多輸入多輸出正交分頻多工系統中利用選擇性映射與分部傳輸序列的混合式策略之降低峰均值功率比技術研究

正交分頻多工(OFDM)系統是利用多載波調變(MCM)技術來提供高速資料傳輸，但也存在著高峰均值功率比(PAPR)的缺點，這缺點會造成射頻功率放大器成本的增加。在本篇論文中，首先我們在多輸入多輸出(MIMO)正交分頻多工系統中提出一個解決的方法，使用結合式(mixed)分部傳輸序列(PTS)策略來達成結合個別式(individual)與並列式(concurrent)的架構，這策略是為了去調整峰均值功率比降低效能與旁資訊位元(side information)之間取得一個平衡點。在降低峰均值功率比中常見的選擇性映射(SLM)以及分部傳輸序列，許多文章都有說明造成快速反傅立葉轉換(IFFT)個數的增加是因為相位旋轉序列以及子區塊數目的增加。因此我們提出數個混合選擇性映射與分部傳輸序列的方式來降低系統複雜度並且維持令人滿意地峰均值功率比降低效能。另外，我們提出的修正型混合式策略(modified hybrid)與傳統型混合式策略(conventional hybrid)相互比較，能夠有效降低系統複雜度並且又能得到優秀的峰均值功率比降低效能。此演算法是利用來自不同相位旋轉序列的子區塊彼此線性結合與互相交換來創造更多可供選擇的正交分頻多工序列，並且這方法不需要增加快速反傅立葉轉換的個數就能達成。最後，我們所提出的修正型混合式策略也可以順利地運用在多輸入多輸出正交分頻多工系統中，並且也有優秀的峰均值功率比降低效能。

關鍵字

峰均值功率比；混合式策略；多輸入多輸出正交分頻多工

並列摘要

Orthogonal frequency division multiplexing (OFDM) systems provide high data-rate transmission with multi-carrier modulation (MCM) techniques, but they still have to cope with the high peak-to-average power ratio (PAPR) problem, which increases the cost of the radio frequency power amplifier. For multiple-input multiple-output (MIMO) OFDM systems, in the beginning of this thesis, the mixed partial transmit sequence (PTS) strategy is employed for the integration of both individual and concurrent configuration in order to reduce the high PAPR for trade-off between system performance and side information. For the PAPR reduction with selected mapping (SLM) and PTS schemes, a survey of the related papers has shown that the number of inverse fast Fourier transform (IFFT) would become large when the number of phase rotation sequences or sub-blocks is increased. Therefore, various hybrid SLM-PTS methods are employed to reduce system complexity and maintain acceptable performance. In addition, the modified hybrid scheme is proposed to obtain superior PAPR reduction performance and reduce system complexity compared with the conventional hybrid scheme. This algorithm consists of linear combination and exchange of the sub-blocks from two phase rotation signal sequences to create more alternative OFDM signal sequences without increasing the number of IFFT. Finally, our proposed modified hybrid scheme is successfully extended to the PAPR reduction of MIMO-OFDM systems with good system performance.