- FCC indicated is now reviewing 1,700 comments before making its next decision.
- NextNav argued that channel hopping will enable Part 15 devices to continue operation in the presence of 5G transmissions over the lower 900 MHz band.
With the doors now closed on the comments and responses period for NextNav’s petition to access the lower 900 MHz band, the FCC is considering its next step. The responses include Virginia-based NextNav’s final appeal against arguments opposing the rule change.
The filing from the communications technology company requested new rulemaking by the FCC in April. In response, the commission invited comments from industry and the public in August, over the following 30 days, followed by a two week period of responses which ended Sept. 20.
An FCC spokesperson said the federal agency is reviewing “the extensive public comments—over 1,700 comments—in the record before deciding any next steps.”
Accessing a Crowded Bandwidth
NextNav’s argument to the FCC is that the bandwidth could be used for location mapping and tracking services such as enhanced 911 (E911) communications, which enable first responders to view location information during emergencies.
The bandwidth in question— 902-928 MHz—has been home to UHF RFID. Other technologies such as medical devices, smart home equipment like baby monitors and cordless phones, tolling solutions, and LoRa systems leverage this frequency band under the same unlicensed parameters.
However, manufacturers of such Part 15 devices are not protected against interference from other users and must be designed to handle interference with techniques such as frequency hopping. If approved, the change would provide priority to the NextNav systems over other devices.
That alarms some of those in the RFID industry and they have been sending their objections to the FCC. The comments have been coming from a broad set of constituents, mostly arguing that the change being requested would interfere with the technology they are using. Tech companies and end-users, industry groups and hobbyists have weighed in on a variety of objections. Last week, NextNav posted its response to those comments in defense of its petition.
Objections from RAIN and AIM
RAIN Alliance CEO Aileen Ryan warned if NextNav’s re-allocation bid for the bandwidth succeeds, it would impact the reliability and functionality of RFID, ultimately affecting “the resilience and efficiency of America’s supply chains, businesses and government agencies.” And because the technology is used as part of global supply chains, “the impact would be felt worldwide,” she added.
The power levels that NextNav proposes using would cause such notable interference that it would render RAIN RFID operation impossible, Ryan warned.
“All those that rely on RAIN RFID devices in the U.S.—across many critical applications in a broad range of industries—would be in danger of being blocked, with this disruption resulting in significant negative socio-economic outcomes,” she said.
NextNav Counters Interference Arguments
As the response period ended, NextNav’s CEO Mariam Sorond issued a public statement Sept. 20, that stated in part that “we are pleased the FCC leadership and expert staff can begin to evaluate NextNav’s proposal, which is the only actionable plan to meet the urgent need for a widescale terrestrial PNT solution at no cost to taxpayers.”
It will, Sorond said “expand the promise of the lower 900 MHz band to unleash 15 MHz for 5G broadband spectrum while preserving numerous coexistence possibilities.”
Just how well NexNav’s terrestrial GPS and additional 5G systems would coexist with RFID and other technologies is a key point of disagreement. If the NextNav petition was awarded, the proposed changes could have damaging impacts on RFID deployments in the U.S., according to industry standards organizations RAIN Alliance and AIM Global in a joint statement.
NextNav Points to Power Hopping
NextNav officials dispute that position, arguing that because UHF RFID technology operates across multiple channels within the 902 to 928 megahertz band there is still the opportunity for the technology to hop to another channel if there is interference.
In some implementations, NextNav reasons, if there is interference to an RFID system from a 5G transmission, a reader could respond by retrying transmission on other channels. Or the reader can use more robust reader modes to mitigate the interference.
For this reason, NextNav maintains claims from companies like Boeing that this interference could make its RFID system inoperable are unrealistic. The company says the devices can hop across the band to find an unoccupied channel.
The company further argues that review by the RAIN Alliance and AIM used flawed analysis as to interference that could be caused by a 5G signal to a RAIN RFID device. NextNav “finds the level of interference projected to be extremely unlikely.”
Questioning Analysis
In their argument against the RFID industry objections, NextNav focused on the methods for simulating an interference event. “The analysis makes several highly atypical assumptions about 5G deployment scenarios which uniformly produce an increase in the resulting levels of interference,” the company stated in their rebuttal.
They point to problems in the analysis such as an assumption of tower height for base stations at 100 meters which is taller than most 5G base stations. They argue that the analysis understated the signal level of RFID transmissions as well.
Additionally, NextNav targeted arguments from Z-Wave Alliance, stating that Z-Wave also has mechanisms in place for coexistence with other systems such as 5G as well. The Alarm Industry Communication Committee (AICC) argued to the FCC that “NextNav’s proposed high power operations, with standard out-of-band emissions limits and unlimited interconnection rights, would create a direct risk of harmful interference and channel crowding to the low power Z-Wave alarm devices that help to protect millions of homes and small businesses.”
The FCC has not given a timeline for when a decision will be made.