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Wavelet Transform for OFDM-IM under Hardware Impairments Performance Enhancement
Published in Mangesh M. Ghonge, Ramchandra Sharad Mangrulkar, Pradip M. Jawandhiya, Nitin Goje, Future Trends in 5G and 6G, 2021
Asma Bouhlel, Anis Sakly, Salama Said Ikki
Moreover, the Fourier basis has long served as the unique basis for signal representation in wireless communication applications before the introduction of wavelets as an alternative base with several advantages [13–15]. The main property of the wavelet transform lies in its flexibility in the time-frequency localization. Hence, several applications of wavelets in wireless communications have been investigated in the literature, such as modeling propagation channels [16–18], antenna design and improving the cost of implementation complexity [19], signal reconstruction from noisy data [20–22], ISI and ICI interference reduction [23] and [24] and, finally, in the context of multicarrier modulations, instead of modulating the input symbols by the Fourier exponential functions, the wavelet functions can be used for data transmission. To overcome the limitations of the classic OFDM, several alternative systems have been proposed including the Wavelet-OFDM. The wide choice of the wavelet type and wavelet transform flexibility makes it a promising technique, [25] and [26]. We are interested in the following applications of wavelets in the field of multicarrier.
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Published in Lars T. Berger, Andreas Schwager, Pascal Pagani, Daniel M. Schneider, MIMO Power Line Communications, 2017
Arun Nayagam, Purva R. Rajkotia, Manjunath Krishnam, Markus Rindchen, Matthias Stephan, Deniz Rende
To overcome these issues, the Institute of Electrical and Electronics Engineers (IEEE) Communications Society sponsored the IEEE 1901 programme to develop a global standard for high-speed communication over the power line. The programme was launched in 2005. In 2007, a consolidated proposal using two of the most popular power line networking technologies was selected. The IEEE 1901 standard was approved and published in December 2010. The two technologies that were chosen were the fast Fourier transform (FFT)-orthogonal frequency division multiplexing (OFDM)-based and wavelet OFDM (W-OFDM)-based technologies. These two technologies are both specified as optional. They are not interoperable and hence an intersystem protocol (ISP) (see Chapter 10) was developed to ensure coexistence (CX) of these two technologies. Having two non-interoperable technologies was determined to be a necessary compromise to buffer for market acceptance of one technology versus the other. This is not something unique to power line technology; it happened before in the original IEEE 802.11 standard that included both direct-sequence as well as frequency-hopping spread spectrum.
Fractional Wavelet Transform based PAPR Reduction Schemes in Multicarrier Modulation System
Published in IETE Journal of Research, 2022
R. Ayeswarya, N. Amutha Prabha
In recent years, wavelet transform (WT) has been considered as an alternative for Fourier transform (FT) where CP is not appended to the signal. In [21], a wavelet-based OFDM system (DWT-OFDM) is studied and its performance is compared with the conventional FFT-OFDM system. Similarly, several works have been done by incorporating WT in the OFDM system. The analysis of PAPR in DWT-OFDM is performed by various researchers. The PAPR analysis of the wavelet-OFDM system using M-ary signaling is first shown in [22], which utilizes the Daubechies family of wavelet. This wavelet gives lowest PAPR than other wavelet families. In [23], a novel DWT-based OFDM system is proposed which uses the threshold control on the mean and reduction of PAPR. The Haar-based wavelet-OFDM is proposed in [24] by searching better tree structures of the wavelet packet. The results are analyzed and compared with Mallat tree structure. In [25], the performance of DWT-OFDM is analyzed with FFT-OFDM with a pre-processing block to increase the orthogonality among the data. The authors computed the PAPR only based on the threshold value and the PAPR reduction techniques are not analyzed for the proposed system. Similarly in [26], the author proposed wavelet packet-based PTS scheme with embedding the side information. This scheme achieves PAPR reduction similar to the existing works. The effective reduction of PAPR is achieved only at small rate by utilizing the WT.
Wavelet OFDM-Based Non-orthogonal Multiple Access Downlink Transceiver for Future Radio Access
Published in IETE Technical Review, 2018
Another promising technology that will help 5G systems achieve better spectral containment is the design of new waveforms. Waveform selection plays a paramount role in systems complexity, transceiver design, and link performance [8]. Moreover, to circumvent inter-symbol interference (ISI), which is one of the challenging problems of dispersive channels, careful choice of the waveform is inevitable [9]. In 3.9/4G, orthogonal frequency division multiplexing (OFDM) is adopted for shaping waveforms because of its ability to provide different advantages, i.e. robustness against multipath, low complexity, and compatibility for multiple input multiple output (MIMO) technologies [2]. Although these benefits increase the system throughput, which results in higher data rates, OFDM still has many limitations. The poor response of inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) filter-banks in OFDM results in spectral leakage [10], and 13 dB low side lobes make it more prone to interference [11]. Another challenging task that OFDM-based systems face is to reduce high peak-to-average power ratio () which is result of a summation of sine wave [12]. Thus, to overcome the aforementioned disadvantages and to satisfy the requirements of 5G, different waveform techniques such as filter-bank multicarrier (FBMC), universal filtered multicarrier (UFMC), and generalized frequency division multiplexing (GFDM) are suggested as alternative approaches [13]. However, FBMC is most widely considered as capable of handling the adequacy of OFDM [8]. FBMC employs high quality tight filters that help in controlling the out of band (OOB) radiations [14]. It is also considered more robust towards ISI because it provides energy containment in the frequency domain [8]. Moreover, absence of cyclic prefix (CP) in FBMC systems increases the spectral efficiency (SE), and frequency offset does not deteriorate its performance significantly [8]. FBMC has different variants, such as cosine modulated filter-bank (CMFB), filtered multi-tone (FMT), etc. [15]. Among them, wavelet OFDM (WOFDM) in the form of perfect reconstruction CMFB has been documented as a standard in IEEE P1901 for power line communication [16].