對於無線通訊系統來說，正交分頻多工(Orthogonal frequency division multiplexing, OFDM)是個非常好的技術，OFDM 系統子載波之間相互正交可以有效的節省頻寬，而且可以抵抗多重路徑通道的衰減，此技術已經應用在許多的通訊標準上；不過OFDM訊號有個主要的缺點，就是過高的峰對平均功率比(peak-to-average power ratio, PAPR)，對於功率放大器來說，過高的PAPR 會使訊號操作於非線性區域，會使輸出訊號產生嚴重的非線性失真，並且會 增加位元錯誤率，降低整體系統的性能。
在過去許多降低 PAPR 的方法中，選擇性映射(Selective Mapping, SLM)有著明顯降低PAPR 的效果，由於SLM 是利用線性運算，所以不會去破壞本身的訊號，因此接收端可以完整的將訊號解調回來，不過SLM 卻有著計算複雜度過高的問題，所以在本篇論文中提出修改SLM 的方法，將SLM 加入子載波切割的概念，此方法與原本的SLM比較起來，能再有相似PAPR 降低效能的情況下降低計算複雜度，從模擬結果可以看到此方法比起原本的SLM 能大幅度地降低計算複雜度。

Orthogonal frequency division multiplexing (OFDM) is desirable technique of wireless communication. Subcarriers of OFDM signal are orthogonally used on the frequency
spectrum, and can resist multipath effect characteristics. Recently, OFDM has been used widely in many kinds of communication standards. But the OFDM signal has a major
disadvantage is high peak-to-average power ratio (PAPR), which can resulted in significant nonlinear distortion when the signal is operated through a nonlinear region of power amplifier, and induces the degradation of bit error rate (BER).
The methods of PAPR reduction, selective mapping (SLM) is effective and uncomplicated. SLM is a linear operation, it doesn’t destroyed the signal itself. The received signal can be demodulated perfectly at receiver. But SLM has a problem of the high computational complexity, in this paper, introduce a modified SLM. The technique uses the concept of partition into subcarriers, called a partial-sequence SLM (P-SLM), which considerably reduces the computational complexity with the similar performance of PAPR reduction compared with the conventional SLM scheme. The simulation results show that it achieves better performance of reduces the computational complexity than the conventional SLM scheme.

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