PAPR reduction in OFDM systems using Quasi Cyclic Invertible Subset LDPC codes

Wireless communication is one of the important aspects of long distance communication. Along with the progress in technology rapid changes has been achieved in the field of wireless communication. Recent advances in wireless communication systems have increased the throughput and reliability of wireless channels. But still the bandwidth and spectral availability demands are endless. Researches in this field show that Orthogonal Frequency Division Multiplexing (OFDM) has become the modulation choice for high data-rate communication systems. But OFDM has the disadvantage of having large fluctuations in signal amplitude which has resulted in a high Peak-to-Average-Power Ratio (PAPR). High PAPR is a major drawback of multicarrier transmission system which leads to power inefficiency in RF section of the transmitter. The important PAPR reduction techniques for multicarrier transmission includes amplitude clipping and filtering, coding, partial transmit sequence and selected mapping. Among which, coding based approaches have inherent error control capability and simplicity of implementation. But this approach has limitations like an exhaustive search to find the best codes and to store large lookup tables for encoding and decoding. We are proposing a novel coding method called as Quasi Cyclic Invertible Subset LDPC (QC-IS-LDPC) codes for PAPR reduction in OFDM systems with low searching complexity and good error correcting performance. An intensive study will be done to compare the PAPR reduction capability and BER performance of QC-IS-LDPC coded OFDM with other PAPR reduction methods. Through this work we also examine the impact of different modulation schemes and coding rate on PAPR reduction.