One of the fastest forms of 5G is disrupted by trees

A recent study from NIST shows the extent to which trees interfere with mmWave 5G, the standard's super-fast, range-limited band.
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Francis Scialabba

· 3 min read

Have you ever wondered how trees affect 5G signals? No?

Well, a team of researchers at the National Institute of Standards and Technology (NIST) have. In fact, they spent the better part of a year studying the effects trees might have on 5G millimeter wave (mmWave) propagation, a fancy term that basically means transmission.

The mmWave band is one of the fastest forms of 5G, and the primary force behind 5G’s low-latency, high-data-transfer vision of the future. The catch is that it doesn’t travel very far and can easily be blocked by physical objects, from buildings to trees, limiting its practicality. Currently Verizon leads all US carriers in mmWave 5G availability, but its users only access the high-speed connection on average 0.8% of the time.

While it’s been known for a long time that trees can interfere with a 5G signal, researchers and telcos didn’t have the particulars on how big of a problem our leafy friends could pose.

Now they do: Overall, trees caused an average propagation loss of around 35.3 decibels. If placed in a dense forest, that could translate to a 1,000x less-powerful 5G signal.

That may sound catastrophic, but Nada Golmie, wireless networks division chief at NIST’s Communications Technology Laboratory, told us that the impact depends on proximity to a tower’s signal.

“It depends on where you place your devices, where all the devices are, and how you want to connect them,” Golmie said. “So there is no absolute good or absolute bad.”

Golmie also emphasized that the link budget, or configuration of transmission towers, can be adjusted as needed, feeding more power or connecting more towers to help a signal get through a congested area.

NIST doesn’t spend all of its time measuring transmission signals passing through leaves or speaking for the trees. It sits under the US Department of Commerce, studying everything from facial recognition to nanomaterials, and was founded in 1901, making it one of the nation’s oldest physical science labs.

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On the 5G front, NIST’s prior research covers the effects that non-tree objects like buildings, cars, or even glass might have on the strength of a 5G signal. All these data points can inform telcos trying to determine the optimal location for building new 5G towers. Verizon, T-Mobile, and AT&T didn’t return requests for comment on how they plan to integrate this research into planning the location of forthcoming 5G towers.

NIST also found that the disruptiveness of the trees varied based on both season and species. Interference was generally lower in the winter, when deciduous leaves had fallen, than in the summer when forests are in full bloom. As far as species go, evergreen trees topped the list of least 5G-friendly trees. And, naturally, propagation loss was highest in the most densely foliated areas.

“It’s like if you’re walking through a forest, the denser the forest, the higher the probability of your walking into a tree, right? It’s just like a signal,” Camillo Gentile, electronics engineer in the wireless networks division at NIST’s Communications Technology Laboratory, told Emerging Tech Brew. “Every time it goes around it, then basically it’s subject to a diffraction, what we call loss.”

Zoom out: 5G operates on multiple parts of the spectrum, whether it’s low-band, mid-band C-band goldilocks spectrum, or mmWave high-band spectrum; 5G operators and telcos like Verizon, AT&T, and T-Mobile have competed over C-band, but telcos are trying to balance the desire of mmWave’s high speeds with its inability to travel long distances.

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