New design of carrier interferometry OFDM with FFT as spreading codes

In this paper, we propose a new design of efficient carrier interferometry orthogonal frequency division multiplexing (CI/OFDM) by using fast Fourier transform (FFT) as spreading codes. First, we propose the use of both positive and negative frequency of the IFFT rather than only using the positive part as in conventional method. It results new CI/OFDM waveforms which only requires a half of FFT points. Second, we replace Cl spreading with FFT for achieving lower complexity because complexity of CI is similar to that of discrete Fourier transform (DFT). Our results confirm that the proposed design is capable of achieving high efficiency and low complexity while providing high performance.