Indoor Power Line Communication Research Articles

In-band full-duplex MIMO PLC systems for relaying networks

In Power Line Communications (PLC), there are regulatory masks that restrict the transmit power spectral density for electromagnetic compatibility reasons, which creates coverage issues despite the not too long distances. Hence, PLC networks often employ repeaters/relays, especially in smart grid neighborhood area networks. Even in broadband indoor PLC systems that offer a notable data rate, relaying may pave the way to new applications like being the backbone for wireless technologies in a cost-effective manner to support the Internet-of-things paradigm. In this paper, we study Multiple-Input Multiple-Output (MIMO) PLC systems that incorporate in-band full-duplex functionality in relaying networks. We present several MIMO configurations that allow end-to-end half-duplex or full-duplex operations and analyze the achievable performance with state-of-the-art PLC systems. To reach this analysis, we get channel realizations from random network layouts for indoor and outdoor scenarios. We adopt realistic MIMO channel and noise models and consider transmission techniques according to PLC standards. The concepts discussed in this work can be useful in the design of future PLC relay-aided networks for different applications that look for a coverage extension and/or throughput: smart grids with enhanced communications in outdoor scenarios, and “last meter” systems for high-speed connections everywhere in indoor ones.

Channel estimation for OFDM-based indoor broadband power line communication systems

State-of-the-art indoor broadband power line communications (PLC) systems use orthogonal frequency division multiplexing (OFDM) signals with constellations up to 10 bits/symbol, which makes channel estimation a key aspect. This paper focuses on the initial channel estimation used in the payload, which might be further adapted by means of a decision-directed strategy. This initial estimate has to be computed on a per-frame basis and can be accomplished from the preamble, the header symbol (assuming that it has been correctly decoded) or from a combination of both. This work proposes simple channel estimation techniques for this problem and derives their most appropriate parameters. They are compared with the linear minimum mean squared-error (LMMSE) estimator and others commonly used in wireless scenarios by considering both their performance and computational complexity. The factors limiting the performance of the estimators based on the preamble and the header symbols are analyzed and the implications of the differences between PLC and wireless channels, such as the absence of fading, in the design of estimation techniques that require knowledge of the channel statistics are discussed. A performance analysis of the considered techniques is accomplished in a set of 171 measured indoor PLC channels. Obtained results indicate that estimators from the header perform better than those based on the preamble symbols and we provide a computationally simple estimator that gives nearly optimum performance by combining estimates from both the preamble and the header symbols.

Performance Analysis of Power Line Communication System for Massive Indoor IoT Applications

This study explores the utilization of low-voltage indoor power line communication (PLC) technology within the framework of a split centralized radio access network (C-RAN) architecture, aimed at enhancing 5G indoor mobile coverage for the Internet of Things (IoT). A primary focus of this investigation is the comprehensive evaluation of the system’s performance in terms of radio and access latency. Several critical variables come into play, including available bandwidth, the chosen transmission technology, and the number of wireless IoT devices within the network. An analytical model, employing queuing theory, Markovian models, and stochastic geometry, is formulated to assess the radio-access delay spanning the air interface and the innovative PLC-based front-hauling system proposed in our previous study. The precision of this model is validated through simulations, ensuring that the proposed system effectively meets the stringent latency constraints required by eCPRI, thus contributing to the improvement of 5G indoor mobile coverage for the IoT network.

High performance binary LDPC-coded OFDM systems over indoor PLC channels

Power line communication (PLC) technology is actually among the most renowned technologies for home environments due to their low-cost installation opportunities. In this study, the bit error rate (BER) performances of binary low-density parity check (LDPC) coded orthogonal frequency-division multiplexing (OFDM) systems have been considered over indoor PLC channels. Performances comparison of diverse soft and hard decision LDPC decoder schemes such as Min-Sum (MS), weighted bit flipping (WBF), gradient descent bit-flip (GDBF), noisy gradient descent bit-flip (NGDBF) and its few variants including the single-bit NGDBF (S-NGDBF), multi-bit NGDBF (M-NGDBF) and smoothed-multi-bit NGDBF (SM-NGDBF) decoders were examined in the modeled network. To evaluate the BER performance analyses three different PLC channel scenarios were generated by using new and more realistic PLC channel model proposal were also employed. All of the simulations performed in Canete’s PLC channel model showed that remarkable performance improvement can be achieved by using short-length LDPC codes. Especially, the improvements are striking when the MS or SM-NGDBF decoding algorithms are employed on the receiver side.

Modelling impulsive noise in indoor powerline communication systems

Powerline communication (PLC) is an emerging technology that has an important role in smart grid systems. Due to making use of existing transmission lines for communication purposes, PLC systems are subject to various noise effects. Among those, the most challenging one is the impulsive noise compared to the background and narrowband noise. In this paper, we present a comparative study on modelling the impulsive noise amplitude in indoor PLC systems by utilising several impulsive distributions. In particular, as candidate distributions, we use the symmetric alpha -Stable (Salpha S), generalised Gaussian, Bernoulli Gaussian and Student’s t distribution families as well as the Middleton Class A distribution, which dominates the literature as the impulsive noise model for PLC systems. Real indoor PLC system noise measurements are investigated for the simulation studies, which show that the Salpha S distribution achieves the best modelling success when compared to the other families in terms of the statistical error criteria, especially for the tail characteristics of the measured data sets.

On the Performance of a Cooperative PLC-VLC Indoor Broadcasting System Consisting of Mobile User Nodes for IoT Networks

A novel mixed cooperative relay assisted indoor power line communication - visible light communication (PLC-VLC) system for indoor broadcasting purpose consisting of mobile end user nodes for Internet of Things (IoT) network is presented in this study. Here, the PLC link acts as a backbone system to the VLC link by connecting to the latter with the help of decode and forward (DF) relay. The channel gain of the VLC systems is considered to be a function of user mobility which is modeled using random waypoint (RWP) mobility model. We present novel expressions for probability density function and cumulative distribution function for the equivalent end to end instantaneous signal to noise ratio (SNR) for this cooperative system. Using these derived statistics, we further evaluate the performance of the system under consideration in terms of link failure probability and average bit error rate.

A Time Domain Noise Measurement and Analysis for Broadband Indoor Power Line Communications

A Time Domain Noise Measurement and Analysis for Broadband Indoor Power Line Communications

Selection of indoor relay node positions for a three‐hop low‐voltage broadband power line communication system

Low-voltage broadband power line communication (PLC) system transmits its information by the power line on the existed infrastructure. However, PLC attenuation and its harsh environment make it difficult to establish a reliable communication between the source and destination nodes, and relay-aided (RA) PLC technology can be used to solve this issue to increase the transmission rate and coverage. In this study, an indoor three-hop RA PLC system is under investigation for the first time. Based on a simple PLC attenuation model, the optimal relay node positions and transmitted power distribution of each node are studied to get the best system performance in theory. Then, a criterion of selection optimal relay node positions in a practical power-line network is derived by solving an optimisation problem. Finally, for a specific power-line network, the criterion for the selection of optimal relay node positions at the existed sockets between the source and destination nodes is verified. The theoretical work in this study could be useful in the design of broadband multi-hop RA PLC systems and their engineering applications.

An Alternate Method for Prediction and Analysis of Notch Characteristics in Indoor Power Lines Under Varied Channel Conditions

One of the challenges faced by indoor power line communication systems is the frequency-selective channels that are time varying and dependent on a large number of variabilities. A probable solution is to extract as much determinism as possible through prediction and statistical analysis of the frequency-selective notches. However, such deterministic tools are available only for simple open- and short-circuit branches and not for complex loads and topologies. This paper proposes an alternate method to predict and analyze notches using a minimum of four parameters without evaluating the transfer function. Termed as the load frequency mapping, the method is applicable for any frequency-dependent time-invariant loads and topologies and also capable of performing statistical analysis of random channels. A high decrease in prediction error (99.46–93.63%) is found for all the channels analyzed. Statistical analysis of 26 power line cables using random loads shows that some cables and loads offer more variations in frequency selectivity than others. For capacitive loads, the variation is more for the low-frequency notches and for those modeled as parallel resonant circuits at the frequencies near the resonance. Maximum variation is found for cables with high characteristic impedance with loads having high resonant frequencies and low quality factor and least for inductive loads. The power line therefore has considerable amount of determinism, and this can be incorporated to complement for fading channels or analysis of variability optimized for dual purpose of power delivery and data transfer.

Multi Band OFDM Alliance Power Line Communication System

This paper describes a new communication system that meets the quality of service requirements for home high speed communications. This system is based on Ultra-Wide Band (UWB) and Power Line Communication (PLC) technologies.The performances of our MBOA-PLC (Multi Band OFDM Alliance - Power Line Communication) system was evaluated by Matlab simulation to predict the efficiency of the UWB over PLC technology and their potential applications in the home network. The system compares the transmitted and received data to calculate the bit error rate (BER), based on the energy per bit to noise power spectral density ratio (Eb / N0). This is achieved by varying the number of information bits transmitted per OFDM symbol and the convolutional coding rate. The BER performance analysis presented in this study aims for a very high-speed transmission on indoor CPL channels, at more than 200 Mbps. The maximum data rate available on the market does not exceed 200 Mbps, despite the use of advanced coding and modulation systems, such as 1024 QAMs and the turbo-codes used for the Homeplug AV standard. The existing technology has little room to increase throughput because the available operational bandwidth limits the capacity of the channel.In the proposed PHY model for indoor PLC communications, QPSK mapping is used to provide good BER performance at high data rates that existing techniques have difficulty obtaining.

Channel model proposal for indoor relay‐assisted power line communications

Due to its tree-like topology, the point-to-point (P2P) indoor power line communication (PLC) channel exhibits a similar broadcasting property as the wireless propagation channel shows. However, after relay nodes are introduced, the relay-assisted PLC (RaPLC) channel shows some notable differences compared with its wireless counterpart. A lot of results about the relay-assisted wireless channel can be found in the literature, but the work of modelling RaPLC channel has rarely been discussed in detail. As the first attempt to fill this gap, we apply the ABCD method to compute the channel transfer function (CTF) of the RaPLC channel. It has been clarified that, in general, the CTF of RaPLC channel cannot be obtained as a cascade of two independent P2P PLC sub-channels located on two sides of the relay node. Also, it is shown that the challenge of generating CTF of the RaPLC channel can be transformed into a group of equivalent P2P PLC channel modelling tasks. Under the time-division duplexing constraint, the relay node changes its working mode from the receiving phase to the transmitting phase, which shows that the RaPLC channel is abruptly time-varying in nature. Following the hybrid bottom-up approach, a statistical channel model with a simple six-segment indoor power grid topology has been developed for simulation. Practical measurements and numerical examples verify our results.

Power line communications under Rayleigh fading and Nakagami noise: novel insights on the MIMO and multi‐hop techniques

This work targets a comprehensive understanding of the impact of the serial-relaying and multiple-input-multiple-output (MIMO) fading mitigation techniques on the performance of indoor power line communication (PLC) systems. While these techniques were studied extensively under additive Gaussian noise, we aim at highlighting the implications of Nakagami-like noise on the achievable performance levels. The author derive approximate closed-form expressions for the bit error rate (BER) under Rayleigh fading and Nakagami-m background noise where the obtained approximations are very close to the exact BERs. The derived expressions are useful for evaluating the achievable diversity orders and for relating the BER to the main parameters of the PLC system in a direct and intuitive way. In this context, we analytically prove that MIMO doubles the diversity order with different combining schemes while the diversity order of a system under Nakagami-like noise is only half the diversity order that would have been obtained under Gaussian noise. The author also shows that multi-hop relaying does not enhance the diversity order.

Optimization for Relay-Assisted Broadband Power Line Communication Systems with QoS Requirements Under Time-varying Channel Conditions

The user experience of practical indoor power line communication (PLC) applications is greatly affected by the system quality-of-service (QoS) criteria. With a general broadcast- and-multi-access (BMA) relay scheme, in this work we investigate the joint source and relay power optimization of the amplify-and-forward (AF) relay systems used under indoor broad- band PLC environments. To achieve both time diversity and spatial diversity from the relay- involved PLC channel, which is time-varying in nature, the source node has been configured to transmit an identical message twice in the first and second signalling phase, respectively. The QoS constrained power allocation problem is not convex, which makes the global optimal solution is computationally intractable. To solve this problem, an alternating optimization (AO) method has been adopted and decomposes this problem into three convex/quasi-convex sub-problems. Simulation results show the fast convergence and short delay of the proposed algorithm under realistic relay-involved PLC channels. Compared with the two-hop and broadcast-and- forward (BF) relay systems, the proposed general relay system meets the same QoS requirement with less network power assumption.

Analysis of Bursty Impulsive Noise in Low-Voltage Indoor Power Line Communication Channels: Local Scaling Behaviour

Power line communication (PLC) channels are prone to multipath propagation due to impedance mismatch, and impulsive noise whose characteristics are still not well established in the literature. Moreover, measurements show that this impulsive noise appear in bursts, non-Gaussian and cyclostationary and as such cannot be modeled as the convenient additive white Gaussian noise (AWGN). Transceivers optimized for AWGN may not necessarily perform well for the PLC noise. Therefore, investigating the characteristics of PLC noise is very important for accurate modeling of the same. This study presents multifractal analysis of bursty impulsive noise measured from power line networks from three different environments. We employ multifractal detrended fluctuation analysis, which is a well-developed multifractal analysis technique for non-stationary time series data and easy to implement to analyze measured noise data. Results show that power line noise exhibits both long-range dependence (LRD) and multifractal scaling behavior with different strengths depending on the environments where they were captured. The multiscaling behavior is due to long-range correlation inherent in the power line noise. The source of this local multiscaling behavior is determined by analysis a shuffled series of the original data captured from the power network. Multifractal analysis is able to show clearly both the strengths and frequency of occurrence of bursts occurring in PLC noise which can then be applied in accurate modeling of the noise. The significance of these results is that new power line noise models should be developed that captures both LRD and multifractal scaling for more accurate performance evaluation of power line communication systems. The existing noise models though able to replicate temporal dependence of PLC noise, are not able to capture this local scaling behavior which results show is inherent in PLC noise.

Effects of Load Distribution on Indoor Power Line Communication

In this paper, we discuss the dependence of the insertion gain between two modems upon the distribution of the loads on the network. The results are deduced from a propagation model applied to a three-wire line configuration and in the presence of one or two branches. The impedances presented by different classes of household appliances are modeled by equivalent electrical circuits, available in the literature. The insertion gain and the Shannon capacity of the link are studied both with and without the presence of the branches. The results of a statistical approach are also described; these are based on numerous observations by randomly choosing the distribution of the loads on the network and the length of one of the two branches. Lastly, the cumulative distribution functions of the coherence bandwidth and of the root mean square delay spread are given.

Channel modeling for high-speed indoor powerline communication systems: the lattice approach

The transmission of high-frequency signals over powerlines, known as powerline communications (PLC), plays an important role in contributing toward global goals for broadband services inside the home and office. In this paper, we aim to contribute to this ideal by presenting a powerline channel modeling approach which describes a powerline network as a lattice structure. In a lattice structure, a signal propagates from one end into a network of boundaries (branches) through numerous paths characterized by different reflection/transmission properties. Due to theoretically infinite number of reflections likely to be experienced by a propagating wave, we determine the optimum number of paths required for meaningful contribution toward the overall signal level at the receiver. The propagation parameters are obtained through measurements and other model parameters are derived from deterministic powerline networks. It is observed that the notch positions in the transfer characteristics are associated with the branch lengths in the network. Short branches will result in fewer notches in a fixed bandwidth as compared to longer branches. Generally, the channel attenuation increase with network size in terms of number of branches. The proposed model compares well with experimental data.

Broadband Characteristics for Multi-Path Power Line Communication Channels: Indoor Environments

In this paper we propose a broadband frequency-domain model for practical indoor power-line communication (PLC) channels. We consider a top-down strategy where the channel is regarded as a multipath propagation environment with frequency-selective fading. The model is based on the physical signal propagation effects of numerous PLC architectures which comprise unknown number of branches and load conditions. We further consider the attenuation of a typical power-line to be increasing with length as well as frequency. The applicability of the model is verified with measurements from real channels from our laboratories and offices within the band 1-30 MHz. The generated channel frequency response (CFR) has a good agreement with measurements results from real PLC channels. Furthermore, to improve the generality of the model application, we study the dispersive nature of these channels through their impulse responses (IR), and then compare our results with findings from elsewhere. The comparison is made in terms of the maximum excess delay, mean excess delay and root mean square (rms) delay spread.

An MTL-Based Channel Model for Indoor Broadband MIMO Power Line Communications

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.

Bit and Power Loading for Narrowband Indoor Powerline Communications

The problem of bit and power loading for bit rate maximization in orthogonal frequency division multiplexing data communications over indoor powerline channels is investigated, and a simple method for bit/power allocation in half a cycle of the mains is developed. The proposed solution is based on the so-called Zadeh’s representation for modeling the linear periodically time-varying behavior of powerline channels. Numerical results show the superiority of the proposed method over other solutions available in the technical literature in a real-world scenario.

High‐resolution and low‐complexity dynamic topology estimation for PLC networks assisted by impulsive noise source detection

Power line communication (PLC) network is a promising solution for smart grid and home broadband applications. However, its topology is not always available and is time-varying due to frequent load changes. The existing topology estimation approaches require installation of a large number of PLC modems or suffer limited resolution. Moreover, they are designed for static PLC networks and need to be repeated at a regular basis to combat topology changes. The authors propose a high-resolution and low-complexity dynamic topology estimation scheme for time-varying indoor PLC networks, which consists of three parts: (i) a time-frequency domain reflectometry based path length estimation method, which requires measurement at a single PLC modem and achieves a much higher resolution than the frequency domain reflectometry based method; (ii) a node-by-node greedy algorithm for topology reconstruction, which is much more computationally efficient than the existing peak-by-peak searching algorithm; (iii) an impulsive noise assisted dynamic topology re-estimation method, which results in a significant complexity reduction over fixed-frequency re-estimation.