Introduction
This article is going to cover the use of radio frequencies for use in WLAN technology in Sweden, where I am based. I have put together my own graphic covering the use of 5 GHz bands and channels in Sweden.
Modern enterprise wireless networks are designed using a combination of different types of access points, antennas, and radio spectrum settings to achieve great coverage where it needs to be and great capacity.
Working with radio frequencies can be tricky sometimes. There are different regulatory bodies throughout the world that regulate which frequencies can be used for which purposes and what kind of transmit powers you are allowed to use.
5 GHz Bands and Channels available in Sweden
Using data from ETSI (European Telecommunications Standards Institute) and PTS (Post- och Telestyrelsen, Sweden’s governing body for radio frequency use, among other things) I have put together the graphic below to illustrate which frequencies, bands, and channels are available for use with wi-fi technology.
Since most of these types of graphics cover either the US frequencies (set by the FCC) or the general European frequencies (set by ETSI) and the UK, I thought it would be useful, at least for myself, to have a graphic covering Sweden specifically.
This is more of a “reminder post” for me if anything, as most people visiting my blog are probably not from Sweden.
Due to most wi-fi solutions usually referencing terms used in the US (like the different UNII band names), I have decided to include these terms in my graphic. In most of Europe, however, the official name for these different bands is RLAN, which stands for Radio Local Area Network.
You can download a high-resolution PDF of this graphic here.
With the graphic out of the way, a short explanation of each RLAN band can be found below.
RLAN Band 1 (equivalent to the UNII-1 and UNII-2 bands)
RLAN Band 1 Sub-band 1 (UNII-1)
This first sub-band of RLAN Band 1 covers channels included within frequencies in the 5150 to 5250 MHz range, which are the channels 36, 40, 44, and 48.
The maximum Effective Isotropic Radiated Power (EIRP) allowed in this band is 23 dBm (200 mW).
RLAN BAND 1 Sub-band 2 (UNII-2)
This second sub-band of RLAN Band 1 covers channels included within frequencies in the 5250 to 5350 MHz range, which are the channels 52, 56, 60, and 64.
The maximum Effective Isotropic Radiated Power (EIRP) allowed in this band is 23 dBm (200 mW).
RLAN Band 2 (equivalent to the UNII-2-Extended band)
This band covers channels included within frequencies in the 5470 to 5725 MHz range, which are the channels 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, and 144.
Channel 144 in this band is legal to use in Sweden (since 2014), but due to being late to the party, it is not widely implemented in most modern WLAN technologies sold here.
The maximum Effective Isotropic Radiated Power (EIRP) allowed in this band is 30 dBm (1000 mW).
RLAN Band 3 (equivalent to the UNII-3 band)
This band covers channels included within frequencies in the 5735 to 5835 MHz range, which are the channels 149, 153, 157, 161, and 165.
Similar to channel 144 of the RLAN Band 2 mentioned above, the channels of RLAN Band 3 are legal to use in Sweden (since 2018), but there has still not been wide adoption of these channels yet.
The maximum Effective Isotropic Radiated Power (EIRP) allowed in this band is 14 dBm (25 mW).
Same Power Level - Different Transmit Power
Since different bands, and their channels, have different ideas of what maximum radiated power means, having two access points of the same model set to the same power level does not necessarily mean that they radiate the same signal strength.
Cisco uses numbers 1-8 for their power levels, where power level 1 means maximum transmit power, and power level 8 means minimum transmit power. Not only do different bands and channels affect the transmit power (in dBm) of the different power levels, but different access point models also differ from one to another.
Take these two 9120AXI access points on the image below, for example. This image is a heatmap from Cisco Prime, the currently most common tool for documenting wireless Cisco networks. The image shows the simulated coverage from these two access points.
Both of the access points are set to Power Level 1, which means that the access points are using their maximum transmit power. As you can see, the access point on the left is set to channel 36 and the access point on the right is set to channel 112. If you go back up to the explanation of each of the different RLAN (or UNII) bands, you can see that the maximum EIRP for channel 36 is 23 dBm and for channel 112 it’s 30 dBm.
The radiation pattern of the right access point looks “stronger” visually, so it is good to see that Cisco Prime is aware of the differences in EIRP, even if the access points themselves are set to the same power level.
If you are running a WLC with AireOS, you can use the command show advanced 802.11a txpower to display the current power levels of all your access points and what kind of transmit power (in dBm) each power level represents.
You can also use the command grep include "<ap-name>" "show advanced 802.11a txpower" to show the Transmit Power levels of only a single or a selection of your access points, in case you are working with a WLC that has way too many access points to scroll through.
In Cisco Prime, if we change the display view of these access points to “TX Power” instead, we can see the Transmit Power being used.
You can disregard the 6 dBm after the slash (“/”), is has nothing to do with the 5 GHz radio.
Calculating EIRP
Effective Isotropic Radiated Power (EIRP) has already been mentioned a few times in this article and it is a value calculated by taking the Transmit Power minus the Cable Loss plus the Antenna gain.
Since the two access points above use internal antennas (meaning no Cable Loss) with an antenna gain of 5 dBi according to Cisco’s datasheet, you only need to add this gain value to the Transmit Power to get the final EIRP value.
For the left access point, this would be 17 + 5 = 22 dBm which is within the allowed maximum 23 dBm EIRP of the RLAN Band 1 (UNII-1-band), where channel 36 resides.
For the right access point, this would be 23 + 5 = 28 dBm which is within the allowed maximum 30 dBm EIRP of the UNII-2-band, where channel 112 resides. Just by looking at this EIRP value, you can tell that the channel used by this access point could never belong to either of the RLAN Band 1 sub-band (UNII-1/UNII-2) since 28 dBm is way too high of an EIRP allowed in those bands.
Final Notes
I am by no means a radio frequency expert, so feel free to point out errors in this article or in the graphic using the comment section below :)