This infographic was inspired by the work of Nigel Bowden and Devin Akin. Nigel wrote this really good article on DFS that you can find on his website wifinigel.blogpost.com. Devin presented a really detailed webinar on DFS in partnership with Netscout. You can find the recording here.

I would encourage you to go and take a look at their ressources.

Note: there are a lot of disparities in the way DFS operations work between the different ​Wi-Fi vendors. It was a challenge to try to standardize it into one graphic. Please perform detailed testing of your own WLAN solution to find out what the actual DFS operations are in your environment.

​Click on the image below to download the infographic in the PDF format:

​Feel free to look at these ressources if you want to learn more about DFS operations:

• Nigel Bowden's Blog post on DFS: http://wifinigel.blogspot.com/2018/05/the-5ghz-problem-for-wi-fi-networks-dfs.html
• Devin Akin's webinar on DFS: https://www.brighttalk.com/webcast/5522/279895/designing-with-dfs-channels
• DFS Regulations in Canada: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf10971.html
• IEEE 802.11-2016 Standards Clause 11.9

I would like to thank Devin and Nigel for their help in reviewing the infographic and providing feedbacks. If you ​think of a way we could improve this infographic, do not hesitate to let me know in the comments below. 

Thank you!

Cheers,
François Vergès

Last year, I have written a blog post entitled "5GHz Band Channel Availability in Canada" explaining what 5GHz channels were available in Canada. This was based on a document from Industry Canada named "RSS-210 - Licence-exempt Radio Apparatus (All Frequency Bands): Category I Equipment" Annex 9 - Local Area Network Devices. If you go visit the Industry Canada's website today, you will see that this annex is no longer applicable and has been replaced in May 2015:

So, in this article, it is time for me to update the information provided in my previous blog post and keep things up to date!

The new document covers the new radio standards specifications for the Wi-Fi equipment operating in all the 5GHz frequency bands:
 - UNII1 (5150-5250MHz)
 - UNII2 (5250-5350MHz)
 - UNII2-Extended (5470-5600MHz and 5650-5725MHz)
 - UNII3 (5725-5850MHz)

Here are the updated radio standards specifications:

As you can see, nothing much changed from the last standards. Basically, the channel availability and the output powers were kept unchanged. 
So what has changed? According to me, two important regulations were added. They are detailed below.

Transmitter Power Control or TPC is a feature that enables a Wi-Fi device to dynamically switch between several transmission power levels in the transmission process. This is mainly used to reduce interference if another device is transmitting on the same frequency.
For Wi-Fi devices operating the UNII2 and UNII2-Extended, Industry Canada states that "devices with a maximum e.i.r.p. greater than 500mW shall implement TPC in order to have the capability to operate at least 6dB below the maximum permitted e.i.r.p. of 1W". This information can be important to keep in mind while designing a WLAN.

Concerning the UNII3 & ISM bands (5725-5850MHz), the conducted output power shall not exceed 1W. If directional antennas are used with a gain greater than 6dBi, the maximum conducted output power shall be reduced  by the amount in dB that the directional gain of the antenna exceeds 6dBi. So basically the maximum e.i.r.p. will never exceed 4W and if the gain of the antenna is greater than 6dBi, the output power will be adjusted accordingly.
However the standards stats that "fixed point-to-point devices operating in this band may employ transmitting antennas with directional gain greater than 6dBi without any corresponding reduction in transmitter conducted power".

Here is an example to explain this regulation:

So, on the left part of the drawing, we are using an antenna gain of 9dBi; which is 3dBi greater than 6dBi. If we were to use the maximum conducted power possible (i.e. 1W), the total e.i.r.p. would be: 30dBm (1W) + 9dBi = 39dBm (8W). 8W is over the maximum allowed (4W). So in order to stay under the regulations, we need to lower the conducted power by the number of the antenna gain dB greater than 6 (in our case 9-6 = 3dB). So the new conducted power would be: 30dBm (1W) - 3dB = 27dBm (500mW).
If we use a conducted power of 500mW we will have the following e.i.r.p.: 27dBm (500mW) + 9dBi = 36dBm (4W). This complies with the regulations!

On the right part of the drawing, we are setting up a point-to-point bridge link with an antenna gain of 13dBi; which is also greater than 6dBi. Even though the e.i.r.p. exceed 4W, we are still allowed to use a maximum conducted power of 1W.

If you are installing Wi-Fi on the 5GHz band in Canada, I would invite you to read the full official document from Industry Canada named "RSS-247 Digital Transmission Systems (DTSs), Frequency Hopping Systems (FHSs) and Licence-Exempt Local Area Network (LE-LAN) Devices". The section #6 details the regulations concerning Wi-Fi devices.

I hope this information will be useful for some of you.

Written by François Vergès

Channel availability in the 5GHz spectrum space is a hot subject right now. It is so, mainly because of the new 802.11ac standard that allows the use of channel width up to 160MHz (for 802.11ac wave 2). Commonly 40MHz and 80MHz channels are mainly used, if possible.

As a Network Engineer, it is then important to know how many channels are available so you can design your wireless network accordingly. The more channels available you have, the better it is. It allows you to avoid CCI (or co-channel interference) which are deadly to any Wi-Fi network.

I found it pretty easy to find the information about 5GHz channels availability in the US. However, it’s very hard to find the same information for Canada. US telecommunications are regulated by the FCC (Federal Communication Commission). In Canada, IC (Industry Canada) is responsible for administering the technical standards and certification of equipment, managing the radio spectrum and the allocation of frequencies. So I dug into the IC’s official documents and finally found the useful information I am about to share with you!

Here are the details about the channels available in the 5GHz spectrum space in Canada :

Canadian Weather Radar operates in the 5600-5650 MHz band (Channel 120, 124 and 128). Industry Canada recommends that no equipment operate in this band, or interference to weather radar will result. In practical, no Wi-Fi operations are permitted on these channels.

What about DFS? DFS (Dynamic Frequency Selection) is a mechanism that allows wireless LANs to coexist with radar systems. It automatically selects a frequency that does not interfere with the radar systems. In Canada, any Wi-Fi devices operating on the channels 52-64, 100-116 and 132-140  have to employ a DFS radar detection mechanism. The use of DFS while implementing a Wi-Fi network is the choice of the Engineer. It allows you to use more channels for sure, however, the frequency change might bring some instability in the network. Moreover, the client devices  are not always certified for DFS band operation which is the case for many portable devices. Therefore, many engineers prefer implementing their network without the use of these "DFS" channels.

The following chart puts the results in perspective illustrating the 5GHz channels with the DFS and Weather Radar restrictions:

This following table  compares the channel availability in the 5GHz band in Canada  with the rest of the world (without the use of DFS):

So channel availability in the 5GHz band in Canada happens to be the same as in the USA. The difference between the 2 countries occurs at the maximum power and EIRP level.

Written by François Vergès


Source : Document from Industry Canada : “RSS-210 - Licence-exempt Radio Apparatus (All Frequency Bands): Category I Equipment”  Annex 9 - Local Area Network Devices