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.

In this article, a channel model for broadband indoor Power Line Communications (PLC) is presented and discussed. The modeling approach is based on the physical structure of the electrical networks inside homes and small offices. The structure has been simplified to derive a parametric model that still preserves the essential behavior of these channels in the HF band (up to 30 MHz). The model provides realistic channels by setting values to a reduced number of physical parameters. In addition, statistical distributions for such parameters that allow generating ensembles of random channels are suggested. The validity of the generated channels is assessed by comparing their behavior to the one of channels measured at several indoor power networks. Hence, this model can be employed to estimate the performance of transmission techniques on PLC channels, to aid in the design of PLC systems or to make prototype conformance tests.

Indoor broadband power-line noise is composed of three main terms: impulsive components, narrowband interferences, and background noise. Most impulsive components have a cyclostationary behavior. However, while some of them consist of impulses of considerable amplitude, width, and repetition rates of 50/100 Hz (in Europe), others have lower amplitude and shorter width but repetition rates of up to hundreds of kilohertz. Classical studies compute statistics of the impulse characteristics without taking into account these significant differences. This paper presents a detailed analysis of these noise terms with a clear distinction between their constituent terms. A classification of the narrowband interferences according to their power spectral density and their statistical behavior is also given. Finally, the instantaneous power spectral density of the background noise and its probability distribution are investigated. Some of the results presented in this paper are available for download from the web site http://www.plc.uma.es/index_eng.htm.

The ergodic capacity of fading channels modeled with aκ-μshadowed distribution is investigated to derive closed-form expressions. Theκ-μshadowed distribution is of particular interest because it contains, as special cases, other classical ones like one-side Gaussian, Rayleigh, Rician, Nakagami-m,κ-μ, and Rician shadowed distributions. The paper discusses the physical meaning of the distribution parameter variations and also their impact on the channel capacity. These results can be used to study the behavior of different channels like the ones in underwater acoustic communications, land mobile satellite systems, body centric communications, and other wireless communication applications. The analytical closed-form expression results are validated with numerical simulations.

Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these frequencies, the fading phenomena has a significant presence in the channel behavior, and the design of a reliable communication link between the network sensors will require a precise characterization of it. Fading in underwater channels has been previously measured and modeled in the audio band. However, there have been few attempts to study it at ultrasonic frequencies. In this paper, a campaign of measurements of ultrasonic underwater acoustic channels in Mediterranean shallow waters conducted by the authors is presented. These measurements are used to determine the parameters of the so-called κ-μ shadowed distribution, a fading model with a direct connection to the underlying physical mechanisms. The model is then used to evaluate the capacity of the measured channels with a closed-form expression.

The recently proposed Fluctuating Two-Ray (FTR) model is gaining momentum as a reference fading model in scenarios where two dominant specular waves are present. Despite the numerous research works devoted to the performance analysis under FTR fading, little attention has been paid to effectively understanding the interplay between the fading model parameters and the fading severity. According to a new scale defined in this work, which measures the hyper-Rayleigh character of a fading channel in terms of the Amount of Fading, the outage probability and the average capacity, we see that the FTR fading model exhibits a full hyper-Rayleigh behavior. However, the Two-Wave with Diffuse Power fading model from which the former is derived has only strong hyper-Rayleigh behavior, which constitutes an interesting new insight. We also identify that the random fluctuations in the dominant specular waves are ultimately responsible for the full hyper-Rayleigh behavior of this class of fading channels.