single channel architecture

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  • Updated 3 years ago
Hi guys, I would like to ask for opinions with regards to Single Channel Architecture, especially on the 2.4 Ghz channels? I happen to frequently deploy in territories where unfortunately, 2.4ghz is pretty predominant.
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Johnny Loh

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Posted 3 years ago

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BJ, Champ

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Hello Johnny, 
Our warehouse environments are still full of b/g clients on 2.4 GHz. What kind of opinions are you looking for? 

Best,
BJ
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Johnny Loh

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Hi BJ,

As I have not come across a deployment that uses Single Channel Architecture (SCA), I need to deploy wifi in a high density environment, I am concerned that putting too many APs with 2.4 radios. I am under the impression that if I were to use the (SCA) I could avert issues like stickiness and stuff. Also since 2.4ghz channels are highly congested anyway, it seems that SCA poses more advantages than a typical multichannel Architecture (MCA)
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Nick Lowe, Official Rep

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Consider that the Wi-Fi capacity is limited by channel, NOT by the radios in APs or other parts of them. You will nearly always run out of channel capacity long before AP capacity.

If you have 2 radios in 2 APs and they can see each other above the CCA (Clear Channel Assessment) threshold, you have the capacity of only 1 radio in 1 AP. It is all about frequency reuse.

Wi-Fi is contention based. Adding an extra AP for more radios when there are already multiple radios in different APs on same channel does not add capacity.

A properly designed MCA deployment in the 2.4 GHz space will, as a rule of thumb, offer around three times the aggregate capacity with a 20 MHz channel width, 3 channel plan (1, 6, 11) over a SCA deployment.

It is possible to use what Meru call channel layering where they run in those three 2.4 GHz channels, but you would need 3 times the number of 2.4 GHz radios to achieve similar capacity. There is a real expense incurred doing this and there are inherent interference concerns, it is like a MCA at this point only with more CCI.

Without that channel layering, you would exacerbate any pre-existing congestion and interference problems at 2.4 GHz by crunching everything down in to a single 20 MHz space.

You could easily hit, in both cases, greater issues with CCC (Co-Channel Contention) and CCI (Co-Channel Interference).

There are well established techniques available, even if not effective 100% of the time, to mitigate sticky clients with MCA deployments.

Most Wi-Fi professionals that I am aware of emphatically prefer to deploy with a MCA, and also to get clients using 5 GHz where possible for capacity and reliability reasons regardless.

I vehemently disagree that a SCA offers more advantages than a MCA, it is quite the opposite. You want to serve your client base as a whole with more spectrum rather than less spectrum.
(Edited)
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Paulo Quizora

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Brilliant explanation Nick! 
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Paulo Quizora

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Hi Johnny 


I came across multiple discussions re SCA but most of them from Meru Networks (now Fortinet). You might want to check the following links. 

http://blog.merunetworks.com/blog/2013/08/single-channel-architecture-sca-and-wfd5-lets-discuss/

https://www.youtube.com/watch?v=j_7IBx4Hhsw


Goodluck!