Reliable cooperative spectrum sensing through multi-bit quantization with presence of multiple primary users in cognitive radio networks

Spectrum sensing is the most important process when cognitive radio (CR) is employed overlay, i.e. that the spectrum is accessed when there is no activity of the primary user (PU). To sense whether the PU is active or not, cooperative spectrum sensing is the most reliable technique where the sensing results of multiple CR users are combined to take a final and global sensing decision. The process of cooperative spectrum sensing is complicated when multiple PU transmitters exist in the vicinity. To reliably sense the activity of all PU users in the vicinity a cooperative spectrum sensing, technique which uses quantized decision combination scheme to have a trade-off between efficiency of spectrum use of hard decision combination and of reliability of soft decision combination, is proposed. The quantized local decisions are combined at the fusion center to take global decisions for all PU transmitters. The performance of the proposed scheme is compared with that of conventional OR rule in terms of detection performance and it is shown that the proposed scheme outperforms the conventional sensing scheme.