Transmission power adaptation for cognitive radios

In cognitive radio (CR) networks, determining the optimal transmission power for the secondary users (SU) is crucial to achieving the goal of maximizing the secondary throughput while protecting the primary users (PU) from service disruption and interference. In this paper, we propose an adaptive transmission power scheme for cognitive terminals opportunistically accessing a primary channel. The PU operates over the channel in an unslotted manner switching activity at random times. The secondary transmitter (STx) adapts its transmission power according to its belief regarding the PU´s state of activity. The objective is to maximize a utility function that is related to the secondary throughput. The function has also a term that penalizes collision with the PU. We quantify and demonstrate, via numerical simulations, the enhanced CR system performance relative to fixed transmission power operation.