Complement Transformation Method For Ofdm Papr Suppression Technique

Orthogonal Frequency-division Multiplexing is a new kind of communication method which transmits data simutaniously on different carriers. Compared with the traditional single carrier communication methods,OFDM is realized by FFT and IFFT, which could combat with the multiple path and is easy to distribute the frequence of the channel. OFDM is accepted by the IEEE 802.11, IEEE 802.16, IFEE 802.20 and the Fourth Generation wireless communication.Because the multiple carriers the OFDM have, the output signal of the OFDM is the combination of the signals in subchannels. As a result, compared with the single carrier modulation, the peak to average power ratio of the OFDM is higher than it in single carrier modulations. To transmit the signals without distoration, the transmitter need a high power amplifier with a high linear requirement, which may lower the efficiency of the transmiting, and increase the requirement of the linearity of the A/D convertor.To solve this problem, some methods such as clipping, performing, selective , coding, are proposed for the reducing of the peak to average power ratio of the OFDM signal.In this paper, a new kind of method which is based on the complementary transform is proposed for the peak to average power reduction in the OFDM systems. In this method, the Gaussi distribution of the amplitude of the real OFDM signal could be ultilized because by using the complementary transform on the real OFDM signals, the amplitude distribution of the signal has been changed to reduce the peak to average power ratio of the OFDM signals. In the receiver, the OFDM signal could be recoveried by the inverse transform. However the AWGN would influence the signal so that the signal could not recoveried in the receiver, which would make the bit error rate increase of the system.In the next part, this paper carefully analyzes the disadvantages of the complementary transform and an orthogonal complementary transform method is proposed. This method adds the label on the signal so that the OFDM singnal would be transmited in orthogonal channels. The simulation shows that this new method could improve the bit error rate and the performance of the system.In the last part of this paper, the performance of the combination method of the orthogonal complementary transform and the clipping methods is analyzed. The simulation shows that it could also reduce the peak to average power of the OFDM signal with the satisfying. In addition, compared with complementary method, it could achieve a lower bit error rate in the OFDM system.