tailieunhanh - Lecture Wireless and mobile computing – Chapter 32: Wireless LAN technology

The following will be discussed in this chapter: Wireless LAN Introduction, defining a WLAN, WLAN design goals, early wireless LANs, modern wireless LANs, pro and cons of WLAN, WLAN deployments, cross-building interconnect,. | Wireless LAN Technology Lecture 32 Wireless LAN Introduction The proliferation of laptop computers and other mobile devices (PDAs and cell phones) created an obvious application level demand for wireless Local Area Networking. Companies jumped in, quickly developing incompatible wireless products in the 1990’s. Industry decided to entrust standardization to IEEE committee that dealt with wired LANs IEEE 802 committee!! Defining a WLAN (Wireless Local Area Network) A communications network that provides connectivity to wireless devices within a limited geographic area. "Wi-Fi" is the universal standard for wireless networks and is the wireless equivalent of wired Ethernet networks. In the office, Wi-Fi networks are adjuncts to the wired networks. At home, a Wi-Fi network can serve as the only network since all laptops and many printers come with Wi-Fi built in, and Wi-Fi can be added to desktop computers via USB. Wi-Fi is achieved with a wireless base station, called an "access point." Its antennas transmit and receive a radio frequency within a range of 30 to 150 feet through walls and other non-metal barriers. WLAN Design Goals Global, seamless operation Low power for battery use No special permissions or licenses needed to use the LAN Robust transmission technology Simplified spontaneous cooperation at meetings Easy to use for everyone, simple management Protection of investment in wired networks Security (no one should be able to read my data), privacy (no one should be able to collect user profiles), safety (low radiation) Transparency concerning applications and higher layer protocols, but also location awareness if necessary Early Wireless LANs Many standards = No standards Limited or no encryption .5 to 2 Mbps throughput High NIC cost High AP cost Limited roaming Modern Wireless LANs IEEE standards based 128 bit encryption ≥ 11 Mbps throughput Low NIC cost Low AP cost Integrated roaming Pro and Cons of WLAN Advantages Very . | Wireless LAN Technology Lecture 32 Wireless LAN Introduction The proliferation of laptop computers and other mobile devices (PDAs and cell phones) created an obvious application level demand for wireless Local Area Networking. Companies jumped in, quickly developing incompatible wireless products in the 1990’s. Industry decided to entrust standardization to IEEE committee that dealt with wired LANs IEEE 802 committee!! Defining a WLAN (Wireless Local Area Network) A communications network that provides connectivity to wireless devices within a limited geographic area. "Wi-Fi" is the universal standard for wireless networks and is the wireless equivalent of wired Ethernet networks. In the office, Wi-Fi networks are adjuncts to the wired networks. At home, a Wi-Fi network can serve as the only network since all laptops and many printers come with Wi-Fi built in, and Wi-Fi can be added to desktop computers via USB. Wi-Fi is achieved with a wireless base station, called an "access .