From owner-freebsd-chat@FreeBSD.ORG Mon Mar 7 02:10:01 2011 Return-Path: Delivered-To: freebsd-chat@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id AED20106566B for ; Mon, 7 Mar 2011 02:10:01 +0000 (UTC) (envelope-from erob@gthcfoundation.org) Received: from relais.videotron.ca (relais.videotron.ca [24.201.245.36]) by mx1.freebsd.org (Postfix) with ESMTP id 7F1808FC0A for ; Mon, 7 Mar 2011 02:10:01 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=ISO-8859-1 Received: from [192.168.0.100] ([184.162.50.38]) by vl-mo-mrz23.ip.videotron.ca (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTP id <0LHO00E040NVD1A0@vl-mo-mrz23.ip.videotron.ca> for freebsd-chat@freebsd.org; Sun, 06 Mar 2011 21:09:31 -0500 (EST) Message-id: <4D743E70.50109@gthcfoundation.org> Date: Sun, 06 Mar 2011 21:09:52 -0500 From: Etienne Robillard Organization: Green Tea Hackers Club User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.16) Gecko/20101227 Icedove/3.0.11 To: Bruce Cran References: <4D73BB23.8020806@gthcfoundation.org> <201103061758.47368.hselasky@c2i.net> <4D73C223.8040009@gthcfoundation.org> <201103061836.39151.hselasky@c2i.net> <4D73F1D2.4000208@gthcfoundation.org> <20110306223910.0000745d@unknown> In-reply-to: <20110306223910.0000745d@unknown> X-Enigmail-Version: 1.0.1 Cc: freebsd-chat@freebsd.org Subject: Re: can somebody explains OFDM in FreeBSD? X-BeenThere: freebsd-chat@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: erob@gthcfoundation.org List-Id: Non technical items related to the community List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Mar 2011 02:10:01 -0000 On 06/03/11 05:39 PM, Bruce Cran wrote: > On Mon, 7 Mar 2011 05:00:42 +0800 > Adrian Chadd 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 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