On the error statistics of turbo decoding for hybrid concatenated codes design

In this paper we propose a model for the generation of error patterns at the output of a turbo decoder using a Context Tree based modelling technique. This model can be used not only to generate the decoder error pattern behaviour with little effort, avoiding simulations, but also to investigate \u2013 with no need of performing neither a turbo code distance spectrum analysis, nor the probabilistic characterization of log-likelihood ratios or of the extrinsic information at a turbo decoder output \u2013 the performance of hybrid concatenated coding (HCC) schemes having a turbo code as component code. These coding schemes combine the features of parallel and serially concatenated codes and thus offer more freedom in code design. It has been demonstrated, in fact, that HCCs can perform closer to capacity than serially concatenated codes while still maintaining a minimum distance that grows linearly with block length

Low-complexity bound on irregular LDPC belief-propagation decoding thresholds using a Gaussian approximation

Since irregular low-density parity-check (LDPC) codes are known to perform better than regular ones, and to exhibit, like them, the so-called \u2018threshold phenomenon\u2019, this Letter investigates a low-complexity upper bound on belief-propagation decoding thresholds for this class of codes on memoryless binary input additive white Gaussian noise channels, with sum-product decoding. A simplified analysis of the belief-propagation decoding algorithm is used, i.e. consider a Gaussian approximation for message densities under density evolution, and a simple algorithmic method, defined recently, to estimate the decoding thresholds for regular and irregular LDPC codes

New Fourier Transform Approach to the Synthesis of Shaped Patterns by Linear Antenna Arrays

A new Fourier Transform (NFT) approach is developed for the synthesis of shaped patterns radiated by linear antenna arrays. The proposed method exploits in an innovative way the FT relation between the source distribution and the radiated pattern. Precisely, the finite dimension of real sources is firstly taken into account by using the sampling theorem to approximate the desired pattern as a band-limited function. It is this step that allows one to obtain an important performance improvement. Then, a continuous source is evaluated from the approximate desired pattern to finally obtain the element excitations. Numerical examples validate the method

3D Millimeter-Wave Peer-to-Peer Networks With Boundary Located Destination

This letter presents a theoretical analysis for estimating the coverage probability and the average link capacity of an interfered peer-to-peer millimeter-wave communication, when the destination lies at the boundary of a three-dimensional cell. The proposed model provides closed-form expressions for the statistics of the desired and undesired signal powers, by accounting for the impact of directional antenna gains, path-loss attenuation, mid-scale fading, interference, and noise

A new accurate approximation of the Gaussian Q-function with relative error less than 1 thousandth in a significant domain

The approximations of the Gaussian Q-function found in the literature have been often developed with the goal of obtaining high estimation accuracies in deriving the error probability for digital modulation schemes. Unfortunately, the obtained mathematical expressions are often too complex, even difficultly tractable. A new approximation for the Gaussian Q-function is presented in the form of the standard normal density multiplied by a rational function. The rational function is simply a linear combination of the first 5 integer negative powers of the same term, linear in x, using only 4 decimal constants. In this paper we make some considerations about the significant interval where to consider the Q-function in telecommunication theory. The relative error in absolute value of the given approximation is less than 0.06% in the considered significant interval

Performance Study of a Class of Irregular Near Capacity Achieving LDPC Codes

This paper investigates the performance of a class of irregular low-density parity-check (LDPC) codes through a recently published low complexity upper bound on their beliefpropagation decoding thresholds. Moreover, their performance analysis is carried out through a recently published algorithmic method, presented in Babich et al. 2017 paper. In particular, the class considered is characterized by variable node degree distributions λ(x) of minimum degree i1 > 2: being, in this case, λ0(0) = λ2 = 0, this is useful to design LDPC codes presenting a linear minimum distance growth with the block length with probability 1, as shown in Di et al.'s 2006 paper. These codes unfortunately cannot reach capacity under iterative decoding, since the achievement of capacity requires λ2 ≠ 0. However, in this latter case, the block error probability might converge to a constant, as shown in the aforementioned paper

Role of the product \u3bb\u2032(0)\u3c1\u2032(1) in determining ldpc code performance

The objective of this work is to analyze the importance of the product \u3bb\u2032 (0)\u3c1\u2032 (1) in determining low density parity check (LDPC) code performance, as far as its influence on the weight distribution function and on the decoding thresholds. This analysis is based on the 2006 paper by Di et al., as far as the weight distribution function is concerned, and on the 2018 paper by Vatta et al., regarding the LDPC decoding thresholds. In particular, the first paper Di et al. analyzed the relation between the above mentioned product and the minimum weight of an ensemble of random LDPC codewords, whereas in the second some analytical upper bounds to the LDPC decoding thresholds were determined. In the present work, besides analyzing the performance of an ensemble of LDPC codes through the outcomes of Di et al.\u2019s 2006 paper, we give the relation between one of the upper bounds found in Vatta et al.\u2019s 2018 paper and the above mentioned product \u3bb\u2032 (0)\u3c1\u2032 (1), thus showing its role in also determining an upper bound to LDPC decoding thresholds

A Simple Blass Matrix Design Strategy for Multibeam Arbitrary Linear Antenna Arrays

Multibeam antenna arrays are currently recognized as one of the enabling technologies for the next-generation communication standards. One of the key components of these systems is the beamforming network (BFN) that implements the array element excitations. This article addresses this issue by presenting a novel strategy to realize an analog feeding network, which allows an arbitrary linear array (LA) to radiate multiple arbitrary beams. In particular, an iterative procedure is conceived to design a Blass matrix using an identical directional coupler for all nodes, resulting in a very simple structure suitable for large-scale production. Two applications with arbitrary directions are illustrated as proofs-of-concept for the developed architecture: a dual-beam configuration with a null involving an aperiodic LA, and a four-beam configuration involving a periodic LA. For this second application, the effectiveness of the proposed solution is further verified by full-wave simulations and experimental measurements carried out on a fabricated prototype

The olfactory bulb: an ignored brain structure in the regulation of cardiovascular activity

Numerous studies have addressed the participation of the central nervous system in the physiological regulation of blood pressure and in the development and/or maintenance of hypertension. The central nervous system plays a key role in the short-term regulation of blood pressure although recent investigations also support its participation in the long-term modulation. Diverse brain regions and areas like the rostral ventrolateral medulla, the nucleus of the solitary tract, the locus coeruleus, amygdala and hypothalamus are intimately involved in the control of cardiovascular activity. Nevertheless, little is known about the role of the olfactory bulb. This mini review summarizes current knowledge regarding the participation of this telencephalic region in the regulation of cardiovascular activity in physiological and pathophysiological conditions.Numerosos estudios han abordado la participación del sistema nervioso central en la regulación fisiológica de la presión arterial y en el desarrollo y / o mantenimiento de la hipertensión arterial. El sistema nervioso central juega un papel clave en la regulación a corto plazo de la presión arterial, aunque investigaciones recientes apoyan su participación en la modulación a largo plazo. Diversas regiones y áreas del cerebro como la médula ventrolateral rostral, el núcleo del tracto solitario, el locus coeruleus, la amígdala y el hipotálamo están íntimamente involucradas en el control de la actividad cardiovascular. Sin embargo, poco se conoce acerca del papel del bulbo olfatorio. Esta breve revisión resume el conocimiento actual en la participación de esta región telencefálica en la regulación de la actividad cardiovascular en condiciones fisiológicas y fisiopatológicas.Sociedad Argentina de Fisiologí