Under the initial pdvWireless proposal, the 3x3 broadband swath would have been established at 898-901 MHz, directly adjacent to narrowband PCS spectrum that supports about 15 million sensor devices from Sensus that utilities use to monitor their networks. Sensus officials repeatedly have expressed concerns that proposed LTE activity in the 3x3 MHz swath could create harmful interference for its sensor devices. Although pdvWireless engineering studies contested this assertion, the interference issue was a problem for the FCC.

In the new pdvWireless proposal, the 3x3 MHz broadband swath would be located at 897.6-900.6 MHz, creating a 400 kHz spectral “buffer” of narrowband LMR usage between any LTE system and the Sensus devices. The Sensus devices have operated on spectrum adjacent to LMR operations for years, so the alteration is expected to allay the primary interference concern.

This 400 kHz adjustment also addresses another concern expressed by incumbents, which was that combiners required greater spectral separation than would be available in the proposed retuned 2x2 MHz narrowband spectrum. Under the new proposal, combiners would have airwaves for the desired spectral separation, O’Brien said.

This adjustment is not a new idea—pdvWireless officials considered the alternative years ago, but such a move would have required cooperation from several railroad entities, which were focused on implementing the federal mandate for positive train control (PTC) at the time, O’Brien said.

However, pdvWireless now has an agreement in principle for pdvWireless to exchange spectrum rights to 10 narrowband channels for 6 narrowband channels currently licensed to railroads, which enables the 400 kHz adjustment in the new pdvWireless proposal.

“The lynchpin of the proposal that we filed is a swap with the railroads that opens up a move down of 400 kHz,” O’Brien said. “That eliminates the Sensus issue and adds separation between the top and the bottom for those narrowband guys who want to have multiple channels on a single tower and didn’t feel like the combiners were going to do a good enough job to allow them to operate with that kind of separation.

“So, it’s kind of a win-win-win [situation], and we’re very happy with that aspect of where we now stand.”