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The rise of the Internet of Things (IoT) presents important challenges for future radio networks. Non-orthogonal multiple access (NOMA), which allows the network to support more than one user per orthogonal resource element, was recently proposed as a promising solution that can ultimately support the daunting requirements of such networks including massive connectivity, high spectral efficiency, and low latency. Nevertheless, numerous ultra-high-reliability applications of IoT present environments that are hampered by impulsive electromagnetic interference, referred to as impulsive noise. Such noise is known to cause degradation to the overall system performance. Moreover, given the non-orthogonal multiplexing in NOMA, such noise is expected to have a relatively more pronounced impact on the system performance. Therefore, this article sheds light on the performance degradation and mitigation of impulsive noise in the context of NOMA-based IoT networks. It proposes a multistage nonlinear processing approach specifically designed for OFDM-based PDM-NOMA systems. To obtain the optimum threshold of the corresponding users, we propose a deep learning approach to estimate the impulsive noise parameters from the received OFDM symbol. This information can consequently be used to evaluate the corresponding optimal threshold using Siegert's ideal observer criterion. Finally, this work sheds light on potential opportunities and challenges that are expected to arise during the implementation of NOMA in impulsive environments. [ABSTRACT FROM AUTHOR]

In this article, we propose an index modulation system suitable for optical communications, where the intensity of the light is modulated along the time, space and frequency dimensions, building a Frequency-Hopping Spatial Multi-Pulse Position Modulation (FH-SMPPM). We analyze its performance from the point of view of its efficiency in power and spectrum, and its implementation complexity and required receiver latency. We analyze its error probability in the case of the non-turbulent free-space optical (FSO) channel. We derive formulas for the average symbol and bit error probabilities, and the simulation results show that they are tight enough for a wide range of signal-to-noise ratios and system parameters. We compare FH-SMPPM with other proposed index modulated systems of the same nature, and we highlight its distinctive advantages, like the flexibility to build an appropriate waveform under different constraints and objectives. Moreover, FH-SMPPM shows to be better performing in BER/SER and/or offer advantages in efficiency with respect to those alternatives, thus offering the possibility to be adopted for a variety of contexts. [ABSTRACT FROM AUTHOR]

In this work, we consider a sparse code multiple access uplink system, where $J$ users simultaneously transmit data over $K$ subcarriers, such that $J > K$ , with a constraint on the power transmitted by each user. To jointly optimize the subcarrier assignment and the transmitted power per subcarrier, two new iterative algorithms are proposed, the first one aims to maximize the sum-rate (Max-SR) of the network, while the second aims to maximize the fairness (Max-Min). In both cases, the optimization problem is of the mixed-integer nonlinear programming (MINLP) type, with non-convex objective functions, which are generally not tractable. We prove that both joint allocation problems are NP-hard. To address these issues, we employ a variant of the block successive upper-bound minimization (BSUM) framework, obtaining polynomial-time approximation algorithms to the original problem. Moreover, we evaluate the algorithms’ robustness against outdated channel state information (CSI), present an analysis of the convergence of the algorithms, and a comparison of the sum-rate and Jain’s fairness index of the novel algorithms with three other algorithms proposed in the literature. The Max-SR algorithm outperforms the others in the sum-rate sense, while the Max-Min outperforms them in the fairness sense. [ABSTRACT FROM AUTHOR]

In this paper, we propose an index modulation system suitable for optical communications, based on jointly driving the time and frequency of the signal: an index time-frequency hopping (I-TFH) system. We analyze its performance from the point of view of its efficiency in power and spectrum and its behavior in terms of error probability for the non-turbulent free-space optical channel. We compare I-TFH with already proposed index modulated systems of the same nature, but where the amplitude or the number of transmitters is driven instead of the signal frequency. We derive and compare approximations for the average symbol and bit error probabilities of all these systems. The simulation results show that said approximations are tight enough for a wide range of signal-to-noise ratios and system parameters. Moreover, I-TFH shows to be better performing in bit error rates and/or power efficiency than the comparative alternatives and may offer interesting properties in a variety of contexts. [ABSTRACT FROM AUTHOR]

This paper analyzes the efficacy of decoupled wireless access in a two-tier heterogeneous network. The decoupled wireless access and its performance benefits have been studied in different scenarios recently. In this paper, an in-depth analysis on its efficacy from spectral efficiency perspective is provided. To achieve this task, (i) new closed-form expressions for probability of association of user equipment with different tiers employing different frequency bands (i.e., microwave and millimeter wave) with different pathloss exponents are derived using univariate Fox's H-functions; (ii) Distributions of the distance to the serving base stations are also derived; (iii) Exact expressions of spectral efficiency for different association cases are further obtained using bivariate Fox's H-functions. Furthermore, rigorous simulation results are provided which validate the aforementioned analytical results. In addition to that, a detailed discussion on the decoupling gain of decoupled wireless access and its efficacy is also provided. Finally, despite the improvement provided by the decoupled wireless access, which is evident from the results presented in this paper, a few questions are raised on its pragmatic value. [ABSTRACT FROM AUTHOR]

Background: The treatment of advanced medullary thyroid carcinoma (MTC) has evolved significantly over the past decade. The discovery of genetic abnormalities in MTC has led to the development of targeted therapies such as vandetanib and cabozantinib. Other kinase inhibitors (KI), such as sorafenib, have been investigated in this setting and are an alternative therapeutic option. The lack of specificity of these KIs to a single target may result in additional, unexpected effects. In this report, we describe a patient with metastatic MTC and Ectopic ACTH (adrenocorticotropic hormone) Syndrome in whom treatment with sorafenib resulted in complete resolution of hypercortisolism. Summary: A 45-year-old male with progressive metastatic MTC presented with clinical manifestations suspicious for Cushing's syndrome. Investigation revealed ACTH-dependent hypercortisolism suggestive of Ectopic ACTH Syndrome. Treatment with sorafenib 400 mg twice a day was initiated resulting in a rapid and significant reduction of cortisol and ACTH levels associated with dramatic clinical improvement. The rapid and effective control of hypercortisolism in the absence of a significant tumor reduction raises the question of whether sorafenib may have a direct effect on ACTH or cortisol hypersecretion. Conclusions: This report suggests a previously unknown potential effect of sorafenib on the pituitary-adrenal axis. Further studies will be necessary to investigate the role of sorafenib in other cases of ACTH excess and to understand the mechanisms by which it alters steroid synthesis, action, or secretion. [ABSTRACT FROM AUTHOR]

Background: The treatment of advanced medullary thyroid carcinoma (MTC) has significantly evolved over the past decade. The discovery of genetic abnormalities in MTC led to the development of targeted therapies such as vandetanib and cabozantinib. Other kinase inhibitors (KI), such as Sorafenib, have been investigated in this setting and are an alternative therapeutic option. The lack of specificity of these KIs to a single target may result in additional, unexpected effects. In this report, we describe a patient with metastatic MTC and ectopic ACTH syndrome in whom treatment with Sorafenib resulted in complete resolution of hypercortisolism. Summary: A 45 year-old male with progressive metastatic MTC presented with clinical manifestations suspicious for Cushing's syndrome. Investigation revealed ACTH-dependent hypercortisolism suggestive of ectopic ACTH syndrome. Treatment with Sorafenib 400 mg twice a day was initiated resulting in a rapid and significant reduction of cortisol and ACTH levels associated with dramatic clinical improvement. The rapid and effective control of hypercortisolism in the absence of a significant tumor reduction raises the question whether sorafenib may have a direct effect on ACTH or cortisol hypersecretion. Conclusions: This report suggests a previously unknown potential effect of sorafenib on the pituitary-adrenal axis. Further studies will be necessary to investigate the role of sorafenib in other cases of ACTH excess and to understand the mechanisms by which it alters steroid synthesis, action or secretion. [ABSTRACT FROM AUTHOR]