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Open spectrum explained for the laity

2
Jerry KindallPerson was signed in when posted
11-11-2002
04:59 PM ET (US)
 Another big problem is that a protocol that could address a lot of these issues, CDMA, is currently patented by Qualcomm. (CDMA lets a lot of transmitters operate on the same frequency without interference.)
1
cypherpunksPerson was signed in when posted
11-10-2002
08:38 PM ET (US)
 It sounds good in theory, but it seems to me that there's a problem in practice.

You need to have agreement on the protocols in order to use a chunk of spectrum in this way. And the problem is, there might be a large number of different protocols that people want to use or experiment with. But they can't all share the same spectrum, because each protocol is using certain conventions which will be incompatible. So we need a way of assigning spectrum to protocols.

On the net, we have packets going around each other successfully, because they all use the IP protocol at the bottom. Then, above that, we use port numbers and other fields to separate out the different protocols.

But with radio, it's not going to be that simple. There is no equivalent of the IP protocol which is so perfect that it can be a universal low-level protocol that all frequencies follow. Different applications will require different conventions and protocols, especially as you move into smarter use of the frequencies. Smartness will only work well if everyone is following the rules. But the rules needed for different smartness protocols will vary.

It's not too hard to find a new port number on the net to use for your new protocol. You can usually find one that other people aren't using. But how will this work with radio? Suppose people want to make a low-power opportunistic mesh network like the one discussed yesterday on slashdot, where they dropped nodes from an airplane and they all hooked up with each other to detect vehicle traffic? They used 990 MHz, which is fine out in the desert, but overcrowded in the cities. This application needs its own frequency band. And so will many others.

It's easy to sit back and call for open spectrum and virtual parks. That's the big picture. But once you get into the details, there's a difficult political question of how you get people to cooperate in the protocols which are necessary for smart messaging to emerge, and which body will set aside certain frequency bands for certain types of smart radio experiments.
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