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5G frequency spectrum forces new look at coverage strategies

New 5G frequency allocations will help make it an amazing technology, but it will also force a rethinking of how those signals are transmitted.

Regardless of the wireless technology in use, the spectrum in which it operates is always one of the most important topics of discussion. Sure, modulation techniques, power levels and security are all interesting, but the most fundamental concern is the frequencies in use. That's because, when we talk about spectrum, we find ourselves at the intersection of science and regulation, and both need to be considered before anything else.

5G is no exception. Let's examine some of the implications of the 5G frequency spectrum the technology will be using.

Uncle Sam makes the rules

In the United States, the Federal Communications Commission (FCC) dictates the law of the land for anything and everything that is capable of transmitting any sort of radio signal -- outside of military and certain other government activities. The FCC provides the regulatory framework that governs everything from amateur radio and AM/FM broadcast to Wi-Fi and cellular technologies.

Companies can't just whip up a communications product and turn it loose on the public. Rather, it all needs to happen within specified power levels and discrete frequency ranges assigned for different technologies and user constituencies.

The FCC's plans for the 5G frequency are detailed here, and what may not be obvious is 5G will play in the same frequency ranges as 4G/LTE (Long Term Evolution), plus some much higher frequencies. That brings us to the science side of the discussion.

Higher doesn't always mean better

As tech consumers, we tend to get conditioned that bigger numbers are better. They mean more speed and throughput, typically. But, when it comes to radio, higher frequencies have a challenge that becomes interesting for 5G.

The higher frequency paradigm also makes things interesting from the IoT device perspective, as there is only so much room for battery and antennas in some gadgetry.

Think about ham radio, even if you've only seen it depicted in movies: Someone speaks into a microphone, and her voice is picked up on the other side of the world. I personally have talked with an Irish ham operator from a dock in upstate New York on less than 5 watts of power, using portable equipment.

Some of what's in play here is wavelength. The lower the frequency, the longer the wavelength, and these longer wavelengths travel farther and penetrate objects more efficiently than something with a higher frequency transmitted at the same level of power.

4G/LTE uses a patchwork of licensed frequencies -- all under 6 GHz. Though its tower-based transmitting framework generally works well, we've all been in buildings that get poor cell coverage, even though those buildings happen to be within the carrier's coverage map.

That's because the building's materials and size can work against the wavelengths and regulation-constrained power of 4G/LTE. These issues will become even more pronounced with 5G frequency, which uses the high-frequency millimeter wave spectrum.

Traditional towers versus new transmitting technology

All the modulation magic, channel widths and other stuff that will make 5G an amazing technology will still be there, but those higher frequencies mean the carriers will have to replace their tower deployments with droves of small cell antennas.

The higher frequency paradigm also makes things interesting from the IoT device perspective, as there is only so much room for battery and antennas in some gadgetry. Whether a simple internal antenna can get the 5G magic out of the device and to the nearest small cell will be interesting to see.

While it's wonderful the FCC and its international counterparts are freeing up 5G frequency spectrum, it's important to realize there is no free lunch. The higher frequencies involved will change the deployment models for cellular in ways that will bear watching but in a framework that may not be as resilient as the old faithful tower strategy.

This was last published in September 2019

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