ITU Contributed by José M. Costa, Acting Chairman, Working Party 5A of ITU’s Radiocommunication Sector (ITU–R)

Next-generation radio technologies will make spectrum use more flexible

A closer look at software-defined radio and cognitive radio systems

With the increasing demand for radio-frequency spectrum, new and emerging technologies are expected to provide more flexibility and improved efficiency to its overall use. Two technologies that could achieve this are software-defined radio and cognitive radio systems. However, these advances do not eliminate the need to continue identifying harmonized spectrum globally, in order to support the high data rate mobile broadband services that are on the horizon.

A software-defined radio (SDR) system is one in which the operating parameters including, but not limited to, frequency range, modulation type or output power, can be set or altered by software. A cognitive radio system (CRS) is one that can sense or be made aware of its operational environment, dynamically and autonomously adjust its radio operating parameters accordingly, and learn from the results of its actions and usage patterns. This not only makes use of the radio-frequency spectrum more efficient, it also helps to avoid interference with other users.

In view of these technical developments and their potential benefits, the World Radiocommunication Conference that took place in Geneva in October–November 2007 (WRC-07) approved an agenda item (1.19) for the next conference in 2011. Under this agenda item, WRC-11 will “consider regulatory measures and their relevance, in order to enable the introduction of software-defined radio and cognitive radio systems, based on the results of ITU–R studies, in accordance with Resolution 956 (WRC-07)”. This resolution asks the ITU Radiocommunication Sector (ITU–R) to carry out specific studies on SDR and CRS.

ITU–R has already been studying such advanced technologies. An important outcome of its work is the report on “Software-defined radio in the land mobile, amateur and amateur satellite services”, published in February 2008. These ITU–R studies have shown that SDR using cognitive control mechanisms is a valuable approach for achieving better spectrum utilization, dynamic spectrum management, and flexible spectrum use.

An ITU seminar examines the issues

Considerable research and development is being carried out by the industry on cognitive radio systems and on related network configurations. In view of this, and the need to start work on agenda item 1.19 for WRC-11, ITU–R held a seminar on 4 February 2008 on software-defined radio and cognitive radio systems. Its aim was to discuss the radiocommunication issues that might be improved through the use of software-defined radio and cognitive radio systems.

ITU/J.M. Ferré Opening the seminar, Valery Timofeev, Director of ITU’s Radiocommunication Bureau, told participants that the new radio technologies are likely to become increasingly important

Opening the seminar, Valery Timofeev, Director of ITU’s Radiocommunication Bureau, told participants that studies concerning Resolution 951 (WRC-07) on “Enhancing the international spectrum regulatory framework” might be lagging behind developments in technology. Thus, he remarked, the topics of the seminar might be even more important for the future than is apparent now.

The seminar looked at the reasons for agenda item 1.19 from the point of view of its main proponents: the Arab States and Europe. This included a discussion of such possibilities as a cognition-supporting pilot channel, use of database information, and the use of white space and dedicated frequency bands in the radio spectrum.

The seminar also heard presentations describing the advanced research being carried out in Canada, Europe and Japan, as well as standardization activities at the Institute of Electrical and Electronics Engineers (IEEE).

One of the four Canadian projects presented uses cognitive radio capabilities to sense unused television channels in the very high frequency and ultra-high-frequency (VHF/UHF) bands, so as to extend broadband access in rural areas with low population densities. The second project explores the use of a coexistence control channel to implement collaborative WiMAX networks, while a third uses a cognitive radio overlay on Wi-Fi in support of improved municipal radio local area network (RLAN) operations, as well as very low-cost backhaul technologies. The fourth Canadian project uses cognitive radio to help manage a mix of multiple input, multiple output (MIMO) and beam-forming techniques to maintain high data rate links.

A presentation was given on the European Commission’s “FP6 E²R Programme”, which was completed recently, and the new “EC FP7 E³ Project” that investigates the concept of a Cognitive Pilot Channel (CPC), among other issues. Another European project, “Urban Planning for Radiocommunications (URC) and Cognitive Radio,” investigates ways to use spectrum in an opportunistic but controlled way (optimized and secured). This includes a network of disseminated sensing to help avoid interference, and the provision of real-time information to regulators on the quality of the spectrum being managed.

In Japan, activities include the development of multi-band and tunable devices (amplifiers, band-pass filters, mixers, and antennas) for the frequency range 400 MHz–6 GHz, including a prototype for cognitive radio.

The IEEE Standards Coordinating Committee 41 (SCC41) is undertaking activities on dynamic spectrum access networks, including tackling some of the challenges of software-defined radio and cognitive radio systems. These include the evolution of global regulations and the development of cooperative relationships among those engaged in standardization.

Market evolution and regulatory challenges

Discussions also focused on how much regulation is required for the new technologies. The need for regulation depends on whether a vertical model or a horizontal model is used. With a vertical model, the operation, functioning and conformity of all hardware and software components of a system are under the responsibility of only one entity. This well-defined responsibility ensures that all the devices will operate within the given regulatory limits. With a horizontal model, many different companies will operate systems using SDR and CRS. Mechanisms will need to be developed to ensure that this does not result in increased interference.

Coexistence scenarios present a difficult regulatory challenge. Two aspects to be considered are the sensing levels for existing radiocommunication systems, which may be different for each frequency segment, and the need to have prior knowledge about systems because some are receive-only. For the cognitive pilot channel, it is very important to authenticate the integrity of users and maintain privacy, in order to prevent unauthorized or malicious users from gaining knowledge of existing systems. It was also pointed out that ownership of the cognitive pilot channel manager needs to be considered carefully, so as to avoid anti-competitive aspects.

Another area of discussion was the contrast between today’s context for operators, including the evolution of ways to assign spectrum, such as auctions, and future business models that will create a new environment for operators and regulators.

If the discussions at the seminar are anything to go by, we can expect stimulating debate on these issues, and more, in the work leading to the World Radiocommunication Conference in 2011.