can somebody explains OFDM in FreeBSD?

[Etienne Robillard]

On 06/03/11 05:39 PM, Bruce Cran wrote:
> On Mon, 7 Mar 2011 05:00:42 +0800
> Adrian Chadd <adrian at freebsd.org> wrote:
>
>   
>> FreeBSD doesn't implement OFDM in the kernel.
>>
>> The various chipsets implement OFDM, not FreeBSD.
>>
>> There's no "software" OFDM. The 802.11 chipsets out there take care
>> of it, not FreeBSD.
>>     
> [moved to freebsd-chat]
>
> OFDM doesn't exist in the digital domain. The furthest you can go in
> software is to use the I-Q pairs that represent the modulated (baseband)
> data - that is, QPSK, BPSK, QAM etc. If you have a card that makes I-Q
> data accessible (and I suspect most wireless cards don't) then you can
> demodulate it using general-purpose software such as Matlab or a DSP
> library.
>
>   
you don't need to make the transformations at the digital domain: only
time domain
is really what you need in a pure sinusoidal function so you could
compute the reverse
using sin-1. Therefore no need to go further than the OFDM layer where a
custom CPU
(the kernel) could 'capture' the raw 802.11 data stream and modulate an
invert current
according to this variable bitrate in Mb/s. 
 

-- 
Etienne Robillard

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