Broadband Power Line Communication Systems Research Articles

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.

Efficient Low-Complexity Optimized Channel Estimating Methods for OFDM-Based Low-Voltage Broadband Power Line Communication Systems

Broadband Power Line Communication (BB-PLC) technology enables data transmission for smart grid applications. Nevertheless, channel equalizers are required in the receiver to estimate and compensate for the nonlinear time-variant impulse response and noise interference effects introduced by the BB-PLC channel. In this paper, we append the Particle Swarm Optimization (PSO) algorithm and its proposed improved version to the commonly used Least-Square (LS) and Linear Minimum Mean Square Error (LMMSE) algorithms to advance four new blocktype pilot-aided hybrid channel estimation algorithms for low-voltage Orthogonal Frequency Division Multiplexing (OFDM)-based BB-PLC systems. Extensive numerical simulation results for four different M-QAM formats (M = 8, 16, 32, 64) show that the proposed algorithms significantly improve the performance of the traditional LS and LMMSE estimators, at least for the parameters of the BB-PLC system studied in this work. In addition, the computational load complexity of the PSO-inspired LMMSE algorithm is lower compared to the conventional LMMSE estimator.

The Effective Secrecy Throughput of a Broadband Power Line Communication System Under the Presence of Colluding Wireless Eavesdroppers

This paper investigates the physical layer security of in-home and broadband power line communications (PLC) systems threatened by colluding wireless communication (WLC) eavesdroppers, which are localized near or far from the transmitter and operate in the same frequency band. In this regard, we show that PLC and hybrid PLC-WLC channels can be considered as uncorrelated random processes. In the sequel, we confirm the severity of a WLC eavesdropper or a group of them located near the transmitter. Also, we show that a group of colluding WLC eavesdroppers located far from the transmitter poses the same security risk of only one WLC eavesdropper located near the transmitter. Finally, a discussion of wiretap code rates for achieving effective secrecy throughput is presented.

Power line communication: A review on couplers and channel characterization

<abstract> <p>Powerline communication is gaining momentum with the rise of the smart grid, the Internet of Things as part of the 4th industrial revolution and associated applications such as transportation and energy efficiency. Coupling and channel characterization are essential parts of a power-line communication system. Therefore, understanding these components allows performance evaluation and prediction of the system. This paper presents an entire review of couplers and channel characterization modeling techniques used in narrow and broadband power-line communication systems. Types and applications of different couplers are presented; a review of different power-line communication channel modeling techniques and the fundamentals allows a clear understanding of factors influencing or affecting the signal propagation through the channel. The purpose of this review is to guide researchers and system designers looking for literature resources on couplers and channel characterization for power-line communication applications.</p> </abstract>

Multi-relay selection scheme for cooperative QAM-FBMC based broadband PLC systems

Selecting the appropriate modulation technique is a major concern in designing reliable broadband power line communication (BPLC) systems. Orthogonal Frequency Division Multiplexing (OFDM) was gaining more attention as a multi-carrier modulation (MCM) technique for cooperative BPLC. Nevertheless, OFDM has some drawbacks that degrade the BPLC performance. Here, the author first proposes a new Quadrature Amplitude Modulation-Filter-Bank Multicarrier (QAM-FBMC) transceiver to improve the bit error rate (BER) performance and to achieve higher throughput in BPLC-based systems. Furthermore, an opportunistic multi-parameter-based multi-relay selection (OMP-MRS) scheme is proposed to future improve the performance of cooperative BPLC-based systems. In this regard, the analytical expressions for outage probability and system throughput are derived and validated with Monte Carlo simulations. The optimal parameters that maximise the BPLC performance are obtained via exhaustive search. The proposed scheme harvesting the high amount of noise exists in PLC, especially impulsive noise to further improve the energy efficiency. Numerical and simulation results validate the consistency of the analytical model and its derivations. Results reveal that the proposed OMP-MRS scheme outperforms the existing multi-relay selection schemes presented in literature with an acceptable computational complexity.

Analysis of typical PLC pulses for sensing high-impedance faults based on time-domain reflectometry

This paper focuses on a comprehensive analysis of typical power line communication (PLC) pulses for sensing high impedance faults in power distribution networks (PDNs) when the pulse compression time-domain reflectometry (TDR) system applies. In this sense, closed-form expressions for the PLC pulses, namely Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM), impulsive ultra-wideband (UWB), and chirp spread spectrum (CSS), and their corresponding autocorrelation functions are presented. Also, parameters based on radar theory (e.g., range resolution, pulse compression ratio, reflectogram distortion, and maximum unambiguous range) are introduced to evaluate the usefulness of these PLC pulses for providing proper TDR measurements (reflectograms). A comparative numerical analysis considering frequency bands that comprise narrowband and broadband PLC systems, with a highlight on well-established regulatory constraints, is discussed. Numerical results show that the use of UWB pulses yields a larger number of reflectograms in a given time interval, while HS-OFDM and CSS pulses provide higher reflectogram quality and better resolution, under the same conditions. Also, narrowband PLC systems are suitable for the majority of PDNs, with the use of broadband PLC ones left for attaining high resolutions at short distances.

Formulation and Performance Analysis of Broadband and Narrowband OFDM-Based PLC Systems.

The aim of this paper is to formulate the physical layer of the broadband and narrowband power line communication (PLC) systems described in standards IEEE 1901 and IEEE 1901.2, which address new communication technologies over electrical networks for Smart Grid and Internet of Things applications. Specifically, this paper presents a mathematical formulation by means of matrices of a transmitter and receiver system based on windowed OFDM. The proposed formulation is essential for obtaining the input–output relation, as well as an analysis of the interference present in the system. It is very useful for simulating PLC systems using software designed to operate primarily on whole matrices and arrays, such as Matlab. In addition, it eases the analysis and design of different receiver configurations, simply by modifying or adding a matrix. Since the relevant standards only describe the blocks corresponding to the transmitter, and leave the set-up of the receiver open to the manufacturer, we analysed four different possible schemes that include window functions in different configurations. In simulations, the behaviour of each of these schemes is analysed in terms of bit error and achievable data rates using artificial and real noises.

Research on the optimised transceiver impedances for low‐voltage broadband PLC system

The design of transceiver impedances is very important to improve the performance of the power line communication (PLC) system. In this study, it infers an expression of signal-to-noise ratio (SNR) related to transceiver impedances for broadband PLCs, and the optimal transceiver impedances are obtained by solving a maximisation problem. By the comparison of the SNR of PLC system with the proposed transceiver impedances and only optimised transmitter or receiver impedance, the conclusions are derived that the PLC system performance with the proposed transceiver impedances is better and the receiver impedance has a greater influence on the performance of the PLC system. To verify the advantage of the optimal transceiver impedances proposed in this study, the authors also make the comparison with the other two kinds of transceiver impedance optimisation methods by simulating SNR and transmission rate of the PLC system. The results show that in theory, the SNR and channel capacity of PLC system ca, maximally increase by 15 dB and 50 Mbits/s, respectively, using the proposed transceiver impedances by comparing with the other two impedance optimisation methods, which proves that the proposed transceiver impedances in this study can obtain the better performance of the PLC system.

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.

EFFECTS OF ELECTROMAGNETIC INTERFERENCE CAUSED BY LIGHTING TECHNOLOGIES IN BB-PLC SYSTEMS

Powerline communication (PLC) is a promising technology that allows data transmission through electric power distribution networks, with the advantage of using an existing infrastructure, reducing costs in maintenance and installation of telecommunication systems. However, once power systems are not designed specifically for data transmission, it may exhibit limiting electromagnetic interference characteristics for desirable system performance. This paper aims to analyze data rate performance of a Broadband PLC system when operating under conditions of conducted and radiated electromagnetic interference caused by lighting devices. The analyzed data transmission system presented good performance when subject to radiated electromagnetic interference, but was shown to be sensitive to conducted disturbances caused by lighting devices.

TV White Space Regulated Broadband Power Line Communication for Point-to-Multipoint Downlink IoT Networks: A Standard Perspective

Broadband power line communication (BPLC) and television white space (TVWS) are regarded as promising candidates for indoor broadband applications of the Internet of Things. However, they share the access to the very high frequency (VHF) band, which could cause harmful interference and performance degradation to each other. In this paper, a TVWS regulated BPLC system is proposed for point-to-multipoint downlink communication, which integrates the requirement of primary user sensing and the permissible transmission power spectral density (PSD) for TVWS users into the BPLC standard, regarding VHF band access. This integration guarantees minimum interference level between TVWS and BPLC and allows higher transmission PSD for BPLC users in VHF, and hence higher capacity and coverage for BPLC.

Two-Stage Single-Relay Channel Model for In-Home Broadband PLC Systems

This paper discusses the two-stage single-relay channel model for in-home broadband power line communication links with up to two hops. This channel model consists of the concatenation of two single-relay channels that can result in eight configurations; however, only five of them are analyzed in this work since they cover up to one relay availability. In this context, a discussion addressing both amplify-and-forward and decode-and-forward cooperative protocols at relay node and maximal ratio combining at destination node is carried out. As the power line channels are frequency selective, the attenuation profile increases along with both distance and frequency, and the additive noise is colored, we discuss achievable data rate analyses using a data set covering the frequency band from 1.7 to 100 MHz, under sum power constraint. Based on the attained results, we state that the two-stage single-relay channel model is the best option for in-home broadband power line communication systems when the source-to-destination link is severely degraded (e.g., high signal attenuation and/or high-power noise presence), while the two-hop channel model is more appropriate when the channel degradation is not severe. Moreover, we show that the single-relay channel model may be remarkably outperformed by the two-stage single-relay channel model.

EPLC-CMAC: An enhanced cooperative MAC protocol for broadband PLC systems

In this work, we introduce an enhanced cooperative medium access control protocol which merges a cooperative protocol with a packet correction technique at the link layer level. The proposed protocol aims to improve data communication reliability of in-home broadband power line communication (PLC) systems. More specifically, the cooperative protocol performs relayed retransmissions according to the relay availability, for assisting data communication between nodes source and destination. In case a data packet retransmission fails, the node destination uses corrupted copies from the transmitted and the retransmitted packets from nodes source and relay, respectively, which are stored in its buffer, in order to detect and correct the erroneous bits. The performance evaluation of the proposed protocol is accomplished by simulations based on measured power line channel frequency responses and an additive noise model of in-home electric power grids, which cover broadband applications and bit error pattern at the link layer level. The physical layer makes use of orthogonal frequency division multiplexing and orthogonal frequency division multiple access schemes. Furthermore, a comparison among PLC systems using the proposed protocol to others using only a cooperative protocol and without any cooperative protocol at link layer is analyzed. Numerical results show that improvements in terms of data communication reliability can be achieved in comparison with previous protocols under the presence of background and impulsive noises.

Approach for modelling of broadband low‐voltage PLC channels using graph theory

Broadband power line is an important way of communication in low-voltage distribution networks because a power line is everywhere nowadays. However, due to the heterogeneity of a practical power-line network and various loads connected to its termination points, modelling and simulation of power-line communication (PLC) channels are difficult and complicated issues. In this work, the authors propose a novel PLC channel modelling approach using graph theory for the first time when knowing the power-line network topologies and cable distributed parameters. The approach utilises simple and effective recursive operations in solving the k -shortest paths to estimate the channel transfer function for a specific power-line network, it overcomes the complicated analytical derivation in computing the channel transfer function by the traditional two-port network in the bottom-up model and avoids to measure the actual channel in a top-down model. Their proposed approach is validated by transmission-line (TL) theory as well as measurement results, and it is also compared with TL theory. The results show that their proposed PLC channel modelling approach herein is simple to be implemented, it is expected to have extensive applications in broadband PLC systems for performance evaluations.

A cognitive TV white space-broadband power line MIMO system for indoor communication networks

Broadband power line communication (BPLC) is a promising solution to satisfy the growing data rate demands for broadband indoor communication networks. However, the BPLC transmission power spectral density (PSD) is restricted in the very high frequency (VHF) band to avoid harmful interference to the existing wireless services. In this paper, a new hybrid system is proposed utilizing BPLC and cognitive radio over TV white space (TVWS) to enhance the system capacity over BPLC in VHF, forming a VHF TVWS BPLC multiple-input multiple-output (MIMO) system. An iterative precoding algorithm is proposed to satisfy the interference limit at the TV primary user (PU) receiver (Rx) and enhance the ergodic capacity. Moreover, a power allocation algorithm is developed for the MIMO system to achieve the maximum ergodic capacity subject to the average total power constraint and limit of interference to TV PU. Simulation results demonstrate the significant enhancement in the achieved capacity by our proposed system in the VHF band compared to both previous cognitive and hybrid BPLC systems.

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.

Evaluation of PLC Channel Capacity and ABER Performances for OFDM-Based Two-Hop Relaying Transmission

Powerline network is recognized as a favorable infrastructure for Smart Grid to transmit information in the network thanks to its broad coverage and low cost deployment. The existing works are trying to improve and adapt transmission techniques to reduce Powerline Communication (PLC) channel attenuation and exploit the limited bandwidth to support high data rate over long distances. Two-hop relaying BroadBand PLC (BB-PLC) system, in which Orthogonal Frequency Division Multiplexing (OFDM) is used, is considered in this paper. We derive and compare the PLC channel capacity and the end-to-end Average BER (ABER) for OFDM-based direct link (DL) BB-PLC system and for OFDM-based two-hop relaying BB-PLC system for Amplify and Forward (AF) and Decode and Forward (DF) protocols. We analyze the improvements when we consider the direct link in a cooperative communication when the relay node only transmits the correctly decoded signal. Maximum ratio combining is employed at the destination node to detect the transmitted signal. In addition, in this paper, we highlight the impact of the relay location on the channel capacity and ABER for AF and DF transmission protocols. Moreover, an efficient use of the direct link was also investigated in this paper.

Coupling for Power Line Communications: A Survey

The advent of power line communication (PLC) for smart grids, vehicular communications, and data network access, has recently gained ample interest among the researchers and industries. Couplers - devices used to inject data communication signals into (Alternating Current or Direct Current) power lines are very important components of a PLC system. There is, however, an obvious gap in literature for a detailed review of existing PLC couplers. In this paper, we present a comprehensive review of couplers, which are required in narrowband and broadband PLC transceivers. We provide, also, a novel classification of PLC couplers based on the type of physical coupling, voltage levels, frequency bandwidth, propagation mode, and number of connections. Prevailing issues that protract the design of couplers and consequently subtended the invention of different types of couplers are clearly described. This survey will guide researchers, and designers alike, into a quicker resourcing when studying coupling in narrowband and broadband PLC systems.

Digitally Controlled Analog Cancellation for Full Duplex Broadband Power Line Communications

Although in-band full-duplexing (IBFD) has long been implemented in various communication media, it was only recently that an IBFD solution was presented for broadband power line communications (BB-PLCs). The maximum attainable echo suppression using this solution is, however, limited by the dynamic range of the analog-to-digital converter (ADC). To counter this critical constraint, we propose echo cancellation in the analog domain, while persisting with a low-complexity frequency domain digital echo estimation. By formulating an expression for the number of ADC bits lost in IBFD over a conventional half-duplex operation, we show that the ADC dynamic range is no longer a limiting factor for our solution. We further extend our solution to present an analog cancellation method for multiple-input multiple-output IBFD BB-PLC systems. Finally, we present simulation results of echo cancellation and data rate gains obtained under realistic in-home BB-PLC settings, to demonstrate that our solution is capable of doubling bidirectional transfer rates in a large number of the tested network conditions.

In-band full duplex broadband power line communications

In this paper, we introduce in-band full duplexing (IBFD) for broadband power line communication (BB-PLC) systems. Inspired by the use of IBFD in digital subscriber lines, Ethernet, cable communication, and recently in wireless communication, we investigate the constraints and requirements for a successful IBFD implementation in BB-PLC. We propose a two-stage IBFD structure consisting of an initial analog isolation using an active hybrid circuit, and a simplified mixed-domain digital echo cancellation procedure to suppress the self-interference. Furthermore, we enhance the digital cancellation filter to better adapt to linear periodically time-varying channel conditions, commonly encountered in PLC scenarios. We evaluate our solution under diverse power line channel and noise conditions to examine the overall data rate gains that can be achieved. Last, we extend IBFD to multiple-input multiple-output BB-PLC systems that enable faster and/or more robust data transmission.