New spreading codes and detection algorithms for low complexity post-coded OFDM systems

Coded OFDM systems are generally employed to overcome the symbol recovery problem in uncoded OFDM systems that is caused due to loss of diversity in uncoded OFDM systems. In this paper, we extend our recent research work on low complexity post-coded OFDM (PC-OFDM) systems. We consider new spreading codes and detection algorithms for PC-OFDM in this paper. PC-OFDM systems introduce frequency diversity in an efficient manner so that the overall computation cost of the system can be significantly reduced. We discuss the design principles of spreading codes for PC-OFDM systems and obtain code construction criterion for minimum error performance. We propose two spreading codes based on these principles. We also investigate different choices for receiver structures suitable for PC-OFDM and compare their performance through simulations on IEEE UWB channels.