1.2.6 Wireless Standards
The world of wireless communications is vast. However, for particular job-related skills, we want to focus on specific aspects of Wi-Fi. The best place to start is with the IEEE 802.11 WLAN standards. These standards define how radio frequencies are used for wireless links. Most of the standards specify that wireless devices have one antenna to transmit and receive wireless signals on the specified radio frequency (2.4 GHz, 5 GHz or 6 GHz). Some of the newer standards that transmit and receive at higher speeds require access points (APs) and wireless clients to have multiple antennas using the multiple-input and multiple-output (MIMO) technology. MIMO uses multiple antennas as both the transmitter and receiver to improve communication performance. Up to eight transmit and receive antennas can be used to increase throughput.
Various implementations of the IEEE 802.11 standard have been developed over the years. The table highlights these standards.
| IEEE WLAN Standard | Radio Frequency | Description |
|---|---|---|
| 802.11 | 2.4 GHz |
|
| 802.11a | 5 GHz |
|
| 802.11b | 2.4 GHz |
|
| 802.11g | 2.4 GHz |
|
| 802.11n | 2.4 GHz 5 GHz |
|
| 802.11ac | 5 GHz |
|
| 802.11ax | 2.4 GHz 5 GHz |
|
Licensed and Unlicensed Bands
Various communications channels transmit signals over the electromagnetic spectrum. The licensed spectrum refers to the bands (range of frequency) that are reserved for radio stations, cellular companies, and broadcast television stations. Media and cellular companies typical pay for the right to transmit over a specific frequency within the licensed spectrum. In the United States, this is done by the Federal Communications Commission (FCC). Other countries have a similar regulatory agency which licenses specific bands for that country.
The unlicensed spectrum is open for anyone to use. The unlicensed spectrum is where we find IEEE 802.11 Wi-Fi technologies and is available free to the public. Anyone can transmit over the unlicensed spectrum.