Most, but not all, of Nokia’s old 4G LTE radios can now be upgraded via software to deliver 5G, the Finnish vendor announced today. This marks the first time the company has released software to upgrade its legacy radio units.

The move also opens a path for operators to upgrade frequency division duplex (FDD) radios to 5G as the industry shifts its attention to reform existing FDD bands to 5G New Radio (NR), according to Nokia.

“More than 80% of Nokia’s Flexi and AirScale FDD installed base is upgradeable to 5G via software,” said Sandro Tavares, global head of mobile networks marketing at Nokia. The vendor claims 359 4G LTE operators have deployed Nokia FDD radios that can be upgraded to 5G with the new software.

Nokia expects at least 1 million 4G LTE radios to be upgraded to 5G shortly, followed by 3.1 million radios by the end of the year, and more than 5 million in 2021.

The scale of the software-only upgrade is significant, noted Chris Nicoll, principal analyst at ACG Research. “5 million radios blunts the opportunity for new equipment to be installed to support 5G, and significantly lowers the cost of delivering 5G services. Cost is a big factor in deploying 5G, but in effect, this brings 5G cost points for the radio access network (RAN) down to 4G levels,” he said.

Most 5G NR deployments thus far have occurred in unpaired spectrum on time division duplex (TDD), but operators will soon benefit from the ability to use different frequencies for uplink and downlink simultaneously on FDD, Tavares explained. TDD systems split apart spectrum channels for the uplink and downlink paths of data and also has a guard band in between the two paths. An FDD system can run the uplink and downlink data paths in the same chunk of spectrum, which allows for more efficient use of the spectrum assets.

“Each band of the 4G and 5G spectrum is defined for either FDD or time division duplex, so the key for this announcement is to make sure that we can refarm 4G FDD spectrum into 5G in the most efficient way,” while reducing the need for site visits, tower climbing, and permitting, Tavares said. Nokia claims the software will save network operators “tens of billions” of dollars.

“Power efficiency of equipment has improved over the past three to five years but not enough to throw away working 4G technology,” Nicoll said. “There may be some other performance improvements with upgraded hardware, but likely not significant enough to warrant replacing working and non-fully depreciated hardware.”

The software release follows a particularly busy and troubling period for Nokia, including last week’s shocking report about Verizon’s plans to end its relationship with Nokia and award Samsung roughly half of its RAN contract going forward. Nokia also recently revealed details about its networking slicing software that will be commercially available later this year as it puts more pieces in place to also putting more pieces in place to at least partially reorient its business model around open RAN.