “one-to-one” technology • You can send data only between two things at once (but increased security?)

    24. Bluetooth • The magic number: 2.45 gigahertz • Radio-frequency also used by baby monitors, garage door openers, and cordless phones • How do you avoid interference? • Bluetooth sends weak signals of 1 milliwatt • Powerful cell phones use 3 watts • Bluetooth devices limited to 10 meters • But they can go through walls better than others

    25. HomeRF (SWAP) • Shared Wireless Access Protocol (SWAP) • Developed by an alliance of businesses • 6 voice channels and one data channel • The data channel is the 802.11 wireless-Ethernet specification by the IEEE • One drawback: SWAP can only be used with computers • Printers and such need to be attached to a computer and used as a resource

    26. HomeRF (SWAP) • Advantages: • Cheap, easy-to-install • Allows multiple-networks in the same location • Can encrypt data • Drawbacks: • Not very fast (typically limited to 1 Mbps) • Limited Range (75 to 125 ft) • Physical obstructions (walls, large metal objects) cause huge interference issues • Difficult to integrate into existing wired networks