Power Line Communication Channel Research Articles

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.

Blind Equalization for Power-Line Communications Using Chaos

In this paper, the use of chaos in power-line communication (PLC) with blind equalization of the multipath effects is considered. After investigating equalization methods for chaotic signals, we propose an minimum phase-space volume-extended Kalman filter (EKF) equalization method to fulfill the practical requirements. First, an EKF-based method is used to replace the inverse filter to overcome the channel noise. Second, a nearest neighbor search method and a fast system identification method are used to reduce the computational complexity. Computer simulations are used to confirm the efficiency of the proposed method. Furthermore, real PLC channel experiments are conducted to demonstrate the effectiveness of this method.

Power-Line Impedance Estimation at FCC Band Based on Intelligent Home Appliances Status Detection Algorithm Through Their Individual Energy and Impedance Signatures

Power-line communication (PLC) systems use the existing power line as a communication channel between the nodes. Understanding the high-frequency behavior of the power line and loads at the PLC frequency band is essential for designing the PLC system to achieve the desired performance. Based on the impedance behavior of the channel, PLC transceivers can adaptively adjust their operating behaviors to operate more effectively and efficiently. Tracking the impedance variation would also enable smart-grid systems to implement channel health monitoring. In this research, an s-domain home power-line impedance model estimation method at the Federal Communications Commission band based on impedance signatures of the loads and cables as well as the load schedules is developed. The model contains the amplitude and phase characteristics of the impedance at the FCC band. The presented home appliance signature contains an s-domain impedance model and complex power consumption at the power-line frequency. Measurements have been made for nine different appliances and a standard cable with proper lengths is typically used in US homes in order to define their high-frequency impedance signatures. The performance of the status detection algorithm is tested for five different scenarios. Based on the experimental tests, we found that the method we proposed for detecting the working status of the appliances and the method for estimating PLC channel impedance works very accurately.

Performance analysis of a power line communication system employing selection combining in correlated log‐normal channels and impulsive noise

The authors analyse an L-channel selection combining (SC) scheme for a power line communication (PLC) system with binary phase-shift keying. The focus is on improving the reliability in data transfer of the system instead of improving the data rate. To enhance the reliability in data transfer, multiple PLC channels are used to send the same information-bearing signal to the receiver. The L PLC channels are subject to log-normal fading, which is modelled by a multivariate log-normal distribution with an exponential correlation. The channels are also corrupted by additive impulsive noise as well as thermal noise. To consider the effect of both types of noises, they adopt a Gaussian mixture noise model, in which the additive noise samples are taken from a Bernoulli–Gaussian process. The system performance is evaluated in terms of the average bit error rate and the average channel capacity, for which approximate closed form expressions are derived. Numerical results showing the impact of the number of PLC channels, the amount of correlation, the noise scenarios, and the fading environments on the performance are presented. The authors' results show that the performance improves with increasing number of PLC channels; however, the amount of improvement reduces with increasing channel correlation.

Physical layer security in power line communication networks: an emerging scenario, other than wireless

The authors consider the secure transmission of information over power line communication (PLC) networks. The focus is on the secrecy guaranteed at the physical layer, named physical layer security (PLS). Although PLS has been deeply investigated for the wireless case, it is not the same for the PLC environment. Thus, starting from the knowledge in the wireless context, the authors extend the results to typical PLC scenarios. In particular, the PLC channel statistics is evaluated and a performance comparison among PLC and wireless channels is performed, in terms of secrecy rate distribution. For the PLC case, the secrecy rate distribution, under a total power constraint, is evaluated for both optimal and uniform power distributions in broadband channels. To provide experimental evidence, the authors consider channel measures obtained in an in-home measurement campaign. The underlying network presents a tree topology, which introduces frequency and spatial correlation among channels, and suffers from the keyhole effect, generated by branches that depart from the same node. As shown by the numerical results, these effects can reduce the secrecy rate. Finally, the authors evaluate the secrecy rate region for the multi-user broadcast channel considering both simulated channel realisations and experimental channel measures.

Multipath Modeling of Automotive Power Line Communication Channels

In this paper, an in-vehicle power line channel mathematical multipath representation is proposed. The selected approach aims at describing the transmission of a signal on a possibly complex power network by means of a finite number of delayed echoes. Model parameters are computed via a well-defined step-by-step procedure from frequency-domain channel characteristics. The feasibility and strength of the method are demonstrated by means of a measurement campaign. Two-port scattering measurements have been carried out on a commercial automobile and the effect of the measurement setup has been considered in the analysis.

Frequency-Shift Filtering for OFDM Signal Recovery in Narrowband Power Line Communications

Power line communications (PLC) has been drawing considerable interest in recent years due to the growing interest in smart grid implementation. Specifically, network control and grid applications are allocated the frequency band of 0-500 kHz, commonly referred to as the narrowband PLC channel. This frequency band is characterized by strong periodic noise which results in low signal to noise ratio (SNR). In this work we propose a receiver which uses frequency shift filtering to exploit the cyclostationary properties of both the narrowband power line noise, as well as the information signal, digitally modulated using orthogonal frequency division multiplexing. An adaptive implementation for the proposed receiver is presented as well. The proposed receiver is compared to existing receivers via analysis and simulation. The results show that the receiver proposed in this work obtains a substantial performance gain over previously proposed receivers, without requiring any coordination with the transmitter.

Statistical Characterization of the Indoor Low-Voltage Narrowband Power Line Communication Channel

This paper presents a novel statistical characterization of the indoor low-voltage (LV) narrowband power line communication (PLC) channel in CENELEC and FCC/ARIB bands. Experimental measurements of electrical network complex transfer functions were used to determine, for the frequency range up to 500 kHz, the statistics of the average channel gain, the delay spread parameters, the coherence bandwidth and the channel capacity. The average measured channel attenuation exhibits values between 16.36 and 26.95 dB with a mean of 20.75 dB in the frequency band from 10 to 500 kHz. The root mean square (rms) delay spread has a mean value of 2.12 μs with 90% of the channels revealing values below 3.20 μs. The minimum coherence bandwidth at 0.9 correlation level is of 1.23 kHz and the mean channel capacity is of 5.32 Mbps. The lognormal behavior is confirmed and justified for the rms delay spread but not for the average channel gain. The negative correlation between these two parameters is examined, and the relationships between the different studied metrics are also explored.

Analysis and improvement of multicast communications in HomePlug AV-based in-home networks

The increasing number of home devices with communication capabilities is propelling the research into new communication technologies for in-home networks. Power Line Communications (PLC) has proven to be a feasible alternative for this purpose, and the HomePlug AV standard has become one of its most popular solutions. However, while multicast communications are demanded by many services commonly used in home scenarios, the HomePlug AV implements an inefficient mechanism in which they are carried out as successive point-to-point transmissions. The aim of this paper is to outline the limitations of such scheme and to propose algorithms that improve the multicast performance of the standard. To this end, we have developed a simulation tool for HomePlug AV-based in-home networks. It implements the physical and MAC layers, as well as traffic models for the most common home network services. One of its distinctive features is the ability to generate PLC channels with similar correlation to the ones established in a given home. This correlation has been traditionally neglected, leading to inaccurate performance estimations and to discard suitable multicast algorithms. The considered multicast schemes are firstly compared in terms of their physical bit rate. Finally, their capacity to deliver a video streaming service is assessed.

A Fractional Lower Order Statistics-Based MIMO Detection Method in Impulse Noise for Power Line Channel

Impulse noise in power line communication (PLC) channel seriously degrades the performance of Multiple-Input Multiple-Output (MIMO) system. To remedy this problem, a MIMO detection meth ...

AN ALTERNATIVE APPROACH IN POWER LINE COMMUNICATION CHANNEL MODELLING

In this paper, we present the measurement methodology and results for a low voltage Power line Communications (PLC) network under difierent conflgurations. Based on the measurements, a correlation of the channel transfer characteristics to the network topology is established and a deterministic model based on two-wire transmission line theory for transverse electromagnetic (TEM) wave propagation is proposed. The channel frequency response in frequency range of 1{30MHz is determined, where the model results agree well with the measurements. The development of accurate power line communication (PLC) channel transfer characteristics models is important as it forms the basis for computer simulations which are useful in appropriate system design, and further enable the analysis of the performance of difierent network conflgurations and loads (1). There is therefore continued research in the characterization of the power line as a communication medium. Difierent techniques which are based on either measurements or theoretical derivations from physical parameters, denoted as top-down or empirical models (2,3), and bottom-up or deterministic models (4{6), respectively, are employed. The empirical model is easy to use as it calls for little computation and is easy to implement. It is however susceptible to measurement errors and cannot be used to reproduce the channel characteristics of a difierent PLC network. The deterministic model difiers from the latter in that it necessitates detailed knowledge of all components and their respective characteristics. Therefore the network behaviour in relation to the model parameters is clearly deflned, and is considered in this work. True to its original purpose, the low voltage power line network within a typical in-building structure is optimized for the transmission of high voltages at low frequencies contrary to data transmission which necessitates the transmission of low voltage at high frequencies. The communication signals therefore sufier some hostile channel parameters. The three most important parameters are noise, impedance mismatch, and attenuation which are frequency, time and location variant (7). Subsequently, accurate approximation of the line parameters, the characteristic impedance Z0, and propagation constant ∞, which in turn are used to determine the PLC channel constants, is essential in the channel transfer function calculations. Meticulous measurements are required in the investigation of the channel parameters and consequent modelling of the same. The behaviour of the channel is better understood by varying difierent components, which in the case of PLC, are: the topology; the cable types; the cable length and number of branches; as well as the loads terminating at each end of the network. Once relations of the variations of these are obtained, any given network can then be su-ciently modelled.

Frequency domain based LS channel estimation in OFDM based Power line communications

This paper is focused on low voltage power line communication (PLC) realization with an emphasis on channel estimation techniques. The Orthogonal Frequency Division Multiplexing (OFDM) scheme is preferred technology in PLC systems because of its effective combat with frequency selective fading properties of PLC channel. As the channel estimation is one of the crucial problems in OFDM based PLC system because of a problematic area of PLC signal attenuation and interference, the improved LS estimation technique is proposed. We investigate and evaluate proposed frequency domain LS channel estimation method for OFDM based power line communication system. Also performance comparing with existing pilot based estimation algorithms towards proposed method in terms of their computational complexity, error correction, and suitability conditions is made.

Research on Power Line as Communication Channel with Multi-Tap and Multi-Branch Configuration

To study the effect of different branch configuration on transmission characteristic in-home low-voltage (LV) communication power line communication (PLC) channel, the influences of branch length, number of branch and tap, and branch terminal impedance on the performance of PLC are investigated. The two type power line network structures of the one-tap with multi-branch (OTMB) and the multi-tap with multi-branch (MTMB) are studied. The transmission characteristics of the PLC channel are simulated by varying the length and terminal impedance of the branch for two configurations. Simulation results show that the length and terminal impedance of the branch have significant influence on the amplitude and phase response of the transfer function. The position and number of notches and crests in the amplitude responses are affected by different branch types and the configurations of branch length and branch terminal impedance. The models developed in this paper can easily handle an arbitrary topology of power line channel and provide accurate calculation for the channel responses of the all kinds of channel branch structures in indoor LV power line network

Dynamic Characterization and Equalization of a Power Line Communication Channel

Power Line Communication (PLC) systems need signal processing algorithms in order to recover the transmitted signals from the high degrading medium. In the literature exist some techniques that work on the basis of a constant, known channel, but it was demonstrated that the PLC channel is time variant, therefore these techniques lose efficiency. This work presents a dynamic equalization algorithm computed in the time domain, where the channel characterization is done by a recursive least squares algorithm using the transmitted data as reference. The proposal was tested with simulations and was statistically validated using in time variant PLC channel models, obtaining a lower error rate than other methods.

Power Line Cable Transfer Function for the Broadband Power Line Communication Channel

PLC (Power line communications) uses the existing power line infrastructure for communication purposes. While the majority of recent contributions have discussed PLC for high data-rate applications like Internet access or multimedia communication serving a relatively small number of users, in this paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. The model has been verified with practical measurements conducted on actual power networks.

PAPR Reduction in CE-OFDM System for Numerical Transmission via PLC Channel

Power Line Communications have been the subject of an important research work. At the same time, the growing demand for multimedia communications provides a good prospect for PLC as a promising transmission technique for the “last mile” access network. Orthogonal Frequency Division Multiplexing (OFDM) is a spectrally efficient multicarrier modulation technique for high speed data transmission over multipath fading channels. High Peak-to-Average Power Ratio (PAPR) is a major drawback of OFDM. The high PAR of the OFDM signal has to be considered when setting the range of the digital-to-analog converter (DAC) and dimensioning the line-driver. This paper introduced an improved PAPR reduction scheme using constant envelope modulation. Furthermore, by utilizing continuous phase modulation (CPM) in a CE-OFDM system, the PAPR can be effectively reduced to 0 dB. The paper describes a CE-OFDM based modem for Power Line Communications (PLC) over the low voltage distribution network. Relying on a preliminary characterization of a PLC network, a complete description of the modem is given.

Modeling of Medium-Voltage Power-Line Communication Systems Noise Levels

The implementation of power-line communication systems requires detailed knowledge of the channel properties, such as transfer function, noise levels, and channel capacity in order to assess the services that can be provided. In this paper, the interference scenario on overhead medium-voltage power distribution lines caused by external electromagnetic (EM) fields is examined by focusing on the noise induced. The external EM fields are considered to be the main source of occurring noise and a novel method capable to calculate the corresponding noise levels is presented. The proposed method is compared to other existing models and its strengths are highlighted. The effect of the induced noise to the overall data capacity of the power-line communication channel is examined. Eventually, the influence of several parameters, such as the magnitude and direction of propagation of the external EM field, network topology, earth's EM properties, and different levels of emissions suggested by various organizations are investigated.

A New Measurement Method of Conducted EMI on the Power-Line Communications Channel

Various kinds of household appliances have been widely deployed in the low-voltage grid. They inject conducted noise into the power line system, which may cause a detrimental effect on the Power-line Communications (PLC) channel. This paper examines a new measurement method of conducted Electromagnetic Interference (EMI) on the PLC channel. The proposed method is to facilitate the noise characteristic research, which overcomes the potential difficulties when the measurement is performed according to CISPR 16-2-1. In particular, taking the hairdryer as an example, the conducted noises when the motor is deemed as the noise source are measured by employing the presented method. Moreover, this paper also analyzes the conducted noise of the hairdryer both in the time domain and in the frequency domain, and interprets the noise generating mechanisms with the working principle of the motor in detail. The central issue in all these studies is to research the conducted electromagnetic noise characteristics on the PLC channel.

On the First-Order Markov Model for the PLC Fading Channel

The power line communications (PLC) channel is noisy one, which can be modeled by the Markov process. The order is the key concerning when used the Markov process. the level of complexity will be incurred from using higher order , while the first-order Markov models may lead to the less accurate channel response. In the paper, the first-order Markov channel is under thoroughly discussion, and it can provide a mathematically tractable model for time-varying channels and uses only the received SNR of the symbol immediately preceding the current one. With the first-order Markov chain, given the information of the symbol immediately preceding the current one, any other previous symbol should be independent of the current one. We show that given the information corresponding to the previous symbol, the amount of uncertainty remaining in the current symbol should be negligible. That means the first-order of Markov process is enough when modeled the PLC channel.

MC-OFDMA FOR MULTI-USER DETECTION SCHEMES IN POWERLINE COMMUNICATION

Support of multiple users in wideband powerline communication (PLC) is essential to enhance the dependence on such emerging systems. This paper presents novel adaptations of the space division multiple access (SDMA) techniques to PLC. Multicarrier data transmission and orthogonal frequency division multiple access (OFDMA) techniques are invoked to mitigate the technical challenges of PLC channel impairments and enhance the spectral efficiency. Performance is enhanced using orthogonal Walsh–Hadamard codes. Linear and nonlinear multi-user detection (MUD) schemes are investigated, including the optimal maximum likelihood (ML) methods and the near-optimal sphere detectors(SDs). Presented results indicate the potential of the proposed scheme to enhance wideband PLC systems.