Energy-Efficient Adaptive Rate Control for Streaming Media Transmission Over Cognitive Radio

In future mobile computing systems, cognitive radio (CR) emerges as a promising solution for alleviating spectrum shortage and satisfying the high bandwidth demand of multimedia streaming, while it presents tough challenges in provisioning user experience-perceived quality of service (QoS) and conserving transmission energy. In this paper, an adaptive rate control (ARC) scheme with the aid of the receive buffer is presented for energy-efficient transmission of streaming media over CR with QoS guarantee. The QoS metric, either display smoothness or transmission delay, is quantified by the state of the receive buffer. Cross-layer information is utilized to form a closed-loop feedback optimal control. A novel analytical model called event-driven discrete-time Markov control process is introduced to formulate the QoS-guaranteed energy-efficient ARC problem. Based on potential theory, a policy iteration algorithm that combines potentials estimation and stochastic approximation is proposed for finding the optimal policy online. By exploiting the system dynamics, this algorithm does not depend on any prior knowledge of channel availability or fading statistics, and it can converge to the global optimum with a low computational cost and reasonable speed. Simulation results demonstrate the effectiveness of the proposed method.