Sensing efficiency in cognitive radio networks

In cognitive networks, cognitive radios utilize spectrum sensing technology to avoid interference to primary users. There are two important factors associated with spectrum sensing: detection probability and false alarm probability. The higher the detection probability, the better the primary users are protected. On the other hand, for cognitive radios the lower the false alarm probability, the more transmission opportunities. However, current radio frequency front-ends cannot perform sensing and transmission simultaneously, which means to spend more time for an accurate sensing will decrease the transmission time. Furthermore, due to the activity of primary users may changes during the cognitive transmission period time, increase the transmission period will increase the risk of interfering to primary users. In this paper, the relationship among cognitive sensing period, transmission period and primary activity is analyzed. Specially, we formulate a mathematical model to obtain the optimal sensing time and transmission time with a constraint of interference to primary users. Finally, the numerical results are given for the optimal model.