A Study on PAPR Reduction Methods for OFDM Signals
|關鍵字:||正交分頻多工系統;均值功率比;選擇性映射;削波;有限脈衝響應濾波器;全通濾波器;OFDM;PAPR;SLM;Clipping;FIR filter;All pass filter|
In order to meet the extreme requirement of data rate, researchers around the world have developed a lot of rate-increasing methods. Recently, orthogonal frequency division multiplexing(OFDM) has been regarded as one of the core rate-increasing technologies. By dividing the entire bandwidth into narrowband subcarriers, OFDM can provide high spectral efficiency. Also, the multipath effect can be easily equalized. Summarizing the above advantages, OFDM has become a key air interface for most modern wireless communication system. However, OFDM system suffers from several difficulties. One of the major drawbacks is the high peak to average power ratio(PAPR) at the transmitter. As signals operate on the nonlinearity of a high power amplifier(HPA), it is distorted and causes in-band distortion and out-of-band radiation. In our research, we propose three different PAPR reduction methods. First, a SLM method with CDMA side information is proposed. The difference between the conventional SLM method and the proposed one is that it provides another channel to transmit the side information, i.e., the index of phase sequence. Second, in order to improve the BER performance of traditional clipping scheme, we exploit some spreading codes to transmit the lost information caused by clipping. Third, a novel idea, in which OFDM waveform is shaped by an FIR filter or an all pass filter, is proposed. The numerical results show that by using the proposed methods, the PAPR of OFDM can be reduced, and the performance of OFDM is improved.
|Appears in Collections:||Thesis|
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