Power line communication channel modelling and performance evaluation

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.

Future smart grid systems will intelligently monitor and control energy flows to improve the efficiency and reliability of power delivery. This monitoring and control requires low-delay, highly reliable communication between customers, local utilities, and regional utilities. A vital part of future smart grids is the two way communication links between smart meters at the customer sites and a (decentralized) command and control center operated by the local utility. To enable these two-way communication links, narrowband power line communication (PLC) systems operating in the 3-500 kHz band are attractive because they can be deployed over existing outdoor power lines. Power lines, however, have traditionally been designed for one-directional power delivery and remain hostile environments for communication signal propagation. In this article, we review signal processing approaches to model channel impairments and impulsive noise and mitigate their effects in narrowband PLC systems. We examine ways to improve the communication performance based on current and emerging standards.

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.

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.

We study the Narrowband Power Line Communications (NB-PLC) system intended to be used for Smart Grid applications. The performance of such system highly depends on the implementation and the used techniques. In this paper the Medium Access Control (MAC) layer of a specific system with the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism is studied. The main feature of the used technique is that it automatically adopts the parameters of the protocol to the dynamically changing network. We investigate the protocol and suggest the improvements that give a higher performance.

In this paper, we analyze a narrowband power line communication (PLC) system under the influence of additive background and impulsive noises. The background noise is modeled as the Gaussian noise, whereas, the impulsive noise is characterized by the Laplace distribution, in order to satisfy the heavy tail requirement of the impulsive noise density function. Moreover, we model the occurrence of impulsive noise in PLC system with Bernoulli and Poisson random variables. We analyze the performance of considered narrowband PLC system in terms of capacity. Specifically, expressions for average channel capacity are derived in case of Bernoulli-Laplace and Poisson-Laplace impulsive noises. The analytical results are supported by the simulations.

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).

A CSMA/CA based MAC protocol for hybrid Power-line/Visible-light communication networks: Design and analysis

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.

Power line communication (PLC) utilizes power lines for the purpose of electronic data transmission. The performance of a PLC system is significantly affected by the additive and multiplicative power line noises; the additive noises are of two types, namely background noise and impulsive noise. Whereas, the multiplicative PLC noise leads to fading in the received signal strength. In this paper, we evaluate the performance of a PLC system over log-normal fading channel under Nakagami-m distributed additive background noise assuming binary phase shift keying modulation scheme. The analysis involving log-normal fading is very complicated. Hence we use a novel gamma approximation to log-normal distribution for our analysis. We evaluate the probability density function of the decision variable. A closed-form expression of the analytical average bit error rate of the considered system is derived. We also compute the diversity order of the considered PLC system. The validity of the derived analytical expressions is closely verified by the simulation results.

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.

The paper presents a methodology proposal for testing and evaluation of communication systems in Smart Grids, especially for Power Line Communication (PLC) systems. The PLC technology is widely used in power grid as a part of Advanced Metering Infrastructure (AMI) allowing mainly data transfers between a management system at utility and customer-premises smart meters. However, the PLC technology on medium voltage (MV) lines is often used for remote control and monitoring of distribution transformers as well. Since power grid and consequently power lines have different transmission parameters affected by their placement and potentially burdened by interferences, the PLC systems have to be evaluated on site before placed to production. In this paper, authors propose a methodology for long-term benchmarking of the PLC systems using newly developed testing tools. The methodology is subsequently tested on real power grid and a selection of results is presented.

HF Band Power Line Communication (PLC) is rapidly gaining popularity with new network systems not only in the home, but also in places where the number of users is relatively large. Since the PLC uses wide frequency band for data modulation, some coexistence conditions with other services were provided. We investigated the performance of three types of PLC systems, HD-PLC, HomePlug and UPA, under unfavorable conditions such as connecting the PLC modem to the uninterruptible power supply (UPS) outlet or simultaneously using it with a different PLC system. Although violating the proper instructions, each PLC system could still transfer data to some degrees. It was confirmed that UPS and PLC act as a source of noise for the other PLC systems and the degree of interference varies with the PLC systems used.

The nature of the Power Line Communication (PLC) equipment is complex because it is considered as an information equipment for Electro-Magnetic Compatibility (EMC) standardization, but it is used to inject High-Frequency (HF) and Very High Frequency (VHF) frequency signals on the existing power network which is not designed to guide these frequencies. This PLC system issue leads to some difficulty to finalize EMC standardization of PLC equipment. This paper shows some EMC issues due to the parasitic radiation of HF and VHF PLC systems. An original method using radiofrequency analysis is used to demonstrate that power lines act as antennas for PLC frequencies, as if the PLC system was a radiofrequency system. So, we can define the PLC system as a "not intended radiofrequency system", i.e. a family product which have to comply not only with EMC standards but also with Radio Equipment Directive (RED) system.

It has been shown that power line communication (PLC) in the high frequency (HF) band is a feasible data transmission method for a future smart grid concept — a low-voltage direct current (LVDC) distribution system. Furthermore, PLC is proposed as a basis of the data network architecture in the LVDC system. In the analysis of the communication channel characteristics and the design of the communication system, channel modeling plays an essential role. A PLC channel model in the LVDC system is presented and analyzed in this paper. The channel model is implemented with a circuit simulator, which provides several advantages for the modeling; for instance, channel characteristics can be analyzed and modeled both in the time and frequency domain. In this paper, the PLC channel gain (including signal attenuation in the power cable) in the LVDC system is modeled in the frequency domain. The channel model is verified by and compared with measurements carried out in the PLC channel in an LVDC laboratory system.