2. Wireless LANs: Different, Slower, Kinda Cheaper Jim Gogan Director, ITS - Networking jim_gogan@unc.edu

3. What They Are Not n Not wireless MANs (but…) n Not wide-area data transmissions over cellular or packet radio n Overlap with point-to-point LAN-LAN bridging n Overlap with PANs (the few feet surrounding a user’s workspace) n NOT a substitute for wired LANs!!!

4. How They Are Connected n Configured with transmitter/receiver (“access point”) that is usually connected to the “wired” network n Accessed by end users with wireless LAN adapters (usually built-in to newer laptops or PCMCIA cards for older notebook computers)

5. 802.11 Evolution n Sept. 1999 - 802.11b (“Wi-Fi”) extension standardized by IEEE; provides for 11 Mb/sec using DSSS technology in 2.4 GHz band n IEEE also ratified 802.11a: uses 5 GHz band to support data rates from 6 Mb/sec to 54 Mb/sec; shares the same wireless LAN MAC protocol as Wi-Fi, but equipment not compatible. n Other standards enhancements completed or underway (more later)

6. Issues: Coverage n Distance: u function of product design and propogation path (radius: less than 100 ft - more than 300 ft) n Throughput: u 802.11b: 1, 2, 5.5, 11 Mb/sec (highest throughput we’ve seen 4-6 Mb/sec) u SHARED bandwidth! n Scalability: u number of clients on each access point depends on number and nature of transmissions (between 15-50 clients)

7. Roaming microcells: similar to cellular telephone system; users get “handed off” thru wired net as they roam limited part of 802.11 standard

8. Issues: Interoperability n 802.11 goal is to allow interoperability at Physical layer n Roaming still an issue n Interference from/coexistence with other WLANs (implications of Bluetooth)

9. Issues: Other n Security: u many security options/provisions included by vendors u 802.11 provides for optional encryption feature (WEP: Wired Equivalent Privacy - encrypts data portion of packet) n Cost: u varies - wildly

10. Issues: Other (cont.) n Battery life on notebooks: u at present, can reduce 3 hour battery life to 2 hours u special techniques from different vendors to maximize battery life u Issues with “stand-by”/hibernate power saving n Safety: u less output power than cell phone

11. Organizations n WLANA - Wireless LAN Alliance u www.wlana.com u includes all previous vendors plus a few others n WECA - Wireless Ethernet Compatibility Alliance u www.wirelessethernet.org

12. Newer/Developing Standards n majority of stuff to-date: 802.11b n 802.11a – different frequency (5GHz band); 54 Mb/sec (27 Mb/sec?) n 802.11g – 2.4GHz range/compatible with 802.11b; 54 Mb/sec (27 Mb/sec? 8 Mb/sec?) n 802.11e – traffic prioritization and bandwidth provisioning (coming) n 802.11i – security (ties in with WPA – Wi-Fi Protected Access) n 802.11r – non-proprietary roaming (2006) n 802.11n – 100 Mb/sec (MIMO)