Nº 1 2012 > In brief
Software-defined radio and cognitive radio systems
Chairman, ITUR Working Party 1B
A definition of adaptive systems was introduced into the Radio Regulations more than a decade ago. Adaptive systems are defined as being capable of modifying their parameters, including frequency and power, in order to improve the quality of reception. Today, such systems are limited to the medium and high frequency bands, where propagation conditions vary significantly. Regulatory provisions applicable to adaptive systems prohibit their operation in the bands used by safety services, as well as by the radio astronomy, radiodetermination, amateur and broadcasting services. Further technological developments have increased the capabilities of adaptive systems. Software plays an important role in this respect, making it possible to analyse the radio environment and adjust system characteristics to specific operational situations. Such a combination of radio equipment and software offers new solutions for resolving the problem of frequency congestion and improves the overall efficiency of spectrum use. With these technological advances, two new concepts have emerged: software-defined radio and cognitive radio systems (see box).
A common concern has been the protection of existing services from potential interference caused by software-defined radio and cognitive radio systems. That is why WRC‑12 will consider regulatory measures and their relevance, in order to enable the introduction of software-defined radio and cognitive radio systems, as well as to facilitate, ensure and enhance coexistence and sharing among radiocommunication services, based on the results of ITU–R studies.
Software-defined radio and cognitive radio system technologies are expected to provide additional flexibility and offer improved efficiency to overall spectrum use. These technologies can be combined or deployed independently, and can be implemented in systems of any radiocommunication service. Any system that uses software-defined radio or cognitive radio technologies must operate in accordance with the provisions of the Radio Regulations.
Cognitive radio systems are a field of research activity, and applications are under study and trial. Systems that use some cognitive features have already been deployed, and some administrations are authorizing these systems (for example, dynamic frequency selection and white space devices). These administrations have national equipment approval processes to protect existing services from harmful interference. A radio system implementing cognitive radio technology may, however, have an impact on neighbouring countries and coordination may be needed. Where there are applications in which cognitive radio systems technology is implemented on a non-interference and non-protection basis, the concerned administration should ensure that interference will not actually be generated.
Software-defined radio technology is now operating in some systems and networks in the land and maritime mobile, broadcasting and broadcasting-satellite, fixed and mobile-satellite services. It offers flexibility in radio system design and may help with forward compatibility.
The full implementation of the software-defined radio and cognitive radio systems concept is likely to be realized gradually for a number of reasons, including the current state of the technology. The use of these technologies in some bands may pose specific and unique challenges of a technical or operational nature, which need to be carefully and comprehensively considered by ITU.
“Software-defined radio is a radio transmitter and/or receiver employing a technology that allows the RF operating parameters including, but not limited to, frequency range, modulation type, or output power to be set or altered by software, excluding changes to operating parameters which occur during the normal pre-installed and predetermined operation of a radio according to a system specification or standard.”
“Cognitive radio system is a radio system employing technology that allows the system to obtain knowledge of its operational and geographical environment, established policies and its internal state; to dynamically and autonomously adjust its operational parameters and protocols according to its obtained knowledge in order to achieve predefined objectives; and to learn from the results obtained.”
Source: Report ITU–R SM.2152.