Search

Spectral efficiency improvement is a key focus in most wireless communication systems and achieved by various means such as using large antenna arrays and/or advanced modulation schemes and signal formats. This work proposes to further improve spectral efficiency through combining non-orthogonal spectrally efficient frequency division multiplexing (SEFDM) systems with index modulation (IM), which can efficiently make use of the indices of activated subcarriers as communication information. Recent research has verified that IM may be used with SEFDM to alleviate inter-carrier interference (ICI) and improve error performance. This work proposes new SEFDM signal formats based on novel activation pattern designs, which limit the locations of activated subcarriers and enable a variable number of activated subcarriers in each SEFDM subblock. SEFDM-IM system designs are developed by jointly considering activation patterns, modulation schemes and signal waveform formats, with a set of solutions evaluated under different spectral efficiency scenarios. Detailed modelling of coded systems and simulation studies reveal that the proposed designs not only lead to better bit error rate (BER) but also lower peak-to-average power ratio (PAPR) and reduced computational complexity relative to other reported index-modulated systems. [ABSTRACT FROM AUTHOR]

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 GHz in the E-band 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 GHz 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. [ABSTRACT FROM AUTHOR]

A new optical spectrally efficient frequency division multiplexing technique, utilizing coherent detection and polarization division multiplexing, is proposed and demonstrated. The proposed system uses non-orthogonal and overlapping subcarriers to provide a significant reduction in both the electrical and optical bandwidth of up to 33%, relative to dual polarization orthogonal frequency division multiplexing (DP-OFDM), with an implementation penalty <3.2 dB. After transmission over 80 km of single mode fiber, it is shown that quadrature phase shift keying-based DP coherent optical spectrally efficient frequency division multiplexing, achieves a 2-dB gain in optical signal-to-noise ratio performance relative to eight-quadrature amplitude modulation-based DP-OFDM, which has approximately the same spectral efficiency. [ABSTRACT FROM PUBLISHER]

Spectrally efficient frequency division multiplexing (SEFDM) improves spectral efficiency, relative to the well known orthogonal frequency division multiplexing (OFDM). A fast Fourier transform (FFT) detector working with a standard Bahl-Cocke-Jelinek-Raviv (BCJR) decoder based on the Turbo principle is proposed to improve iteratively the system performance. In the presence of multipath fading channel, system modelling results show that the new system with 1024 sub-carriers can save up to 40% of bandwidth compared to the OFDM system. In addition, this work proves that by using the FFT detector, complexity is reduced. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a new optical spectrally efficient frequency division multiplexing (O-SEFDM) system, where non-orthogonal and overlapping sub-carriers are employed to provide higher spectral efficiency relative to optical-orthogonal frequency division multiplexing (O-OFDM). The O-SEFDM technique can increase spectral efficiency in both the electrical and optical domains. It is experimentally shown that for bandwidth saving up to 25%, we can achieve the same performance as O-OFDM. This is the first experimental verification of 25% optical faster than the Nyquist rate. Furthermore, for approximately the same spectral efficiency, 4QAM O-SEFDM outperforms standard 8QAM by 1.6 dB. It is experimentally shown that a lower-order modulation format can achieve a better performance by replacing a higher one. [ABSTRACT FROM PUBLISHER]

This letter proposes a hybrid soft iterative method together with Fixed Sphere Decoding (FSD) concurrently optimize performance and complexity. We show that for bandwidth compression factors of up to 25 percent, we can achieve the same performance as Orthogonal Frequency Division Multiplexing (OFDM). For systems with bandwidth compression higher than 25 percent, the complexity/performance trade-offs of the hybrid method are better than those of Truncated Singular Value Decomposition-FSD (TSVD-FSD). [ABSTRACT FROM PUBLISHER]