Korea Telecom executives say a 5G network using 28-GHz spectrum requires four times as many outdoor cell sites as does a 4G Long Term Evolution network using low band spectrum. And that is good news, not bad news.
It is good news because it is completely in line with the traditional rule of thumb about cell geometry: reducing the cell radius by 50 percent quadruples the number of cell sites.
In other words, a 5G network that is more dense might not cause any greater increase in required cell sites than any other reduction of cell radii by 50 percent.
And that seems to be the case whether it is 3.5-GHz or 28-GHz spectrum that underpins the densification effort.
Dr. Won-Yeol Lee, director of the 5G access team at KT’s Infra Lab, says it took 4.6 times the number of LTE sites that KT had in the Olympic coverage area to provide 5G outdoor coverage.
KT had the Olympic venues covered with 46 LTE sites, but it took 212 sites to provide equivalent 5G outdoor coverage, he said. To some, that might be alarming.
For network engineers who have conducted densification efforts in the past, the math is consistent with any resizing of cells that makes the coverage radius 50 percent smaller.
That requires some context. Traditionally, the two big tools for increasing network capacity were to acquire new spectrum or shrink cell sizes. The 5G network will require some mix of both approaches, which implies the possibility of higher spending on spectrum, and perhaps an increase in network capex (though that is evolving, and might not actually require more capital, even as the number of cells quadruples).
Apparently, there was not a big difference between coverage geometry using 3.5-GHz or 28-GHz frequencies, which many of us might say is a clear and perhaps unexpected benefit.
One might have expected that 3.5-GHz signals would propagate significantly further than 28-GHz signals.
Still, Lee characterized the infrastructure and spectrum costs as “extremely high.” That might, or might not, be the case in all other markets.
Some other mobile operators, including Verizon, might not agree that deployment costs (facilities and spectrum) will prove unmanageable.
