The FCC this week rejected requests to set aside spectrum for exclusive wireless broadband licenses in the 3650 MHz band. The rejection was part of the commission's Memorandum Opinion and Order (FCC 07-99), which addressed petitions for reconsideration in response to its Report and Order on wireless broadband services in the 3650-3700 MHz spectrum.
"We remain convinced that these provisions will operate together effectively to ensure the goal of efficient spectrum use by multiple licensees in the 3650 MHz band," the FCC said. "Accordingly, we are retaining the non-exclusive licensing scheme for the band."
Under current rules, licensees using the band are required to employ a contention-based protocol in fixed, base and mobile equipment to avoid interference to other devices. The FCC, however, limited operations of certain protocols, such as "restricted" protocols that are capable of avoiding interference only to other co-frequency devices using the same protocol, to the lower 25 MHz of the 3650 MHz band.
"We find that this modification will further reduce the potential for co-channel interference, provide additional protections to the multiple users in the band under the current licensing regime, and create incentives for the rapid development of broadly interoperable contention technologies," the commission said.
While it didn't adopt Part 101 rules as the sole means for coordination of 3650 MHz licenses operating in the exclusion zones established around grandfathered FSS earth stations, the FCC said parties are free to adopt the Part 101 rules or they may prefer to structure their coordination process differently.
The FCC also rejected requests from the Satellite Industry Association to require a carrier-to-noise interference ratio of at least 22 dB for protecting C-Band satellite reception. "We believe this value to be conservative as it incorporates a large protection factor which would essentially limit the level of an interfering signal to approximately 10 dB below the noise floor of a C-band satellite receiver. More specifically, the C/I value consists of two factors, the carrier-noise value, which is the operating margin above the noise floor, and the interference-noise value that is an additional protection level to account for any potential interference that may be received. A typical C/N for C-Band earth stations is 12 dB, which, based on a C/I of 22 dB results in a calculated I/N of -10 dB. We note that an I/N of -10 dB has an effect of raising the noise floor by only 0.4 dB, which only reduces the operating margin for a C-Band satellite receiver by a negligible amount. Thus, use of a more reasonable I/N value further reduces instances where SIA's models predict interference due to out-of-band signals."
The FCC indicated it was sensitive to the concerns SIA raised about the potential for interference to C-Band satellite reception. If a transmitter was placed or proposed for construction near the main beam and within line of sight of a satellite earth station, the commission said it might require greater suppression of the transmitter's out-of-band emissions.
SIA's concerns about overload to C-Band LNAs were also rejected. The FCC noted that C-Band users have been aware the FCC allocated the 3650-3700 MHz band for terrestrial operations since 2000. In dismissing the request, the FCC said, "It appears that, for economic reasons, satellite operators may have chosen not to install the appropriate filters in response to the Commission's 2000 action. If that is the case, we decline at this point to relieve them of the consequences of their business decisions."
The Memorandum Opinion and Order (FCC 07-99)
has more information on the FCC response to the petitions for reconsideration and a copy of the modified rules.