AT&T’s 5G Network Gets More Dynamic

AT&T just beat Verizon at getting dynamic. The company announced in a blog post today that it just launched Dynamic Spectrum Sharing (DSS), a new technology that quickly switches between 4G and 5G networks on existing airwaves to optimize speed and coverage.

According to an AT&T spokesperson, “DSS will be available first in parts of our network in North Texas, and as we continue our rollout, we will continue to announce 5G market launches when available. It’s currently available on the LG V60 ThinQ 5G, Samsung Galaxy Note 10 Plus 5G and Samsung Galaxy S20 line, with more devices to follow.”

DSS will let carriers glide more smoothly from 4G to 5G as more of their users buy 5G phones.

“The term “dynamic” in DSS refers to the ability to allocate resources to each technology based on demand,” AT&T’s Igal Elbaz said in the blog post. “This requires that DSS is traffic-aware, and able to respond to changes. The performance of DSS will depend in large part on how frequently traffic demand changes and the granularity of the resource allocations.”

Verizon also plans to use DSS later this year, but hasn’t given a firm date for when it will roll out. T-Mobile has talked down DSS, but also has said it will deploy the technology in the future.

The Samsung Galaxy S20 Ultra will support DSS.

Desperate for DSS

AT&T and Verizon are both desperate for DSS because unlike T-Mobile, both carriers currently lack dedicated mid-band airwaves on which to deliver 5G.

5G networks are generally divided into three groups. Low-band networks have great range, but their speeds aren’t easily distinguished from 4G because the channels available at low frequencies are very narrow. High-band millimeter-wave networks have great speeds, but lousy coverage. Mid-band, from 2-6GHz, is starting to look like the sweet spot. T-Mobile has a lot of it unused, but AT&T and Verizon do not.

The US is making about 300MHz of mid-band spectrum, known as the C-Band, available later this year, and advocates such as 5G Americas are lobbying for another 400MHz to be freed up. But until that happens, AT&T and Verizon largely have to work with the mid-band airwaves they’re already using for 4G.

DSS does that; it “dynamically” switches spectrum between 4G and 5G depending on how heavily a band is being used. The carriers haven’t predicted how DSS will improve performance, but it isn’t likely to initially be by much. That’s because DSS uses 4G channel sizes, which aren’t wide enough for the amazing 5G speeds you hear about. (5G works best in channels of 50MHz or larger; DSS channels will be 20MHz or smaller.)

That said, both AT&T and Verizon could use some 5G help from DSS. For AT&T, it’s about coverage and capacity. Take a look at this map from Allnet Insights, which shows where AT&T could potentially have low-band 5G right now. It doesn’t cover the whole country, and in most places is no larger than 10MHz. DSS lets AT&T fill in the blank spots with its other frequencies, and takes pressure off the low-band channels if they’re clogged.

Here’s AT&T’s presumed maximum low-band coverage (Source: Allnet Insights)

For Verizon, it’s very much about coverage. Verizon’s 5G network right now only covers parts of 35 city centers. DSS will let Verizon claim nationwide coverage based on its 4G network, which it needs to compete with AT&T and T-Mobile right now.

We will continue to follow the carriers’ 5G rollouts on our Race to 5G page.

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