眾所皆知的感知無線電(CR)允許用戶使用主用戶(PU)的頻段在其非使用中時，與非連續正交分頻多工系統可以有效地解決目前頻寬資源的分配問題，並減緩頻譜資源的匱乏。非連續的子載波在感知無線電系統可以更加靈活的使用頻譜資源並適應動態的頻譜環境，基於感知無線電系統NC-OFDM兩個主要的缺陷分別為高的峰均功率比以及大的旁波柱。本論文提出一個有系統的編碼的方法，同時降減峰均功率比值以及抑制在主用戶頻段上的旁波柱。首先，建立根據脈衝整形的方法來降低峰均功率比值，其次再用奇異值分解(SVD)來重建編碼矩陣來實現最低的錯誤率(BER)，最後再抑制未知的旁波柱來達到我們的目標。透過對旁波柱的最小化，找到一個最佳的旁波柱抑制矩陣，使得訊號的峰均功率比與主用戶上的旁波柱抑制是同時完成的，模擬結果顯示，我們的方法具有好的降減峰均功率比值以及抑制旁波柱的性能。與其他方法相比，也顯示出該方法的簡單性以及低複雜度。

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.

Chinese Abstract i
English Abstract ii
致謝 iv
CONTENTS v
LIST OF FIGURE vi
Chapter 1 1
Chapter 2 4
2.1 Orthogonal Frequency Division Multiplexing (OFDM) 4
2.11 Guard Interval 9
2.2 Peak-to-Average Power Ratio 11
2.3 Cognitive Radio (CR) System 13
2.4 NC-OFDM based CR 15
Chapter 3 16
3.1 Precoding Matrix Set Up Through Pulse-shape Functions for OFDM Systems 16
3.2 Precoding Techniques for PAPR Reduction 20
3.3 Procedure for Establishing the Minimum Error Probability Based Precoding Matrix 24
3.4 The Sidelobe Suppression Scheme with the Modified PAPR Reduction Matrix 26
3.5 Construct precoding matrix 28
Chapter 4 29
4.1 Simulation Conditions 29
4.2 NC-OFDM System with Precoding for Pulse Shapping 29
4.3 Performance of the Sidelobe Suppression 34
Chapter 5 36
Reference 37

[1] S. Haykin, “Cognitive Radio: Brain-Emprowered Wireless Communications.” IEEE JSAC. vol. 23, no.2, Feb 2005.
[2] C. Tellambura, "Computation of the continuous-time PAR of an OFDM Signal with BPSK subcarriers", IEEE Commun. Lett., vol. 5, no. 5, pp. 185-187, May 2001.
[3] L. Wang, C. Tellambura, “An overview of peak-to-average power ratio reduction techniques for OFDM systems”, IEEE International Symposium on Signal Processing and Information Technology, pp. 840-845, 2006.
[4] T. Jiang, Y. Yang, and Y. Song, “Exponential companding transform for PAPR reduction in OFDM systems,” IEEE Trans. Broadcast., vol. 51, no. 2, pp. 244–248, June 2005.
[5] M. Niranjan, S. Srikanth. “Adaptive active constellation extension for PAPR reduction in OFDM systems”, International Conference ICRTIT, pp.1186-1189, Jun. 2011.
[6] S. H. Han and J. H. Lee, “An overview of peak-to-average power ratio reduction techniques for multicarrier transmission”, IEEE Wireless Commun., vol. 12, pp. 56-65, Apr. 2005.

[7] E. Doron and T. Genadiy, "PAPR reduction in MIMO OFDM using unitary matrix precoding," Proc. of 18th European Wireless Conference,2012. EW, pp.1-3, 18-20 April 2012.
[8] C.-D. Chung, “Correlatively coded OFDM," IEEE Trans. Wireless Commun., vol. 5, no. 8, pp. 2044-2049, Aug. 2006.
[9] S. B. Slimane, “Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding, “IEEE Transactions on vehicular technology, vol. 56, no. 2, pp. 686–695, Mar. 2007.
[10] M.-J. Hao and C.-H. Lai, “Precoding for PAPR reduction of OFDM signals with minimum error probability,” IEEE Trans. Broadcast., vol.56, no. 1, pp. 120–128, Mar. 2010.
[11] D. Qu, Z. Wang, and T. Jiang, “Extended active interference cancellation for sidelobe suppression in cognitive radio OFDM systems with cyclic prefix,” IEEE Transactions on Vehicular Technology, vol. 59, no. 4, pp. 1689-1695, May 2010.