Time Precoding Enabled Non-Orthogonal Frequency Division Multiplexing

In this paper, we propose a time precoding scheme for cancelling inter-carrier interference in non-orthogonal frequency division multiplexing for the first time. Achieving high spectral efficiencies is a recurring and key challenge in wireless communications systems and researchers generally use high order and advanced modulation formats to approach this problem, in particular, non-orthogonal modulation formats are a topic of particular interest. Fast orthogonal frequency division multiplexing (F-OFDM) doubles the throughput of conventional OFDM by violating orthogonality of the quadrature carrier, causing interference in the real and imaginary domains. Here, we propose a precoding scheme that enables self-interference cancellation without the need of the interference level calculation. The proposed scheme is implemented in the context of a narrowband internet-of-things (NB-IoT) system and verified on a software define radio (SDR) testbed with realistic AWGN and multiple path channels from channel emulator for concept proving. By comparing with the standard OFDM transmission, the time precoded F-OFDM outperforms around 3dB by BER with same signal-to-ratio (SNR) level.