Adaptive and Iterative Multi-Branch MMSE Decision Feedback Detection Algorithms for MIMO Systems

In this work, decision feedback (DF) detection algorithms based on multiple processing branches for multi-input multi-output (MIMO) spatial multiplexing systems are proposed. The proposed detector employs multiple cancellation branches with receive filters that are obtained from a common matrix inverse and achieves a performance close to the maximum likelihood detector (MLD). Constrained minimum mean-squared error (MMSE) receive filters designed with constraints on the shape and magnitude of the feedback filters for the multi-branch MMSE DF (MB-MMSE-DF) receivers are presented. An adaptive implementation of the proposed MB-MMSE-DF detector is developed along with a recursive least squares-type algorithm for estimating the parameters of the receive filters when the channel is time-varying. A soft-output version of the MB-MMSE-DF detector is also proposed as a component of an iterative detection and decoding receiver structure. A computational complexity analysis shows that the MB-MMSE-DF detector does not require a significant additional complexity over the conventional MMSE-DF detector, whereas a diversity analysis discusses the diversity order achieved by the MB-MMSE-DF detector. Simulation results show that the MB-MMSE-DF detector achieves a performance superior to existing suboptimal detectors and close to the MLD, while requiring significantly lower complexity.Comment: 10 figures, 3 tables; IEEE Transactions on Wireless Communications, 201

Tree-structured complementary filter banks using all-pass sections

Tree-structured complementary filter banks are developed with transfer functions that are simultaneously all-pass complementary and power complementary. Using a formulation based on unitary transforms and all-pass functions, we obtain analysis and synthesis filter banks which are related through a transposition operation, such that the cascade of analysis and synthesis filter banks achieves an all-pass function. The simplest structure is obtained using a Hadamard transform, which is shown to correspond to a binary tree structure. Tree structures can be generated for a variety of other unitary transforms as well. In addition, given a tree-structured filter bank where the number of bands is a power of two, simple methods are developed to generate complementary filter banks with an arbitrary number of channels, which retain the transpose relationship between analysis and synthesis banks, and allow for any combination of bandwidths. The structural properties of the filter banks are illustrated with design examples, and multirate applications are outlined

Lattice Qcd for Neutrinoless Double Beta Decay: Short Range Operator Contributions

The Standard Model (SM), the fundamental theory of particle physics, very success- fully describes the world around us, and with a only a few tantalizing exceptions, all the experiments we have performed to understand the fundamental laws of nature. However, the SM accounts for only 4-5% of the matter and energy in the universe, with approxi- mately 25% composed of dark matter (DM) and the remaining 70% composed of the more mysterious dark energy. Further, the SM content of the universe is composed of an excess of matter over anti-matter of about 1 part per billion. Despite being a small excess, it is orders of magnitude larger than can be explained by the SM alone. These observations strongly suggest there is new physics Beyond the Standard Model (BSM). One of the most exciting prospects for searching for physics BSM is 0νββ. Detecting 0νββ is one of the current top scientific priorities of The Nuclear Science Advisory Committee and a new initiative, a ton-scale 0νββ experiment, is described in their Long Range Plan for Nuclear Science [1]. There are many experiments designed world wide to search for evidence of physics BSM, however, the ton-scale search for 0νββ in large nuclei is the most prominent new nuclear physics (NP) experiment. 0νββ, if allowed, is an extremely rare nuclear decay, which violates one of the fundamental symmetries of the Standard Model (SM). There- fore, if observed, 0νββ may provide a possible explanation for the observed abundance of matter over anti-matter in the universe as this lepton number violation could be converted to baryon number violation very early in the universe. 0νββ would happen in a process where two neutrons decay simultaneously into two protons and two electrons but without the emission of any neutrinos. If the neutrinos are their own antiparticles (Majorana-like), the most plausible case, a neutrino emitted from one of the beta-decaying neutrons can be absorbed by the other neutron. This interaction would happen at short distance scales. Thus, a series of calculations based on Quantum ChromoDynamics (QCD), the fundamen- tal theory of nuclear strong interactions, will be required to interpret the results of 0νββ experiments, along with many other NP experiments. However, the only way to perform such calculations to the required accuracy is by using a numerical technique known as lattice QCD (LQCD)

Meson Photo-Couplings From Lattice Quantum Chromodynamics

We explore the calculation of three-point functions featuring a vector current insertion in lattice Quantum Chromodynamics. These three-point functions, in general, contain information about many radiative transition matrix elements simultaneously. We develop and implement the technology necessary to isolate a single matrix element via the use of optimized operators, operators designed to interpolate a single meson eigenstate, which are constructed as variationally optimized linear combination of meson interpolating fields within a large basis. In order to frame the results we also explore some well known phenomenology arising within the context of the constituent quark model before transitioning to a lattice calculation of the spectrum of isovector mesons in a version of QCD featuring three flavors of quarks all tuned to approximately the physical strange quark mass. We then proceed to calculate radiative transition matrix elements for the lightest few isovector pseudoscalar and vector particles. The dependence of these form factors and transitions on the photon virtuality is extracted and some model intuitions are explored

Projectability disentanglement for accurate and automated electronic-structure Hamiltonians

Maximally-localized Wannier functions (MLWFs) are a powerful and broadly used tool to characterize the electronic structure of materials, from chemical bonding to dielectric response to topological properties. Most generally, one can construct MLWFs that describe isolated band manifolds, e.g. for the valence bands of insulators, or entangled band manifolds, e.g. in metals or describing both the valence and the conduction manifolds in insulators. Obtaining MLWFs that describe a target manifold accurately and with the most compact representation often requires chemical intuition and trial and error, a challenging step even for experienced researchers and a roadblock for automated high-throughput calculations. Here, we present a very natural and powerful approach that provides automatically MLWFs spanning the occupied bands and their natural complement for the empty states, resulting in Wannier Hamiltonian models that provide a tight-binding picture of optimized atomic orbitals in crystals. Key to the success of the algorithm is the introduction of a projectability measure for each Bloch state onto atomic orbitals (here, chosen from the pseudopotential projectors) that determines if that state should be kept identically, discarded, or mixed into a disentangling algorithm. We showcase the accuracy of our method by comparing a reference test set of 200 materials against the selected-columns-of-the-density-matrix algorithm, and its reliability by constructing Wannier Hamiltonians for 21737 materials from the Materials Cloud

Review of Recent Trends

This work was partially supported by the European Regional Development Fund (FEDER), through the Regional Operational Programme of Centre (CENTRO 2020) of the Portugal 2020 framework, through projects SOCA (CENTRO-01-0145-FEDER-000010) and ORCIP (CENTRO-01-0145-FEDER-022141). Fernando P. Guiomar acknowledges a fellowship from “la Caixa” Foundation (ID100010434), code LCF/BQ/PR20/11770015. Houda Harkat acknowledges the financial support of the Programmatic Financing of the CTS R&D Unit (UIDP/00066/2020).MIMO-OFDM is a key technology and a strong candidate for 5G telecommunication systems. In the literature, there is no convenient survey study that rounds up all the necessary points to be investigated concerning such systems. The current deeper review paper inspects and interprets the state of the art and addresses several research axes related to MIMO-OFDM systems. Two topics have received special attention: MIMO waveforms and MIMO-OFDM channel estimation. The existing MIMO hardware and software innovations, in addition to the MIMO-OFDM equalization techniques, are discussed concisely. In the literature, only a few authors have discussed the MIMO channel estimation and modeling problems for a variety of MIMO systems. However, to the best of our knowledge, there has been until now no review paper specifically discussing the recent works concerning channel estimation and the equalization process for MIMO-OFDM systems. Hence, the current work focuses on analyzing the recently used algorithms in the field, which could be a rich reference for researchers. Moreover, some research perspectives are identified.publishersversionpublishe