Fabio Versolatto

Bottom-Up Statistical PLC Channel Modeling—Part I: Random Topology Model and Efficient Transfer Function Computation

We propose an efficient bottom-up power-line communication (PLC) channel simulator that exploits transmission-line theory concepts and that is able to generate statistically representative in-home channels. We first derive from norms and practices a statistical model of European in-home topologies. The model describes how outlets are arranged in a topology and are interconnected via intermediate nodes referred to as derivation boxes. Then, we present an efficient method to compute the channel transfer function between any pair of outlets belonging to a topology realization. The method is based on a systematic remapping technique that leads to the subdivision of the network in elementary units, and on an efficient way to compute the unit transfer function referred to as the voltage ratio approach. The difference from the more conventional and complex ABCD matrix approach is also discussed. We finally show that the simulator can be configured with a small set of parameters and that it offers a theoretical framework to study the statistical PLC channel properties as a function of the topology characteristics, which is discussed in Part II of this work.

Bottom-Up Statistical PLC Channel Modeling—Part II: Inferring the Statistics

We investigate the statistical behavior of power-line communication (PLC) channels. It is inferred from the results obtained with a statistical bottom-up channel simulator (described in Part I of this paper) that uses an in-home topology model derived from the observation of wiring practices and norms. It computes channel transfer functions via the application of transmission-line theory. The comprehensive study includes the analysis of the statistics of the path-loss profile, the average channel gain, the root-mean-square delay spread, and the channel capacity. We highlight the dependency on topological information as the network layout area, the intensity of outlets, the backbone length, etc. We furthermore propose a channel classification based either on average capacity or topological information (e.g., the belonging of outlets to rooms served by the same derivation box). We show that the developed channel simulator constitutes a powerful theoretical framework for the generation and analysis of statistically representative channels with a strong connection to physical reality and close match to the results obtained in the measurements campaigns.

An MTL Theory Approach for the Simulation of MIMO Power-Line Communication Channels

We propose a bottom-up power-line communication (PLC) channel simulator for networks that deploy multiconductor cables and enable establishing a multiple-input multiple-output (MIMO) communication link between two nodes. We show that the fundamental multiconductor transmission-line (MTL) relations are a matrix form extension of the two-conductor transmission-line equations, and that they allow the application of the voltage ratio approach for the computation of the channel transfer function (CTF). Thus, any complex network can be remapped to obtain a simple representation in terms of MTL elementary units. Then, the MIMO CTF is computed as the product of the insertion loss of the units. We discuss the analytical computation of the per-unit-length (p.u.l.) parameters for two electrical cables, that we refer to as symmetric and ribbon. Further, we propose using an improved cable model for ribbon cables that accounts for the dielectric nonuniformity. We report the comparison between simulation and experimental measures for two test networks. The results are in good agreement. This validates the proposed MIMO PLC channel simulation approach.

A Fitting Algorithm for Random Modeling the PLC Channel

The characteristics of the power-line communication (PLC) channel are difficult to model due to the heterogeneity of the networks and the lack of common wiring practices. To obtain the full variability of the PLC channel, random channel generators are of great importance for the design and testing of communication algorithms. In this respect, we propose a random channel generator that is based on the top-down approach. Basically, we describe the multipath propagation and the coupling effects with an analytical model. We introduce the variability into a restricted set of parameters and, finally, we fit the model to a set of measured channels. The proposed model enables a closed-form description of both the mean path-loss profile and the statistical correlation function of the channel frequency response. As an example of application, we apply the procedure to a set of in-home measured channels in the band 2-100 MHz whose statistics are available in the literature. The measured channels are divided into nine classes according to their channel capacity. We provide the parameters for the random generation of channels for all nine classes, and we show that the results are consistent with the experimental ones. Finally, we merge the classes to capture the entire heterogeneity of in-home PLC channels. In detail, we introduce the class occurrence probability, and we present a random channel generator that targets the ensemble of all nine classes. The statistics of the composite set of channels are also studied, and they are compared to the results of experimental measurement campaigns in the literature.

In-Home Power Line Communication Channel: Statistical Characterization

A statistical characterization of the in-home power line communication channel is performed from the study of a wide set of measured channels in the 1.8-100 MHz frequency band. The study provides new insights on (a) the relation between the line impedance and the channel frequency response (CFR), and (b) on the spatial relation between the channels that share either the transmitter or the receiver outlet. Furthermore, it confirms the validity of some results presented in the literature that are limited to the 30 MHz band. The study comprises the analysis of the average channel gain, the root-mean-square delay spread and the coherence bandwidth, as well as the relation between such quantities and the phase of the CFR. Closed-form expressions are provided to model the quantities and their relations. Finally, the coverage, i.e., the relation between the maximum achievable rate and the distance, as well as the achievable rate gain offered by the use of the frequency band up to 300 MHz, are studied.

Opportunistic Relaying in In-Home PLC Networks

We consider the use of a relay to provide capacity improvements and range extension for in-home power line communication networks. In particular, we focus on opportunistic relaying where the relay is exploited only if it provides improved capacity w.r.t. the use of direct transmission between the source and the destination. The relay applies a decode and forward scheme and the channel is shared in a time division multiple access mode. The performance is studied in statistically representative in-home power line communication (PLC) networks via the use of a statistical topology model together with the application of transmission line theory for the computation of the channel transfer function among network nodes. The statistical topology model allows determining the capacity improvements as a function of the relay position. Furthermore, we determine the optimal time slot duration for each considered relay configuration, as well as we propose the use of a globally optimal time slot duration that maximizes the average network capacity. The numerical results show that significant capacity improvement can be obtained via opportunistic relaying in in-home PLC networks. The gains are more significant for low SNR scenarios and for networks composed by sub-networks each connected to the main panel via a circuit breaker that introduces signal attenuation.

A MIMO PLC random channel generator and capacity analysis

We propose a bottom-up power line communication (PLC) channel generator that exploits multi conductor transmission line (MTL) theory combined with a random topology generation algorithm to generate statistically representative inhome multiple-input multiple-output (MIMO) PLC channels. We focus on in-home PLC networks that deploy three conductors and thus provide two different circuits sharing the same return conductor. Therefore, we consider a 2×2 MIMO PLC system. We evaluate the capacity gain achieved by the MIMO configuration w.r.t. the single-input single-output (SISO) case, i.e., when only two wires are used. We further compare the simulated results with the experimental ones presented in the literature, and we show their convergence in statistical terms.

A Top-Down Random Generator for the In-Home PLC Channel

We propose a random channel generator for in-home power line communications (PLC). We follow a statistical top-down approach and we model the multipath propagation effects of the PLC channel in the frequency domain. Then, we introduce the variability into the model, i.e., we let the parameters associated to the reflections be random, according to a certain statistics. Finally, we fit the model to the experimental data. We target the average path loss and root-mean-square (RMS) delay spread of the measured channels. According to this methodology, we show that the randomly generated channels are in good agreement with the experimental ones in terms of the main metrics.

Analysis of the PLC channel statistics using a bottom-up random simulator

We consider a top-down statistical channel generator where the transfer function between pair of nodes is computed using transmission line theory applied to a randomly generated in-home network topology. We describe the random topology model that has been derived from the observation of regulations and common practices in real scenarios. This approach allows a strong connection with physical reality and constitutes a theoretical framework that makes it possible to derive considerations on the statistical channel characteristics. We focus on the study of the statistics of the channel, we investigate the dependency from the model parameters, and we show that the generated channel responses can be classified in terms of average capacity, or in terms of the location of the associated nodes within the topology layout.

Power savings with opportunistic decode and forward over in-home PLC networks

We consider a cooperative system to provide power saving, quality of service, and coverage extension over in-home power line communications (PLC) networks. We focus on a cooperative relay scheme, where the communication between source and destination nodes follows an opportunistic time division decode and forward (ODF) protocol. At the physical layer we assume the use of a multi-carrier scheme. We show that the joint problem of power and time slot allocation for the multi-carrier time division decode and forward (DF) protocol is not convex. To reduce the complexity, we propose an heuristic algorithm that considers two convex sub-problems. The validation of the algorithm is done over statistically representative in-home PLC networks. Through extensive numerical results, we show that the use of relaying allows for saving several dBs of transmitted power, yet achieving the same rate of the direct transmission. Furthermore, over multiple sub-topologies networks interconnected through circuit breakers, e.g., a multi-floor house, the relay increases the network coverage.