Improper signaling for SISO two-user interference channels with additive asymmetric hardware distortion

Hardware non-idealities are among the main performance restrictions for upcoming wireless communication systems. Asymmetric hardware distortions (HWD) happen when the impairments of the I/Q branches are correlated or imbalanced, which in turn generate improper additive interference at the receiver side. When the interference is improper, as well as in other interference-limited scenarios, improper Gaussian signaling (IGS) has been shown to provide rate and/or power efficiency benefits. In this paper, we investigate the rate benefits of IGS in a two-user interference channel (IC) with additive asymmetric HWD when interference is treated as noise. We propose two iterative algorithms to optimize the parameters of the improper transmit signals. We first rewrite the rate region as an pseudo-signal-to-interference-plus-noiseratio (PSINR) region and employ majorization minimization and fractional programming to find a suboptimal solution for the achievable user rates. Then, we propose a simplified algorithm based on a separate optimization of the powers and complementary variances of the users, which exhibits lower computational complexity. We show that IGS can improve the performance of the two-user IC with additive HWD. Our proposed algorithms outperform proper Gaussian signaling and competing IGS algorithms in the literature that do not consider asymmetric HWD.The work of M. Soleymani, C. Lameiro and P. J. Schreier was supported by the German Research Foundation (DFG) under grants LA 4107/1-1, SCHR 1384/7-1 and SCHR 1384/8-1. The work of I. Santamaria was supported by MINECO of Spain and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN)

Improper Gaussian signaling for the K-user MIMO interference channels with hardware impairments

This paper investigates the performance of improper Gaussian signaling (IGS) for the K-user multiple-input, multiple-output (MIMO) interference channel (IC) with hardware impairments (HWI). HWI may arise due to imperfections in the devices like I/Q imbalance, phase noise, etc. With I/Q imbalance, the received signal is a widely linear transformation of the transmitted signal and noise. Thus, the effective noise at the receivers becomes improper, which means that its real and imaginary parts are correlated and/or have unequal powers. IGS can improve system performance with improper noise and/or improper interference. In this paper, we study the benefits of IGS for this scenario in terms of two performance metrics: achievable rate and energy efficiency (EE). We consider the rate region, the sum-rate, the EE region and the global EE optimization problems to fully evaluate the IGS performance. To solve these non-convex problems, we employ an optimization framework based on majorization-minimization algorithms, which allow us to obtain a stationary point of any optimization problem in which either the objective function and/or constraints are linear functions of rates. Our numerical results show that IGS can significantly improve the performance of the K-user MIMO IC with HWI and I/Q imbalance, where its benefits increase with the number of users, K, and the imbalance level, and decrease with the number of antennas.The work of Mohammad Soleymani and Peter J. Schreier was supported by the German Research Foundation (DFG) under Grant SCHR 1384/8-1. The work of Ignacio Santamaria was supported in part by Ministerio de Ciencia e Innovacion of Spain, and in part by AEI/FEDER funds of the E.U. under Grants TEC2016-75067-C4-4-R (CARMEN) and PID2019-104958RB-C43 (ADELE)

NOMA-based improper signaling for multicell MISO RIS-assisted broadcast channels

In this paper, we study the performance of reconfigurable intelligent surfaces (RISs) in a multicell broadcast channel (BC) that employs improper Gaussian signaling (IGS) jointly with non-orthogonal multiple access (NOMA) to optimize either the minimum-weighted rate or the energy efficiency (EE) of the network. We show that although the RIS can significantly improve the system performance, it cannot mitigate interference completely, so we have to employ other interference-management techniques to further improve performance. We show that the proposed NOMA-based IGS scheme can substantially outperform proper Gaussian signaling (PGS) and IGS schemes that treat interference as noise (TIN) in particular when the number of users per cell is larger than the number of base station (BS) antennas (referred to as overloaded networks). In other words, IGS and NOMA complement to each other as interference management techniques in multicell RIS-assisted BCs. Furthermore, we consider three different feasibility sets for the RIS components showing that even a RIS with a small number of elements provides considerable gains for all the feasibility sets.The associate editor coordinating the review of this manuscript and approving it for publication was Prof. Sangarapillai Lambotharan. The work of Ignacio Santamaria was supported by the Project ADELE funded by MCIN/ AEI /10.13039/501100011033, under Grant PID2019-104958RB-C43. The work of Eduard Jorswieck was supported by the Federal Ministry of Education and Research (BMBF, Germany) through the Program of Souverän. Digital. Vernetzt.” joint Project 6G-RIC, under Grants 16KISK020K and 16KISK031

Lateral Diffusion Along Curved Lipid Bilayers

Biomembranes are thin, encapsulating, lipid-based double-layered films prevalently crowded by membrane proteins, and the interactions between the lipids and the embedded proteins are an active field of study with vital relevance for cell biology and biomedicine. Many of these studies approximate lipid bilayers as flat planar structures, even though highly curved membranes, such as membrane tethers and buds, vesicles and liposomes, and in structures like cristae in mitochondria are prevailing. So far, it has been sufficient for scientists to answer simpler questions regarding biomembranes by focusing mainly on planar lipid bilayers. However, the advancements in experimental and computational methods allow and call for a deeper understanding also on how membrane curvature can affect the properties of membranes. This thesis sheds light on the diffusion of proteins and lipids in curved lipid membranes. By presenting the first molecular dynamics simulations on the diffusion of transmembrane proteins in membrane tubes, the dynamics of the lateral diffusion in curved environments are studied in detail. The presented results highlight the importance of nanoscale curvature and compare the effect to macromolecular crowding, another currently confirmed factor related to lateral diffusion in lipid membranes. After a careful comparison between the results of this thesis and both experimental and computational work performed previously, pointers are given on how membrane curvature facilitated effects on lateral diffusion can be studied in the future

PROGRAM and PROCEEDINGS THE NEBRASKA ACADEMY OF SCIENCES 1880-2017 Including the Nebraska Association of Teachers of Science (NATS) Division Nebraska Junior Academy of Sciences (NJAS) Affiliate and Affiliated Societies

FRIDAY, APRIL 21, 2017 7:30 a.m. REGISTRATION FOR ACADEMY, Lobby of Lecture wing, Olin Hall 8:00 Aeronautics and Space Science, Session A, Olin 249 Aeronautics and Space Science, Session B, Olin 224 Chemistry and Physics, Section A, Chemistry, Olin A Collegiate Academy, Biology, Session A, Olin B Collegiate Academy, Biology, Session B, Olin 112 Collegiate Academy, Chemistry and Physics, Session A, Olin 324 8:30 Biological and Medical Sciences, Session A, Smith Callen Conference Center 9:10 Aeronautics and Space Science, Poster Session, Olin 249 9:40 Applied Science and Technology, Olin 325 10:00 Chemistry and Physics, Physics, Section B, Planetarium 10:30 Aeronautics and Space Science, Poster Session, Olin 249 11:00 MAIBEN MEMORIAL LECTURE, OLIN B – Scholarship and Friend of Science Recipients also announced. 12:00 LUNCH, PATIO ROOM, STORY STUDENT CENTER Aeronautics Group, Sunflower Room 1:00 p.m. Anthropology, Olin 111 Biological and Medical Sciences, Session B, Smith Callen Conference Center Collegiate Academy, Biology, Session A, Olin B Collegiate Academy, Biology, Session B, Olin 112 Collegiate Academy, Chemistry and Physics, Session B, Olin 324 Earth Science, Olin 249 1:05 Applied Science and Technology, Olin 325 1:15 Teaching of Science and Math, Olin 224 Chemistry and Physics, Section A, Chemistry, Olin A 2:45 Environmental Sciences, Olin 249 4:30 BUSINESS MEETING, OLIN B Abstracts of papers 2016-2017 EXECUTIVE COMMITTEE 2016-2017 PROGRAM COMMITTEE 2016-2017 POLICY COMMITTEE FRIENDS OF THE ACADEMY FRIEND OF SCIENCE AWARD WINNERS FRIEND OF SCIENCE AWARD TO KACIE BAUM FRIEND OF SCIENCE AWARD TO TODD YOUNG Author Index 141 p

Error-rate in Viterbi decoding of a duobinary signal in presence of noise and distortions: theory and simulation

The Viterbi algorithm, presented in 1967, allows a maximum likelihood de- coding of partial response codes. This study focuses on the duobinary code which is the first member of this family and has been specified for the digital part of television systems recommended by International Organizations. Up to now the error-rate, which is the main criterion of the performance, has been evaluated by simulation. Although there exist the- oretical bounds, these bounds are not satisfactory for a channel such as broadcasting (by terrestrial transmitters, cable networks or satellite) which is strongly impaired by noise, and linear and non-linear distortions. Analytical methods, verified by simulation, are presented here in order to evaluate the theoretical and exact values of the error-rate, in the form of series of numerical integrations, for a transmission in baseband or in radio-frequency with quadriphase modulation (or AM/VSB for cable networks) and coherent demodulation, in presence of noise and several distortions. This methodology can be later extended to other partial response codes, to convolutional codes and their concatenations