By: Consuelo Azuaje
Future data rate expectations are among the challenges developers have had to face on their trek to 5G (which the ITU dubbed “IMT-2020” in 2015). While attempting to chisel away at this particular obstacle, professionals across the industry have come to favor radio frequencies that sit higher in the spectrum because they possess much greater data capacity on the “mmWave” (>20 Ghz—frequencies). It hasn’t been established which exact radio frequencies that carriers will use, but the march through the radio spectrum—as Ericsson and Nokia have already demonstrated—is definitively upwards. The industry is moving away from the current sub-3 GHz, ultra-high frequency (UHF) norm and into a new 1-100 GHz range which spans both the SHF and EHF radio frequency (RF) spectra. Therefore, a new approach will be needed to allocate radio frequencies, which Ericsson’s CTO, Ulf Ewaldsson, predicts will become as precious and scarce to the tech industry as crude is to the oil industry.
One of the challenges of transitioning to higher frequencies is that they die out over short distances, have trouble penetrating building walls, and cannot go around corners in city blocks. To solve this problem, some have proposed sending radio signals in tight beams, rather than using today's blanket approach which covers “large swaths” of area. Mark Cudak, one of Nokia's principal research scientists, has reported that “highly directional” antennas may be the solution needed to deliver the desired data rate.
Massive Multi-User Multiple Input Multiple Output (MU-MIMO) is expected to deliver Gbps data-rates going forward, and will require the 2-4 antenna elements that are placed at 4G base stations be replaced with hundreds or even thousands of antenna elements. These massive antenna arrays would generate "ultra-narrow beam patterns” that could be precisely directed towards an intended audience and “simultaneously suppress… energy to unintended ones.” Called “precision beamforming,” it's an extremely efficient technique because its highly precise nature precludes interference created by misaimed (and therefore, wasted) radio beams—improving spectral efficiency; also, it boosts signal power by several orders of magnitude by eliminating interference, a factor which would otherwise weaken signal power.
According to Marcus Weldon, CTO and President of Bell Labs, the strategies to realizing 5G can be summed up by three terms: spectrum, spatial efficiency, and spectral efficiency. Let's tackle “spectrum” first: While higher frequencies can't cover the same distance that lower freq's can without dying out, their greater data capacity on the mmWave spectrum make them the natural next step in the transition to 5G. The mmWave-frequencies' shorter lifespans could easily be overcome that by building more base stations and small cells, and by re-using old ones, increasing spatial efficiency, overall. Lastly, network spectral efficiency could be boosted by using new types of waveforms which require neither rigid timing nor strict frequency synchronization. New radio and antenna designs that could up frequency capacity could help, too. For the uninitiated, “waveform” in this context refers to a radio signal's shape as it travels through space. It might seem like a minute detail, but it's a tiny choice that casts a long shadow, and at the end of the day it could greatly increase the data-transfer rate, latency, and energy efficiency across the network.