How Is Radio Spectrum Allocated? Dividing Something Nobody Can Fence

Spectrum is coordinated globally through a United Nations agency whose radio arm maintains a table dividing the usable frequencies into bands and assigning each band to services, meaning categories of use such as broadcasting, mobile, aeronautical, maritime, satellite, radio astronomy and amateur. That table is revised at World Radiocommunication Conferences held every few years, where states negotiate changes, and the negotiations are intensely political because moving a band between services can create or destroy industries. The world is divided into three regions with somewhat different allocations reflecting historical use, which is why equipment sold in one region may be illegal in another. Countries then produce national tables that must be consistent with the international one, and coordination between neighbours handles the fact that signals cross borders, with agreements on power limits and frequency coordination along frontiers. Satellite orbital slots and their associated frequencies are registered through the same system on a first-come basis, which has produced a scramble for filings and a persistent complaint from developing countries that the resource was allocated before they could use it.

Within a band, the right to transmit is handed to specific users by one of several methods, each with a different theory behind it:

• •Administrative assignment, where the regulator simply decides, which is how most spectrum was handled historically and how safety and government services are still handled
• •Comparative hearings, where applicants argue their case, which proved slow and susceptible to lobbying
• •Lotteries, tried in the United States for mobile licences and abandoned after winners resold them immediately for large sums
• •Auctions, now the dominant method for commercial bands, which raise revenue and are intended to put spectrum in the hands of those who value it most
• •Licence-exempt bands, where anyone may transmit within technical rules without an individual licence, which is what wireless networking, cordless devices and many sensors use
• •Shared and dynamic access, where a database or sensing system lets secondary users transmit where the primary user is not currently active

Spectrum auctions became a major source of public revenue and occasionally a cautionary tale. The European third-generation mobile auctions around 2000 raised extraordinary sums, with the British and German auctions each producing tens of billions, and the winning operators subsequently struggled under the debt while the services took years to justify the prices, which is a textbook case debated ever since as either a successful transfer of value to the public or a destructive overbid driven by auction design and market exuberance. Auction design itself became a serious field of economic engineering, since the format determines whether bidders can collude implicitly, whether small entrants can win anything and whether packages of licences that are only valuable together can be assembled, and the economists who developed the formats received a Nobel award for the work. Regulators now routinely attach conditions to licences, including coverage obligations requiring a proportion of the population or geography to be served within a set period, which converts part of the price into infrastructure rather than cash.

Demand keeps rising and the supply is fixed, so the recurring question is what to take spectrum away from. Television broadcasting has repeatedly given up bands to mobile services in what is called a digital dividend, made possible because digital transmission fits more channels into less space, and the reallocations required retuning or replacing equipment at public expense. Radio astronomy and satellite Earth observation depend on quiet bands where specific natural emissions occur, and these cannot be moved because the frequencies are set by physics rather than convenience, which has produced sharp disputes when adjacent commercial services leak into them, including a well-documented concern about interference with the water vapour frequencies used in weather forecasting. Military and government holdings are large and historically untouchable, and sharing arrangements are the main route to releasing them. Underneath all of it sits a genuine disagreement about whether spectrum is best treated as property to be traded, as a commons to be shared under technical rules, or as a public resource to be administered, and current policy is an uneasy mixture of all three.

Signals cross borders, so a United Nations agency maintains a global table dividing frequencies among services, revised at conferences where moving a band can make or break industries. Countries then assign the rights by administrative decision, auction or licence exemption. The European third-generation auctions around 2000 raised tens of billions and left operators struggling. Radio astronomy and weather bands cannot be relocated, because physics fixes the frequencies.