Wi-fi

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Wi-fi

  1. 1. Wi-Fi
  2. 2. Evolution of Wireless LAN <ul><li>Early experiences (1970-72): IBM, HP, Motorola </li></ul><ul><ul><li>Abandoned due to limited performance and unavailability of frequency bands </li></ul></ul><ul><li>Early challenges: </li></ul><ul><ul><li>Complexity and cost </li></ul></ul><ul><ul><li>Bandwidth </li></ul></ul><ul><ul><li>Coverage </li></ul></ul><ul><ul><li>Interference </li></ul></ul><ul><ul><li>Frequency administration </li></ul></ul><ul><li>Emergence of unlicensed bands </li></ul><ul><ul><li>Release of Industrial, Scientific and Medical (ISM) bands in 1985 </li></ul></ul><ul><li>Applications: military, home and enterprise networks, mobile networks, teetherless access </li></ul>
  3. 3. <ul><li>Wi-Fi is based on 802.11 technology </li></ul><ul><li>It is originally intended to provide wireless computing for staffs within businesses and commercial organizations </li></ul>
  4. 4. IEEE 802.11 <ul><li>Standardization group formed in 1990, first standards completed in 1997 </li></ul><ul><li>IEEE 802.11 is the first WLAN standard; only one to secure a market </li></ul><ul><li>802.11a: PHY layer supports 11Mbps using CKK (complementary code keying) technology </li></ul><ul><li>802.11b: PHY layer supports 54 Mbps using OFDM </li></ul><ul><li>Uses CSMA/CA for contention data </li></ul><ul><li>Supports both infrastructure as well as ad hoc modes </li></ul>
  5. 5. 802.11a – higher speeds, smaller coverage, more channels <ul><li>Wi-Fi is also sold to hotspot operators particularly hotel, convention centres, cafes, airports </li></ul><ul><li>Hotspots offer higher-speed Internet access than most cellular network’s data offering and cost less to build than cellular base station </li></ul><ul><li>802.11 wireless standards are based on Ethernet protocols </li></ul><ul><li>802.11a is the only 802.11 standard that operates at 5 GHz </li></ul><ul><li>The use of 5 GHz band avoids interference from microwave ovens, Bluetooth equipments and cordless phones that operate at 2.4 GHz </li></ul><ul><li>Disadvantage is the signal fade faster </li></ul>
  6. 6. 802.11b <ul><li>When they were first available, 802.11 equipments were equipped with only 802.11b chips </li></ul><ul><li>Now most use b and g which are designed to interoperate </li></ul><ul><li>Because home broadband connections are slower than 802.11 networks, no advantage is gained </li></ul>
  7. 7. 802.11g <ul><li>Support higher data rates than 802.11b </li></ul><ul><li>Use 2.4 gHz bands </li></ul><ul><li>The higher speeds and capacity of g and a are required to support voice over IP on WLANs </li></ul>
  8. 8. 802.11n <ul><li>Backward compatibility with a, b and g </li></ul><ul><li>Improve coverage by overcoming a certain amount of interference </li></ul><ul><li>Increase speeds and supports more users per access point </li></ul>
  9. 9. Benefits.. <ul><li>Residential customers adopted Wi-Fi faster than enterprises because of its simplicity, fewer concerns about security and the benefit of avoiding the expenses for cabling </li></ul><ul><li>Its advantage is low equipment cost and easier installation </li></ul><ul><li>Benefits were also immediately noticed for healthcare, education, retailing and warehousing </li></ul>
  10. 10. Disadvantages.. <ul><li>Because of the casual nature of Wi-Fi users, most of them don’t protect their Wi-Fi networks with strong passwords – This weakness can be exploited by unauthorized persons which (advertently) can gain access to the Wi-Fi and can exploit it to satisfy their personal or professional needs. </li></ul>

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