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Re: Larry Page wants "Wi-Fi on Steroids"
From: David Farber <dave () farber net>
Date: Mon, 26 May 2008 18:13:51 -0400
Begin forwarded message:
From: "David P. Reed" <dpreed () reed com> Date: May 26, 2008 1:55:26 PM EDT To: David Farber <dave () farber net> Cc: ip <ip () v2 listbox com> Subject: Re: [IP] Re: Larry Page wants "Wi-Fi on Steroids"
While ducting is an interesting phenomenon, as are other propagation modes, one should be a little cautious about claims of "interference" that rely on analogies from long-range AM or FM broadcast propagation. Neither AM nor FM is a digital modulation technology, neither usesmodern coding techniques. (FM has a bit of a "capture effect" but thatdepends on the particular receiver architecture employed - it's not digitally coded). Superposition of signals that result from "ducting" need not disrupt channels. For example, NTSC TV pictures degrade badly based on noise because so little of the NTSC channel capacity is devoted to picture signal (lots is devoted to retrace pulses and other things). But a comparable digitally encoded picture given the same channel will tolerate a great deal of superposed noise, without any loss of picture quality.When we are talking about "white spaces" it is crucial to understand thesystems design of the system being used. Ducting may or may not be crucial. It may be possible to design around ducting. It may be possible to ensure that ducted signals don't disrupt legacy systems, because the legacy systems are largely of fixed design.Ham radio operators are NOT necessarily experts in information theory or electromagnetic waves. To get a ham license, one merely has to answer aset of multiple-choice questions that are based on cookbook understanding of radio systems that go back 50 years. That said, the converse is not true. Many ham radio operators ARE at the highest end of one or more areas of technology that pertain to radio. So I would suggest that the proper way to understand these issues is to discuss them based on the physics and information theoryand circuit designs that are used in radio systems. Claims of authority from experience with unrelated systems are less valuable when looking atnewly invented technologies (like the best whitespaces work). David Farber wrote:________________________________________ From: ken [Ken () new-isp net] Sent: Saturday, May 24, 2008 12:07 PM To: David Farber Subject: Re: [IP] Larry Page wants "Wi-Fi on Steroids" Dave, As any HAM radio operator will confirm, when you use the lower end of the RF spectrum, a phenomenon known as "ducting" or "skipping" occurs when certain atmospheric conditions occur. http://www.tvtechnology.com/features/On-RF/f-DL-signals.shtmlThis is a phenomenon many of us older folks will recall from childhood,back in the day when all television programming was delivered off-air and television stations used to routinely shut down overnight.Growing up in the Boston area our three television stations used to stop broadcasting early in the evening on weekdays and once in a great while I could enjoy Philadelphia programming, in perfect clarity, since theybroadcast later into the night. The "White Space" band we are about to put into use for broadband is exactly that same slice of spectrum and the same problem is going to occasionally occur, one that will cause incredible difficulty if we look at the potential for interference this will provide. While I support any additional spectrum that might be added to the available bands, this is not what I would consider to be an optimal choice. An alternative suggestion that I would prefer to see implemented, onethat the FCC has shown a willingness to allow, is the spectrum sharing concept. This idea would mandate licensed bands accommodate a "low power underlay" that would regulate output power equal to today's 2.4GHz WiFi equipment. As you are probably aware, many of the licensed bands in the US lay fallow in most, if not all, of this country and even in locations where these bands are currently in use, they are granted a far greater output power than these proposed devices. Naturally, this would make itimpossible for any low power device to cause interference with them. Respectfully, Ken DiPietro/CEO NextGenCommunications Home/Office (301)789-2968 www.NextGenCommunications.net Communications without ConcessionsPS - I would like to give credit to Dewayne Hendricks for pointing this issue out to me. While I was previously aware of the ducting phenomenonI had not thought about the possible issue as it applied to this use. On Sat, 2008-05-24 at 11:17 -0400, David Farber wrote:Why insanity? On May 24, 2008, at 8:42 AM, ken <Ken () new-isp net> wrote:Perhaps Congress can initiate steroid abuse investigations into thisinsanity, as well. Respectfully, Ken DiPietro New-ISP/NextGenCommunications On Sat, 2008-05-24 at 08:00 -0400, David Farber wrote:<http://googlepublicpolicy.blogspot.com/2008/05/larry-page-talks-about-googles-vision.html ------------------------------------------- Archives: http://www.listbox.com/member/archive/247/=now RSS Feed: http://www.listbox.com/member/archive/rss/247/ Powered by Listbox: http://www.listbox.comKen DiPietro/CEO NextGenCommunications Home/Office (301)789-2968 www.NextGenCommunications.net Communications without Concessions ------------------------------------------- Archives: http://www.listbox.com/member/archive/247/=now RSS Feed: http://www.listbox.com/member/archive/rss/247/ Powered by Listbox: http://www.listbox.com
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Current thread:
- Larry Page wants "Wi-Fi on Steroids" David Farber (May 24)
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- Re: Larry Page wants "Wi-Fi on Steroids" David Farber (May 24)
- Re: Larry Page wants "Wi-Fi on Steroids" David Farber (May 26)