On cooperative coding for narrow band PLC networks

Although Power Line Communication (PLC) is not a new technology, its use to support data transmission over low voltage (LV) distribution networks is still the focus of ongoing research. This thesis focuses on the channel modelling and performance evaluation of narrowband (NB) PLC system. First, the channel modelling approaches of PLC are studied. Then, the proposed PLC channel modelling method based on the bottom-up approach for LV narrowband PLC in a frequency band between 9 kHz and 490 kHz is presented. This proposed model employs the transmission and scattering matrix methods to calculate the transfer function of a typical LV PLC network which comprises two common cable types (copper cables and aluminium conductor steel reinforced). Unlike the top-down approaches, this model is scalable as the network complexity increases and can better describe the network behaviour as a function of physical parameters.In addition, the noise characteristics and popular noise reduction techniques of PLC are studied. The major impairment to the PLC is the impulsive noise which is mainly generated by the switching transient in the network. Hence, a new technique is proposed to mitigate the impact of impulsive noise on data transmission over power lines. This proposed technique is an optimal Clipping/Blanking nonlinearity technique which is based on the minimum bit error rate (BER) search. Results obtained from the simulation of this technique demonstrate that performance has been enhanced in the NB-PLC system. The performance of the narrowband PLC system is also evaluated in both physical (PHY) and medium access control (MAC) layers. Since Orthogonal Frequency Division Multiplexing (OFDM) is a suitable modulation scheme for hostile environment of the power line, it is used to evaluate the PHY layer performance. As a result of the PHY layer performance analyses, it is found that the BER performance between neighbouring points in the typical LV PLC network is reasonable, but communication beyond one hop have to rely on upper layer protocols. In the MAC layer performance evaluation of the PLC system, the widely known random access MAC protocol that uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) will be utilised. The MAC performance evaluation of the PLC system demonstrates a significant packet loss in LV PLC network even with a light traffic condition due to the noisy channel. Furthermore, the goodput declines abruptly once the individual transmission rate is high enough to block the network. In addition, the simulation results show that the channel errors can be reduced by adjusting the MAC parameters to allow the re-transmissions mechanisms to recoup the lost packets.

This paper considers an adaptive orthogonal frequency-division multiplexing (OFDM) transmission scheme for narrowband (NB) power line communication (PLC). The NB PLC channel is found to show strong cyclostationary characteristics due to the periodic mains voltage. However, conventional systems do not use these time-varying channel features. An improvement of the performance is achieved by exploiting the cyclic properties of the channel. Therefore, adaptive bit and power loading methods are of great interest for PLC. In this work, we will evaluate a cyclic loading method for an OFDM system in the CENELEC A-band. Our analysis is based on noise measurements at three different locations over an observation time of 23 hours. Our contribution includes an OFDM system model comprising both additive noise and channel attenuation. Furthermore, we present a method for limiting the amplitude and power spectral density to comply with narrowband regulations. In conclusion, our proposed method achieves a lower bit error rate at all locations. The improvement reaches up to a 102 times lower bit error rate compared to non-adaptive carrier allocation at the same data rate.

Advanced Metering Infrastructure (AMI) is the foundation of the Smart Grid system. One of the most important parts of AMI is smart meter communication. Power Line Communication (PLC) technology utilizes the existing power line network for communication media between smart meters and Data Collector Units (DCU). One of the biggest challenges of communication using PLC is the noise level due to residential loads. In this study, laboratory test set up to measure noise caused by PV rooftop and residential loads are observed. Each PLC frequency band was measured and observed to determine the suitable frequency for PLC communication which was the low noise level. Some experiments in the field were conducted to determine the performance of the PLC. Laboratory test measurement result shows the FCC band (150-490 kHz) was outside the range of PV rooftop and residential load noise. On the other hand, the Cenelec A (35-90 kHz) frequency range was in the range of noise signal. Therefore, NB-PLC G3 using FCC frequency band was proposed to achieve robust data communication and lower noise level. G3 PLC FCC band was tested in the real field residential area, the experimental results showed 97.62% successful rate within one-week data collection.

Exponential demand for broadband applications has elicited renewed interest in characterizing noise in power line communication (PLC) networks for optimal error performance analysis. PLC is economical and ubiquitous, however due to multipath phenomena and nonstationary impulsive noise, the PLC channel is very harsh to signal transmission. Recent studies reveal that PLC noise is cyclostationary and modelling its characteristic should exploit the spectral and temporal redundancy. In addition, preliminary research shows that PLC noise exhibits self-similarity and can be predicted by fractal theory. In modelling noise employing fractal theory, the Hausdorff dimension (D) needs to be approximated. D is related to Hurst parameter (H), which is a measure of self-similarity. Hence, it is important to estimate H for accurate noise prediction using fractal theory. H parameter estimators assume stationarity in time series data. Therefore, preprocessing is required for the case of PLC noise before estimating H to make it stationary as periodicity and nonstatioanrity affects the H estimators. In this study, we remove the periodicity hidden in the PLC noise obtained from measurement campaign within several university offices, workshops and laboratories. Then long-range dependence is estimated from this pre-processed noise data by employing three estimation algorithms: R/S (rescaled adjusted range) method, aggregated variance method and absolute values of aggregated series method. Results from the said estimation methods though not the same, show that the Hurst parameters obtained from various noise measurements are greater than 0.5, implying presence of self-similarity with long-term memory. Results from this study will find valuable applications in PLC noise modelling using fractal and chaos theory and in error performance analysis in both narrowband and broadband PLC systems.

Non-stationary, non-Gaussian noise severely limits the performance of narrowband (NB) power line communication (PLC) systems. Due to the periodic mains voltage, substantial parts of the noise are known to show time-periodic features. Exploiting these features can significantly improve noise canceling methods and thus the overall performance of PLC systems. A prerequisite for this is an accurate estimation of the statistical properties of the power line noise which is also an important part of the channel characterization. In this work, we perform a spectral correlation analysis to evaluate the strongest cyclic frequencies of the noise encountered in low-voltage NB-PLC applications. Our analysis is based on time-synchronized noise measurements at five different locations with a total observation time of 24 hours. Our contribution includes the implementation and estimation of the cyclic coherence function up to 500 kHz, the extraction of the strongest cyclic frequencies, as well as a short- and long-term analysis of the cyclic features. Finally, we present a statistical analysis of the cyclic frequencies based on the complete set of measurements. This analysis shows that cyclostationarity can be observed in the complete NB frequency range and confirms that the dominant cyclic frequency is twice the mains voltage frequency.

In recent times, power line communication (PLC) has an ability of communicating the signals and messages making use of the existing power lines without going for new mediums such as optical fibers or radio waves. Considering the voltage, electrical networks are rated as low (1 kV), medium (1–100 kV), and high (>100 kV) networks and the communication problems in these networks increase with increase in voltage. In order to establish high-speed data communications with data rates in the range of megabit/s over power line networks, dedicated communication systems considering the hostile channel properties are required. In addition to signal distortion, losses in cables and multipath propagation, noise from the system also plays a key role to alter the digital communication over power line networks which is dealt in this project. In this work, the signals are obtained with less bit error rate (BER) using Rayleigh fading channel improving the efficiency of the whole system. Different modulation techniques are compared in narrowband power line communication (PLC) systems, and some suggestions are made for the improvement of data transmission in narrowband systems. The best compromise for single-carrier PLC modules between efficiency and architecture complexity is being investigated in this project.

Narrowband (NB) powerline communication (PLC) is extensively adopted by utilities for the communication in advanced metering infrastructure (AMI) systems. PLC technology needs to overcome channel disturbances present in certain grid segments. This study analyzes improvement proposals of the physical layer of the main narrowband PLC technologies approved by international communication organizations that are currently deployed in Europe: Powerline Intelligent Metering Evolution (PRIME) 1.3.6, PRIME 1.4, and G3-PLC, in order to improve PLC performance under channel disturbances. This thorough study is based on simulations carried out by an innovative ad hoc Virtual PLC Lab, developed by the authors, applied in replicable, fully-automated, and cost reduced test scenarios. The analysis is performed by applying standardized test methods and metrics, and by evaluating the influence of a set of representative channel disturbances defined by the European Telecommunications Standards Institute (ETSI) and selected noises generated by distributed energy resources (DER) in normal operation. PLC performance improvements in terms of equalizer curve fitting, error correction codes, and noisy subcarrier suppression mechanisms are presented. The performance gain due to each physical improvement proposal is accurately measured and compared under the same conditions in a replicable and automated test environment in order to evaluate the use of the proposals in the evolution of future PLC technologies.

Power Line Communication is becoming more common each passing day. Narrowband Power Line Communication systems use a frequency range from 3 kHz to 500 kHz. Nonlinear loads are common in residences and unfortunately they produce harmonics. It is possible that some harmonics produced by the nonlinear loads may interact with the power line communication system. AC dimmers produce impulse noise. In this study, Fourier series of an AC chopper is computed and its current harmonics magnitudes which is in Narrowband Power Line Communication frequencies are examined with and without a smoothing inductor. Their harmonic magnitudes in the power line communication frequencies are compared. It has been found that the smoothing inductor performs well to decrease the AC chopper harmonics within the Narrowband power line frequencies.

Advanced Metering Infrastructure (AMI) is a key enabler of the Smart Grid. Narrowband Power Line Communication (PLC) technology is currently the preferred choice for many AMI use cases. Different PHY/MAC standards and dedicated routing protocols are emerging. New trustworthy models and simulation tools are needed for their evaluation in large scale deployments. This paper presents a realistic model for the latest generation of OFDM-based narrowband PLC standards. The model has been implemented in a popular network simulator - OPNET. Furthermore, the model and the simulator are validated against a real-world testbed. Finally, we present the calibration process and the scalability of the simulator. The results show that it is possible to simulate large topologies of up to 1000 smart meters under a proactive (RPL) or reactive (LOAD) packet routing.

This keynote discusses the behavior of noise in indoor power line communications (PLC) channels. Some ideas to improve system performance based on the knowledge of PLC noise are also introduced. The power-line noise at an outlet is the sum of noise waveforms produced and emitted to the lines from the appliances connected to the power-line network. In the design and the analysis of wireless communication systems, stationary additive white Gaussian noise (AWGN) is often assumed. In PLC systems, however, the statistical behavior of the man-made noise is quite different from that of the stationary AWGN. The fact that the noise in power-lines is not AWGN is often believed to be a cause of low quality of communications. However, Gaussian is the distribution of the largest entropy, and communications under non-Gaussian noise may achieve better performance if the system is designed to adapt the noise statistics. In other words, PLC systems retain large potential for performance improvement if the behavior of the noise is clarified and taken into account in the system design. For narrow-band indoor PLC, we have a mathematically tractable and accurate model based on experimental measurements. In this model, the noise is expressed as a Gaussian process whose instantaneous variance is a periodic time function. With this assumption and representation, the cyclostationary features of power-line noise can be described in close form formula with a small set of parameters. In wide-band indoor PLC, we have made measurements with high speed sampling (50MHz) with long observation duration (10.4s).

Narrowband power line communication: Medium voltage cable modeling and laboratory experimental results

Power lines (PLC), mainly dedicated and optimized for delivering electricity, are, nowadays, used to transfer data. Its low cost and wide coverage makes it one of the pivotal technologies in building up smart grid. The actual role of PLC technology is controversial while some preconize that PLC systems are very good candidates for some applications others discard it and look at wireless as a more elaborated alternative. It is obvious that Smart Grid will include multiple types of communications technologies ranging from optics to wireless and wireline. Among wireline solutions, PLC appears to be the only technology that has deployment cost comparable to wireless as power installation and line are already existent. Narrowband PLCs are a key point in smart grid that is elaborated to support several applications such as Automatic Meter Reading (AMR), Advanced Metering Infrastructure (AMI), demand side management, in-home energy management and Vehicle-to-grid communications A critical stage in designing an efficient PLC system remains in getting sufficient knowledge about channel behavior characteristics such as attenuation, access impedance, multiple noise scenarios and synchronization. That's why; characterizing power line network has been the interest of several research works aiming to compromise between robustness of powerline communication and higher data rate. This interest in narrowband PLC systems to find the adequate one is inciting to deeply focus on channel characterization and modeling methods. It represents a first step to simulate channel behavior then propose a stand-alone hardware for emulation. Authors are investigating the building blocks of a narrowband PLC channel emulator that helps designers to evaluate and verify their systems design. It allows a reproduction of real conditions for any narrowband PLC equipment (single carrier or multicarrier) by providing three major functionalities: noise scenarios, signal attenuation and zero crossing reference mainly used for single carriers systems. For this purpose, authors deploy a bottom up approach to identify a real channel transfer function (TF) based on a prior knowledge of used power cables characteristics and connected loads. A simulator is, then, defined based on Matlab that generates a given TF according to defined parameters. The AC mains zero crossing variation is also studied. In field exhaustive measurements of this reference have shown a perpetual fluctuation presented as a jitter error. It is the reflection of variant AC mains characteristics (frequency, amplitude) which could be related to non-linearity of connected loads at network and used detection circuit in PLC systems. Authors propose a ZC variation model according to system environment (home/ lab, rural). This model will be embedded on channel emulator to reproduce ZC reference variation. Regarding noise, few models are found in literature, specific to narrowband PLCs. An implementation of some models is done and tested on a DSP platform which will include the two previous elements: TF and ZC variation.

Narrowband Power Line Communication for Smart Metering and Street Lighting Control

SummarySeveral techniques for a state‐of‐the‐art advanced metering infrastructure (AMI) within the smart grid are being extensively studied and evaluated around the world. Advanced metering infrastructure provides an enhanced and efficient energy management infrastructure that can facilitate the latest demands of electric utilities, consumers, and smart grid. In the past few years, standardization process for the implementation of AMI using narrowband power line communications (NB‐PLC) transceivers has been completed by ITU‐T and IEEE. This paper is focused on the utilization of CENELEC band of NB‐PLC for deployment aspects. The power transformer model of 200 and 75 kVA transformers for 9 to 90 kHz frequency range that lies in CENELEC‐A band of NB‐PLC is also proposed. The proposed model is more simple than previously presented models in the literature and has the capability to evaluate the transformers working not only under normal condition but also under resonance condition for frequency of interest. Moreover, the efficient procedure for field measurements that provides a generalized NB‐PLC channel model for low voltage access network to deploy AMI within Lahore, Pakistan, is presented. A Simulink model is developed to validate the results. The analysis of measured and simulated results illustrates a close agreement of channel transfer functions. This research work proposes an improved and more accurate NB‐PLC channel model especially for South Asian countries.

This review paper reveals the broadband potential of overhead and underground low-voltage (LV) and medium-voltage (MV) broadband over power lines (BPL) networks associated with multiple-input multiple-output (MIMO) technology. The contribution of this review paper is fourfold. First, the unified value decomposition (UVD) modal analysis is introduced. UVD modal analysis is a new technique that unifies eigenvalue decomposition (EVD) and singular value decomposition (SVD) modal analyses achieving the common handling of traditional SISO/BPL and upcoming MIMO/BPL systems. The validity of UVD modal analysis is examined by comparing its simulation results with those of other exact analytical models. Second, based on the proposed UVD modal analysis, the MIMO channels of overhead and underground LV and MV BPL networks (distribution BPL networks) are investigated with regard to their inherent characteristics. Towards that direction, an extended collection of well-validated metrics from the communications literature, such as channel attenuation, average channel gain (ACG), root-mean-square delay spread (RMS-DS), coherence bandwidth (CB), cumulative capacity, capacity complementary cumulative distribution function (CCDF), and capacity gain (GC), is first applied in overhead and underground MIMO/LV and MIMO/MV BPL channels and systems. It is found that the results of the aforementioned metrics portfolio depend drastically on the frequency, the power grid type (either overhead or underground, either LV or MV), the MIMO scheme configuration properties, the MTL configuration, the physical properties of the cables used, the end-to-end distance, and the number, the electrical length, and the terminations of the branches encountered along the end-to-end BPL signal propagation. Third, three interesting findings concerning the statistical properties of MIMO channels of distribution BPL networks are demonstrated, namely, (i) the ACG, RMS-DS, and cumulative capacity lognormal distributions; (ii) the correlation between RMS-DS and ACG; and (iii) the correlation between RMS-DS and CB. By fitting the numerical results, unified regression distributions appropriate for MIMO/BPL channels and systems are proposed. These three fundamental properties can play significant role in the evaluation of recently proposed statistical channel models for various BPL systems. Fourth, the potential of transformation of overhead and underground LV/BPL and MV/BPL distribution grids to an alternative solution to fiber-to-the-building (FTTB) technology is first revealed. By examining the capacity characteristics of various MIMO scheme configurations and by comparing these capacity results against SISO ones, a new promising urban backbone network seems to be born in a smart grid (SG) environment.