An impressive number of broadcasters, engineers, manufacturers and organizations, and the National Association of Broadcasters (NAB) sent a letter to the FCC jointly urging "the Commission to authorize quickly use of Distributed Transmission techniques" in DTV broadcast operations. The FCC asked for comments on Distributed Transmission in its Notice of Proposed Rulemaking (NPRM) in the second periodic review of the DTV conversion. The letter requested the FCC authorize Distributed Transmission in a Report and Order, expected to be released soon, to address some of the issues raised in this NPRM.
The letter listed the advantages of using Distributed Transmission for DTV. These include "(1) more uniform and higher level signals can be distributed over a wider area while causing less interference to neighboring operations, (2) gaps in coverage caused by terrain can be filled in, and (3) a variety of natural and man-made phenomena that inhibit reception of DTV signals in numerous situations can be overcome." The letter also noted that Distributed Transmission uses spectrum more efficiently because interference to outside service areas is reduced compared to using higher-powered transmitters on tall towers.
Adoption of the ATSC Distributed Transmission Standard, and a Recommended Practice for implementing it is expected sometime this summer. The May 12, 2004 version of ATSC Candidate Standard CS110C - Synchronization Standard for Distributed Transmission can be downloaded from the ATSC web site.
The letter concludes, "Distributed Transmission technology holds great promise to enable broadcasters to use their assigned channels more efficiently while improving service to the public. Because the Commission can modify its rules to enable broadcasters to pursue these benefits while ensuring that no additional interference will be created beyond what its rules already allow, the undersigned organizations submit that the authorization of Distributed Transmission technology is decidedly in the public interest and respectfully request that the Commission authorize the routine licensing of Distributed Transmission systems in its forthcoming Report and Order."
For information on how Distributed Transmission works, refer to my RF Technology columns, Single Frequency Networks for DTV Part 1 and Minimizing Delays In Single Frequency Networks.
