What's the status of 802.11AC support?

Pontus Karlsson pontusjoncarlsson at gmail.com
Tue Aug 5 09:09:37 EDT 2014




On 5 Aug 2014 at 14:37:15, Arend van Spriel (arend at broadcom.com) wrote:

On 08/05/14 10:56, Pontus Karlsson wrote: 
> Hi Arend, and thanks a bunch for the configuration! 
> 
> As far as I understand it, the higher speeds of 11ac is dependent on 
> both modes operating simultaneously 
> and in cooperation. Is this correct? 

Not sure what you mean by modes, but I tend to say no here. 
It appears this was a misinterpretation from my part, as I said I am very fresh with wireless networking
and the details that it revolves around.

When I read about the specifications for several different adapters I was under the impression that
for example adapters advertising themselves as 1750Mbps max rate in their specifications meant
that they would work under 2.4Ghz and 5Ghz simultaneously to combine a maximumd rate of
1750Mbps. Now however after I’ve read a bit further I realize that the max rate is merely the max rate
of their 2.4Ghz mode and 5Ghz, but not at the same time. So for 1750 that means a max of 1.3Gbps for
the 5Ghz and 450Mbps for the 2.4Ghz mode.



> You’re saying that all my STAs needs to be 11ac compatible, but one of 
> the main reasons I’m switching to 11ac is due to 
> the vary of different clients that connects to our network, there’s even 
> a few 802.11g clients (cellphones mainly). 
> According to different sources and specifications 11ac is supposed to be 
> compatible with both a/b/g/n/ac, 
> I suppose this is due to it’s operation on both modes as well? 

For the higher speeds your STAs should be 11ac compatible. Upon 
connecting the capbilities are negotiated. 

> I’m curious, what speeds do you measure with that setup, and with what 
> chipset / NIC? 

Not a question to ask me. I am biased as my employer is a wireless 
vendor :-p 
Ah I see that now. But then perhaps you could answer me this;

The ASUS PCE-AC68 features the Broadcom BCM4709 chipset. One of the features they brag with is the
Broadcom TurboQAM feature, which supposedly would combine the 2.4Ghz data rate with the 5Ghz data rate
providing an “AC1900”-adapter. Does this mean that there’s two separate radios? I know it’s dual band, but doesn’t
say whether i can use them simultaneously or not.



Regards, 
Arend 

> 
> On 5 Aug 2014 at 10:10:10, Arend van Spriel (arend at broadcom.com 
> <mailto:arend at broadcom.com>) wrote: 
> 
>> On 08/05/14 06:53, Pontus Karlsson wrote: 
>> > I’m considering upgrading my WiFi NIC in my router and need to know, 
>> > if I were to get an ASUS PCE-AC68 
>> > (http://www.asus.com/us/Networking/PCEAC68/>> > What could I expect from this running hostapd in terms of speed and 
>> > reliability? 
>>>> > Bare in mind I’m very fresh when it comes to hostapd, I usually end up 
>> > with a simple configuration 
>> > that partially works for my needs and stick with that for a few years. 
>>>> > As far as I understand it, 802.11AC in order to achieve higher speeds it 
>> > needs to operate in both 
>> > 2.4Ghz mode and 5Ghz mode simultaneously. Does this work properly in 
>> > hostapd? 
>> 
>> Hi Pontus, 
>> 
>> The higher speeds in 11ac are depending on bandwidth doing 80MHz and 
>> higher and some more stuff that falls under the term MCS. Anyway, 11ac 
>> is only available in 5GHz. Probably stating the obvious but both AP and 
>> STA clients must be 11ac capable. Attached is a sample config I used. It 
>> is a bit tricky. The channel indicates the operating channel. I used 
>> channel 36 and for 11ac you have to specify the center frequency using 
>> vht_oper_centr_freq_seg0_idx, which is 42 in my case for 80MHz bandwidth 
>> (vht_oper_chwidth=1). If I am not mistaken vht_oper_centr_freq_seg1_idx 
>> is only used for 80+80 bandwidth. 
>> 
>> Regards, 
>> Arend 

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