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rick merritt
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Weightless aint so light
rick merritt   8/28/2013 4:57:53 PM
You are right David. This will require heavy lifting. How about global regulatory issues? And there are other big powers such as Google pushing for SuperWifi over white spaces.

White spaces are cool and spectrum is indeed scarce, but its not like IoT is hurting for a lack of wirleless options.

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Didn't we already discuss this?
Bert22306   8/28/2013 7:18:33 PM
I think we already discussed the fact that *if* IoT is done wirelessly, *then* this would require a hefty amount of "frequency reuse" to scale at all.

And that the long range prowess of TV frequencies, since that is the feature of TV frequencies that is being touted as particularly useful here, is exactly what you DON'T want, if you need a lot of frequency reuse. For good frequency reuse, you need to create small cells, not cells that can be multiple tens of miles in diameter.

My suggestion is, mentioning TV spectrum "white spaces" because, at least in some parts of the country, they are available spectrum is okay. However mentioning the long range is a counter-argument that blows the whole case.

I did some numbers last time around. The way to improve on my *clearly* unimpressive result was to reduce the range of the RF link. So  to be consistent, it makes more sense to talk about short range use of TV white spaces, e.g. as wireless mikes do, and show just how much of an interference problem the low TV frequencies create, in this scenario. And keep the long range capabilities sort of under the table.

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Re: Didn't we already discuss this?
Bert22306   8/28/2013 7:30:21 PM
Oh, and there's anbother point that keeps getting overlooked. The power levels required for long range (say in the multiple miles) reliable communications, ESPECIALLY for tiny devices with likely tiny antennas, operating in the TV bands, are not going to be low.

This is all easy enough to calculate. If you expect efficient use of the limited TV white space spectrum, where thousands or millions of devices would coexist in a few 6 MHz slices of spectrum, the power will be nowhere near the low milliwatt region. Even if each device doesn't need a lot of b/s of network capacity.

Best to do the numbers, IMO.

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Re: Didn't we already discuss this?
LarryM99   8/28/2013 7:38:36 PM
I agree completely regarding the disadvantages of using frequencies that propagate well. It actually makes more sense to me to work within the ISM spectrum with a P2P protocol that is frequency-agile. This is simpler both in terms of certification and in terms of minimizing interference with critical functionality. This is where most of the ad-hoc networking experiments are taking place anyway.

As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

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