Comparison between LDPC Codes and QC-LDPC Codes in Term of PAPR in OFDM System with Different Encoding Techniques

摘要

Peak to Average Power Ratio (PAPR) is known to be a traditional problem in Orthogonal Frequency Division Multiplexing (OFDM). The peak value of power signals bring to many other problems, thus the implementation of OFDM system in many wireless applications are growing slowly. There are many techniques have been discussed to reduce PAPR in OFDM systems and one of them is PAPR reduction through coding. In this paper, a comparison between two coding; Low Density Parity Check Codes (LDPC) codes and Quasi Cyclic LDPC (QC-LDPC) codes has been discussed and additionally two types of encoding technique; G-Matrix and Approximate Triangular that is used in LDPC/QC-LDPC has been compared. The results show that PAPR reduced about 13% in case of QC-LDPC Codes from the original OFDM system and 8% in case of encoding process using Approximate Triangular from G-Matrix. The comparison result between LDPC and QC-LDPC can be the proof that QC-LDPC codes are better than LDPC codes while the second result shows that encoding process also contributes a significant impact to PAPR reduction. These results could lead to further investigation in the future.