--George D. Miller
After seven years of development, the 802.11 standard covering wireless local area networks (lans) was ratified by the Institute of Electrical and Electronics Engineers (ieee--Piscataway, NJ) standards activity board in late June. Acceptance of the standard, which defines the air interface between wireless lan stations and between stations and access points, promises to let information technology professionals breathe a little easier when they attempt to select wireless lan products and incorporate them into existing wired lans.
The 540-page document is titled ieee STD 802.11-- "1997 Wireless lan Media Access Control (mac) Physical Layer (phy) Specifications." Committee chairman Vic Hayes of Lucent Technologies Wireless Communications and Networking Div. (Murray Hill, NJ) has led the standard development effort since its inception.
The phy specification encompasses three transmission options: one infrared option and two radio-frequency options--direct-sequence spread spectrum and frequency-hopping spread spectrum. The mac protocol, known as carrier sense multiple access with collision avoidance, works seamlessly with standard Ethernet, making wired and wireless nodes on an enterprise lan logically indistinguishable. Features such as roaming and power management are incorporated into the mac protocol.
For those who are considering a wireless lan implementation, ratification of the standard will do much to increase their comfort level with wireless lan technology. According to Hayes, the specification was developed by "wireless lan experts from 42 companies," all of whom will offer products based on the standard. Adds Angela Champness, Lucent director of Wavelan product development during a Lucent press conference announcing the ratification, "802.11 gives customers peace of mind that what they are purchasing is supported by all major wireless lan vendors. It also paves the way for mass-market components that will help drive down wireless lan prices."
Champness also contends that "interoperability [among the same phys] is provided by the 802.11 standard. Similar to Ethernet, which defines both a phy and mac layer, 802.11 does the same over the air rather than over cable." This means that if vendors implement according to the standard, products will be interoperable.
"One of the issues raised last year within 802.11," explains Champness, "was that the definitions in the standard were not clear enough for vendors to implement--some things were subject to interpretation. This was rectified by the inclusion of state diagrams: 142 pages of protocol flow diagrams explaining precisely what is required." She adds that inclusion of the state diagrams is the main reason the standard was not approved last year.
Many of the 42 companies that participated in development of the standard will now turn their energies toward interoperability testing with other vendors. "This is to verify that we have all indeed implemented 802.11 and ensure that we can correctly position how our products work together on a feature/function level," adds Champness.
This story was adapted from Wireless Integration, another PennWell publication.
