Ali Panahandeh, Ir  

Following the emergence of new wireless communication networks in recent years, it becomes more and more difficult to release new frequency bands for new communication systems. However, if we observe the effective use of theses frequency bands, we realize that there is a real under-utilization of these resources. The Cognitive Radios are communication systems that reuse the unused resources at a given time by the primary service users, to establish their communications, without interfering theses existing services. In this project the polarization of electromagnetic waves is used, first of all to increase the reliability of detection of a primary user within a frequency band and so decrease the interferences with the primary network, and secondly as a new dimension of communication other than the frequency to communicate within the secondary network. The objectives of this research program are thus : 1-To define a dynamic model of polarization in the context of Cognitive networks. This objective includes an experimental part of channel measurement and modeling of its stationary properties. 2-To develop spectrum sensing methods for the multi-polar case. 3-To model the heterogeneous channel, formed by the superposition of the primary and secondary network and to deduce from it, communication techniques that use the polarization as a new dimension of communication within the secondary network.