The Research On Reducing PAPR Of OFDM System

Multicarrier communication has been employed for wire-line communications and has been adapted for use in the future mobile communication systems. In multicarrier modulation transmission schemes, the most commonly used schemes are Orthogonal Frequency Division multiplexing (OFDM). Due to OFDM's robustness against multipath fading with certain implementation advantage over single-carrier system, OFDM has become a popular technique in various high-speed wireless data transmission system. One of the main implementation disadvantages of OFDM is the high peak-to-average power ratio (PAPR) of the transmitted signals.First, this paper studies the development and the principles of OFDM system and makes an intensive study of the technology of reducing PAPR. And then, it studies the performance of each method and makes a comparison of them and analyzes the advantages and disadvantages.Based on the intensive research, the paper improved the grouping and kernel transform algorithm to reduce the PAPR in OFDM system. The grouping and kernel transform method to reduce PAPR by grouping subcarriers, then applying the IFFT operation, and after that this algorithm uses the average amplitude of multiple signals to replace the amplitude of one in order to reduce the PAPR of the OFDM system. After analyzing the inverse property of the transform kernel T, the paper proves the inverse transformation doesn't always exist, thus the generalized inverse matrix is introduced in this paper to slove this problem and improve the schema. The theoretical derivation proves a new way to find the suitable kernel fot this algorithm. The simulation by using MATLAB provides the performance of this schema, which proves that it is better than the traditional SLM schema to reduce the PAPR of the OFDM system.Moreover, Based on the intensive research on matrix transform algorithm, two new matrixes, the orthogonal matrix Jacket,CAZAC Sequence and constructed matrix T, are used in the matrix transform algorithm to lower non-periodic correlation and finally to restrain the PAPR of the OFDM signal. The peak-to average power ratio (PAPR) reduction scheme using Jacket matrix. MATLAB simulation provides the performance between three new matrixes and Hadamard, P4 matrix. Secondly, the matrix transform algorithm with clipping is proposed, and the MATLAB simulation proves that this algorithm can improve PAPR performance further without the increment of complexity. Based on all above, another new improved matrix transform algorithm is proposed. After IFFT operation, the data sequences are multiplied with multiple matrixes and the OFDM symbol with the best performance is sent. This paper provides the MATLAB simulation results to prove this improved algorithm can restrain PAPR better and without lower complexity.At last, the simulation of matrix transform algorithm by using Simulink isprovided to analyze the performance of BER.