Sensing techniques for Cognitive Radio - State of the art and trends

Rapport, 2009

This document was initiated in the framework of the IEEE Standards Coordinating Committee 411 (Dynamic Spectrum Access Networks) within the 1900.6 Working group (Spectrum Sensing Interfaces and Data Structures for Dynamic Spectrum Access and other Advanced Radio Communication Systems). This documents aims at identifying the spectrum sensing techniques being used of researched and that may be considered for the 1900.6 standardization activities. Although it gathers State of the Art material, this document does not aim at being a scientific paper in that regard that the equations are not always justified or demonstrated. However, it provides sufficient information to have a good perspective on the problems to solve, the techniques that have been proposed and the one that may emerge in the next few years. Links to a wide bibliography section is systematically provided to enable the reader to get more technical details. Since 1900.6 deals with Spectrum Sensing, the focus is put on this issue in this paper. Section 3 deals with single sensor spectrum sensing. In this section, the level of a priori knowledge about the signal to detect is discussed and different techniques are presented according to this parameter. Section 4 is somehow an extension of section 3 in which the problem is extended to the identification of systems in presence through the estimation of key specific parameters. The example of OFDM signal is highlighted for which sub-carrier spacing one of the parameters considered to differentiate the standards. Section 5 extends the scope of section 3 by considering several sensors. Cooperative sensing and collaborative sensing are discussed in this section. Section 6 briefly discussed the estimation of the load of a system. This information may be a determining parameter to decide on the network to get connected to. Section 7 provides application examples of the spectrum sensing techniques described previously in scenarios involving standardized wireless systems. Performance of the techniques is discussed. Section 8 reminds that a cognitive radio often has to sense information that is not captured by spectrum sensing. For instance, battery lifetime may be relevant for decision making in battery operated devices.