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

This is a video showing you how to retrieve the scale of a floor plan in AutoCAD in order to scale it in Ekahau. 

This video follows the one we published to explain how to export PDF floor plans from AutoCAD: www.semfionetworks.com/blog/preparing-floor-plans-for-ekahau-in-autocad

Written by François Vergès

Floor plans are very important for us WLAN professionals. We need them to do our designs and surveys. Sometimes, the quality of the floor plans we receive from our customer (when we receive some) is not always the best.

Just like a baker needs quality flour to produce good bread. As Wi-Fi Engineers we need quality floor plans in order to produce accurate designs.

In this article, I will show you how to export good quality PDF files from an AutoCAD .dwg file. You could then import this PDF file into Ekahau (or other preferred site survey software) to perform your design.

When receiving floor plans in a .dwg file format from a customer, you have the choice to import it directly into Ekahau. Ekahau has the ability to parse the different views and layers and gives you the ability to pick and choose the view and layers you want to incorporate into your project. It even draw the walls for you!

However, there are some limitation to this process. Here are examples:

• The views define in the CAD file don't represent what you want to see in Ekahau (for example, it is dividing the building into multiple areas when what you want is to see the full building on one view)
• The floor plan is not centred on the view and there is a lot of white space around it. It won't look good in the report.
• There is only one view in the CAD file when you actually need to divide the building into multiple section.

In all of these situations, I like to open the CAD file with AutoCAD and export exactly the views I want into different PDF files.
I use AutoCAD LT on macOS and I pay the monthly subscription when I need it (67$ a month).

Once I am done, I go back to Ekahau and import the PDF files to start working on my design.
And yes, this means I am drawing the walls myself! I care about providing a quality document to my customers, that's why I take the time to make sure, the input floor plan file is good.

This video clip shows how to export different views of a floor plans from AutoCAD:

You can also find this video on youtube: youtu.be/mdL-Wi-vaKM

As WLAN Engineers, do you think we should spend more time learning about AutoCAD?

​
Written by François Vergès

​Free Space Path Loss (or FSPL) represents the amount of energy that a given radio wave loses as it travels through the air away from its source.  Understanding FSPL will help us understand how far a Wi-Fi signal can go. It is also widely used by Wi-Fi survey tools to predict Wi-Fi signal propagation.

It is something that we can calculate by applying this mathematical formula (d in km and f in GHz):

FSPL is not specific to Wi-Fi waves, it can be applied to any other waves using other frequencies.

In a Wi-Fi environment, FSPL refers to the amount of power a Wi-Fi signal losses as it travels away from the transmitter (it can be an AP or a station).

This loss is relative to 2 main components:

• Frequency
• Distance

The following diagram shows exactly how much energy a Wi-Fi wave will lose as it travels away from an AP:

Let’s start with frequency. Here, we are talking about the frequency of the radio wave.  As you can see in the formula above, the higher the frequency is, the higher the loss will be. In Wi-Fi, this means that a 2.4GHz signal is less prone to loss than a 5GHz signal. We commonly say that 2.4GHz travels further away than 5GHz.

Another factor is affecting « how far » a Wi-Fi signal is travelling. And this is related to a specific receive characteristic. Any dual band receivers will need 1 antenna to listen to 2.4GHz signals and another one to listen to 5GHz signals. Because the wavelength of a 2.4GHz signal (12 cm) is longer that the one of a 5GHz signal (6 cm), the size of the antenna needs to be bigger. This means that the 2.4GHz receiver will have a larger receive aperture and will be able to better "hear" the incoming signal.

The FSPL formula in Wi-Fi defines that, in the first meter:

• A 2.4GHz signal is loosing about 40dB
  • Calculation for channel 1: 20log(0.001) + 20log(2.412) + 92.45 = 40.09dB
  • Calculation for channel 11: 20log(0.001) + 20log(2.462) + 92.45 =  40.28dB
  • Calculation for channel 13: 20log(0.001) + 20log(2.472) + 92.45 = 40.31dB
• A 5GHz signal is loosing about 47dB
  • Calculation for channel 36: 20log(0.001) + 20log(5.180) + 92.45 = 46.74dB
  • Calculation for channel 52: 20log(0.001) + 20log(5.260) + 92.45 = 46.87dB
  • Calculation for channel 100: 20log(0.001) + 20log(5.500) + 92.45 = 47.26dB
  • Calculation for channel 149: 20log(0.001) + 20log(5.745) + 92.45 = 47.64dB
  • Calculation for channel 165: 20log(0.001) + 20log(5.825) + 92.45 = 47.76dB

​Here, we are talking about the distance travelled by the Wi-Fi wave away from the source. Common sense tells us that it would make sense if the signal was to lose power as it travels away from its source.
The FSPL formula tells us exactly by how much following the inverse square law.

The inverse square law, developed by Isaac Newton, tells us that as the distance from the source doubles, the energy is spread out over 4 times the area. This results in the signal loosing 4 times it's original amplitude. In other words, the Wi-Fi signal is loosing 6dB every time the distance from the source is doubled (This is represented in red in the diagram above).

​
So, if we know the power of our signal leaving the access point, we can calculate how far this signal will go. This is assuming there is no source of attenuation between the transmitter and the receiver.

What happens when we introduce a wall between the transmitter and the receiver?

As expected, the wall will attenuate the signal. The FSPL will be applied to the signal as it travels to the wall and away from the wall as explained on this following diagram. The amount of attenuation will depend on the structure of the wall.

If we know the amount of power that the Wi-Fi signal will have leaving the AP (Equivalent Isotropically Radiation Power or EIRP), we can calculate the size of our desired cell.

Here is an example if we have an AP using an EIRP of 14dBm (or 25mW) for band frequency bands:

It is now easy for us to see that the 2.4GHz cell will be twice as big at the 5GHz cell if the same EIRP is used.

​In order to obtain the same cell size for both frequency bands, we can offset the EIRP of the 2.4GHz by 7dB. The way we can do it is by decreasing the 2.4GHz transmit power by 7dB. Most Wi-Fi system will only let us increase or decrease transmit power by an increment of 3dB. Therefore, the best we can do it decreasing the 2.4GHz transmit power by 6dB:

• Wikipedia article on Free Space Path Loss: https://en.wikipedia.org/wiki/Free-space_path_loss
• Effect of Transmit power changes on AP by Nigel Bowden: http://wifinigel.blogspot.ca/2014/11/effect-of-transmit-power-changes-on-ap.html
• Wi-Fi Free Space Loss Calculator by Nigel Bowden:  http://wifinigel.blogspot.ca/2014/05/wifi-free-space-loss-calculator.html
• FSPL diagram by Devin Akin: http://divdyn.com/so-called-ghost-frames-not-exist/

written by François Vergès

This year WLPC was another great event. If you missed it and would like a recap, listen to the ClearToSend podcast episode #111 Rowell and I recorded.

​Glenn Cate and I proposed a talk on Warehouse Wi-Fi and we were fortunate enough to be selected as one of the main sessions.

Here is how our presentation turned out:

We talked about how it is sometimes required to think outside of the box when designing Wi-Fi for a warehouse.

Do you have any experience working in a warehouse? Did you find any other ways of thinking outside of the box to implement your Wi-Fi design?

PDF version of the presentation: https://d2cpnw0u24fjm4.cloudfront.net/wp-content/uploads/Session-3_-Francois-Verges-Glenn-Cate-The-Wild-Wacky-Weird-World-of-Warehouse-Wi-Fi.pdf
​
All other WLPC presentations: https://www.wlanpros.com/resource/?wpv-category=2018-phoenix&wpv_aux_current_post_id=2623&wpv_view_count=464-TCPID2623

I would like to thank Glenn for giving me the opportunity to work with him.

Thank you!

written by François​ Vergès

This blog article describe the process of upgrading an Aruba controller. It provide a checklist of tasks to perform in order to prepare, perform and validate the software upgrade. You can also download the PDF version of this checklist.

You can get the full detailed procedure in each Aruba OS release notes.

Thank you for reading.

Cheers'


written by François Vergès

This article will explains how to convert a CAPWAP AP to a Cisco Mobility Express AP. The AP model used as an example in this article is a Cisco Aironet 2802i.

Note: if you are planning on doing an AP-on-a-stick site survey with a Cisco Aironet 2800 or 3800, you will have to convert the AP to mobility express first.  Then, read this article on how to configure the mobility express AP for an APoS site survey.
​

The first thing that you will need to do is download the proper software images.

Here are the different software images you will need: 

• The latest AireOS image available for the AP you are using (​Ex: ap3g3-k9w8-tar.153-3.JF1.tar)  (Optional: not required if AP is running v8.3 and up)
• The latest Mobility Express image available for the AP you are using (Ex: AIR-AP2800-K9-ME-8-3-133-0.tar)

Note: If your CAPWAP AP is currently running a AireOS code lower than 8.3, you will need to upgrade to a version 8.3 or higher before converting the AP to Mobility Express.

Use the “show version” command in order to find out which AireOS version your AP is running. In my case, the AP was running version 8.2.151.0:

Here is my setup:

​The AP was powered on by a power injector and was directly connected to my laptop via an ethernet cable. This will be used to establish the network connectivity between the laptop and the AP for the TFTP transfer.
The AirConsole unit was connected to the console port of the AP. This will be used to establish the console connection to the AP for initial configurations.

Here is how I configured my wired NIC on my laptop:

The AP will later be configured with the 192.168.88.10/24 IP address.

But first, we need to connect to the AP using the console connection.
In order to do so, I have to connect to the AirConsole Unit via Bluetooth. I have detailed how I do this on this following article: www.semfionetworks.com/blog/easily-use-airconsole-on-macosx

You should then be able to login into the AP using the default credentials:

• Username: Cisco
  
• Password: Cisco

Note: I like using the logging console disable command as soon as I login in order to keep the log messages away from the console interface. Therefore, they won’t get in my way while I configure the AP and upgrade the software images.

You now can configure the network interface of the AP so it can establish connectivity with your laptop on the 192.168.88.0/24 networks. In order to do so, enter the following command:

• capwap ap ip 192.168.88.10 255.255.255.0 192.168.88.1

You can validate this configuration by using the show ip interface brief command:

You can validate that you have network connectivity with your laptop using ping: ping 192.168.88.1.

At this point, you are ready to upload the new software images and convert the AP.

You will need a TFTP server to transfer these software images to your AP. In my case, I am using the application called  tftpServer on macOS.

Here is what you need to do regarding the TFTP server setup:

• Star the application
  
• Once the application is started, validate that it is listening on the 192.168.88.1 IP address
  
• Validate what is the TFTP root directory (Ex: /private/tftpboot/)
  
• Place the software images that you download in the TFTP root directory

If you want to double check that the TFTP server is up and running and listening on the right port, issue the following command in a terminal session: netstat -an | grep LISTEN | grep .69.

From the console connection, via CLI, enter the following command:
ap-type mobility-express tftp://<IP_TFTP_SERVER>/<IMAGE_FILENAME>

Here is an example: ap-type mobility-express tftp://192.168.88.1/ap3g3-k9w8-tar.153-3.JF1.tar

​The AP will reboot and install the new version.
Once the AP is back up, log back in using the default credentials (Cisco/Cisco) and issue the show version command in order to validate that the new version has been installed:

From the console connection, via CLI, enter the following command:
ap-type mobility-express tftp://<IP_TFTP_SERVER>/<ME_IMAGE_FILENAME>

Here is an example: ap-type mobility-express tftp://192.168.88.1/AIR-AP2800-K9-ME-8-3-133-0.tar

You will now need to reboot the AP in order to install the new code using the following command:
reload

The AP will reboot and install the mobility express version.
Once the AP is back up, log back in using the default credentials (Cisco/Cisco) and issue the show version command in order to validate that the new version has been installed:

You can now see that the Mobility Express code version 8.3.133 has been installed on this AP.
The AP Image type is now MOBILITY EXPRESS IMAGE
The AP Configuration is now MOBILITY EXPRESS CAPABLE

Depending on what you will use this AP for, these following articles will help you configure your Mobility Express AP and controller:

• Configure the AP for an APoS site survey: https://www.semfionetworks.com/blog/configure-a-cisco-mobility-express-ap-for-an-apos-site-survey
• Cisco Wave2 site survey how-to by Sam Clements: https://sc-wifi.com/2017/03/20/cisco-wave2-site-survey-how-to/
• Configure the AP and ME controller for production by Rowell Dionicio: https://www.packet6.com/deploying-cisco-mobility-express/

• Cisco Mobility Express Deployment Guide–Release 8.3.102.0: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_Cisco_Mobility_Express_Deployment_Guide/b_Cisco_Mobility_Express_Deployment_Guide_chapter_010.html

Thank you for reading!

Cheers'



written by François Vergès

This article explains how to configure a Cisco Mobility Express AP for an AP-on-a-Stick site survey using the CLI (Command Line Interface). It is also possible to do it using the provisioning SSID.

Right before configuring the AP for the survey, I had to convert it from the CAPWAP mode to the Mobility Express mode.

​When the AP boots for the first time in the Mobility Express mode, you are presented with a setup wizard. We will use the wizard to configure the following parameters:

• IP address of the Mobility Express management interface: 192.168.88.11/24 (Note: The IP address of the Mobility Express controller has to be different from the AP IP address!!)
• IP address of the gateway: 192.168.88.1
• DHCP server for the Wi-Fi clients: 192.168.88.100-200
• Time
• Host name of the controller: surveyWLC
• Admin credentials: Admin / Cisco123

You will notice that I am not configuring any WLAN profile yet. This will come later.

​Here is how I configured mine (these parameters can be changed to match your environment):

Wait for the AP to reboot. You will be able to login into the controller using the admin username and the Cisco123 password.

When I do AP-on-a-stick site surveys I like to configure the following SSIDs:

• Open SSID called survey24 on the 2.4GHz band only
• Open SSID called survey5 on the 5GHz band only

Here is how you can configure them on the Mobility Express controller via CLI:

I also like to keep control on the channel and transmit power used for the survey on both frequency bands. In this example, we are configuring the 2.4GHz radio on channel 1 with a transmit power level of 4 and the 5GHz radio on channel 36 with a transmit power level of 2.
Use the show config ap 802.11b ap_name and show config ap 802.11a ap_name commands to find out which power level corresponds to which dBm value for your AP.

First, you need to make sure that the AP joined the controller using the show ap summary command. In our case the name of the AP was surveyAP. If the AP didn't join, make sure that you are using different IP addresses for the AP and the Mobility Express controller. Also, check out this article from Packet 6: Troubleshoot AP Joining Issues - Cisco Mobility Express.

Here is how you can configure these radio settings on the Mobility Express controller via CLI:

Now, if you are using a Cisco Aironet 2800 or 3800 series AP, you will not have the 802.11b radio available. Instead, you will configure the 802.11-abgn radio.
If you try to configure the 802.11-abgn radio the same way we configured the 802.11b radio above, you will get the following error:

This is because, by default, the 802.11-abgn radio is set to the auto role.
We need to change the role to manual client-serving in order to be able to configure the custom transmit power. 

Here is how to configure the 802.11-abgn radio:

Once everything is configured, here are a couple of useful show commands that you could use to validate your configurations:

• show ap summary
• show advanced 802.11b summary
• show advanced 802.11-abgn summary
• show advancde 802.11a summary
• show ap config 802.11b ap_name
• show ap config 802.11-abgn ap_name
• show ap config 802.11a ap_name

You should now see both SSIDs being broadcasted by the AP.
As a validation, I try to associate to both SSIDs and wait to receive an IP address.

Here are a few commands that you could use on the Mobility Express controller to validate the client connections:

• show client summary
• show dhcp leases

Don't forget to save your configurations using the save config command.
You are all set!

Here are a few useful and related links:

• Complete guide from Cisco: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_Cisco_Mobility_Express_Deployment_Guide/b_Cisco_Mobility_Express_Deployment_Guide_chapter_01101.pdf
• Mobility Express Command Line Interface document: ​https://www.cisco.com/c/en/us/td/docs/wireless/access_point/mob_exp/83/cmd-ref/me_cr_book.html
• Troubleshoot AP Joining Issues – Cisco Mobility Express: https://www.packet6.com/troubleshoot-ap-joining-issues-cisco-mobility-express/

Thank you for reading. Let me know how you do it!

Cheers'


written by François Vergès

Visiting the IEEE website, we can find the details about the IEEE 802.11 standards and amendments displayed on a table: http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm

In order to put them into perspective, I have displayed them on a timeline. 
As the new amendments and standards are released, this timeline will be updated.

Feel free to download and use the timeline as much as you want. As always, please feel free to share your feedbacks so we can make it better together.

The process made me realize that the 802.11 standard is 20 years old this year!

Click on image to open the PDF version:

Note: the timeline only displays the published amendments and standards. This is why you won't find 802.11ax for now!


written by François Vergès

The Magic Quadrant for the Wired and Wireless LAN Access Infrastructure has been released by Gartner on October 17th:

Just like last year, the same companies have been identified as leaders: Cisco and HPE Aruba. To me, this is no surprising at all, they lead and dominate the market. However, we can note that they are positioned a little closer to the visionaries section than last year.

Talking about the visionaries, we can see that Extreme Networks is clearly catching up and getting closer and closer to the leaders. Gartner has recognized the successful acquisitions made by Extreme over the past few months. If you want to learn more about it, Rowell Dionicio and I recorded a Clear To Send podcast episode about it with Mike Leibovitz from Extreme.

Among the new comers, Mist Systems has been positioned as a visionary by Gartner. I believe this was expected knowing that the startup has been growing at a fast pace over the past couple of years. They also focus heavily on AI and, therefore, I am not surprised to see them as visionaries.

The appearance of Mojo Networks as a new comer is also interesting, I believe. Mojo decided to advocate the open networking standards and is actively part of the Open Commute Project. This has modified their business model and impacted the company in a good way. They also focus on AI and machine learning.

We can also note that Ubiquiti Networks is not included in this Magic Quadrant. Having following their progress on the Uni-Fi brand, I believe that they are offering good products. However, according to Gartner, they “do not currently meet our inclusion criteria, but they can address enterprise access layer connectivity in certain usage scenarios. In some cases, these vendors sell to customers outside the traditional IT organization”. I would be interested to see how the company reacts to this MQ knowing the difficult times that they are experiencing right now.

The trend is clearly around software defined networks, artificial intelligence and machine learning. Gartner believes that more and more automation will happen at the access layer of our networks. Here is their prediction: "By 2022, more than 60% of IT organizations will use access layer network automation, up from less than 5% today."

Earlier this year, the Mobility Field Day 2 outlined this trend with presentations from vendors such as Mist Systems, Mojo Networks, Cape Networks and Nyansa.

I believe that, as Network Engineers, we need to prepare for the future and learn more about network automation, scripting and programming.