The European Union (EU) is preparing to start a market for trading the gaps in radio spectrum called white spaces to meet its targets for rural broadband coverage and stimulate mobile services including TV. This will follow the conclusion at the end of 2012 of its COGEU project, which has been defining the technical, business and regulatory requirements for use of white spaces liberated as a result of TV digital switch-over.
A major technical requirement is to develop intelligent cognitive radio systems that take advantage of the favorable propagation characteristics of white spaces whose spectrum, typically in the 500MHz to 800MHz range, has greater range and superior in-home penetration, than say WiFi in the higher-frequency 2.4GHz zone. The regulatory requirement is largely to ensure that emerging white space services comply with trading rules and do not interfere with existing transmissions such as digital terrestrial TV.
Then, the business requirement has been to develop a model for secondary trading, so called because it involves selling on spectrum already acquired by cellular providers and others. Traditionally, spectrum is first partitioned into different use bands and then auctioned off to the highest bidder in what is known as primary trading. Secondary trading allows these primary buyers to retain their allocations but sell them on wholesale to new parties, if necessary changing the use of the spectrum (from mobile telephony to TV, for example) or to some other application such as machine-to-machine communications.
If white space secondary trading takes off and proves successful, it could lead to a reform in the way all spectrum is managed and sold worldwide, at a primary level as well, by providing a framework for effective trading and allocation of spectrum on a per use basis. This could enable spectrum, which is a scarce and finite resource, to be allocated more fairly and efficiently. Such trading could enable new applications (for example, to serve large events such as major concerts that can overload existing cellular services in a given locality). Using secondary-trading technology perfected in the white space arena, spectrum could be made available temporarily in a given location for video and voice services.
But, for the EU, the main immediate target of white-space technology will be rural broadband services. Currently, the EU is halfway towards achieving its goal of ensuring that all citizens have access to super-fast broadband services defined as 30Mb/s or above by 2020, according to a study by broadband specialist research group Point Topic. But, getting such services to the remaining 50-percent more remote locations will prove increasingly hard as the total gets nearer 100 percent. EU states are considering a new version of WiFi operating at these lower frequencies, and therefore enjoying the greater range and building penetration. One option is Microsoft’s WiFi-NC (Narrow Channel), which works by splitting the spectrum into small chunks, and transmitting from an array of small, low-data rate transmitters and receivers. Each of these is assigned to one of the chunks, so broadcasting and receiving in a different, narrow, range of spectrum. They are then effectively multiplexed together to provide the throughput of a normal Wi-Fi radio, but with the ability to switch between white-space frequencies.
Meanwhile, some individual EU member states are taking their own steps towards white spaces. The UK comms and broadcasting regulator Ofcom has published detailed proposals for a framework to allow the allow use of white spaces in that country. Ofcom too is talking about rural broadband and enhanced Wi-Fi as leading candidate applications. Its framework has been designed to ensure that devices do not interfere with existing licensed users of the spectrum, which includes digital terrestrial and wireless microphone users. Ofcom is proposing to allow white space devices to operate without the need for a license, although the government will have to enact new legislation for this to happen.
