Foreword - cognitive radio: from equipment to networks

Cognitive radio is a technology that is of growing interest internationally. Currently, there is a highly active worldwide community of academic and industrial researchers working in this field. Efforts focus on the many technical questions as well as the economic and political challenges of moving this new technology from research concept to reality [1, 2]. Cognitive radio holds much promise not just in the military domain but increasingly in the civil and commercial domain. The boom of wireless commercial markets started in the early 1990s and has resulted in an ever-increasing demand for wireless connectivity and greater capacity to facilitate the variety of data applications in daily use. In the world of mobile communications, UMTS/3G networks are part of the response to that demand. The birth of 3G services served to highlight the demand for spectrum with recordbreaking prices paid for the 3G bands in many countries in Europe. The management of 3G spectrum and indeed management of spectrum in general has lead to much discussion and debate—in general, there is a strong belief that the perceived scarcity of spectrum is very much related to how it is managed. Crucially in this debate, cognitive radio is seen as a technology that can facilitate new and more dynamic ways of providing access to spectrum and addressing the scarcity problem. It is time to reconsider the century-old paradigm of fixed dedicated frequency allocations. But it is hard to change habits of tens of years. However, we already see evidence of change. The Federal Communications Commission (FCC) in the USA has been working since 2001 on software-defined radio [3] in which the operating parameters of frequency range, modulation type, or maximum output power (either radiated or conducted) can be altered by making a change in software that controls the operation of the device without making any changes in the hardware components that affect the radio frequency emissions. In 2002, the FCC maintained that authorizing more flexible spectrum uses promises both immediate and future innovations without consuming additional spectrum resources [4], opening the door to cognitive radio. On 4 November 2008, the FCC voted 5–0 to approve the unlicensed use of white space (there are five FCC commissioners). This was followed by the release of what is known as a SecondReport and Order, ETDocket no. 04-186 and ET Docket no. 02-380, which detail the rules under which unlicensed devices could use the TV white spaces. The rules provide for the operation of both fixed and portable unlicensed devices in the TV bands. As cognitive radio is seen as a key player in the use of TV white space, this has served to further open the door for cognitive radio. Even in Japan where spectrum is fully controlled by the government, there is a large demand to move to a more dynamic spectrum management and national research projects regarding the cognitive radio technology is ongoing [5]. In the UK, the regulator Ofcom has also made encouraging remarks. In fact, as December 2007, Ofcom proposed to C. Moy (*) SUPELEC/IETR, Rennes, France e-mail: [email protected]