Ericsson has filed a Petition for Waiver with the Federal Communications Commission (FCC) to create one radio that will handle two different spectrum bands in the U.S.
The two spectrum bands are both mid-band spectrum: The 3.45-3.55 spectrum, which was recently awarded in Auction 110; and the 3.7-3.98 GHz spectrum, which was awarded in Auction 107. The two bands surround the CBRS spectrum in the 3.55-3.7 GHz band.
Mark Racek, director of spectrum policy with Ericsson, filed the FCC waiver request for the company. Speaking with Fierce, Racek said, “It’s a little bit unusual because in the past every time you would add a band, then you would generate another radio. So you have multiple radios. In this particular case, what Ericsson is trying to do, because of a desire for efficiency is to reduce the number of radios in 3.45 and 3.7 into one radio.”
Asked if there are other similar multi-band radios in the U.S. that have been approved, Racek said, “Not that I know of.”
He said sometimes more than one radio is put in the same enclosure to deal with different bands.
Carrier aggregation
Carriers in the U.S. are already using carrier aggregation, where they combine different channels of spectrum for more capacity. But they have been using two different radios. “The secret to this sauce is it’s a single radio with two modes of operation,” said Racek.
“With this radio, wireless providers that hold licenses in both bands will be able to deploy in these two bands in a cost- and energy-efficient manner,” stated Ericsson in its FCC filing.
“From a network energy standpoint, you don’t have the duplication of the power amp or necessary heat sink flanges,” said Racek.
Cutting two radios down to one would also save a lot of space on towers. “On a tower with multiple radios, trying to find additional room for multiple radios is a difficult thing,” he said. “If you can reduce the size and weight it makes it easier to co-locate this radio with other radios. It’s going to make it faster to deploy equipment.”
Ericsson’s waiver request
The reason Ericsson is asking for a waiver from the FCC relates to out-of-band-energy (OOBE) approvals. Racek said when a radio is transmitting within its band some of the energy falls outside of its band. The FCC has OOBE regulations governing how much energy is allowed to spill in order to control interference with other bands.
Racek explained that when all of the transmitters of the multiband radio are transmitting at the same time, the highest emission level must not exceed the level already set for a single band radio. Ericsson’s proposed radio would comply with this OOBE rule.
“The only relief Ericsson seeks with this waiver request is for when the multiband device transmits in carrier aggregation mode with 3.7 GHz and 3.45 GHz operations, and only with respect to 3.45 GHz service OOBE levels,” states Ericsson’s FCC petition.
In other words, the 3.45 GHz elements of the radio will increase in emissions levels, but when the radio is working in both bands, its combined emissions will not exceed existing regulated levels.
Racek is optimistic the FCC will approve the radio. He said, “We actually provide improvement for interference to the band in between — which is CBRS.”
Ericsson has not yet begun manufacturing any of these radios. It’s waiting for FCC approval. But it has done bench testing on the design prototype.