By 2012, there is expected to be about 1.8 billion broadband subscribers globally, with around 1.2 billion on mobile 3G (IMT-2000) networks. The International Telecommunication Union (ITU) estimates that around 700-1200MHz of additional spectrum is needed to handle public mobile-broadband services up to 2020, subject to specific situations and market, meaning that current levels of available radio spectrum need to be doubled or almost tripled.

Radio-frequency spectrum is a limited natural resource and is regarded as a national asset. To coordinate use of spectrum on a global level, the ITU periodically arranges a World Radiocommunication Conference (WRC) to decide on the international regulatory framework. The next conference, WRC-07, is scheduled to take place in Geneva, Switzerland, from October 22 to November 16, 2007, and will consider spectrum allocation and the identification of spectrum for IMT-Advanced (systems beyond 3G) from about 2015 onwards.

Håkan Ohlsén, director, Access Standardization at Group Function Technology, says granting additional spectrum is critical to fulfill future demands for mobile-broadband services and the associated enhancements in the mobile technology area, especially as it can take up to a decade between the spectrum identification and the actual commercial use.

"By 2010, more traffic will be generated by data services than by voice in mobile networks," Ohlsén says. "In some markets, such as Japan, this has already happened, yet until about 2015, the only additional internationally and currently agreed spectrum identified for 3G technologies is the IMT-2000 extension band, being 2500-2690MHz."

Additional spectrum will therefore be harmonized to enable international roaming and generate economies of scale in both devices and network equipment. New spectrum is needed in lower frequencies, such as the 470-862MHz range, to enable cost-effective wide-area coverage, and in higher ones, such as the 2300-2400MHz and the 3400-4200MHz bands, to allow for high-capacity traffic needs in more densely populated areas.

"There is a certain amount of negotiation, and willingness to compromise is necessary at these events," Ohlsén says. "The candidate spectrum bands that are identified as being suitable are of course currently used by other services, such as terrestrial broadcasting TV in the 470-862MHz band, and satellite and radars in the 3400-4200MHz band."

The 2300-2400MHz band has backing from Asia and Africa, and Ohlsén says that, although it has a good chance of being identified, this band will not be enough by itself. "There is support from different countries and regions for the candidate bands, but when it comes to allocating radio spectrum, mobile communications represent a piece of a much bigger puzzle," he says.