When it comes to deploying 5G, spectrum is a key differentiator for operators. And while 24 GHz millimeter wave (mmWave) spectrum is currently being auctioned specifically for 5G, mid-band spectrum will be critical for operators to get widespread 5G coverage across their markets. That’s why a technology called dynamic spectrum sharing (DSS) is so compelling. This technology, which is part of the 3GPP Release 15, allows operators to dynamically allocate some of their existing 4G LTE spectrum to 5G and use existing radios (as long as they are 5G NR-capable) to deliver 5G services by deploying a software upgrade.

DSS was explained to me this way. Without DSS, an operator that has 20 MHz of mid-band spectrum would have to split that spectrum in two. In other words, they would have to allocate 10 MHz of spectrum to 4G LTE and cram all their LTE users into that 10 MHz of spectrum. Then the remaining 10 MHz of AWS spectrum could be used for 5G, even though initially there will only be a minimal number of 5G users. With DSS, an operator doesn’t have to split that mid-band spectrum or have dedicated spectrum for either 4G LTE or 5G. Instead they can share that 20 MHz of spectrum between the two technologies.

DSS is expected to be deployed later this year. European operator Swisscom has said that it will use DSS from Ericsson as part of its 5G deployment. Swisscom said it expects to have 90% of its population covered with 5G by year-end.

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Paul Challoner, vice president of network solutions for Ericsson North America, said that he expects “multiple large customers” to use DSS around the second half of the year. While he noted that Swisscom mentioned using DSS in its recent announcement about its 5G deployment, he said the operator isn’t necessarily going to be the first to use it.

DSS will only work with 5G-ready equipment, so operators that haven’t upgraded their network gear in the past couple of years won’t be able to use DSS. Challoner said that most of the large operators have upgraded their networks with 5G-ready equipment, but he noted that smaller operators may need to look at DSS as an extra incentive to upgrade their networks quickly. “This is a capex friendly way to get to 5G,” he said.

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Analysts I spoke with were hesitant to call DSS a “game-changer,” but they did say that the technology will allow operators to have some flexibility in migrating to 5G. Ed Gubbins, senior analyst with GlobalData, said that the value of DSS really depends upon the operator’s spectrum assets and their 5G rollout plans. Some operators aren’t planning to use overlapping spectrum for 4G and 5G, so they won’t need DSS. He also noted that DSS is really intended to be used by each vendor’s existing 4G customers. In other words, Ericsson customers will likely use Ericsson’s DSS product and Nokia’s customers will use Nokia’s product. The same will occur with Huawei and Samsung, which also offer spectrum sharing solutions.

Steve Scarlett, head of technology for Verizon customer business at Nokia, said that the timing of DSS deployment really depends upon the availability of 5G handsets that have the spectrum sharing capability because existing LTE handsets won’t be able to take advantage of the network upgrade, and operators need to be careful so DSS doesn’t impact existing LTE customers. “There are timing signals in LTE that can’t be messed with,” Scarlett said.

Roaming and More

While DSS will allow operators to expand their 5G coverage areas, experts say the real advantage to having DSS will be when operators start to upgrade their core networks to 5G. When that occurs, which will likely happen in 2020, DSS will play a role in making network slicing possible and allow operators to allocate spectrum for certain use cases.

And Scarlett also said that he believes DSS will eventually be critical for 5G roaming because the spectrum bands where LTE is deployed are already being used globally for LTE roaming. Once 5G becomes more pervasive, operators will need to figure out a way for users to roam and still get the same 5G services.

Some may think DSS is just be another tool in the 5G toolbox, but it certainly seems like a big step forward in how operators can migrate from one generation of technology to another. Having written about every wireless evolution from 2G upward, I find this concept pretty intriguing. I will be watching to see if it works as seamlessly as it was described to me. —Sue