Peter, re: "How can anyone reliably sense whether the devices are being used by valid license holders, (about half of the Part 74 licenses are lapsed ;-) ), or the responsible parties do not enjoy protection?"
Under the picture of multi-dimensional and sometimes unbounded (in certain dimensions) ambiguity painted by just the Part 74 rules you linked to (i.e. forget about sensing challenges under other Part xx rules for now), and not limiting the discussion to just the TVWS range, you're right you can't reliably sense "validity" (if we group unauthorized, expired, and unprotected devices under the one label "invalid"), because "validity" is an administrative attribute, not an electromagnetic attribute. **
"Validity" could be made into an electromagnetic attribute, e.g. a retrofit requirement that all devices subject to Part 74 rules transmit an authentication message, and the absence of such authentication means the device is not valid and its detection should be automatically reported to a database somewhere). However, that would eventually result in forged authentication, and isn't a practical retro-fit requirement considering the affected scale and scope of in-place equipment regardless of forging.
So, "validity" as an administrative attribute lends itself to a database query solution, but I'm not sure it's perfectly reliable either. However it seems it is the most plausible near-ideal in the case of identifying valid devices at fixed locations. But what happens when you add valid mobile devices to the mix? Doesn't sensing provide a second-level "electromagnetic attribute" verification that a database alone is not capable of meeting?
footnote from above:
** Not counting cases of errant transmitters exceeding power or band-edge limits, which is a form of "electromagnetic & administrative invalidity" but you wouldn't try to shout through them and would move on to another channel anyway. Also, in cases where modulation formats are mandated by regulation, if that is being violated, that is also an "electromagnetic & administrative invalidity" but not one that is of top-level importance (I don't think) for determining whether you attempt to share the spectrum. |
