1 / 27

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.

luigi
Télécharger la présentation

Ryan Heaton Dick Al-Bayaty

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related