Energy-efficient transmission strategy for Cognitive Radio systems

Spectrum sensing and compulsory idling are two important functionalities of the overlaid Cognitive Radio (CR) to facilitate the opportunistic spectrum access and incumbent protection for primary user systems. Since both the spectrum sensing and compulsory idling introduce energy-overheads to CR users, it is critical for CR to balance between these additional energy-overheads and its energy consumption for effective data transmission. We thus propose energy-efficient transmission policies for CR that aims at minimizing its total cost (including both energy consumption and delay cost) to deliver a target traffic payload. We formulate this problem as a stochastic shortest path Markov decision process and obtain the optimal rate-adaptation policy via the value iteration. We further propose a low-complexity rate-adaptation policy through the certainty equivalent control with approximation to save computational complexity. Numerical results show the low-complexity policy achieves comparable performance as the optimal policy.