Differentially Modulated Spectrally Efficient Frequency-Division Multiplexing

This letter proposes a differentially modulated non-orthogonal spectrally efficient frequency-division multiplexing (D-SEFDM) architecture, which allows us to dispense with any pilot overhead needed for channel estimation at the receiver, while increasing the bandwidth efficiency in comparison to the orthogonal frequency-division multiplexing counterpart. While it is a challenging task to carry out differential-modulation-assisted non-coherent detection for multi-carrier transmissions in the presence of a severe inter-carrier interference (ICI), in the proposed scheme ICI elimination and symbol demodulation are implemented in a non-coherent manner, by exploiting the fact that ICI imposed by D-SEFDM is deterministically given, once we have a compression factor of non-orthogonal subcarriers. It is verified in our simulations that the proposed D-SEFDM exhibits a higher performance than the conventional coherent SEFDM scheme, especially for the scenarios of a high Doppler frequency.

I. Introduction

The classic differential modulation technique allows us to dispense with the pilot transmission and channel estimation (CE) [1], and hence the CE-error-induced performance degradation, which is typically imposed by its coherent counterpart, is avoided in differential non-coherent detection. Differential modulation was employed for orthogonal frequency-division multiplexing (OFDM) [2], by assuming that differentially modulated symbols in each subcarrier experience the non-dispersive frequency-flat channel. However, it is a challenging task to carry out such differential modulation and non-coherent detection in the frequency-selective channel, since equalization is inapplicable to non-coherent detection.