Date: Sun, 6 Mar 2011 10:06:29 -0500 From: Diane Bruce <db@db.net> To: Hans Petter Selasky <hselasky@c2i.net> Cc: freebsd-current@freebsd.org, erob@gthcfoundation.org, bschmidt@freebsd.org Subject: Re: can somebody explains OFDM in FreeBSD? Message-ID: <20110306150629.GA29990@night.db.net> In-Reply-To: <201103061533.32138.hselasky@c2i.net> References: <4D7398C6.8030800@gthcfoundation.org> <201103061533.32138.hselasky@c2i.net>
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On Sun, Mar 06, 2011 at 03:33:32PM +0100, Hans Petter Selasky wrote: > On Sunday 06 March 2011 15:23:02 Etienne Robillard wrote: > > Hi, as the subject line implies, can someone explains why OFDM (Orthogonal > > Frequency Division Multiplexing) is required for running run(4) ? Is there > > any (safer) alternative to OFDM? Orthogonal Frequency Domain Multiplexing (OFDM) Is simply the transmission of multiple carriers in one spectrum. It is used for DSL modems for example. Each carrier contributes a portion of the bandwidth. Coded Orthogonal Frequency Domain Multiplexing is a newer form of OFDM where the signals are coded to minimise interference with other carriers. Look for articles on COFDM Here is one such that looks pretty complete. http://www.andreas-schwope.de/ ASIC_s/Schnittstellen/Data_Lines/body_multiplexing.html This is a nice article as well: http://www.digitalradiotech.co.uk/cofdm.htm > > > > If not, could the FreeBSD security team verify the the safety of OFDM > > derived > > drivers (in particular wireless ethernet based nics) so that no ones get > > hurt being > > a WLAN (802.11ng ethernet-class) subcarrier ? Security is not a problem. COFDM is a hardware level transmission layer 1 and some layer 2. Amusingly OFDM is a form of spread spectrum which originally had military uses, it's harder to jam or decrypt. > > As per my knowledge OFDM is a carrier format which is handled by the hardware. > Is there anything in particular you want to high-light? Yep. I think they are worried about the encryption (WEP vs. WMA etc.). > --HPS - Diane (VA3DB) -- - db@FreeBSD.org db@db.net http://www.db.net/~db
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