Spatial cooperative diversity and asynchronous spectrum sensing for cognitive radio networks

Cognitive radio (CR) has been considered as a frequency-efficient communication scheme to relive scarcity of limited, licensed frequency resources. Spectrum sensing technique in cognitive radio networks firstly detects primary user and opportunistically provides unused frequency to the secondary user. However, the performance of spectrum sensing is often degraded and compromised due to the effects of fading, shadowing, and time-varying natures occurred in typical wireless channel environments. In order to combat multipath fading and enhance the quality of wireless links, we hereby investigate spatial cooperative diversity and spectrum sensing in terms of asynchrony, where the cognitive radio user with high signal-to-noise ratio (SNR) finishes the frequency detection earlier than one with low SNR, and fusion center makes a final decision depending on the local decision earliest made. Our analysis on the cooperative diversity and asynchronous spectrum sensing for CR is followed by the numerical validation with comparison of cooperative diversity and error performances.