All those new '5G standards'? Here's the science they rely on

Spectrum sharing

Which leads to the discussion of spectrum sharing, something The Register has discussed in the past.

Dutkiewicz's interest in spectrum sharing is to research the cognitive radio techniques that will get the world past the slow and relatively inflexible arrangements that exist today.

Right now, he said, sharing is done on a long timescale: the incumbent leases out the spectrum for “six months, or maybe twelve months, so that the operator has the certainty of having the spectrum for a reasonable length of time.”

That makes spectrum sharing pretty static: it's based on database lookups.

“That's the beginning. What we'd like to be able to do is shorten the timescale as much as possible, so the secondary user can get access … on a very short timescale of seconds, or even milliseconds. That's the ultimate goal of what's called cognitive radio.“

That means the equipment – the handsets and the base stations – need to be able to tell what's going on at any given moment, and that has to be represented in standards.

His group is working on “how to do resource management at the algorithmic level”, Dutkiewicz said. “For that, we need to produce RF maps very accurately and with very little overhead, because before you decide what spectrum to use where, you have to know what's going on.”

That's more complex than it seems at first sight. For example, Dutkiewicz explained, a mobile carrier's base station might be too distant to a primary user's transmitter or receiver to detect it, and might grab the spectrum and cause interference to the primary user.

Hence the reason that handsets might have to be involved in the cognitive radio environment – the handset might see the primary user's interference and report that back to the base station. The base station would then negotiate a different frequency with the handset.

“So we are also looking at putting appropriate hardware interfaces on the mobile handset – how to make the RF front-end more dynamic in terms of looking for spectrum, and responding to changes in spectrum.”

The opposite is also true: the cognitive radio system has to avoid reporting false positives. Otherwise, vacant spectrum might be considered “in use” and unnecessarily left unused.

And all of this needs reasonably high resolution in multiple dimensions: the radio spectrum is one dimension, the dimensions of the spectrum mapping, and the time dimension.

“We need to know a reasonable spatial resolution of the channel state. At the moment we don't have that. LTE is doing rudimentary channels state measurements, but if you move 10 metres to the right, it changes.

“Some people in the literature suggest putting an infrastructure in, consisting of a sensor network, continuously take the information and send it to the base station. Make the base station the central entity that knows what's going on.”

Dutkiewicz suspects that the end goal of a fully automatic, highly responsive cognitive radio system will probably “not be quite met in time for 5G.” The year 2020 is too close: at best, he said, components of this will be ready in time.