| Summary: | 碩士 === 國立高雄第一科技大學 === 電腦與通訊工程研究所 === 102 === It is well known that the cognitive radio (CR) allows the spectrum of the primary user (PU) is employed at its inactive period by other users. It can effectively solve the current problems in bandwidth resource allocation and make up for deficiency. With the non-continuous orthogonal frequency division multiplexing system (NC-OFDM), featured with non-continuous subcarriers, the CR systems can be more flexible and more convenient to use spectrum resources and effectively adapt to the dynamic spectrum environment. The NC-OFDM based CR system has the drawback of high peak-to-average power ratio (PAPR) values and large sidelobe power. This thesis propose a precoding matrix method to jointly reduce PAPR and suppress sidelobes of signals in the PU band. A systematic procedure is developed to establish such a matrix. First, a precoding matrix according to the pulse shaping method is established for reducing PAPR values. Second, a singular value decomposition (SVD) and reconstruction process is performed on the precoding matrix to achieve the minimum bit error rate (BER) performance. Finally, a block diagonal matrix constituted of the PAPR reduction matrices and an unknown sidelobe suppression matrix is constructed and a following objective function is defined. By minimizing the objective function, an optimum sidelobe suppression matrix is found such that the PAPR reduction and sidelobes suppression performance of signals in the PU band are accomplished concurrently. Simulation results show that our method has excellent PAPR reduction and sidelobe suppression performance. Compared with other methods the proposed method also shows its advantages of simplicity and low complexities.
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