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

Radio professor tells us how wireless will get faster in the real world

Antenna technologies

Antennas are also big in the research. After all, take a look at what's coming: massive MIMO, millimetre-wave technologies, and handsets that might have to deal with base stations communicating at a bunch of different wavelengths.

If your handset looks way too small for more than a couple of antennas, that's probably because you're thinking of handsets operating at (relatively) low frequencies. At 800 MHz, the wavelength is 37 centimetres, and a 1/4-wave antenna is still 9.25 cm long.

At 20 GHz, a quarter wave is a much more tolerable 3.75 mm, and at the 60 GHz favoured by WiGig and other high-frequency standards, a quarter-wave is in the vicinity of 1 mm.

That's physically feasible in quite a small form factor, even if the short propagation range at that frequency means it would be restricted to handoffs to micro-cells.

Interestingly, even at such very close separation between antennas, Dutkiewicz said MIMO techniques still work – with Australian research house CSIRO's Ngara system operating on-campus, there was a chance to test this.

“One of our undergraduate students had a project to measure the impact of antenna separation of MIMO performance at millimetre wavelengths. She found that the impact was not very significant."

“If you're unlucky and make the separation one wavelength, you will be destructively interfering.”

But as long as antennas are separated enough to avoid that, MIMO works even with closely-spaced antennas.

The other problem that 5G poses is that antenna topology is, of course, different according to wavelength. While it's early days, Dutkiewicz told The Register that this is another research priority in the lead-up to 5G: wideband, intelligent, self-configuring antennas.

There's no guarantee that the spectrum your mooted 5G handset needs to use is contiguous (one 20 MHz chunk might be at in the 800 MHz band and the other at the 2.3 GHz band, for an extreme example).

“We would like antennas that can reconfigured themselves fast enough to respond to changes in the primary spectrum – if the channel disappears, the system has to find another channel quickly enough that the user doesn't know it's happening. The antenna and RF front-end have to make that seamless”.

Power consumption

By now, alert readers will have seen the other croc in the duckpond: power consumption. Take another look at the checklist:

  • Faster data transmission means higher power consumption.
  • Higher frequencies mean greater transistor power consumption.
  • Extra functions (such as high-sensitivity channel sensing) means higher power consumption.
  • More antennas mean more radios means higher power consumption.

“You don't want to have your handset burning in your pocket,” Dutkiewicz said – not to mention that nobody wants smartphones with a battery life of ten minutes.

So there will be lots and lots of patents to come out of researchers working out how to do all of this – without needing to attach phones to brick-sized batteries – before 5G becomes the all-gigabit all-the-time reality that engineers are dreaming about. ®

Bootnote: The author thanks Professor Dutkiewicz for his extensive and detailed briefing. Any errors are The Register's own. ®

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