Steady-State Rate-Optimal Power Adaptation in Energy Harvesting Opportunistic Cognitive Radios with Spectrum Sensing and Channel Estimation Errors
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We consider an uplink cognitive radio (CR) network that can access a wideband spectrum licensed to a primary network, which is divided into non-overlapping narrowband channels. The secondary users (SUs) are equipped with rechargeable batteries of finite capacity that solely powered by energy harvesting from the ambient environment. The SUs which are aware of the available energy in their batteries, sense the activity of the primary transmitter. If the result of spectrum sensing is idle, SUs send pilot symbols to the secondary access point (AP) and AP estimates the secondary channel power. Then, AP feeds back the channel gain to SUs. Knowing the battery state and the feedback information, SUs optimally adapt their transmit power to AP such that the steady-state sum rate of SU-AP link is maximized, subject to average interference constraint (AIC) imposed on the primary receiver and the causality constraint of the batteries. We illustrate the effect of the AIC, energy arrival rate and battery capacity on the steady-state distribution of battery, CR network rate, battery energy outage probability, and transmission outage probability via simulation.
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