802.11a describes the 1st generation of the WiFi. Read more about this first WiFi network standard.

General specifications

802.11a standard, was released in 1999 by IEEE as an amendment to IEEE 802.11. The story of the fascinated wireless technology has started. You could also find the name IEEE 802.11a-1999 for the same thing. The standard works on the frequency of 5 GHz – unlicensed band. Standard hit the market in late 2001, when there were three main chipset vendors: Intersil, Cisco and Atheros Communications.

IEEE 802.11a and 5 GHZ frequency

802.11a

802.11a

Disadvantages of 5 GHz frequency:

  • Higher losses
  • Lower range
  • Large power consumption

Advantages of 5 GHz frequency:

  • Less interference
  • Bigger speed

On the higher frequencies there are higher losses with the distance. This implies that 802.11a access points have the lower range. The much greater density of the access point is required, to cover the same area. Higher frequency also leads to large power consumption.

The big advantage of the 5GHz frequency compared to the 2.4 GHz is less interference. The 2.4GHz band is used by many other technologies. It is a much larger possibility for degradation of signal caused by interference. On more advantage of 802.11a higher speed.Β The maximum speed is 54Mbps, which is nearly 5 times greater comparing to 802.11b.Β 802.11a usesΒ OFDM – Orthogonal Frequency Division Multiplexing.

As you see from the table above, this standard has been divided into twelve channels. First two channels (36, 40, 44 and 48) have allowed power of 40 mW, and the rest of the spectrum of eight channels (52, 56, 60, 64, 149, 153, 157 and 161) has four times bigger power threshold of 200 mW.

The difference in first eight channels is 20 MHz or 0.020 GHz, while 8th and 9th channel have 425 MHz band gap. The rest of the channels have the difference of 20 MHz.

Read more about newer version of the 802.11 family – 802.11b, 802.11g, 802.11n and latest so-called 5th generation of WiFi – 80.11ac .