Resource Allocation Scheme for Cognitive Radio System Based on COFDM Signaling Considering Secondary User's Channel Uncertainty

摘要

One of the most important challenges in cognitive radio (CR) system is its robustness against primary user jamming problem. Anti-jamming coding mechanism and distributing power properly among subcarriers has been introduced to overcome this problem. In order to increase system performance and secondary network reliability, radio environment information has to be present for designing CR system. In this paper, the erasure probability (Pr_(e,i)) for the secondary user receiver is used to select idle subcarriers and to determine the code rate to make a reliable link to transfer secondary user's data. An adaptive coding rate with a proper bit distribution can decrease the negative impacts of primary user's activity, which may be performed better than employing an unpredictable LT code. Furthermore, a multi-level water-filling algorithm is proposed to assign subcarriers' power in coded orthogonal frequency division multiplexing-based CR system. In this algorithm, the interference channel gain is used as a maximum power mask. Simulation results show that the proposed approach can increase the power efficiency and also, at the same time, it reduces the interference on the primary network.