WiFi Router Channel Bandwidth 3 Options only

[^Tripper^]

Hi folks.

Something I've noticed with my Asus RT-AC87U running Merlin. The router gives me only 3 options for bandwidth on 5GHz;

20
40
80

Isn't there suppose to be a fourth option, 20/40/80?

Thanks!

 

[pege63]

Beamforming: standard-based and universal
256QAM high data rate
20/40/80 MHz bandwidth
So NO support for 80+80/160 MHz bandwidth for your router

 

[RMerlin]

Hi folks.

Something I've noticed with my Asus RT-AC87U running Merlin. The router gives me only 3 options for bandwidth on 5GHz;

20
40
80

Isn't there suppose to be a fourth option, 20/40/80?

Thanks!

Depends on the wireless radio manufacturer. Quantenna is the provider of the 5 GHz radio on the RT-AC87U, and they do not offer the same options as Broadcom.

Anyway, 80 MHz is backward compatible with 40 and 20, I never understood the point in listing a specific 20/40/80 setting.

 

[sfx2000]

Something I've noticed with my Asus RT-AC87U running Merlin. The router gives me only 3 options for bandwidth on 5GHz;

20
40
80

Isn't there suppose to be a fourth option, 20/40/80?

That's a max bandwidth setting - 80 supports 80/40/20, 40 support 40/20, 20 is 20MHz only...

 

[ColinTaylor]

That's a max bandwidth setting - 80 supports 80/40/20, 40 support 40/20, 20 is 20MHz only...

But that's the question though isn't it. What is the difference between the two settings "80" and "20/40/80"?

Just a wild guess but is it something like... when the router powers up, "80" forces it to use 80MHz bandwidth even if some of those channels are in use, whereas "20/40/80" will let it fall-back to lower bandwidths?

 

[sfx2000]

Just a wild guess but is it something like... when the router powers up, "80" forces it to use 80MHz bandwidth even if some of those channels are in use, whereas "20/40/80" will let it fall-back to lower bandwidths?

Study 11ac - and perhaps study the drivers...

Basically it comes down to 11ac being very friendly for backwards compatibility - it's required to support 11a/11n, and while 11ac clients are required to support 80Mhz channels - 11ac does allow for 20/40/80/160 (both 160 and 80+80) for the clients to use when attaching to an 802.11ac AP.

So the 20MHz mode - the control channel is going to define things, obviously... it's still going to use 11ac signalling and modulation schemes...

With 40MHz Mode - you're into a control channel +/-1 - just like 11n - but it's still 11ac

In the setting you quote - it's just the AP saying we support 80 MHz channels, and we'll use it - so the 80/40/20 setting isn't really needed... it's basically the same as us saying we support 80MHz channels.

 

[sfx2000]

Anyway, 80 MHz is backward compatible with 40 and 20, I never understood the point in listing a specific 20/40/80 setting.

Exactly - and believe it or not - the channel width can be and often is dynamic - the control channel is normally fixed, but the supplemental channels - they all need to do a clear air check before jumping in - just like 802.11n in 2.4GHz with Wide Channels.

From a network planning perspective, it's not a bad idea to limit a 11ac AP to 20 or 40MHz - esp if one is in a dense wireless environment with many AP's - think enterprise - where that can be beneficial to reduce interference, but still get some gain from 11ac efficiency over 11n/11a...

 

[^Tripper^]

I see. Seems counter intuitive to have that option on 2.4 and not 5 but the explanations make sense. Thank you all for the clarifications.