Dynamic spectrum sharing (DSS) is set to be an important technology in the operators’ 5G arsenals, because it allows 4G and 5G to run in the same spectrum, resources allocated dynamically according to user requirements.
This could improve the economics of early 5G by enabling MNOs to use their spectrum reserves to the maximum without the long process of refarming; to improve overall coverage and capacity with a combination of LTE and 5G; and even to be able to introduce new base station vendors, and to migrate to Standalone 5G, more easily than with dual connectivity alone.
All the major vendors plan to support DSS from next year, though it makes heavy demands on baseband processing, so may require additional investments in hardware from some operators, as well as the standards-based software upgrade. Ericsson has so far come closest to commercial roll-out of DSS, and scored points over rivals Nokia and Samsung when Verizon indicated it would deploy DSS first in Ericsson-supplied markets (from early 2020), because the Swedish vendor was the most ready.
Verizon has carried out several DSS tests in recent weeks, and the latest was a proof of concept demonstration in Ericsson’s lab in Richardson, Texas, also working with Qualcomm. This PoC involved an over-the-air DSS 5G data call using Ericsson’s Spectrum Sharing solution.
Introducing DSS is particularly important for US operators because they have limited access to midband spectrum such as 3.5 GHz, which provides 5G capacity but with better coverage, and fewer engineering challenges, than the millimeter wave bands in use at Verizon, AT&T and T-Mobile (Sprint is the exception, since it will use some of its 2.5 GHz 4G spectrum for 5G; AT&T and TMO are also planning coverage-oriented deployments in sub-GHz spectrum soon).
With DSS, operators like Verizon will be able to use some of their 4G spectrum in a flexible way to improve 5G performance, without having to adopt rigid refarming processes or switch off legacy networks too quickly. And devices are promised soon, since any handset equipped with Qualcomm’s Snapdragon X55 modem will support DSS.
“We will continue to focus on providing 5G over millimeter wave – especially in high density areas like airports, stadiums and urban areas – in order to continue to deliver the unique experience customers associate with 5G and that are only possible on mmWave technology,” said Adam Koeppe, SVP of network planning at Verizon. “However, with DSS we will be able to supplement mmWave deployments and accelerate the deployment of 5G in low and midband spectrum for customers.”
Another pioneer of DSS is Swisscom, though this operator has very different spectrum holdings, and DSS motivations, from those of Verizon. Its 5G licences are in the 700 MHz, 1400 MHz and 3.5 GHz bands but it could also start to use 4G spectrum in 2.6 GHz or even 800 MHz for flexible signalling. Swisscom’s main driver to adopt DSS is to accelerate the provision of broad 5G coverage, ahead of competitors.