<P> Originally described as clause 17 of the 1999 specification, the OFDM waveform at 5.8 GHz is now defined in clause 18 of the 2012 specification, and provides protocols that allow transmission and reception of data at rates of 1.5 to 54 Mbit / s . It has seen widespread worldwide implementation, particularly within the corporate workspace . While the original amendment is no longer valid, the term 802.11 a is still used by wireless access point (cards and routers) manufacturers to describe interoperability of their systems at 5 GHz, 54 Mbit / s . </P> <P> The 802.11 a standard uses the same data link layer protocol and frame format as the original standard, but an OFDM based air interface (physical layer). It operates in the 5 GHz band with a maximum net data rate of 54 Mbit / s, plus error correction code, which yields realistic net achievable throughput in the mid-20 Mbit / s . </P> <P> Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively unused 5 GHz band gives 802.11 aa significant advantage . However, this high carrier frequency also brings a disadvantage: the effective overall range of 802.11 a is less than that of 802.11 b / g . In theory, 802.11 a 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 802.11 b . In practice, 802.11 b typically has a higher range at low speeds (802.11 b will reduce speed to 5.5 Mbit / s or even 1 Mbit / s at low signal strengths). 802.11 a also suffers from interference, but locally there may be fewer signals to interfere with, resulting in less interference and better throughput . </P> <P> The 802.11 b standard has a maximum raw data rate of 11 Mbit / s, and uses the same media access method defined in the original standard . 802.11 b products appeared on the market in early 2000, since 802.11 b is a direct extension of the modulation technique defined in the original standard . The dramatic increase in throughput of 802.11 b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11 b as the definitive wireless LAN technology . </P>

An advantage of implementing 802.11a wireless protocol is that it
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