Energy-efficient feedback communication based on the S-K scheme in cognitive radio systems

Feedback is very useful in wireless communications. As one of the classic feedback coding schemes, the Schalkwijk-Kailath (S-K) scheme proposed by Schalkwijk and Kailath can approach the Shannon capacity with an error probability decreasing doubly exponentially. In this paper, we introduce S-K coding scheme into the cognitive radio system, where the interference from the primary user inevitably degrades the transmission performance in the case of imperfect sensing. In particular, a slotted sensing-transmission model which incorporates both the energy detection and the feedback transmission based on the S-K scheme is considered. The power consumption and error probability of the S-K coding scheme due to the interference from the primary user are quantitatively analyzed. Based on this, an energy-efficient optimization problem is formulated, which aims to find optimal power allocation between sensing and transmission in order to minimize the total power consumption while simultaneously guaranteeing the sensing and transmission performance. For this optimization problem, a power allocation algorithm is proposed. At last, simulation results verify our analysis and the efficiency of the proposed algorithm.