Unlicensed frequency bands
The origin of wireless can be found in the release of the 2.4 GHz band because this is considered an “accepted band”. Wi-Fi bands, therefore, are unlicensed bands. This means that a licence does not have to be applied for, in order to use them from the Belgian Institute for Postal services and Telecommunications (BIPT) or the 'Antennebureau' (the information agency of the Dutch government concerning antennas). The opposite is true for frequency bands such as 18, 23 and 38 GHz, which are frequently used bands. You must apply for admission to use them and the regulator has determined exactly which frequency (channel) you may use. The advantage is that a minimum of interference can be guaranteed in this manner.
The difficulty is that the different (sub)bands are also linked to different regulations in different countries. This, for example, means that the information that you can find on the Internet does not apply to you.
When discussing statutory provisions, it is important that reference is made to the concept of “EIRP”, that is, Effective Isotropic Radiated Power. This is the power that is discussed by the regulator. EIRP represents the quantity of theoretical power that an isotropic antenna which radiates the signal proportionally in all directions should radiate to achieve the same as the peak power value of the real system in the direction of the maximum antenna gain. This, therefore, refers to a theoretical power and an equation. In addition, we refer to a peak power at one carefully determined location. Everything around this location will be radiated with a far smaller power.
The 2.4GHz band runs from 2400 to 2483 MHz and must meet fairly simple statutory provisions:
- Indoor and outdoor use
- Maximum EIRP of 20dBm or 100 mW
This means that 2.4 GHz is easy to use and has quite some popular applications besides Wi-Fi such as babyphones, wireless remote controls for vehicles, helicopters, drones etc. as well as wireless alarm systems, keyboards, mice, etc.
The 5 GHz band is further split up into different subbands:
- 5.15-5.25GHz: UNII-1
- 5.25-5.35GHz: UNII-2
- 5.47-5.725GHz: UNII-2 extended
- 5.725-5.825Ghz: UNII-3 (the ISM band is also in here as an overlap: 5.725 - 5.875 GHz)
These bands must meet different provisions in different countries.
- 5.15 - 5.25 GHz: 200 mW/23 dBm, only indoors
- 5.25 - 5.35 GHz: 200 mW/23 dBm provided that TPC is used, if not, maximum of 100 mW/20 dBm, DFS, only indoors
- 5.47 - 5.725 GHz: 1W/30 dBm provided that TPC is used, if not, maximum of 500 mW/27 dBm, DFS, indoors and outdoors
- 5.725 - 5.825 GHz: for 5.725 - 5.875 GHz and, therefore, the ISM band; a maximum EIRP of 25 mW/14 dBm applies. Wi-Fi channels are not permitted.