Maximum-minimum spatial spectrum detection for cognitive radio using parasitic antenna arrays

The spatial spectrum indicates the energy distribution in all directions. If we can get the spatial spectrum, then the spectrum holes in space are known. In spatial spectrum sensing of cognitive radio, an electronically steerable parasitic antenna receptor (ESPAR) divides the space into sectors which are accessed by directional beamforming on a time division basis. Hence, the energy at different direction can be collected respectively, that is, the spatial spectrum is available. In this paper, we first propose a new sensing method using the ratio of maximum-minimum spatial spectrum. Considering the situation of multiple primary users, we then propose an algorithm extension scheme based on the ratio of average-minimum spatial spectrum. The proposed methods can not only overcome the noise uncertainty problem, but also achieve high performance with low complexity. Theoretical performance analysis of the proposed methods is provided. Simulation results based on Nakagami-m fading channel are presented to verify the efficiency of proposed methods.