FCC details proposals for small cell band in 3.5GHz

US regulator the FCC has issued more details of its proposals to open up the 3.5GHz band for mobile small cells, though these would have to share space with incumbent users, mainly in radar.

FCC chairman Julius Genachowski told a US Senate hearing on Wednesday: "Later today I expect my colleagues and myself to approve 100MHz of spectrum in the 3.5GHz band for broadband." In its 'notice of proposed rulemaking', the agency repeated its enthusiasm for adding this spectrum to its targets for new mobile broadband capacity. The high frequencies are problematic for conventional cellular deployments because they have short range and poor indoor penetration, but provide significant capacity and are well suited to small base stations, many of which are deployed inside.

The FCC note said: "The 3.5GHz band appears to be an ideal band in which to propose small cell deployments and shared spectrum use. Deploying 10 small cells in a location in place of a single macrocell could result in a tenfold increase in capacity."

Under the FCC proposals, priority tiers would be established within the 100MHz of spectrum, for federal and local government use. The incumbent government and satellite users would be in the top tier, and when their applications are using any part of the spectrum, all other users would be offline. The second tier would be reserved for hospitals, utilities, government facilities and public safety agencies, which would be given priority access in specified geographic areas. The third tier would be open to anyone - established operators or other providers - to deploy small cells, which would use the 'spectral gaps' between the public sector services. These firms would use a dynamic spectrum database, similar to the one set up for the white spaces in the TV band, to know when and where frequencies were free for their transmissions.

However, there will be no quick decisions. There will be a long period of comment and response to the recommendations, lasting well into next spring, and the FCC has not set a firm timescale for a final decision.

So far, T-Mobile USA has come out in support of the plan and kicked off a spectrum sharing trial with government users, but the two biggest carriers are concerned at the implications of having to share the band with other operators and with federal incumbents - both the technical complexities, and the prospect of rivals gaining access to broadband capacity at low cost, when they have invested heavily in their own bands.

Grant Seiffert, president of the TIA (Telecommunications Industry Association) commented in a statement: "The FCC's adoption of the NPRM is a commendable and significant step towards addressing the looming spectrum crunch and meeting the national goal of making 500MHz newly available for broadband use within 10 years. After careful and exhaustive planning to avoid harmful interference occurrences within and surrounding it, we believe that the 3.5GHz band could be used advantageously for small cell use, and that more efficient use of this band could help decrease congestion in other bands."