以預先編碼與非線性壓縮擴展混合方式降低OFDM系統峰均值功率比之研究

正交分頻多工(簡稱OFDM)是多載波調變技術的一種，高頻譜使用效率與高速資料傳輸的優點，使此項技術廣泛為許多無線通訊系統所採用。但是OFDM系統中有一項主要的缺點就是會產生較高的峰均值功率比(簡稱PAPR)。預先編碼(Precoding)方法為一種符元擾亂技術，與其他符元擾亂技術相比如SLM或PTS，Precoding方法有較好的PAPR降低效果與較低的計算複雜度。Pilot子載波為OFDM系統中最重要的一個參數，在OFDM系統中用來作通道估計的重要功能，但Pilot子載波插入到OFDM符元時也會造成PAPR問題。本篇論文研究一些簡單且實用的方法如振幅偏移、調變擴展方法及非線性壓縮等方法在頻域與時域上與Precoding方法進行結合，改善因Pilot子載波的插入而造成PAPR改善程度不如預期的效果。透過模擬結果證明結合非線性壓縮擴展與預先編碼方法能在Pilot子載波加入後仍有效的改善PAPR。

關鍵字

峰均值功率比；預先編碼；非線性壓縮擴展；符元擾亂技術

並列摘要

The Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation scheme that provides efficient bandwidth utilization and high-speed data transmission. One of the major drawbacks is that the OFDM signal would generate high peak-to-average power ratio (PAPR). “Precoding” is one of symbol scrambling technique of PAPR reduction and compared with other scrambling techniques of SLM and PTS; this method has best capability of PAPR reduction and lower computational complexity. Pilot subcarrier is the best important parameter in OFDM system for channel estimation. However, Pilot subcarrier inserted into OFDM system which impacted to the PAPR reduction. This paper study other simple and practical method combined with “Preceding” method to improvement when pilot inserted effect to the PAPR reduction degradation problem. This paper proposed combination of Precoding and Nonlinear Companding Method to improve the PAPR reduction when Pilot subcarrier was insertion.

並列關鍵字

Nonlinear compading ； Precoding ； PAPR ； symbol scrambling technique

參考文獻

[2]Richard Van Nee and Ramjee Prasad, OFDM wireless Multimedia Communication, Artech House, 2000.

[3]Slimane Ben Slimane, “Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding,“ IEEE Transactions on Vehicular Technology, Vol. 56, No. 2, March 2007.

[5]A. Vallavaraj, B.G. Stewart, D. K. Harrison, and F. G. McIntosh, “Reduction of peak to average power ration of OFDM signals using companding,” Communications Systems, 2004. ICCS 2004. The Ninth International Conference, p160-164, 7 Sept 2004.

[7]H. Sakran, M. Shokair, and A. Abou Elazm, “COMBINED INTERLEAVING AND COMPANDING FOR PAPR REDUCTION IN OFDM SYSTEMS” Progress In Electromagnetics Research C, Vol. 6, 67–78, 2009

[9]IEEE Std. 802.16e-2005, pp.357

國際替代計量

以預先編碼與非線性壓縮擴展混合方式降低OFDM系統峰均值功率比之研究

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