Oh, I don't argue against the fact that there is signal present and can interfere with other systems beyond what I consider usable. I was just saying I don't think we're going to be able to efficiently have systems that go 50 miles.
---------- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com -------------------------------------------------- From: "Brian Webster" <[EMAIL PROTECTED]> Sent: Wednesday, November 05, 2008 3:20 PM To: "Tom DeReggi" <[EMAIL PROTECTED]>; "WISPA General List" <wireless@wispa.org> Subject: Re: [WISPA] Theoretical TVWS coverage > That's my point, the noise will be much lower in these bands if things are > deployed in a sane way. Wimax gear has receive sensitivity in the -93 > to -98 > range and from the reports I have heard, works very well at those levels. > While a WISP may be trying to set a network up for max modulation, the FCC > will look at the contour a whitespace station creates in a much different > way. It will be based on the RF energy it creates, not the signal margin > above the receiver threshold needed to achieve the better modulation rate. > If you map a realistic footprint based on a signal level down as low > as -98, that might be closer to the contour they will create in their > geolocation database. This contour will be the one they use to see if you > will encroach on any TV contour or other protected/semi protected users of > the spectrum. The WISP operator will not get to determine the contour > limits > based on their own desired modulation rate. I was saying that you should > be > able to use the -90 number in your mapping to get a more realistic sense > of > where the signal will be going and what size polygon you might have to > deal > with as you register it in a geolocation database. > > Remember, even though you may not agree that a particular signal level is > adequate for your purposes at a certain level, the signal that still > remains > on the air at the lower levels, will be an interfering/undesired signal to > all other systems. The FCC is charged with managing the total signal > emitted, it's affects over distance, and the other users of the spectrum. > They have the big picture to look at, while as a WISP it can be easy to > overlook those other factors. I am not sure what the signal level will be > that the FCC determines must be protected for TV receivers, but whatever > that number is you would be wise to do RF plots that show signal down to > that level. It may not be useable as a data network but it will certainly > be > able to bother TV reception at that level. WISP use of whitespaces will be > a > secondary use to LICENSED users of the band. And homeowners with off air > TV > reception will be considered licensed in this case. That is a different > mindset from what most are used to. It will create the need for different > thinking when planning a network. This is not bad news, just a new and > different way to think about your RF planning. > > > > Thank You, > Brian Webster > > > > > > -----Original Message----- > From: Tom DeReggi [mailto:[EMAIL PROTECTED] > Sent: Wednesday, November 05, 2008 3:41 PM > To: [EMAIL PROTECTED]; WISPA General List > Subject: Re: [WISPA] Theoretical TVWS coverage > > >> I would say that -90 should be a safe signal >> level to use and still have good modulation rates. > > I'm a little confused on that statement. > > With our Aperto live testing a few years back (pre-wimax), the best > modulation we could get was qam16 at the -85 levels. > And that was before considering the 25db SNR required above the noise. > What > good is sensitivity, if the noise ends up being higher than the > sensitivity? > > Sure TV broadcasters shot for -120, but thats one direction broadcasting, > with no expense cut for technology. > > Tom DeReggi > RapidDSL & Wireless, Inc > IntAirNet- Fixed Wireless Broadband > > > ----- Original Message ----- > From: "Brian Webster" <[EMAIL PROTECTED]> > To: "Mike Hammett" <[EMAIL PROTECTED]>; "WISPA General List" > <wireless@wispa.org> > Sent: Wednesday, November 05, 2008 8:46 AM > Subject: Re: [WISPA] Theoretical TVWS coverage > > >> >> Obviously we are still speculating here because the rules are certainly >> not >> clear. With technology development and the results I am hearing from >> those >> who are using WiMax equipment, I would say that -90 should be a safe >> signal >> level to use and still have good modulation rates. To assume TVWS will >> always get full modulation and then try to also claim that it is the most >> cost affective way to reach the low population density areas will be >> difficult. Site footprints have to be looked at lowest modulation rates >> because that RF signal is still out there. It is important to look at how >> far that signal will still be traveling even though you can't achieve >> full >> rates. The transmitted carrier will still be out there as part of the >> contour for your base and must be considered in the process of >> "registration". Your footprint will still be very large even though you >> don't prefer to operate at the slower rates, which for others would be >> "noise". >> >> To design a network with site footprints and spacing to achieve only full >> rates is an inefficient of spectrum because your undesired signal is >> still >> traveling a great distance preventing others from reusing that same >> spectrum. >> >> >> >> Thank You, >> Brian Webster >> >> >> -----Original Message----- >> From: Mike Hammett [mailto:[EMAIL PROTECTED] >> Sent: Wednesday, November 05, 2008 8:29 AM >> To: [EMAIL PROTECTED]; WISPA General List >> Subject: Re: [WISPA] Theoretical TVWS coverage >> >> >> I chose -80 because in current operations, anything less isn't really >> utilizing the available spectrum. I try to engineer all of my links for >> full modulation. Anything less is a waste. I know -80 isn't full >> modulation, but it's not far away. Perhaps with more clean spectrum, >> receivers will be better, but the same was said about 3650 and that >> hasn't >> materialized. >> >> When browsing around on Channel Master's site that one of their DACs >> required -83 to -5 dBm with a SNR of 15 dB to operate. If TVWS devices >> are >> supposed to receive 30 dB below TV, then we should be able to receive >> signals that are -113 dBm. >> >> >> ---------- >> Mike Hammett >> Intelligent Computing Solutions >> http://www.ics-il.com >> >> >> >> -------------------------------------------------- >> From: "Brian Webster" <[EMAIL PROTECTED]> >> Sent: Wednesday, November 05, 2008 7:20 AM >> To: "WISPA General List" <wireless@wispa.org> >> Subject: Re: [WISPA] Theoretical TVWS coverage >> >>> I would imagine you will be able to have receive signals down to >>> almost -95 >>> or -98 dBm. Remember this should be relatively clean spectrum (and >>> hopefully >>> stay that way). According to Sascha the current white space devices that >>> were in testing were supposed to receive signals 30 db below the signal >>> required to receive a DTV signal. >>> >>> >>> >>> Thank You, >>> Brian Webster >>> >>> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >>> Behalf Of Mike Hammett >>> Sent: Wednesday, November 05, 2008 8:12 AM >>> To: WISPA List >>> Subject: [WISPA] Theoretical TVWS coverage >>> >>> >>> Based on TV antenna, it looks like the largest gain CPE will be around >>> 10 >>> dB >>> for all but the lowest of frequencies. >>> >>> I just ran a Radio Mobile coverage area using a guesstimate at a white >>> spaces system... EIRP of 20 dBm, 16 dBi sector, 10 dBi CPE, -80 dBm >>> minimum >>> allowed receive. The range wasn't much more than 2 miles in flat >>> country >>> land. >>> >>> With those same measurements with a 36 dBm EIRP, we have 10 miles, but >>> terrain comes more into play here. >>> >>> For the extreme rural areas, this is where tower height comes into play. >>> For everyone else, this is your foliage beater. In these areas we still >>> need small cells for bandwidth capacity and interference rejection. >>> >>> Remember, the only signal levels mentioned were 40 mw for personal >>> portable >>> devices. Anything else is just speculation at this point. They may >>> very >>> well give fixed stations 4 W as they do in all other unlicensed bands. >>> >>> >>> ---------- >>> Mike Hammett >>> Intelligent Computing Solutions >>> http://www.ics-il.com >>> >>> >>> >>> ------------------------------------------------------------------------- > - >> -- >>> ---- >>> WISPA Wants You! 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