The Spectrum Challenge

Imagine you’re a regulator and your job is to find some space in the spectrum map to meet the demand for mobile broadband. Here’s a close approximation of the existing allocation map for the sweet spot between 300 MHz and 3 GHz (click for larger image:)

Here’s a more detailed breakout. The US is in international region 2.

What do you move, where do you move it, and how do you justify your choices?

It seems to me that the hardest question is how we justify the re-arrangement of the map, and to do that we need to establish some basic criteria. One thing that really jumps out at me is the large number of special-purpose allocations that have been made for on an application-by-application basis.

There are a large number of allocations for very narrowly-defined services, such as time signals, meterological aids, aeronautical mobile communication, aeronautical radio navigation, radio navigation satellites, aeronautical telemetering, and a number of satellite services. Do all of these things need to be supported as custom applications, or can a more general-purpose system take their place more efficiently?

The allocation seems to have been made for a two-dimensional world, in that they ignore the fact that some services, say airplanes communicating with satellites while in the air, take place well above the realm of terrestrial radio communications from a radio tower down to the ground. Isn’t it possible to aim radio beams such that planes use the space above 10,000 feet and smartphones use the space below 300 feet? It seems plausible to me.

And what happens when we consider the fact that multiple digital services can use the same frequencies without interfering with each other as long as their encodings don’t collide, the CDMA principle? And can’t we use Spatial Division Multiple Access (SDMA) to create directional tunnels that don’t interfere with each other? Seems to me that we can.

So let’s pretend that the map represents a set of services rather than a specific allocation and devise a scheme for re-packing the services more efficiently in the 300M – 3G spectrum. It should be a fun exercise, and I’m going to ask some spectrum experts to weigh in with their recommendations.

Spread the word and comment. The best suggestions will be recorded in future posts here.