IEEE 802.11 (legacy mode)
{{Short description|Wireless networking standard}}
{{Wi-Fi Generations}}
IEEE 802.11 (legacy mode){{snd}} or more correctly IEEE 802.11-1997 or IEEE 802.11-1999{{snd}} refers to the original version of the IEEE 802.11 wireless networking standard released in 1997 and clarified in 1999. Most of the protocols described by this early version are rarely used today.
Description
It specified two raw data rates of 1 and 2 megabits per second (Mbit/s) to be transmitted via infrared (IR) signals or by either frequency hopping or direct-sequence spread spectrum (DSSS) in the Industrial Scientific Medical frequency band at 2.4 GHz. IR remained a part of the standard until IEEE 802.11-2016, but was never implemented.{{cn|date=March 2021}}
The original standard also defines carrier sense 0 access with collision avoidance (CSMA/CA) as the medium access method. A significant percentage of the available raw channel capacity is sacrificed (via the CSMA/CA mechanisms) in order to improve the reliability of data transmissions under diverse and adverse environmental conditions.
IEEE 802.11-1999 also introduced the binary time unit TU defined as 1024 μs.{{cite book |last=Maufer |first=Thomas |url=https://books.google.com/books?id=GB-87qyhc8sC&pg=PA142 |title=A Field Guide to Wireless LANs: For Administrators and Power Users |date=2004 |work=The Radia Perlman Series in Computer Networking and Security Series |publisher=Prentice Hall Professional |isbn=9780131014060 |page=144 |id=0131014064 |access-date=2015-10-27}}
At least seven different, somewhat-interoperable, commercial products appeared using the original specification, from companies like Alvarion (PRO.11 and BreezeAccess-II), BreezeCom, Digital / Cabletron (RoamAbout), Lucent, Netwave Technologies (AirSurfer Plus and AirSurfer Pro), Symbol Technologies (Spectrum24), and Proxim Wireless (OpenAir and Rangelan2). A weakness of this original specification was that it offered so many choices that interoperability was sometimes challenging to realize. It is really more of a "beta specification" than a rigid specification, initially allowing individual product vendors the flexibility to differentiate their products but with little to no inter-vendor interoperability.
The DSSS version of legacy 802.11 was rapidly supplemented (and popularized) by the 802.11b amendment in 1999, which increased the bit rate to 11 Mbit/s. Widespread adoption of 802.11 networks only occurred after the release of 802.11b which resulted in multiple interoperable products becoming available from multiple vendors. Consequently, comparatively few networks were implemented on the 802.11-1997 standard.{{Citation needed |date=April 2024}}
Comparison
{{802.11 network standards}}
Notes
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References
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Further reading
- {{cite book |date=1997-11-18 |author=IEEE 802.11 Working Group |title=IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications |doi=10.1109/IEEESTD.1997.85951 |isbn=1-55937-935-9}}
- {{cite book |date=1999-07-15 |author=IEEE 802.11 Working Group |title=IEEE Standard for Information Technology- Telecommunications and Information Exchange Between Systems- Local and Metropolitan Area Networks- Specific Requirements- Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications |doi=10.1109/IEEESTD.2003.95617 |isbn=0-7381-1857-5}}
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