The regulatory requirements for wireless LANs in the European Union are specified by The Centers of Excellence (CE). Below is the maximum allowed EIRP as specified by the CE.
|Frequency Band (MHz)||Max Power Level (EIRP) (mW)||Max Power Level (dBm)||Indoor/Outdoor|
EIRP is calculated using by adding the transmit strength of the radio and gain of the antenna while subtracting the loss of the cabling between the radio and antenna. These values are available provided by the manufacturer.
EIRP = transmit strength (dBm) + antenna gain (dBi) – cable loss (dB)
For example if you an AP's output power is 21dBm, the cable loss is 1dB, and the max EIRP for the band is 1W or 30dB, an antenna with a gain of up to 10dBi can be used within the legal maximum EIRP.
EIRP on Access Points that support beamformingBeamforming gain can be calculated with the below equation, accounting for how many antennas an Access Point has.
EIRP = transmit strength (dBm) + antenna gain (dBi) + 10 log10(number of spatial streams) (dBi) – cable loss (dB)