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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