Spectrum 101

Spectrum-101

A tremendous amount of ink has been ‘shed’ over the last 3+ years debating the various technical proposals for LTE operation in unlicensed spectrum (Ruckus has certainly weighed in when we’ve had something worthwhile to say). But maybe it’s time to back up and reexamine why these proposals are so contentious in the first place. And that will take us up to a 100,000- foot view of spectrum – how it is managed and how it is utilized.

Spectrum is managed and allocated by policymakers and/or regulators, with different countries and regions having their own unique approaches. For the sake of illustration, let’s look at the US. In the US, responsibility for spectrum management is given to the National Telecommunications and Information Administration (NTIA) and to the FCC, with the NTIA overseeing federal spectrum usage (for DoD, NASA, etc.) and the FCC overseeing commercial and other non-federal usage. Spectrum allocated by the FCC for commercial uses can further be broken down into licensed and unlicensed categories.

So, this leaves us with a US spectrum management and allocation structure roughly like this:

NTIA

  • Federal Spectrum Uses

FCC

  • Commercial Licensed Uses
    Commercial Unlicensed Uses
    Public Safety, Health, Education Uses (non-Federal)

Not surprisingly, the services that have been developed to use these different types of spectrum have been tightly aligned with a specific category. For instance, over-the-air TV, broadcast radio, cellular and commercial satellite services have made use of dedicated licensed spectrum; while cordless telephones, garage door openers, Bluetooth and Wi-Fi have made use of shared unlicensed spectrum.

This is one reason that proposals to link unlicensed usage with a licensed spectrum holding are hard for some to accept, because, ‘it’s never been done that way before’. But perhaps these proposals are also highlighting one of the limitations such a strict spectrum management regime imposes. And the need to identify additional spectrum for commercial uses is drawing attention to another issue with the current paradigm—some previously allocated bands (especially some allocated for federal use) are very lightly used, or not used at all in many locations.

Which will set us up nicely for a follow on introduction to coordinated shared spectrum (CSS) regimes. These new spectrum management proposals will provide regulators with an option to allocate bands for flexible use, spanning the entire range of needs from federal to commercial (both licensed and unlicensed).

AUTHOR: Dave Wright, Advanced Technologist

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