A Study on Spectral Efficiency of Physical Layer over Cognitive Radio

Despite the conclusive potential of cognitive radio for provisioning the dynamic and flexible spectrum/channel allocation, the research community should study the performance gain of physical layer over such a radio with cognition capabilities. To this end, several mechanisms of physical layers such as adaptive modulation, multipleinput multiple output antennas; channel coding and/or combination of them should be studied. These studies should be accomplished in terms of spectral efficiency. Therefore, the gain of cognitive radio in wireless networks available into the market will be identified practically. Another issue under consideration should be the performance evaluation of cognitive radio assuming a cross-layer combination between the cognitive physical and the upper layers. To this direction, this paper presents a study on spectral efficiency at the physical layer with cognitive capabilities. In sequel, we study a crosslayer combination of physical layer with upper layers in the same cognitive context. The performance gain of cognitive radio in such a physical layer is realized practically as well as a few cross-layer design issues have been raised.