On September 8 and 9, 2009 the Silicon Flatirons Center convened a closed‐door meeting of legal, economic, technical and regulatory experts in Boulder to explore ways of defining rights and obligations regarding inter‐channel operation that would facilitate investment in radio systems and the resolution of conflicts among rights holders.
Engineers and regulators have traditionally sought to maximize concurrent radio operation by minimizing overlaps in geography, frequency, and time. This event geographical and temporal overlaps to focus on frequency spillovers – often referred to as out‐of‐band or adjacent channel interference – because they are the technical basis for a number of highly publicized cases where traditional approaches for managing interference have not worked well.
The meeting used three US case studies to ground the discussion: 800 MHz rebanding, WCS/SDARS and AWS‐3. Difficulties in the 800 MHz band were due to a conflict between public safety’s right to interference protection and Nextel’s right to operate in the same band using a geographically different network topology. In WCS/SDARS, both parties wanted new rights, using claims of interference as leverage. The AWS‐3 conflict has aspects of both the preceding cases: a lack of clarity over the meaning
of extant rights, and a political tussle over the creation of new rights.
There was consensus that increasing service diversity, flexible license rights, and the shift to mobile and ad hoc operation had brought the industry to an inflection point where past methods of governance were no longer adequate. Attendees felt that properly defined rules and rights could shift some of the coordination burden from regulators to the market.
The participants agreed that interference problems were rooted in boundary conflicts between different technical architectures and/or commercial interests, whether due to changes in the use of a band, unforeseen new operating requirements, or unexpected variances in the ability of receivers to reject interference. However, there was no agreement on whether the problems exemplified in the case studies were due to poorly defined rules or other some cause, e.g. poor governance or commercial self‐interest.
The role of receiver performance in interference was a recurring theme. There was broad support for taking receivers into account more explicitly when drafting rules, for example by regulating resulting signal levels rather than in terms of the customary rules on individual transmitters. However, there was debate about implementation, particularly the difficulties of using models rather than measurement to determine interference.
Attendees agreed that scenarios, explicit or implicit, were unavoidable when crafting rules even though they inevitably encoded assumptions, some of which would turn out to be wrong. There was support for clustering similar services together to limit inter‐channel interference conflicts.
While there was extensive discussion of the institutional frailties of the Federal Communications Commission (FCC), no consensus was reached about the causes or extent of the problem, or whether the FCC should be replaced by the courts as the venue for dispute resolution.