Editing IEEE 802.11 (section)

===802.11a (OFDM waveform)===
{{Main|IEEE 802.11a-1999}}

802.11a, published in 1999, uses the same data link layer protocol and frame format as the original standard, but an [[OFDM]] based air interface (physical layer) was added.

It operates in the 5&nbsp;GHz band with a maximum net data rate of 54&nbsp;Mbit/s, plus error correction code, which yields realistic net achievable throughput in the mid-20&nbsp;Mbit/s.<ref>{{cite web |url=http://www.oreillynet.com/wireless/2003/08/08/wireless_throughput.html |title=Wireless throughput |access-date=2011-09-29 |url-status=dead |archive-url=https://web.archive.org/web/20111103014005/http://www.oreillynet.com/wireless/2003/08/08/wireless_throughput.html |archive-date=2011-11-03 }}</ref> It has seen widespread worldwide implementation, particularly within the corporate workspace.

Since the 2.4&nbsp;GHz band is heavily used to the point of being crowded, using the relatively unused 5&nbsp;GHz band gives 802.11a a significant advantage. However, this high [[Center frequency|carrier frequency]] also brings a disadvantage: the effective overall range of 802.11a is less than that of 802.11b/g. In theory, 802.11a signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength, and, as a result, cannot penetrate as far as those of 802.11b. In practice, 802.11b typically has a higher range at low speeds (802.11b will reduce speed to 5.5&nbsp;Mbit/s or even 1&nbsp;Mbit/s at low signal strengths). 802.11a also suffers from interference,<ref name="ACIisharmfull">{{Cite journal| last1 = Angelakis  | first1 = V.| last2 = Papadakis | first2 = S.| last3 = Siris | first3 = V.A.| last4 = Traganitis | first4 = A.| title = Adjacent channel interference in 802.11a is harmful: Testbed validation of a simple quantification model| journal = Communications Magazine| volume = 49| issue = 3| pages = 160–166| publisher = IEEE| date = March 2011| issn = 0163-6804| doi = 10.1109/MCOM.2011.5723815| s2cid = 1128416}}</ref> but locally there may be fewer signals to interfere with, resulting in less interference and better throughput.