Alternating Renewal Framework for Estimation in Spectrum Sensing Policy and Proactive Spectrum Handoff

In wireless communication, radio spectrum is a resource. Dynamic spectrum access or cognitive radio is a viable method to increase spectrum utilization. The unlicensed users access the unused portion of radio spectrum opportunistically. The unlicensed users must vacate the spectrum as soon as the licensed users appear on the channel. Since, the licensed users or Primary Users (PUs) have paid licensing fees for the spectrum, the unlicensed users or Secondary Users (SUs) must not cause interference to PU transmissions. In order that SUs can continue to operate, they must find another spectrum hole on another channel and switch to that channel. These so called, spectrum sensing and spectrum handoff, are the basic foundations of CR technology. We model the random channel as an ON-OFF process and applied renewal theory to build a framework to observe the PU activity. Then from the observations, we estimate the likelihood of PU arrival to perform spectrum handoff. We then propose a spectrum access decision making policy based on the spectrum handoff time. We then numerically evaluate our proposal and make comparisons.