On Spectrum Probing in Cognitive Radio Networks: Does Randomization Matter?

In cognitive radio networks, dynamic spectrum access is achieved by allowing secondary users (SUs) to probe the spectrum and utilize available channels opportunistically. Spectrum probing mechanisms should be efficient and fast to avoid harmful interference with primary users (PUs). Periodic probing has been commonly adopted as a default spectrum probing mechanism. In this paper, we attempt to study different spectrum probing mechanisms and evaluate a performance metric called the probing delay, i.e., how quickly a probing mechanism can detect a channel change. We find that randomization in the probing strategy does affect the probing delay. Specifically, in the independent sensing scenario, periodic probing indeed achieves the smallest probing delay. In the cooperative sensing scenario, however, randomization can drastically reduce the probing delay.