The Society of Broadcast Engineers is questioning the entire concept of unlicensed TV band devices (TVBDs, also called white space devices) in its most recent filing with the FCC.
SBE said the availability of "white spaces" in the remaining TV channels below Channel 52 cannot be assumed or quantified. In its filing, "Consolidated Opposition to Petitions for Reconsideration", the association disputes the basis of the rules, stating, "The Commission is prohibited from promulgating rules on the basis of inadequate data. Where the data submitted in the record of a rulemaking proceeding is at substantial odds with the vague conclusion of the Commission that the failed technology nonetheless has somehow 'proven the concept,' the Commission is inviting a remand. The vague conclusion that the tests prove the concept of TVBDs is substantially at variance with the test results, and, in any case, the summary conclusion cannot substitute for a reasoned explanation of the Commission's action."
With regards to the rules' ability to protect licensed services from interference, SBE argues, "the entire concept of enforcement after the fact with Part 15 devices presupposes that the Commission can authorize Part 15 devices with a significant interference potential to licensed radio services. This, it simply cannot do, and the interference potential is exposed by the very studies that the Commission has in the record in this proceeding, in which in an interpretation, (the logic of which is difficult to grasp) it claims proves the 'concept'."
SBE said that "the presumption that TVBD testing has satisfied some unspecified and unquantified 'proof of concept' is premised, in part, by certain technical errors in the proceeding." SBE lists the Commission's errors:
- • Applying the UHF DTV threshold to calculating the required sensitivity for TVBDs operating at VHF high band and VHF low band;
- • Failure to consider the dipole factor as it applies at UHF;
- • Lack of criteria for what constitutes a "professional installation" for fixed TVBDs;
- • Using the horizontal plane azimuth pattern in CDBS for DTV stations, resulting in inaccurate results for DTV stations employing mechanical beam tilt;
- • Invalid assumption of 3 dB of polarization discrimination since a portable TVBD can have any orientation, and
- • Lack of a height limit for portable TVBDs.
After outlining the problems with the current rules regarding the protection of licensed services, SBE requested higher power for both portable and fixed TVBDs, elimination of the wireless microphone sensing requirement, removal of restrictions on the use of TV channels 14-20, removal of protection for cable headends outside a TV station's protected contour and allow TV band spectrum to be used for protected Part 15 back hauls.
In conclusion, the SBE called the FCC's white spaces decision "seriously flawed."
"As the Commission has failed to properly analyze the interference potential from these devices, it is unreasonable to postpone that analysis to the equipment authorization stage on a case-by-case basis, the association said. "Most urgently, the Commission should not adopt the rule relaxations proposed by Adaptrum, PISC, Motorola, FT/SN/COMPTEL/RTG, Dell/Microsoft, WIPA, SCTDV, The Wi-Fi Alliance, and IEEE802. Rather, far more strict provisions to prevent interference to licensed services ex ante, especially for broadcast and broadcast auxiliary operations on television broadcast channels, are required and must be implemented."
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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