Time-domain channel equalization for subcarrier spacing compressed FDM with SC-MMSE turbo equalization receiver

Abstract

Subcarrier spacing compressed frequency division multiplexing (SSC-FDM) has been widely researched as one of the digital multi-carrier modulation schemes for the beyond 5th generation mobile communication system. The SSC-FDM arranges subcarriers non-orthogonally in the frequency domain and improves spectral efficiency by compressing the channel bandwidth compared to the conventional orthogonal frequency division multiplexing (OFDM). On the other hand, the inter-carrier inference (ICI) mainly caused by overlapped adjacent subcarriers deteriorates the communication quality. The SSC-FDM using soft canceller followed by minimum square error filter (SC-MMSE) turbo equalization has been reported to remove the ICI in the additive white Gaussian noise (AWGN) environment, while no meaningful result in the multipath fading environment has been reported at present. In addition, the SSC-FDM poses considerable difficulties in proper channel estimation and equalization in the frequency domain due to the non-orthogonal subcarrier arrangement. In this paper, we propose a receiver architecture in which time-domain equalization schemes are applied to the SSC-FDM using SC-MMSE turbo equalization, assuming the mobile communication system. In addition, the usefulness of the proposed scheme is discussed with regard to the block error rate (BLER) and throughput performance in the multipath fading environment by computer simulation.