The road to 5G

07 Mar 2017

Interference needs new solutions

5G mobile data promises to deliver a world of new services and capabilities, but interference remains an issue which must be solved if networks are to meet performance expectations.

The 5G environment will be so much denser than anything we know today. There will be so much more capacity in a given area through the use of more antennas and small cells.

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A denser environment demands efficient measures and new approaches to mitigating interference, as well as new modulation schemes to improve spectral and power efficiency and minimize out of band interference.

Right now, engineers throughout the industry are working hard on ensuring that the almost ubiquitous transmissions across a multitude of frequencies and billions of devices - many of them mobile - do not interfere with each other.

They are looking beyond the lower frequency spectrum - 700-MHZ and 2.6-GHz - used by most carriers today, and heading towards 6-GHZ and up to 38-GHz and beyond into the extremely high frequency bands known as millimeter wave.

Existing frequency bands below 6-GHz will still be utilized in next generation networks, but 5G will also push the adoption of millimeter-wave bands, some of which is likely to remain unlicensed.

The effective use of these millimeter waves will require newly-developing techniques so that signals can reach user devices without generating too much interference or overly consuming energy resources.

These higher frequencies have the advantage of using beamforming, which instead of broadcasting signals in all directions send them directly to devices, be they mobile or fixed.

Beamforming, which can be described as similar to the way a spotlight illuminates a target, allows for the installation of hundreds of antennas in small spaces, all of them delivering narrow beams with very specific uses and targets.

Working in concert with millimeter-wave and beamforming is MIMO technology (multiple input, multiple output), where equipment can have multiple antennas.

This is likely to create better data rates, spectral and energy efficiency, and become the antithesis of broadcasting. MIMO will improve the capacity and signal quality of a cell.

A combination of MIMO and beamforming together mitigate the signal and path loss typically experienced in higher frequency bands, facilitating access to millimeter-wave frequency ranges which have up until now been considered unsuitable for many mobile applications.

Millimeter-wave has the advantage, in the 5G context, of having a short range and an abrupt drop-off in signal strength. This means they can be deployed in high density scenarios with lower interference between adjacent cells.

Understanding the propagation of millimeter-wave frequencies and how to manage potential radio interference is still something of a work in progress as the industry counts down to 5G.

This article first appeared on Telecom Asia 5G Insights February 2017 Edition


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