Spectrum sensing and data transmission trade-off in cognitive radio under outage constraints

For a cognitive radio, there is a trade-off between time used for spectrum sensing and the achievable throughput. For given constraints on the probability of detection, finding the optimum sensing time that maximises secondary users´ throughput is of great importance. This issue has been addressed previously but the effect of the unknown fading channel was not taken into account. When the fading channel is random and unknown, the constraints on the probability of detection cannot be met for all instantaneous signal-to-noise ratios. Here, a more realistic approach is adopted, which allows the constraint on the probability of detection to be in outage with a specified percentage. The spectrum sensing time/secondary user´s achievable throughput trade-off is then formulated and optimised accordingly.