正交分頻多工(orthogonal frequency-division multiplexing，簡稱OFDM)是一種非常有效率的多載波系統，但是OFDM系統的輸出信號會產生峰值對平均功率比(peak-to-average power ratio，簡稱PAPR) 的問題。為了解決這個問題，因而發展出許多的峰值對平均功率比降低技術。其中，選擇性對映(selected mapping，簡稱SLM)和分部傳輸序列(partial transmit sequences，簡稱PTS)是兩種非常重要的峰值對平均功率比降低技術，但是，這兩種方法卻有著需要傳送額外訊息 (side information)的缺點。將導引混成編碼(guided scrambling coding) 應用在這兩種技術上，便解決了需要傳送額外訊息的問題。將導引混成編碼中的增量位元(augmenting bits)插入到原來的資料序列之前，在經過混成編碼之後，不同的增量位元會產生不同的序列，在經過映像(mapping)和快速傅利葉反轉換(inverse fast Fourier transform，簡稱IFFT)模組之後，其中一個峰值對平均功率比最低的序列將被選擇並且被傳輸，在導引混成編碼技術的接收端，我們只要經過反混成編碼，並且移除增量位元，就可以得到原始的傳輸訊號。雖然使用導引混成編碼的選擇性對映和分部傳輸序列技術不需要傳送額外資訊，但仍需要使用許多的快速傅利葉反轉換模組，造成計算複雜度的增加。
在這篇論文中，我們將專注在如何降低導引混成編碼的選擇性對映和分部傳輸序列技術的計算複雜度。我們將增量位元和資料序列的操作分離，將不同的增量位元所產生的結果事先求出，並且存在唯讀記憶體(ROM)中。如此一來，在資料序列的部份經過處理之後，只要加上唯讀記憶體中不同的增量位元所產生不同的結果，便可以選擇其中一個峰值對平均功率比最低的序列傳送。藉由這個方法，我們就可以有效的率低峰值對平均功率比。而所需要的條件，只要一個唯讀記憶體、一些加法器，和一個快速傅利葉反轉換模組即可。經由模擬和比較結果，我們也可看出所提出的低複雜度技術，卻實可以降低系統之複雜度，並且還能維持不錯的峰值對平均功率比之表現。

Orthogonal frequency-division multiplexing (OFDM) is an efficient transmission scheme for multicarrier systems, but its output signals may exhibit high peak-to-average power ratios. To deal with the high PAPR problem, many PAPR reduction methods have been proposed. Selected mapping (SLM) and partial transmit sequences (PTS) are two important techniques for PAPR reduction, but they need to transmit side information at the transmitter side. Guided scrambling (GS) SLM and GS-PTS techniques augment the binary data sequence with several bits in the first data bit position. The augmenting bits set the scrambler’s initial condition in the GS-SLM and GS-PTS methods. Thus with different patterns of the augmenting bits, the candidate signals to be selected for transmission can be generated by passing different augmented data sequences through the scrambler, the constellation mapping block, and the IFFT block. At the receiver in the GS-SLM and GS-PTS methods, the received sequence is unscrambled and the augmenting bits are removed directly. GS-SLM and GS-PTS do not require the transmission of side information, but they still need a bank of IFFT’s, i.e., involving high computational complexity.
In this thesis, we focus on reducing the high computational complexity of the GS-SLM and GS-PTS methods. We separate the operations of the augmented data sequence into the operations of the augmenting bits and the operations of original data sequence. Different augmenting bits are processed in advance and the results are saved into a ROM. After the operations of the data sequence are performed, the result is added by previous computed signals in ROM to generate a set of candidate signals. One candidate signal with the lowest PAPR will be selected for transmission. The proposed methods only need one IFFT, few adders, and a ROM and thus significantly reduce the computational complexity of the original GS-SLM and GS-PTS methods. The simulation results also show that the proposed GS-SLM and GS-PTS methods have almost the same PAPR performance as the original ones.

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