Spectrum on 5 GHz getting busy

By | February 3, 2017

In my last few visits to customers I started to notice the spectrum utilization getting higher on 5 GHz. As now we are seeing more devices that work on 5 GHz so planning your channels has become more and more important.

Case 1:

Click share seems to be gaining gain lot of popularity; it’s a solution to present your Laptop to big screens in meeting rooms.

Click Share

The unit is connected behind the TV on the HDMI port and would broadcast the SSID and the USB dongle associated to it. When user connects the USB dongle to the Laptop it uses WLAN to project to the screen.  With just one of this pair working, the utilization was about 13% on the channel on which it was broadcasting.

With the customer I was working with the each floor was about 12,000 sq feet and had 15 such devices in their mix of small/Big meeting rooms on each floor and they had 2 floors.

Now imagine the Management overhead that this would bring to the table, they did not want me to change any configuration on these devices but for now my advice to them was to dedicate a channel or two for these devices and exclude those channels from your Wi-Fi channel plan.

Most of them were seen occupying channel 36@20 MHz but I saw the SSID on other channels as well so at this point I am not even sure if you could configure the device to use a static channel (this is something I would be looking to test, when I get my hands on one of these devices).

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Some more details on the device

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Case 2:

Now some vendors have Wireless TV receivers which also use 5 GHz band on 40 MHz channel width, it would create a SSID of its own.

A TV running all the time in lunch room, the spectral utilization was sitting at 52% on the channel it was broadcasting its SSID on. The meeting room next to the lunch room had the AP on same channel and they were experiencing poor performance.

Again I did not have access to the TV receiver to see if I could statically assign it a channel, for now I moved  AP on the different channel and issue was resolved and asked the customer to keep an eye on the channel, the TV receiver was broadcasting in case it use RRM 🙂 and changes it.

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Some more details on the device

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Case 3:

It’s not always that we will see a neighbor or different device broadcasting on your channels to cause performance issue. This case was of a power user who had a lot going, on his two laptops that were associated to the AP.

Were all his applications work related (well I’ll let their local IT team deal with it) but to identify such user in a poor performance area can help troubleshoot the issue. If for business requirements he needs that kind of throughput, well may be we need to dedicate him with an AP. (As if 1 AP per class room was not an issue that now we will be looking at AP per user).

A monitoring system here can be very useful to better understand the trends; unfortunately this customer did not have it.

When during the survey I saw the Channel utilization close to 90% and on further looking into the controller it was 1 user with his two laptops passing all the data.

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This was the first time I saw the utilization shoot up so high on 5 GHz with 40 MHz channel width

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Recommendation

Ekahau hit a master’s stroke by integrating Spectrum visibility into their great product after launch of 8.5 Version. Now when you do your site survey just add two more DBX cards on you laptop to monitor both the bands. This will give you an advantage to catch any non Wi-Fi interference before your deployment or can be instrumental in troubleshooting any issues post implementation.

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