Bayan S. Sharif

Selective mapping (SLM) and partial transmit sequence (PTS) are attractive schemes for mitigating the high peak power inherent in orthogonal frequency division multiplexing (OFDM) signals. However, the high computational complexity and redundant side information (SI) bits have been identified as the main limitations for such techniques. The high computational complexity is mainly due to the need to perform several inverse fast Fourier transforms (IFFTs), and phase optimization process at the transmitter side. Therefore, this paper presents new SLM and PTS designs using a low complexity T-transform rather than IFFT. The use of the T-transform with SLM achieves a considerable computational complexity and peak-to-average power ratio (PAPR) reduction. Furthermore, we apply the T-transform to PTS and derive two different configurations that compromise the SI requirements and PAPR reduction. All the proposed schemes do not affect the original power spectrum of OFDM signals. The complexity analysis show that the proposed schemes have much lower complexity as compared to conventional schemes. Moreover, simulation results demonstrate that the proposed schemes are resilient to dispersion arising from multipath propagation, which is due to the frequency diversity introduced by the T-transform.

Precoding is proved to be highly efficient to improve the bit error rate (BER) of orthogonal frequency division multiplexing (OFDM) in frequency-selective fading channels. Nevertheless, most of the work reported in the literature ignores the radio frequency impairments such as carrier frequency offset (CFO), which is known to be of significant impact on OFDM. Consequently, this paper considers the performance evaluation of precoded OFDM (P-OFDM) in the presence of CFO. The performance of the considered P-OFDM is evaluated in terms of the signal-to-interference plus-noise-ratio (SINR) and BER. Various channel models are considered and closed-form analytical expressions are derived for the exact SINR. The obtained analytical results, corroborated by simulation, show that P-OFDM is substantially more sensitive to CFO compared with conventional OFDM. Generally speaking, if the normalized CFO is about 18%, then OFDM will outperform P-OFDM for most practical channel models. It is also interesting to note that the subcarriers in P-OFDM may experience different SINRs, which is not the case for conventional OFDM. The paper also considers the SINR of OFDM after the equalization process. The obtained results show that ignoring the impact of the equalization process results in inflated SINR degradation.

This work considers the bit loading problem for communication systems that utilize orthogonal frequency division multiplexing (OFDM) in conjunction with precoding (POFDM) or time-domain interleaving (IOFDM). In particular, we propose a new bit loading algorithm for P/I-OFDM that has substantially higher effective throughput and less computational complexity, when compared to bit loading in conventional OFDM systems. The obtained results show that the effective throughput of P/I-OFDM can be more than fourfold the conventional OFDM while the complexity is less than 1.5%. Moreover, the results show that the peak-to-average power ratio (PAPR) properties of the considered systems are preserved under the adaptation process.

The proliferation of mobile Internet and connected devices, offering a variety of services at different levels of performance, represents a major challenge for the fifth generation of wireless networks and beyond. This requires a paradigm shift toward the development of key enabling techniques for the next generation wireless networks. In this respect, VLC has recently emerged as a new communication paradigm to provide ubiquitous connectivity by complementing radio frequency communications. One of the main challenges of VLC systems, however, is the low modulation bandwidth of the light-emitting diodes, which is in the megahertz range. In this article, a promising technology, referred to as O-NOMA, is presented, which is envisioned to address the key challenges in the next generation of wireless networks. We provide a detailed overview and analysis of the state-of-the-art integration of O-NOMA in VLC networks. Furthermore, we provide insights on the potential opportunities and challenges as well as some open research problems that are envisioned to pave the way for the future design and implementation of O-NOMA in VLC systems.

Non-orthogonal multiple access (NOMA) has been recently proposed as a viable technology that can potentially improve the spectral efficiency of fifth generation (5G) wireless networks and beyond. However, in practical communication scenarios, transceiver architectures inevitably suffer from radio-frequency (RF) front-end related impairments that can lead to degradation of the overall system performance, with in-phase/quadrature-phase imbalance (IQI) constituting a major impairment in direct-conversion transceivers. In the present work, we quantify the effects of joint transmitter/receiver IQI on the performance of NOMA based multi-carrier (MC) systems under multipath fading conditions. Furthermore, we derive the asymptotic diversity order of the considered MC NOMA set up. Capitalizing on these results, we demonstrate that the effects of IQI differ considerably among NOMA users and depend on the underlying system parameters. For example, it is shown that the first sorted user appears more robust to IQI, which indicates that higher order users are more sensitive to the considered non-negligible impairment.

Biosignals are considered as important sources of data for diagnosing and detecting abnormalities, and modeling dynamics in the body. These signals are usually analyzed using features taken from time and frequency domain. In theory‚ these dynamics can also be analyzed utilizing Poincaré plane that intersects system’s trajectory. However‚ selecting an appropriate Poincaré plane is a crucial part of extracting best Poincaré samples. There is no unique way to choose a Poincaré plane‚ because it is highly dependent to the system dynamics. In this study, a new algorithm is introduced that automatically selects an optimum Poincaré plane able to transfer maximum information from EEG time series to a set of Poincaré samples. In this algorithm‚ EEG time series are first embedded; then a parametric Poincaré plane is designed and finally the parameters of the plane are optimized using genetic algorithm. The presented algorithm is tested on EEG signals and the optimum Poincaré plane is obtained with more than 99% data information transferred. Results are compared with some typical method of creating Poinare samples and showed that the transferred information using with this method is higher. The generated samples can be used for feature extraction and further analysis.

The proliferation of mobile Internet and connected devices, offering a variety of services at different levels of performance, represents a major challenge for the fifth generation wireless networks and beyond. This requires a paradigm shift towards the development of key enabling techniques for the next generation wireless networks. In this respect, visible light communication (VLC) has recently emerged as a new communication paradigm that is capable of providing ubiquitous connectivity by complementing radio frequency communications. One of the main challenges of VLC systems, however, is the low modulation bandwidth of the light-emitting-diodes, which is in the megahertz range. This article presents a promising technology, referred to as "optical- non-orthogonal multiple access (O-NOMA)", which is envisioned to address the key challenges in the next generation of wireless networks. We provide a detailed overview and analysis of the state-of-the-art integration of O-NOMA in VLC networks. Furthermore, we provide insights on the potential opportunities and challenges as well as some open research problems that are envisioned to pave the way for the future design and implementation of O-NOMA in VLC systems.