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Ryan Heaton Dick Al-Bayaty

Ryan Heaton Dick Al-Bayaty. Wi-Fi How Wireless Communication works. Overview . What is Wi-Fi History Ethernet IEEE standards 802.11(amendments a,b,g,n ) 2.4GHz /5GHz differences. What is Wi-Fi.

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Ryan Heaton Dick Al-Bayaty

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  1. Ryan Heaton Dick Al-Bayaty Wi-Fi How Wireless Communication works

  2. Overview • What is Wi-Fi • History • Ethernet • IEEE standards 802.11(amendments a,b,g,n) • 2.4GHz /5GHz differences

  3. What is Wi-Fi • Wi-Fi is a means which allows for electronic devices to talk to one another or exchange data through radio waves. • Common devices utilizing Wi-Fi: • Computers • Smartphones • Video game consoles • Tablets

  4. The History • 1985: FCC releases ISM band • 1991: Wi-Fi creates by NCR Corporation/AT&T • 1992 & 1996: CISRO obtains patents for methods that were used to “Unsmear” the Wi-Fi signal • 1999: Wi-Fi name trademarked

  5. The History • Initially meant for cashier systems, the first wireless products were brought on the market under the name WaveLAN with speeds of 1Mbps/2Mbps • It is continually advancing under IEEE amendments 802.11a →802.11b → 802.11g → 802.11n

  6. The History

  7. ISM Band • ISM stands for industrial, scientific, and medical. • ISM bands are set aside for equipment that is related to industrial or scientific processes or is used by medical equipment. • The ISM band is license-free, provided that devices are low-power. • The 802.11 standard is contained by the ISM band.

  8. ISM Band

  9. U-NII (Unlicensed National Information Infrastructure) Bands 802.11n can operate at the 5G U-NII bands: • U-NII Low (U-NII-1): 5.15-5.25 GHz(indoor use only) • U-NII Mid (U-NII-2): 5.25-5.35 GHz. • U-NII Worldwide: 5.47-5.725 GHz. • U-NII Upper (U-NII-3): 5.725 to 5.825 GHz.

  10. 2.4GHz vs. 5GHz • 2.4 GHz band is divided into 11 overlapping channels spaced by 5 MHz. • 5GHz band is less likely to be congested. • 2.4GHz is more prone to interference, commonly used. • The 5GHz band offers much higherthroughput with the same channel width.

  11. 2.4GHz vs. 5GHz • 2.4GHz covers a substantially larger range than 5GHz. • Higher frequency wireless signals of 5GHz networks do not penetrate solid objects nearly as well as 2.4GHz. • In general, the higher the frequency of a wireless signal, the shorter its range.

  12. 2.4GHz vs. 5GHz • 5GHz and 2.4GHz are simply different frequencies, each with its advantages and disadvantages. To get the best of both worlds, some recent routers have the capability for dual-band operation in both ranges simultaneously. • 5GHz offers higher throughput at a shorter distance, while 2.4GHz offers increased coverage and higher solid object penetration.

  13. Protocol Stack

  14. Wireless LAN Networks

  15. Wireless LAN Networks • Ad-Hoc • Point-to-point • Mesh • Infrastructure • Star topology

  16. WLAN Architecture—Ad Hoc • Ad-Hoc mode: Peer-to-peer setup where clients can connect to each other directly.

  17. WLAN Architecture — Mesh • Mesh: Every client in the network also acts as an access or relay point, creating a “self-healing” and (in theory) infinitely extensible network. • Not yet in widespread use, unlikely to be implemented residentially.

  18. Infrastructure network

  19. Comparison of Two Structures Infrastructure Ad hoc Expansion X Flexibility X Control X Routing X Coverage X Reliability X

  20. How does the RF propagate?

  21. Antennas • WLAN equipment usually comes with a built-in omni-directional antenna, but some select products will let you attach secondary antennas that will significantly boost range.

  22. Antennas • Antennas come in many shapes and styles: • Omni-directional: • Vertical Whip • Ceiling mount • Directional: • Yagi • “Pringles can” • Wall mounted panel • Parabolic dish

  23. How Can Several Users Communicate Simultaneously? There is a difference between a network designed for voice conversation and one for data exchange. • For voice conversations, like telephone and cell phone calls, each person has a dedicated channel during the entire conversation. • For data exchange, many users can share one channel. A user sends information when no one else is sending. • 802.11e: QoS facilitates prioritization of data, voice, and video transmissions.

  24. Share One Channel in Data Communication • In data communication, data are grouped into packets/frames. Each packet/frame contains a number of bits of information. • Devices (phones, computers, etc.) do not communicate simultaneously, similar to the concept of sharing a single connection (the air in this case); only one person can use it at one time.

  25. Share One Channel in Data Communication • Send RTS packet • Receive CTS packet • Send data packets • Send EOB packet • Receive EOBC packet • No CTS packet • Generate random wait time • Resend RTS • Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA)

  26. Security • 802.11i provides security enhancements • WEP – Wired Equivalent Privacy • Additional Security Measures • WPA – Wi-Fi Protected Access • WPA2

  27. Questions/Comments

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