正交分頻多工系統在限制錯誤率下降低均峰值功率比之線性壓縮轉換法之設計

Design of a Linear Companding Transform Method in OFDM Systems to Minimize the Peak-to-Average Power Ratio with Bit Error Rate Constraint

張翰杰(Han-chieh Chang)

指導教授 ： 呂振森

國立臺北科技大學/電資學院/電機工程系所/碩士(2010年)

摘要

本篇論文針對正交分頻多工(OFDM)系統具有較高的均峰值功率比(PAPR)，探討在錯誤率限制下使用壓縮轉換(Companding)技術降低其均峰值功率比。在傳輸端訊號通過功率放大器時，瞬時功率高的訊號容易進入非線性區域,使訊號被削減掉，造成訊號的失真。壓縮技術是在發射端使用壓縮器(Compressor)以壓縮訊號振幅動態範圍，達到降低PAPR的效果，接收端使用解壓縮器(Expander)重建訊號振幅範圍。線性非對稱壓縮轉換函數複雜度較低且容易實現，經由適當的調整參數可同時縮小振幅過大的訊號及放大振幅較小的訊號。在本論文中，將探討在錯誤率限制下設計一個搜尋線性非對稱壓縮轉換的參數機制，找出一組最合適的最佳化參數後，以電腦模擬，與原始OFDM訊號的PAPR及經過A法則壓縮、μ法則壓縮，指數型壓縮及線性對稱壓縮等方法後OFDM訊號的PAPR做比較。

關鍵字

正交分頻多工 ； 均峰值功率比 ； 壓縮轉換 ； 峰值消減技術

並列摘要

This thesis focuses on the high Peak-to-Average Power Ratio (PAPR) reduction of OFDM systems using companding transform technique with bit error rate constrained. In transmitter, the output signal will be severely distorted due to the high instantaneous power input signal passing through the nonlinear region of power amplifier. The companding transform technique uses a compressor in transmitter to compress the dynamic range of signal’s amplitude. In receiver, it uses an expander to rebuild the dynamic range of signal’s amplitude. The linear nonsymmetric companding transform (LNST) function is a low complexity peak cancellation technique which is easy to be implemented. It can decrease large signals and enlarge small signals simultaneously by adjusting parameters appropriately. In this thesis, we aim to design a LNST method by a searching mechanism of finding the best parameters. After finding an optimal set of parameters, we use computer simulation to compare the PAPR of this method with the PAPRs of the original OFDM signals and of some other compressing OFDM signal methods, including A-law companding, μ-law companding, exponential companding, and linear symmetric companding.

並列關鍵字

OFDM ； PAPR ； Companding Transform ； Peak Cancellation Technique

參考文獻

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