CSMAC Report Calls for Phase Out of ‘Dumb’ Unlicensed Devices

First among the committee’s recommendations is that NTIA put in place requirements, in cooperation with the FCC, “that reduce reliance on post-hoc regulatory enforcement of interference by turning to technology-based solutions for ‘connected devices,'” the report said. “NTIA, in coordination with the FCC, also should proactively educate policymakers concerning the secondary status of unlicensed devices in shared bands and the obligation of consumers and manufacturers to accept interference."

The subcommittee sought more review of regulatory treatment of “cheap, dumb” devices, such as garage door openers. “The Committee generally recommends that in the future ‘unconnected’ devices should be restricted to legacy bands of spectrum where they are already prevalent (e.g., 900 MHz, 2.4 GHz),” the report said. “Policymakers should consider whether such devices should even be further restricted in the future, phasing out their access to very high-quality bands over an appropriate time period."

The subcommittee suggested taking consumers out of the “loop” for mitigating interference when problems occur. “The vast majority of sharing opportunities are likely to involve devices that are inherently connected to the Internet in some way, or at least capable of connecting,” the report said. “Once we assume that interesting future cases will involve connected devices, it becomes easier to put the heaviest burden of mitigation on manufacturers, where the expertise to understand the issues exists. For example, certification might require that a device reauthorize itself by contacting its manufacturer over the network every so often (e.g., once per week). Failure to do this (allowing reasonable margin for network outages) would, by rule, require the device to disable sharing sensitive spectrum until such reauthorization can be done.” In cases where non-compliant devices are “knowingly not operating within the rules to prevent interference, or when ‘avoidance through technology’ measures fail, NTIA should consider recommending that the FCC strengthen enforcement measures to provide better deterrents, so that interference mitigation may be addressed more proactively than reactively,” the report said.

"There aren’t any perfect answers” to how to address interference from devices, Obuchowski said. “But we would strongly recommend that the bands in which they operate be circumscribed, closed out in essence, to historic bands.” More intelligent devices “are at a price point that we think enforcement through technology is the better course,” she said. Obuchowski said the “onus” should be on the FCC to make sure that interference issues are addressed quickly through a shot clock of some kind. “It is absolutely useless to have an interference problem and wait for weeks if months to get that resolved,” she said. “There’s also, basically, almost uniform belief that the FCC is going to have to upgrade its monitoring capability."

"Perhaps the only thing that could be done, and we hope it could be more effective, is for NTIA, with the FCC, to more proactively educate policymakers concerning the secondary status of unlicensed devices,” said Michael Calabrese of the New America Foundation, the subcommittee’s other co-chairman. “That means that when the calls from the garage door opener people start coming in to congressional offices, that shouldn’t be the first time that those telecom [aides] are hearing that garage-door openers actually work on federal bands."

CSMAC also approved a recommendation that NTIA initially focus its data accuracy and clean-up effort on the fast-track and priority spectrum bands under review for near-term repurposing to wireless broadband use. These bands include: 1675-1710 MHz, 1755-1850 MHz, 3500-3650 MHz, 4200-4220 MHz and 4380-4400 MHz. The CSMAC meeting was still underway at our deadline.

NTIA also released as part of the CSMAC meeting a document responding to recommendations made in November 2010 by CSMAC’s Interference and Dynamic Access Subcommittee. Among the recommendations was that guardbands continue to have a role in mitigating the effects of out-of-band emissions (OOBE) and adjacent channel interference.

"NTIA agrees that given the practical limitations on transmitter and receiver filter technology, the use of guardbands to protect adjacent band receivers will continue for the foreseeable future,” the agency said in its formal response (http://xrl.us/bnh2g6). “However, spectrum managers and system implementers should seek to minimize the amount of spectrum used in guardbands. OOBE limits can be an effective method of protecting adjacent band receivers.” Getting OOBE limits right is difficult, NTIA conceded. “OOBE limits that are too stringent can place unnecessary cost and operational constraints on a transmitter, while limits that are too relaxed will not adequately protect adjacent band receivers,” the agency said. “The OOBE level will depend on the operational scenario(s) under consideration for the transmitter and receiver (e.g., fixed-to fixed, fixed-to-mobile, mobile-to-mobile) which dictates technical factors such as minimum separation distance, propagation modeling, antenna coupling, and the receiver interference protection criteria."

The subcommittee suggested the guardband be the responsibility of the new entrant. NTIA agreed in principle. “However, this approach could be difficult to implement, especially in situations where the new entrant expects access to the boundary of the licensed spectrum, for example when they obtain spectrum through an auction process,” the agency said. “NTIA believes other approaches should be considered before relying on guardbands which essentially mean vacant spectrum. For example, interference may be avoided by filtering some locations or changing locations. Furthermore, it seems reasonable to ask the new entrant to bear the responsibility only if adjacent band receivers meet minimum performance requirements.” The subcommittee recommended the use of “virtual” guardbands that make use of dynamic spectrum access techniques. “This recommendation does not provide enough information for NTIA to assess how ‘virtual guardbands’ can be used in addressing adjacent band interference,” the agency’s response said.

The subcommittee recommended that the government move forward on “a complete spectrum inventory to assist all future spectrum coordination efforts.” NTIA agreed, but “is not free to release the records of the Government Master File,” the agency said. “Efforts by NTIA at producing an inventory have focused on producing readable descriptions of agency operations by band, similar to presentations in Spectrum Resource Assessment previously prepared by NTIA,” it said. “Still NTIA will need to seek the support of the agencies to release information about their operations.”