Wifi is good when you reach your goal!!

 

I am writing this article regarding my home wifi connection. If you have any question/suggestion or something I am open to hear you. Contact me via LinkedIn or twitter account you can found here in this blog


Recently one of my colleagues brought me one 2504 WLC for lab/home use. Thanks to him!

Also I had some 3702i APs bought from eBay for lab purposes.

Thus, I changed my home wifi setup with cisco devices.


Let’s start with my internet connection. My home internet connection is 120 Down 20 Up and I have no any further internal infrastructure. Saying this to explain that the maximum internet speed I need (via wireless) is to reach my connection limit. ßThe goal

 

! Configuration

I have statically configured the channel width to 40MHz. I am in cisco local mode, transmit power and channels are managed by RRM.


! Monitoring

As we can see from client view of the cisco WLC, my client is 1ss capable, and my connection speed is 200Mbps.





By looking the mcs table we can see that I am reaching the highest data rate available in 1 SS at 40MHz




Running a speed test from the specific mobile I can see that I am able to reach this speed.



! Conclusion

I have reached my goal!! 

 

Some considerations 

Why 40MHz ?

Firstly, I set the width at 20MHz.

When I looked mcs I saw that the maximum data rate I could have was 87 (It’s obvious that we will fail here!!) For testing I configured the WLC and verified that also



By running the speed test again I saw that the limit was my wifi connection!!




Why not 80MHz?


According to mcs with 1ss  at 80MHz we have maximum speed of 433Mbps.

See below client view from wlc. My phone is connected at maximum speed.



Lets now perform the speed test again.



We can see that we have almost the same results. We don’t have any benefit of using 80MHz in this scenario, as the limit is my home internet connection and not my wifi settings.


Yes, but why not 80MHz even I don’t have any benefit? 


Attending many wireless courses like Ekahau ECSE Design, CWNP courses many online presentations, Books, CCNP Enterprise, Cisco live presentations, some years of experience and many APs deployed I know that

è SNR drives the data rate!

è Every time we are doubling the width -> +3DB penalty (to maintain the same modulation/coding)


*As a note, from my experience many times I had complains from customers regarding disconnections etc. Its almost every time that RRM kind of algorithms set the width at 80MHz. I don’t know why. The developers know that!!  Anyway, when was statically configuring the channels in enterprises mainly or 40 or 20 (it depends) I had better reviews from clients. If anyone faced this and have more info please share it.

Maybe the reasons I wrote above? Maybe interference due to the use of all the spectrum??

Below some nice resources

https://www.reddit.com/r/HomeNetworking/comments/p5jgu7/why_does_doubling_wifi_channel_width_result_in_3/h96fom1/

https://www.duckware.com/tech/wifi-in-the-us.html#SNR

http://wifinigel.blogspot.com/2018/02/noise-floor-penalty-of-wider-channels.html

https://www.mist.com/power-spectral-density/

https://www.wirelesstrainingsolutions.com/understanding-ofdm-part-4-refresh/


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