As wireless engineers, at some point of our career, we have come across these questions on what is the maximum allowed radiated power from an access point or what is the max EIRP allowed in a particular radio band. I am just putting these basics down so the it is easier to co-relate future discussions or contents in the blog.
2.4 GHz WLAN channel selection
In view of the differences in spectrum allocations around the globe and different requirements for the regulatory authorities, not all the WLAN channels are available in every country. The table below provides a broad indication of the availability of the different Wi-Fi channels in different parts of the world.
Please note that channels 1, 6 and 11 are non interfering channels in this radio band.Few countries also use 1, 5, 9,13 but a small amount of over lapping occurs in this frequency selection.
5 GHz WLAN Channel selection
Note 1: Additional regional changes for countries including Australia, Brazil, China, Israel, Korea, Singapore, South Africa, Turkey.
Additionally Japan has access to some channels below 5180 MHz. Australia’s regulatory body (ACMA) states that channels 36-64 should be restricted for indoor use.
Note 2: DFS = Dynamic Frequency Selection; TPC = Transmit Power Control; SRD = Short Range Devices 25 mW max power.
Recommendations:
- On 2.4 GHz, it is recommended to use channels 1, 6, and 11.
- On 5 GHz frequency, it is recommended to use non DFS channels in any deployment . Channels (36-48) in UNII 1 and Channels (149-165) in UNII 3.
However, for large deployments, it becomes implossible to restrict ourselves to these channels.
Please note that in an event of radar detection, these channels will change frequencies to a non DFS channel and clients will loose connectivity.
FCC 2.4 radio bands maximum and allowed frequencies
| Maximum Power from Intentional Radiator *1 | Maximum Antenna Gain (dBi) | EIRP (dBm) | EIRP (watts) |
| 30dBm or 1 watt | 6 | 36 | 4 |
| 27dBm or 500mW | 9 | 36 | 4 |
| 24dBm or 250mW | 12 | 36 | 4 |
| 21dBm or 125mW | 15 | 36 | 4 |
| 18dBm or 63mW | 18 | 36 | 4 |
| 15dBm or 32mW | 21 | 36 | 4 |
| 12dBm or 16mW | 24 | 36 | 4 |
FCC 5 GHz radio bands maximum and allowed frequencies
| BAND | Frequency (GHz) | Channels | Permitted Use Location | Point‐to‐ Point Max. Intentional Radiator Power *1 | Point‐to‐ Point Maximum EIRP *2 | Point‐to‐ MultiPoint Intentional Radiator Power *1 | Point‐to‐ MultiPoint Maximum EIRP *2 |
| UNII (Low) | 5.15‐5.25 | 36, 40, 44, 48 | Indoor Only | 40mW 16dBm | 160mw 22dBm | 40mW 16dBm *4 | 160mW 22dBm |
| UNII‐2 (Middle) | 5.25‐5.35 | 52, 56, 60, 64 | Indoor or Outdoor | 200mW 23dBm | 800mW 29dBm | 200mW 23dBm *4 | 800mW 29dBm |
| UNII‐2 Extended | 5.470‐ 5.725 | 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140 | Indoor or Outdoor | 200mW 23dBm | 800mW 29dBm | 200mW 23dBm *4 | 800mW 29dBm |
| UNII‐3 (Upper) | 5.725‐ 5.825 | 149 to 161 | Typical Outdoor | Antenna to 23dBi *3 | 200 watts | 800mW 29dBm *4 | 3200mW 35dBm |
*1 The FCC terminology of Intentional Radiator is the transmitter power of the wireless equipment, such as a wireless access point, router or bridge.
*2 Equivalent Isotropically Radiated Power (EIRP) is terminology for the total RF power radiated by the antenna.
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