NAB told the FCC in comments filed Feb. 22 that it is “premature” to expand unlicensed access to the 6 GHz band and that easing restrictions would fail to protect licensed operators in the band, including TV broadcasters who use the band for electronic newsgathering (ENG).
The comments address a call from proponents of Remote LAN (RLAN) to relax Low Probability of Interception (LPI) rules to allow client-to-client communications if each C2C device is enabled with an authorizing signal transmitted from an access point.
“NAB has previously explained that ENG receivers are ‘hidden nodes’ because ENG receivers are passive and therefore cannot be detected by unlicensed devices (whether LPI access points or client devices),” NAB said in its comments.
PLUS: NAB: No Evidence for Increasing Unlicensed Power Limits in 6 GHz
The client-to-client proposal would exacerbate the problem because “the enabling access point may be located thousands of feet from a client device and will fail to detect a passive ENG receiver” that could be located near a transmitting client device, it said.
“Under these circumstances, it would be grossly premature to reverse the FCC’s previous conclusions regarding client-to-client communications,” the comments said.
NAB urged the agency to postpone any possible changes until after a record of “practical experience” has been established that demonstrates whether and under what conditions incumbent users experience interference, it said.
However, if the FCC decides to loosen the rules, it should prevent the use of client-to-client devices in a portion of the 6 GHz band to create a safe harbor for ENG operations, NAB said.
In its comments, NAB also told the agency that it should not extend less protection to licensed 6 GHz users than it would for unlicensed operations if it followed recommendations from RLAN proponents.
The laboratory division of the FCC’s Office of Engineering and Technology has specified that LPI access points must detect incumbents using a contention-based protocol (CBP) with a threshold level of -62 dBm/20 MHz, which corresponds to a power density of -75 dBm/MHz, the filing said.
However, RLAN proponents suggest a threshold for client-to-client devices of -99 dBm/MHz. “This is a difference of 24 dB, meaning that the threshold for protection of licensed devices would be over 250 times higher than the detection threshold required for the authorizing signal of client-to-client devices,” the filing said.
Further, the comments argued it is hard to “read this as anything other than a concession” that OET’s energy detection threshold for CBP is “insufficiently sensitive to detect other operations, whether licensed or unlicensed,” the comments said.
“Providing far greater protection to unlicensed devices than licensed devices would turn the entire premise of Part 15 of the commission’s rules on its head,” it said. TVTechnology