正交分頻多工系統中利用新型切塊式選擇性映射策略來降低峰均值功率比之研究

Novel Block Selected Mapping Schemes for PAPR Reduction of OFDM Systems

林炳佑(Ping-You Lin)

指導教授 ： 林容杉

國立暨南國際大學/科技學院/電機工程學系/碩士(2012年)

https://doi.org/10.6837/NCNU.2012.00284

摘要

正交分頻多工(OFDM)技術是利用多載波來傳輸資料並且提供高資料傳輸速率，但高峰均值功率比(PAPR)是正交分頻多工技術中主要的缺點之一。高峰均值功率比會降低系統之效率以及增加發射端射頻(RF)功率放大器的成本。在過去幾十年中，有許多降低峰均值功率比的方法已經被研究且提出，就選擇性映射(SLM)型式而言，它是最普遍用來改善峰均值功率比的方法之一。經回顧許多與選擇性映射法相關的文獻之後可發現，當相位旋轉序列增加時，會造成快速傅立葉轉換(IFFT)的使用個數大為增加。

因此，我們提出一種較低運算複雜度之新型切塊式選擇性映射(block SLM)策略來達到降低峰均值功率比的效能。我們提出的演算法是將頻域中的正交分頻多工符元(symbol)切為數塊並與相位旋轉序列進行相乘，且進一步利用切塊後的訊號進行任意組合來創造出更多可供選擇的正交分頻多工訊號序列。因此，我們提出的新型切塊式選擇性映射策略有潛力去得到更佳的峰均值功率比之降低效果。除此之外，我們也提出兩個衍生性的方法，即修正型切塊式選擇性映射(modified block SLM)策略以及混合型切塊式選擇性映射(hybrid block SLM)策略來更進一步得到更佳的峰均值功率比之降低效果。最後，所有我們提出之方法將會擴展到多輸入多輸出(MIMO)正交分頻多工系統的應用中，以求能夠進一步提升降低峰均值功率比的效能。

關鍵字

正交分頻多工 ； 峰均值功率比 ； 選擇性映射 ； 多輸入多輸出

並列摘要

The orthogonal frequency division multiplexing (OFDM) techniques using multi-carriers to transmit data provide a high data-rate transmission, but the high peak-to-average power ratio (PAPR) problem is one of their major drawbacks. High PAPR reduces system efficiency and hence increases the cost of radio frequency (RF) power amplifiers. In the last decades, a lot of PAPR reduction techniques for OFDM systems have been developed and investigated. For example, the selected mapping (SLM) scheme is one of the most popular methods for the improvement of PAPR reduction. A survey of the SLM-related papers has shown that the number of inverse fast Fourier transform (IFFT) would become larger when the number of phase rotation sequences is increased.

Therefore, a novel block SLM scheme is proposed to obtain better PAPR reduction performance with lower computational complexity. The proposed algorithm is capable of partitioning the OFDM symbol sequence into several blocks multiplied by various phase rotation sequences in frequency domain, and further employs appropriate combination of block signals to create more alternative OFDM signal sequences. As a result, our proposed scheme has the potentials to provide excellent PAPR reduction performance. In addition, both modified and hybrid block SLM schemes are developed and investigated for further improvement of PAPR reduction. At last, all of these block SLM schemes are extended to the applications of multiple-input multiple-output (MIMO) OFDM systems for enhanced PAPR reduction performance.

並列關鍵字

OFDM ； PAPR ； SLM ； MIMO

參考文獻

[1] R. van Nee and R. Prasad, OFDM for Wireless Multimedia Communications, Boston: Artech House, 2000.

[2] T. Hwang, C. Yang, G. Wu, S. Li and G. Y. Li, “OFDM and Its Wireless Applications: A Survey,” IEEE Transactions on Vehicular Technology, Vol. 58, No. 4, pp. 1673-1694, May 2009.

[3] H. G. Myung and D. J. Goodman, Single Carrier FDMA: A New Air Interface for Long Term Evolution, Chichester, U.K.: J. Wiley & Sons, 2008.

[4] W. Y. Zou and Y. Wu, ”COFDM: An Overview,” IEEE Transactions on Broadcasting, Vol. 41, No. 1, pp. 1-8, Mar. 1995.

[5] O. Edfors, M. Sandell, J.-J. van de Beek, D. Landstrom and F. Sjoberg, ”An Introduction to Orthogonal Frequency-Division Multiplexing,” Division of Signal Processing, Lulea University of Technology, Lulea, Sweden, Research Report No. 1997:03, pp. 1-50, 1997.