Where we are now and where we are going

Promise in the air

Cognitive Radio is one of the most talked-about developments in spectrum use for many years. Its early life has been mainly theoretical, bringing predictions that computer code and related advances will revolutionise the approach to spectrum management, bypassing the regulator and enabling the efficient use of large amounts of spectrum that existing users waste. Waste through inefficiencies of design, or the limitations of conventional technology, or the determination of incumbent users to protect what they regard as an exclusive right to their existing spectrum allocation.

But that analysis is a mix of much truth and some misunderstanding. We know how technology advances, and we should expect it to offer us more than just the improvements in physical efficiency of radio transceivers.

Most serious considerations of what Cognitive Radio could offer focus on it overlaying its use on an existing, more conventional environment. Cognitive is therefore seen as a 'secondary' use, coexisting with itself and with the primary service. This means it has to protect the primary service from interference, and cannot expect any regulated protection from it; so it has to arrange its own protection.

The ECC has been actively working since early 2009 to get past the rhetoric and establish some common understanding as a step towards practical regulatory initiatives.

White spaces: an early opportunity?

As in the USA and elsewhere, the ECC's early attention has focused on the use of 'white space devices' (WSD) in the UHF television bands (effectively now 470-790MHz). These frequencies have very useful propagation characteristics, and TV transmitters have large coverage areas and therefore even larger unused areas between them where signals are getting gradually weak enough for the frequency to be reused for more TV reception.

There may also be secondary uses such as Programme Making and Special Events (PMSE) which are there at some times but not others. Figure 1 attempts to illustrate the concept.

This creates opportunities: the lower power applications (PMSE) which use these frequencies already, such as theatre microphones and wireless TV cameras, are usually based on managed databases which identify where the white space opportunities are. This principle of 'geolocation' - with better and more detailed databases, is at the heart of ideas for use of white space spectrum by cognitive devices - cognitive as part of a wider system of management.

The more autonomous element of 'cognitive' behaviour in radio transceivers is 'sensing', i.e. being able to detect what other signals are present and to respond accordingly to reduce the chance of interference. This principle is already used in techniques such as 'listen before talk' (LBT), and the Dynamic Frequency Selection (DFS) used in 5 GHz Radio Local Area Networks (RLANs) to ensure coexistence with radars. This is even used with consumer equipment: one after-market in-car DAB digital radio receiver finds an unused FM radio frequency to use in order to feed its audio into the car's existing FM radio.

“Report 159” - set to become another well-known number?

The ECC set up a Project Team, PT SE43, to look at the compatibility issues between the relevant services using 'white spaces' in the UHF TV bands. After 19 months' work, SE43 delivered ECC Report 159 in January 2011. Its conclusions about the technical and operational requirements of WSDs are not so different from those of the FCC in the US (the FCC has already approved operators of databases for cognitive WSD devices). The report identified a picture of steady development which could open new opportunities, but that the technological breakthroughs needed for a more revolutionary paradigm shift remain for the longer term.

PT SE43 has considered the cognitive techniques of geo-location databases, autonomous sensing and the use of beacons to inform the devices. Most of SE43's efforts considered the appropriateness of geo-location databases and/or autonomous sensing to provide protection to the incumbent services. SE43:

Other ECC activities

The ECC's Regulatory Affairs group, WG RA, has now started work to produce a report complementary to the ECC Report 159. This will focus on different regulatory models for the management of Cognitive Radio databases, in particular:

This comes at a time when some industry players are advocating a more formally licensed environment of cognitive devices in order to achieve a quality of performance which would enable them to offer further mobile broadband capacity. The concept is called 'Authorised Shared Access'.

The ECC's Frequency Management group, WG FM, in February 2011 tasked a Correspondence Group to develop a regulatory framework for using cognitive technology for Programme Making and Special Events, based on Chapter 11 of ECC Report 159.

More to come

The ECC's work is part of a set of developments which represent a large effort to achieve some practical realisations of Cognitive Radio. The IETF (the Internet Engineering Task Force) recently issued a Memo stating that Cognitive Radio and TV white space technology is now in the process of being approved by regulatory bodies around the world. The interface between the white space devices and databases is over the Internet and uses IP connectivity.

You can keep up with the ECC's work on cognitive radio on a special page on our www.cept.org/ecc. Follow the links under 'topics' on the front page. This is a central point to get an overview, and there are also short summaries and links on activity within ETSI, within the EU Research Framework Programme.

Many have questioned the business models which would lead to commercial development of white space devices. And the ECC's work has clearly identified that some aspects of Cognitive Radio can be made reality well before others. But there is little doubt that Cognitive Radio can play a large role, increasing over time, to improve overall spectrum efficiency, and that could have far-reaching economic and social benefits.

Mark Thomas, Director of the ECO, and Stella Lyubchenko
ECO Expert in Spectrum Engineering