Advances in Power Line Communications

This tutorial focuses on recent advances in Power line communication (PLC). It covers the application scenarios of PLC, channel characterization and modeling, signal processing at the physical layer, analog-front-end design, and the main aspects of PLC networking with emphasis to the state-of-the art and challenges. Recent ideas of using PLC as a sensing technology in power grids beyond communications will also be presented.

An overview of the various application scenarios of PLC (such as in-home, in-vehicle, smart grids) and a summary about the evolution of PLC technology and narrow band (NB) and broad band (BB) PLC standards will be provided. Their use to deliver Smart Grid services (as automatic meter management, grid monitoring, vehicle-to-grid communication, home energy management) as well as high speed networking will be discussed.

The important topics of channel and noise modeling will be presented. Results of experimental channel characterization by different teams in different countries will be shown. A distinction will be made between SISO and MIMO channel scenarios, indoor and outdoor PLC channels, LV and MV network segments.

Up-to-date results about statistical channel modeling, MIMO channel modeling, and noise/disturbances modeling will be reported. Similarities and differences with the wireless channel behavior will be highlighted.

The main challenges of physical layer design for both narrow-band (NB-PLC) and broad-band PLC (BB-PLC) to encompass the presence of channel attenuation and frequency selectivity, periodically time variant behavior, interference, and various noise sources will be addressed. In particular, we will describe existing and emerging filter bank modulation approaches (as PS-OFDM, DWMT, FMT), and ultra wide band techniques.  The pros and cons of different transmission techniques will be analyzed and specific aspects that make PLC different from wireless communications will be emphasized. In this part of the tutorial, we will cover the MIMO solutions that have been recently standardized in BB PLC. Then, we will summarize the main approaches proposed in the literature to cope with the severe disturbances introduced by impulsive noise and narrow band interference.

We will then consider the analog front-end design and discuss line impedance matching techniques (which is a very peculiar aspect of PLC systems) and their impact in the overall system performance.  

PHY layer security has only recently attracted attention in PLC.  We will describe the main idea behind PHY layer security and report recent results about the analysis of the secrecy rate that can be granted in PLC channels. Signal propagation in PLC networks is affected by some level of determinism that significantly affects the channel statistics and introduces correlation between the channel of the intended user and that of the eavesdropper. All of this influences the secrecy rate as it will be explained.

We will then turn the attention into networking aspects. We will briefly discuss the MAC protocols that have been adopted in PLC (as adaptive TDMA which is peculiar to PLC and which exploits the channel cyclo stationarity). We will discuss cooperative systems (as relaying) to enhance coverage and capacity in both home and smart grid PLC networks. Full duplex PLC will also be addressed. 

Finally, recent proposals and results about the exploitation of PLC devices as sensing units to offer new functionalities, beyond communications, will be presented.