Date: Sun, 06 Mar 2011 20:07:29 -0500 From: Etienne Robillard <erob@gthcfoundation.org> To: Bruce Cran <bruce@cran.org.uk> Cc: Adrian Chadd <adrian@freebsd.org>, freebsd-chat@freebsd.org, Hans Petter Selasky <hselasky@c2i.net> Subject: Re: can somebody explains OFDM in FreeBSD? Message-ID: <4D742FD1.3080706@gthcfoundation.org> In-Reply-To: <20110306223910.0000745d@unknown> References: <4D73BB23.8020806@gthcfoundation.org> <201103061758.47368.hselasky@c2i.net> <4D73C223.8040009@gthcfoundation.org> <201103061836.39151.hselasky@c2i.net> <4D73F1D2.4000208@gthcfoundation.org> <AANLkTikopx8kmjQGgkaG%2BzE5P8GXehJdQaj462hBr6nn@mail.gmail.com> <20110306223910.0000745d@unknown>
next in thread | previous in thread | raw e-mail | index | archive | help
On 06/03/11 05:39 PM, Bruce Cran wrote: > On Mon, 7 Mar 2011 05:00:42 +0800 > Adrian Chadd <adrian@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. > > Not sure I'm following well but thanks for the pointer. If a OFDM chipset have the required hardware to demodulate high frequency waves into the corresponding 802.11 layer using hardware interrupts, then it should also be possible to inverse the modulated data back into an electric current one way or another using the very same hardware and inverse DFT function as explained here: http://www.digitalradiotech.co.uk/cofdm.htm -- Etienne Robillard Company: Green Tea Hackers Club Occupation: Software Developer (and CEO) E-mail: erob@gthcfoundation.org Work phone: 450-936-2123 Website (Company): https://gthc.org/ Website (Blog): https://gthc.org/blog/ PGP public key fingerprint: F2A9 32EA 8E7C 460F 1728 A1A7 649C 7F17 A086 DDEC During times of universal deceit, telling the truth becomes a revolutionary act. -- George Orwell If a free society cannot help the many who are poor, it cannot save the few who are rich. -- John F. Kennedy
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4D742FD1.3080706>