SIMPLIFIED REALIZATION OF PSEUDO- ORTHOGONAL CARRIER INTERFEROMETRY OFDM BY FFT ALGORITHM K. Anwar, M. Saito, T. Hara, M. Okada and H. Yamamoto Graduate School of Information Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara, Japan 630-0192, Tel: +81-743-72-5348, Fax: +81-743-72- 5349, E-mail: {anwar-k, saito, takao-ha, mokada, heiichi}@is.naist.jp Abstract: This paper proposes new simplified design of Pseudo-orthogonal Carrier Interferometry Orthogonal Frequency Division Multiplexing (PO-CI/OFDM) system by utilizing IFFT/FFT algorithm as a substitute of PO-CI spreading and despreading. We also propose a separator design for guaranteeing that the resulted codes are still (pseudo) orthogonal to each other. This solution is capable of reducing the complexities of PO-CI/OFDM implementation significantly. Difficulties of generating PO-CI codes as complex spreading codes are successfully solved by employing two IFFT/FFTs with the proposed separator. In this paper, we show that PO-CI/OFDM using FFT algorithm (further called PO-CI-FFT/OFDM) is a very simple and low cost technique while providing good performance as the original PO-CI/OFDM. Additional multiplications and additions for PO-CI spreading/despreading and additional memory for storing the generated codes is not required when utilizing the proposed design. This solution is capable of making PO-CI/OFDM closer to the reality. Key words: pseudo-orthogonal; carrier interferometry; OFDM; peak-to-average power ratio (PAPR); Fourier transform; complexity. 1. INTRODUCTION Carrier Interferometry (CI) codes and its derivative, called Pseudo- Orthogonal Carrier Interferometry (PO-CI) codes, have been introduced for Orthogonal Frequency Division Multiplexing (called CI/OFDM and PO- K. Fazel and S. Kaiser (eds.), Multi-Carrier Spread-Spectrum: Proceedings from the 5 th International © 2006 Springer. Printed in the Netherlands. 167 Workshop, 167–174.