Research And Realization Of The Algorithm For Peak To Average Power Ratio Reduction Of OFDM Signals Based On The DSP Chip

Orthogonal Frequency Division Multiplexing(OFDM) has been developed quickly because of its high spectrum efficiency and the property of anti_multipath.During OFDM technology is widely used, more and more attention is paid to its drawback of high peak to average power ratio(PAPR).The technologies of decreasing PAPR in OFDM system can be divided into three types:signal distortion techniques,probabilistic techniques and coding techniques.The clipping scheme and compression-transform method of the signal distortion techniques and the selective mapping scheme and the partial transmit sequence method are mainly studied in this dissertation.The first kind techniques have very stable performance in decreasing the PAPR while they make the performance of bit error rate(BER) of OFDM system poor.On the other hand, the probabilistic techniques have no influences on the BER performance.However they have the feature of high computation complexity and the problem of side information.Based on the analysis and research of these existing algorithms,three advanced algorithms are proposed after further deducing the SLM algorithm in this dissertation.The SLM scheme without side band information is available and it improves the efficiency of the OFDM system through controlling the constellations reversal.The receiver can decode without side band information. By setting the threshold of PAPR and the iteration times,the adaptive SLM scheme is able to low the computational complexity.The proper OFDM signals can be exported directly and the others should be conducted again until the number of times reaches the limitation.The third method introduces the a interleaver into the SLM scheme to generate a set of sufficient different OFDM symbols. To decrease the computational complexity of the method, the adaptive scheme is also introduced into the technique.And it is called adaptive interleave SLM method.Through the simulation,these three schemes are proven effective to decrease the PAPR of OFDM symbols. However, they also have shortcomings.For examples,the SLM without side band information scheme brings high average power.The adaptive SLM scheme brings time delay to the system.And the interleave SLM has a feature of high computational complexity. In addition,the OFDM signal with frame header,signal domain and data domain is achieved based on the platform of PXI vector signal source project.Based on the mode of random waveform, the OFDM modulation uses BPSK with 16 subcarriers and 32-point IFFT. The generation of OFDM signals is mainly achieved in DSP and the digital up converter is available mainly in FPGA.After the DA module, the signals are exported. The detailed procedure and the picture of the time domain and frequency domain signals will be demonstrated in the dissertation. Based on these, the proposed algorithms are then added into the OFDM system.The data of OFDM symbols before and after using the algorithms will be derived into the MATLAB software. The analysis shows the methods can effectively decrease the PAPR of OFDM system.The effect is a little worse than the theoretical results.