多輸入多輸出正交分頻多工(MIMO-OFDM)技術已被廣泛運用在近代通訊系統中，但與正交分頻多工訊號擁有相同的缺點即為高峰均功率比(PAPR)，當訊號經高功率放大器(HPA)後會產生嚴重的非線性失真，造成頻譜擴散以及系統接收位元錯誤率提升等問題。一般文獻採用選擇性映射 (Selected Mapping, SLM)方法降低MIMO-OFDM訊號高峰均功率比並以minmax (PAPR)為準則。波束集成或預編碼(SVD)技術經常被應用在MIMO-OFDM系統以增加傳送端的多樣性(diversity)及接收端的訊號雜訊比，此等技術的運用將使得各傳送天線訊號的平均功率不相等。考慮放大器非線性(nonlinear)效應除PAPR外仍需考慮各別天線平均傳送功率，僅以PAPR為選擇準則並不恰當，因此本論文針對MIMO-OFDM系統提出minmax (Peak Power)的選擇準則以獲得優於傳統準則的系統性能。另外，Cubic Metric (CM)已被應用於3GPP標準中作為判斷訊號受非線性影響準則之一，因此本論文在降低MIMO-OFDM訊號的能量大小動態變化量之議題上分別以PAPR及CM作為判斷依據，並比較兩者對系統性能的提升效果。

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technique has been widely adopted in modern wireless communication systems. However, the drawback of high peak to average power ratio (PAPR) is the same as OFDM signals. The most conventional schemes applied selected mapping (SLM) method with minmax (PAPR) criterion to reduce PAPR for MIMO-OFDM signals. On the other hand, the precoding technique is usually employed in MIMO-OFDM systems and it results in unequal average transmission power of individual antenna. In practice, not only PAPR but also average transmission power should be taken into account for the nonlinear effect of power amplifiers. Hence, this thesis proposes a new criterion of minmax (Peak Power) for the SLM scheme to obtain better performance compared with conventional criterion. Recently, cubic metric (CM) is becoming a new criterion to judge the nonlinear effect. In this thesis, we also study and compare the performance of MIMO-OFDM systems based on different criteria of PAPR and CM.

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