Improved Decoding Algorithms To Reduce The PAPR Of OFDM Systems Using Coding Methods

The major drawback of OFDM (Orthogonal Frequency Division Multiplexing) is the existence of high PAPR (Peak to Average Power Ratio). There are three main methods to reduce PAPR——Pre-distortion method, Coding method, and Scrambling method. This paper proposes some improved decoding algorithms to reduce the PAPR of OFDM systems using coding method. The main contents are as follows:Construct complementary sequence sets based on Golay complementary sequences and Reed-Muller codes. Using BPSK (binary phase shift keying) modulation and Golay complementary sequences in the OFDM system, it shows that the PAPR can be strictly limited in3.01dB. Because of the defects of BPSK, construct code sets based on GCS for quadrature amplitude modulation (QAM), we analyze the performance of the OFDM system using the parameters:the PAPR value, the error detection and correction performance and information rate.We expand the ordered statistic decoding (OSD) algorithm of binary linear block code to ZM. In the OSD algorithm, candidate codewords mainly generate at phase-l of order-l reprocessing, and the information bits outside the MRIPs are not used. Utilize the iterative OSD decoding algorithm we can reduce the number of candidate codewords and the complexity of the algorithm. Because of the high complexity of seeking the first k most reliable independent information bits (MRIPs) in the hard decision process of OSD algorithm, we present a POSD algorithm which we only order the first k most reliable independent information bits. The simulation results show that the complexity of the POSD algorithm has a significant reducing with respect to OSD algorithm, but this reducing is at the expance of the bit error rate (BER). Since the reliabilities of MRIPs become irrelevant after we find the MRIPs in the OSD algorithm and the complexity of the OSD algorithm increases exponentially with l increasing, we divide the MRIPs of the received sequence into two separate segments and present an OSD (i1|k1,i2|k2) algorithm. It shows that we can set parameters to have the BER performance as well as the decoding complexity between those corresponding to the order-l OSD and order-(l+1) OSD. Furthermore, in order to improve the BER performance of POSD algorithm, we combine the POSD algorithm and the OSD(i1|k1,i2|k2) algorithm to get the POSD(i1|k1,i2|k2) algorithm, the simulation results show that the BER performance of POSD(i1|k1,i2|k2) algorithm is better than POSD algorithm, however, the complexity of the algorithm will increase.