Broadcom Announces 802.11ac SoC

[thetoad30]

Can someone please explain to me the benefit of a switchable 802.11n 2.4GHz and an 802.11ac chip? These are two entirely different technologies in two different bands...

To me, this makes absolutely no sense. If this was a dual-band simultaneous chip, then I'd be raising an eyebrow since you could have your 11n clients on the 2.4GHz band and your high-speed devices on your 11ac band.

Now, can 802.11ac coexist with 802.11n in the 5Ghz band? Me-thinks that's not going to happen, but I'm wondering if it will just downshift to 11n speeds much like 11n downshifts to 11g speeds in the 2.4 GHz band.

 

[thiggins]

11ac is 5 GHz only. So 11n is needed for 2.4 GHz.
Like 11n falls back to 11g and even 11b as signal levels drop, 11ac will fall back too.

 

[thetoad30]

Thank you for the explanation.

So if I'm reading and comprehending correctly, 802.11ac incorporates 11n backwards compatibility in the 5 GHz band, correct?

If so, then yes, this chip now makes a lot of sense. I was initially thinking that 11ac was a completely different way of transferring wireless signals and therefore wouldn't be compatible.

 

[stevech]

I haven't read up on 11ac, but wonder: originally all "WiFi" in 5.8GHz was 802.11a and not 11g. A very few products did 11g in 5.8GHz. More now do 11g/n in 5.8GHz. So I wonder if 11ac requires backward compatibility to 11a/g/n or just some, and which 11n options are mandatory in 11ac.

 

[somms]

I haven't read up on 11ac, but wonder: originally all "WiFi" in 5.8GHz was 802.11a and not 11g. A very few products did 11g in 5.8GHz. More now do 11g/n in 5.8GHz. So I wonder if 11ac requires backward compatibility to 11a/g/n or just some, and which 11n options are mandatory in 11ac.

Broadcom identifies the 802.11a band (4915 thru 5825MHz) for my network as 802.11an. Suppose this would change to 802.11ac if using this new standard?

 

[stevech]

In the US, the unlicensed bands exclude 4.9GHz (That's for public safety). In Japan, 4.9GHz is unlicensed.

In the US, the 5.4GHz band is unlicensed but has onerous low power limits.
The 5.8GHz band in the US and elsewhere is 11a and later.

 

[thiggins]

Probably acn or for dual band abcgn.
Don't worry it will be plenty confusing.

 

[thiggins]

I haven't read up on 11ac, but wonder: originally all "WiFi" in 5.8GHz was 802.11a and not 11g. A very few products did 11g in 5.8GHz. More now do 11g/n in 5.8GHz. So I wonder if 11ac requires backward compatibility to 11a/g/n or just some, and which 11n options are mandatory in 11ac.

802.11ac uses the same building blocks as
11n. The main way it gets higher bandwidth is by using more channels.
That's why it is 5 GHz only. There is not enough spectrum in 2.4

 

[stevech]

what then does 11ac do to improve on 11n when used in 5.8GHz?

 

[thiggins]

what then does 11ac do to improve on 11n when used in 5.8GHz?

Mostly MAC level tweaks I think