This paper proposes a novel ultra-dense nonorthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of orthogonal frequency-division multiplexing (OFDM). In order to eliminate the detrimental effects of NOFDM-specific intercarrier interference and correlated additive noises, eigenvaluedecomposition-aided precoding is conceived. The classical capacity formula is extended to one supporting our precoded NOFDM scheme. Optimal power allocation (PA) is developed in order to maximize the derived capacity of the proposed scheme. Furthermore, truncated PA is developed to combat the limitations due to significantly low eigenvalues, which are specifically imposed by the proposed ultra-dense NOFDM. Through analytical and numerical results, we demonstrate that the proposed NOFDM schemes with optimal and truncated PA outperform the conventional NOFDM and the classical OFDM schemes.

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This paper first investigates the effects of interframe interference (IFI) on the recent eigendecompositionprecoded (EVD) non-orthogonal frequency-division multiplexing (NOFDM) transmission scheme, where subcarrier spacing is set smaller than that of orthogonal frequency-division multiplexing (OFDM). More specifically, the system model of EVD-NOFDM is generalized to support multi-frame transmission, and we propose an optimal power allocation for the multi-frame EVD-NOFDM architecture. The NOFDM scheme's information rate bound is derived and evaluated by our theoretical analysis by assuming the presence of IFI, whereas most previous NOFDM studies ignored IFI effects. Our performance results demonstrate that the proposed multi-frame NOFDM scheme eliminates the detrimental IFI effects while attaining its specific benefits of bandwidth efficiency.

This paper proposes a novel ultra-dense nonorthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of OFDM. Eigenvalue-decomposition-aided precoding is conceived for eliminating the detrimental effects of NOFDMspecific inter-carrier interference and correlated noises. The classic capacity formula is extended to that supporting our precoded NOFDM scheme. Optimal power allocation (PA) is developed for maximizing the derived capacity of the proposed scheme. In analytical and numerical results, we demonstrate that the proposed NOFDM scheme with optimal PA outperforms the conventional NOFDM and the classic OFDM schemes.