子載波能量分配在多載波分頻多工系統之研究

A Study on the Power Allocation of Subcarriers for Multicarrier OFDM Systems

李俊彥(Chun-yen Lee)

指導教授 ： 黃永發 ； 鄭佳炘

朝陽科技大學/資訊學院/資訊與通訊系/碩士(2010年)

摘要

在正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)系統下，能量負載問題是非常重要的議題。因此我們主要探討在固定的傳輸能量下，如何降低位元錯誤率(Bit-Error Rate , BER)。並且我們也針對在固定位元錯誤率下，如何使系統容量提升。在本論文中，我們提出新的能量分配演算法分配傳輸能量，使位元錯誤率降低，系統效能提高。在我們的演算法中，利用接收端回傳通道狀態訊息，使得傳送端可以使用我們所提出的演算法計算新的能量分配，因此通道效能較好的子載波會搭配較低的能量進行資料傳輸，反之通道效能較差的子載波會分配較高的傳輸能量。為了使位元錯誤率能有效改善，我們將設定一個門檻值，去選擇效能較好的子載波來傳輸資料。
最後我們探討位元錯誤率與系統容量之間的平衡，主要針對限制不同的位元錯誤率，觀察系統容量的效能。我們利用系統子載波使用率來配置我們提出的能量分配方法，使系統的位元錯誤率和系統容量之間得到平衡，達到提升整體系統效能的目的。

關鍵字

子通道。 ； 訊號與雜訊比 ； 通道增益 ； 位元錯誤率 ； 能量分配 ； 正交分頻多工

並列摘要

The problem of power loading in Orthogonal Frequency Division Multiplexing (OFDM) systems that provide minimization of the bit-error rate (BER) performance under a fixed transmit power (or equivalently minimization of the transmit power under a fixed value of the BER) is addressed in this work. We also discuss how to upgrade the system capacity in a fixed bit error rate. In this thesis, we propose a new algorithm for allocation of transmission power to reduce the bit error rate and increase system efficiency. In the transmitter, we use channel state information from the receiver to compute the new power allocation algorithm. Hence subcarriers will be well performance with lower power to transmit; otherwise worse performance of subcarrier will be assigned a higher transmission power. In order to effectively improve the bit error rate, we will set a threshold value and choose the well performance of subcarriers to transmit.
Finally, we will discuss the trade-off between the bit error rate and capacity of the system in different limits of bit error rate. The selection of subcarriers is used to configure our proposed method of power allocation so that it can achieve the trade-off between bit error rate and system capacity to improve overall system performance. Therefore, with efficient power allocation, the performance of OFDM systems can be improved.

並列關鍵字

OFDM ； BER ； Power Allocation ； SNR ； Channel Gains ； Subcarrier.

參考文獻

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