Practical Evaluations of SEFDM: Timing Offset and Multipath Impairments

The non-orthogonal signal waveform spectrally efficient frequency division multiplexing (SEFDM) improves spectral efficiency at the cost of self-created inter carrier interference (ICI). As the orthogonal property, similar to orthogonal frequency division multiplexing (OFDM), no longer exists, the robustness of SEFDM in realistic wireless environments might be weakened. This work aims to evaluate the sensitivity of SEFDM to practical channel distortions using a professional experiment testbed. First, timing offset is studied in a bypass channel to locate the imperfection of the testbed and its impact on SEFDM signals. Then, the joint effect of a multipath frequency selective channel and additive white Gaussian noise (AWGN) is investigated in the testbed. Through practical experiments, we demonstrate the performance of SEFDM in realistic radio frequency (RF) environments and verify two compensation methods for SEFDM. Our results show first frequency-domain compensation works well in frequency non-selective channel conditions while time-domain compensation method is suitable for frequency selective channel conditions. This work paves the way for the application of SEFDM in different channel scenarios

Experimental Demonstration of Spectrally Efficient Frequency Division Multiplexing Transmissions at E-Band

This paper presents the design and the experimental demonstration of transmission of spectrally efficient frequency division multiplexing (SEFDM) signals, using a single 5-GHz channel, from 81 to 86 CHz in the E-hand frequency allocation. A purpose-built E-band SEFDM experimental demonstrator, consisting of transmitter and receiver GaAs microwave integrated circuits, along with a complete chain of digital signal processing is explained. Solutions are proposed to solve the channel and phase offset estimation and equalization issues, which arise from the well-known intercarrier interference between the SEFDM signal subcarriers. This paper shows the highest transmission rate of 12 Gb/s over a bandwidth varying between 2.67 to 4 CHz depending on the compression level of the SEFDM signals, which results in a spectral efficiency improvement by up to 50%, compared to the conventional orthogonal frequency division multiplexing modulation format

Mathematical Modelling and Signal and System Design for Spectrally Efficient Future Wireless Communications

This thesis addresses engineering studies and design of a multi-carrier signalling format known as spectrally efficient frequency division multiplexing (SEFDM), in which higher spectral efficiency compared to conventional orthogonal frequency division multiplexing (OFDM) is achieved by compressing the spacing between subcarriers below the orthogonality limit. Work reported in this thesis comprises: i) Critical revision of existing studies of multi-carrier modulation formats and techniques developed for improving the spectral efficiency, with special emphasis on SEFDM system. ii) Mathematical modelling of interference in SEFDM and its potential capacity advantages. iii) The introduction of powerful channel coding techniques to mitigate the effect of interference in SEFDM, and the design of successive interference cancellation method, with a special case for broadband and broadcasting applications (DVB-S2) being considered. iv) A novel channel estimation scheme is developed to enhance channel estimation accuracy and to reduce its complexity for SEFDM signals for 5G systems. v) An experimental demonstration of successful SEFDM signals transmission over the E-Band frequency range 81-86 GHz. The systems proposed are described in detail with numerical simulations of the newly proposed system models to compare their performance to conventional OFDM systems. It is shown that SEFDM with the aforementioned techniques can achieve significant spectral efficiency gains at the expense of moderate increase in receiver complexity or increase in the transmitted power level compared to OFDM. Overall, theoretical, simulation and experimental results show key advantages of SEFDM signals and systems over other signal formats, thus paving the way to practical inclusion of SEFDM in future wireless standards