802.11a Standard On 5 GHz

Read here about the 802.11a standard and frequencies on which it is working. Its products work on the frequency of 5 GHz, which is an unlicensed band. Standard hit the market in late 2001. There were three main chipset vendors: Intersil, Cisco (you have guessed this one for sure) and Atheros Communications.

Higher frequencies have higher path losses. This means also that 11a Access Points have the lower range. Much greater density is needed. Higher frequency requires a greater power – more power consumption.

Use of the 5GHz band gives you a great advantage compared to the 2.4 GHz. The 2.4GHz band is used by many other technologies. It is a much greater possibility for degradation of signal caused by conflicts with different signals on the same frequency. Good side of a standard is also the bandwidth. The maximum bandwidth is 54Mbps, which is almost 5 times greater comparing to 802.11b.

11a uses OFDM – Orthogonal Frequency Division Multiplexing.

As you see from the table above, this standard has been divided into 12 channels. First two channels (36, 40, 44 and 48) have allowed power of 40 mW, and the rest of the spectrum of 8 channels (52, 56, 60, 64, 149, 153, 157 and 161) has 4 times bigger power threshold of 200 mW.

The difference in first 8 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.

All new WiFi devices are using 802.11g and 802.11n standards.

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