This paper focuses on the parameterization of the multipath propagation model (MPM) for indoor broadband power line communications (PLC), which up to now has been established in an heuristic way. The MPM model was initially proposed in the PLC context for outdoor channels in the band up to 20 MHz, but its number of parameters becomes extremely large when used to model indoor channel frequency responses (CFR), which are much more frequency-selective than outdoor ones, and the band is extended to 80 MHz. This work proposes a fitting procedure that addresses this problem. It allows determining the model parameters that yield the best fit to each channel of a large database of single-input single-output (SISO) experimental measurements acquired in typical home premises of different European countries. Then, the statistics of the MPM parameters are analyzed. The study unveils the relation between the model parameters and the main characteristics of the actual CFR like the frequency selectivity and the average attenuation. It also estimates the probability density function (PDF) of each parameter and proposes a fitting distribution for each of them. Moreover, the relationship among the main parameters of the model, as well as their impact on the performance of PLC communication systems are also explored. Provided results can be helpful for the development of MPM-based models for indoor broadband PLC.

We introduce, characterize and validate the independent fluctuating two-ray (IFTR) fading model, which consists of two specular (dominant) components that fluctuate independently, plus a diffuse one resulting from the reception of multiple scattered waves. The IFTR model complements the fluctuating two-ray (FTR) model, in which the specular components are fully correlated and fluctuate jointly. The chief probability functions of the received SNR of this new model, including the PDF, CDF and MGF, are given in closed-form. The IFTR model is empirically validated using measured data from Line-Of-Sight (LOS) millimeter-wave channels, showing a better fit than the FTR model and other models previously used in these channels, and providing a remarkable improvement at 73 GHz.

Orthogonal frequency division multiplexing (OFDM) signals with rectangular pulses exhibit low spectral confinement. Shaping their power spectral density (PSD) is imperative in the increasingly overcrowded spectrum to benefit from the cognitive radio (CR) paradigm. However, since the available spectrum is non-contiguous and its occupancy changes with time, the spectral shaping solution has to be dynamically adapted. This work proposes a framework that allows using a reduced set of preoptimized pulses to shape the spectrum of OFDM signals, irrespective of its spectral width and location, by means of simple transformations. The employed pulses combine active interference cancellation (AIC) and adaptive symbol transition (AST) terms in a transparent way to the receiver. They can be easily adapted online by the communication device to changes in the location or width of the transmission band, which contrasts with existing methods of the same type that require solving NP-hard optimization problems.

This letter introduces a new approach to the problem of approximating the probability density function (PDF) and the cumulative distribution function (CDF) of a positive random variable. The novel approximation strategy is based on the analysis of a suitably defined sequence of auxiliary variables which converges in distribution to the target variable. By leveraging such convergence, simple approximations for both the CDF and PDF of the target variable are given in terms of the derivatives of its moment generating function (MGF). In contrast to classical approximation methods based on truncated series of moments or cumulants, our approximations always represent a valid distribution and the relative error between variables is independent of the variable under analysis. The derived results are then used to approximate the statistics of positive-definite real Gaussian quadratic forms, comparing our proposed approach with other existing approximations in the literature.

Orthogonal frequency division multiplexing (OFDM) signals with rectangularly windowed pulses exhibit low spectral confinement. Two approaches usually referred to as pulse-shaping and active interference cancellation are classically employed to reduce the out-of-band emission (OOBE) without affecting the receiver. This paper proposes a spectral shaping method that generalizes and unifies these two strategies. To this end, the OFDM carriers are shaped with novel pulses, referred to as generalized pulses, that consist of the ones used in conventional OFDM systems plus a series of cancellation terms aimed at reducing the OOBE of the former. Hence, each generalized pulse embeds all the terms required to reduce its spectrum in the desired bands. This leads to a data-independent optimization problem that notably simplifies the implementation complexity and allows the analytical calculation of the resulting power spectral density (PSD), which in most methods found in the literature can only be estimated by means of simulations. As an example of its performance, the proposed technique allows complying with the stringent PSD mask imposed by the EN 50561-1 with a data carrier loss lower than 4%. By contrasts, 28% of the data carriers have to be nulled when pulse-shaping is employed in this scenario.

This note corrects a recurrent erratum in Section VII of our paper “An MTL-based channel model for indoor broadband mimo power line communications”[1]. Errors are concerned with the quantification of the spatial correlation of MIMO channels by means of the condition number of the channel matrix. According to the definition given in expression (25) of the paper, the higher the condition number, the higher the spatial correlation. However, Section VII is written as if high condition numbers correspond to low spatially correlated channels. Hence,whenever it is said that a given fact reduces the spatial correlation or, equivalently, that it yields lower spatially correlated channels, it should say exactly the opposite, i.e, the referred fact increases the spatial correlation or yields higher spatially correlated channels; and vice versa.

The recent release of indoor power line communication (PLC) standards with multiple-input multiple-output (MIMO) capabilities has led to the need for channel models that reflect the multiconductor nature of the grid. This paper proposes a model, based on the multiconductor transmission line theory, along with a random PLC channel generator operating in the frequency range from 1 to 100 MHz. Its distinctive features are the modeling of three key elements: the asymmetry in the layout caused by the derivations to the light switches, the impedance of the devices connected to the three wires of the grid, and the variable distance between the conductors in loose wiring deployments. The influence of these elements in the spatial correlation between the streams of the MIMO links is studied and compared with measurements.

In this work, a network simulator for power line communications based in the Homeplug-AV technology is presented. The simulator implements both the physical and the MAC layers, along with an in-home power line channel generator, which makes it very useful in a wide variety of network optimization procedures. To the authors' knowledge, performance evaluation of the MAC layer of Homeplug-AV by means of simulations has been always accomplished assuming excessively simplistic channel conditions. Therefore, this simulator represents an important contribution, as it includes a realistic physical model along with the CSMA/CA protocol described in the standard. In this paper, the proposed simulator is employed to evaluate the performance of the Homeplug-AV standard in an in-home network. The obtained results are then applied to video services planning in networks based in this standard.

This paper presents a statistical characterization of in-vehicle power lines, based on channel measurements carried out in a automobile. In particular, the impact of the engine speed on the characteristics of the channels is analyzed. Performance of an Orthogonal Frequency-Division Multiplexing (OFDM) system is assessed using the channel measurements.

In this paper, an FPGA-based channel emulator for indoor power line communications (PLC) is described. It has been designed for a band up to 30 MHz and is able to emulate time-varying channels and to generate a great variety of disturbances.

Discrete multitone (DMT) modulation is a suitable technique to cope with main impairments of broadband indoor power-line channels: spectral selectivity and cyclic time variations. To attain higher bit rates, in those subbands with good transmission conditions a high number of bits per symbol must be allocated and, hence, synchronization issues become an important concern. This paper analyzes the performance of a conventional DMT timing recovery scheme designed for linear time-invariant (LTI) channels, like digital subscriber lines, when employed over indoor power-lines. The influence of the channel short-time variations and the sampling jitter on the synchronization scheme performance is assessed. Proper parameterization of the timing recovery scheme is provided on the basis of reducing the impact of channel time variations while maintaining the ability to track the sampling jitter.

The purpose of this paper is to analyze the properties of indoor power line communications channels when they are used for broadband transmission. It will be shown that these channels exhibit a short-term variation, due to the fact that high-frequency parameters of electrical devices depend on the instantaneous amplitude of mains voltage. This phenomenon leads to a channel model proposal based on a linear periodically time-varying system and cyclostationary random noise. A measurement system, designed to capture these time variations in real power networks, and some of the most significant results obtained with it, are presented. In addition, a statistical analysis of the measurements performed in several indoor power line scenarios is included, so that the relevance of time variations in actual channels can be evaluated.