Overview

S. Galli, A. Scaglione, Z. Wang, "For the Grid and Through the Grid: The Role of Power Line Communications in the Smart Grid," Proceedings of the IEEE - Special Issue on Smart Grid, vol. 99, no. 6, June 2011
A comprehensive and up to date review of PLC standards, with focus on the possible role of PLC in the Smart Grid.

Ultra-narrowband (UNB) PLC

S. Mak and D. Reed, "TWACS, a new viable two-way automatic communication system for distribution networks. part I: outbound communication," IEEE Transactions on Power Apparatus and Systems, vol. 101, no. 8, pp. 2941-2949, Aug. 1982.
S. Mak and T. Moore, "TWACS, a new viable two-way automatic communication system for distribution networks. part II: inbound communication," IEEE Transactions on Power Apparatus and Systems , vol. 103, no. 8, pp. 2141-2147, Aug. 1984.
Two-Way Automatic Communications System (TWACS) is an UNB-PLC technology that has found substantial deployment in the USA, especially in rural areas. TWACS uses disturbances of the voltage waveform for outbound (substation to meter) communication and of the current waveform for inbound (meter to substation) communication. TWACS is used for both AMR and distribution automation and, despite its very low data rate (~100 bps), it is today used in the largest AMI and Direct Load Control Demand Response systems in the world (Florida, USA).

Narrowband (NB) PLC

I. Berganza, A. Sendin, A. Arzuaga, M. Sharma, and B. Varadarajan, "PRIME interoperability tests and results from field," IEEE International Conference on Smart Grid Communications (SmartGridComm), Gaithersburg, MD, Oct. 4-6, 2010.
K. Razazian, K., M. Umari, A. Kamalizad, V. Loginov, and M. Navid, "G3-PLC specification for powerline communication: overview, system simulation and field trial results," 2010 IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), 28-31 March 2010.
There is today a renewed interest in multi-carrier based NB-PLC technologies that are able to deliver higher data rates than the single carrier ones, e.g. ISO/IEC 14908-3 (LonWorks), ISO/IEC 14543-3-5 (KNX), CEA-600.31 (CEBus), etc. These two papers give a nice overview of two multi-carrier based NB-PLC industry specifications that are today gaining traction. These two specifications have also been included as Annexes in the ITU-T G.hnem recommendation today under development.

Broadband (BB) PLC

M.K. Lee, R.E. Newman, H.A. Latchman, S. Katar, and L. Yonge, "HomePlug 1.0 powerline communication LANs - protocol description and performance results," International Journal of Communication Systems, Special Issue: Powerline Communications and Applications, vol. 16, no. 5, pp. 447-473, June 2003.
M.Y. Chung, M.-H. Jung, T.-J. Lee, and Y. Lee, "Performance analysis of HomePlug 1.0 MAC with CSMA/CA," IEEE Journal on Selected Areas in Communications, vol.24, no.7, pp. 1411-1420, July 2006.
The world's first BB-PLC ANSI standard to be approved was the TIA-1113. The standard is largely based on the HomePlug 1.0 specifications and defines a 14 Mbps PHY based on OFDM. The first paper gives a comprehensive description of the MAC and PHY specification of the protocol and the second paper gives a good description of the CSMA/CA-based MAC and also analyzes in depth its performance.

K.H. Afkhamie, S. Katar, L. Yonge, and R. Newman, "An overview of the upcoming HomePlug AV standard," 2005 International Symposium on Power Line Communications and Its Applications (ISPLC), Vancouver, BC, Canada, pp. 400-404, 6-8 April 2005.
B. Mashburn, H. Latchman, T. VanderMey, L. Yonge, and K. Tripathi, "Signal processing challenges in the design of the HomePlug AV powerline standard to ensure co-existence with Homeplug 1.0.1," IEEE Workshop on Signal Processing Advances in Wireless Communications, New York, NY, 2005.
These two papers provide a description of the 2nd generation HomePlug AV specification targeted at attaining an order of magnitude improvement in throughput over HomePlug 1.0 in order to support emerging multimedia traffic. The first paper gives an overview of the MAC and PHY design, with details of improvements in frequency ranges, modulation order, channel adaptation and error control coding, while the second paper outlines the design decisions from a signal processing point of view that enables coexistence and inter-operability with the earlier HomePlug 1.0 standard.

S. Galli, H. Koga, and N. Kodama, "Advanced signal processing for PLCs: Wavelet-OFDM," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Jeju Island, Korea, April 2-4, 2008.
This paper gives some details on the Panasonic solution for a BB-PLC transceiver which is based on Wavelet-OFDM. Comparisons with windowed OFDM are also made. This technology has been included as one of the two PHYs of the ratified IEEE 1901 standard and it is the first standard ever made that includes wavelets in its specifications.

J. Abad, A. Badenes, J. Blasco, J. Carreras, V. Dominguez, C. Gomez, S. Iranzo, J.C. Riveiro, D. Ruiz, L.M. Torres, and J. Comabella, "Extending the power line LAN up to the neighborhood transformer," IEEE Communications Magazine, vol.41, no.4, pp. 64-70, April 2003.
This paper provides a description of the FFT-based 45Mbps and 200 Mbps OFDM PHY and CSMA/CA MAC developed by DS2/UPA. The paper also describes several large scale PLC test results involving thousands of PLC nodes using this technology.

S. Galli and O. Logvinov, "Recent developments in the standardization of power Line communications within the IEEE," IEEE Communications Magazine, vol. 46, no. 7, pp. 64-71, July 2008.
The IEEE 1901 Working Group was established in 2005 with the goal of developing a standard for high-speed (>100 Mbps) communication devices using frequencies below 100 MHz and addressing both HAN and access applications. The standard was recently ratified at the end of 2010. This paper gives an overview of the IEEE 1901 Broadband over Power Lines standard. Although the paper is some years old, the technical proposal has not changed between 2008 and 2010 when the standard was ratified so the information given in the paper is accurate.

S. Goldfisher and S. Tanabe, "IEEE 1901 access system: An overview of its uniqueness and motivation," IEEE Communications Magazine, vol. 48, no. 10, pp. 150-157, Oct. 2010.
This paper addresses the access part of the IEEE 1901 standards, and explains the underlying rationale for the features of the access specifications. Particular emphasis is given to topological aspects of the access cluster.

V. Oksman and S. Galli, "G.hn: the new ITU-T home networking standard," IEEE Communications Magazine, vol. 47, no. 10, Oct. 2009.
The ITU-T started the G.hn project in 2006 with a goal of developing a worldwide recommendation for a unified HAN transceiver capable of operating over all types of in-home wiring: phone lines, power lines, coax and Cat 5 cables. The G.hn PHY and MAC were ratified by the ITU-T as Recommendations G.9960 and G.9961. The paper provides an overview of the G.hn PHY and MAC and shows similarities in the channel characteristics of several wireline channels.

Coexistence

S. Galli, A. Kurobe and M. Ohura, "The inter-PHY protocol (IPP): A simple coexistence protocol for shared media," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Dresden, Germany, March 29 -April 1, 2009.
The topic of PLC coexistence is receiving growing attention due to the presence of multiple non-interoperable PLC standards, e.g. IEEE 1901 Wavelet-OFDM, IEEE 1901 FFT-OFDM, and G.hn. This paper gives an overview of the coexistence mechanism that has been included as mandatory in the IEEE 1901 standard and has also been ratified by the ITU-T as Recommendation G.9972.

Channel transfer function (in part also additive noise)

H. Philipps, “Performance measurements of power line channels at high frequencies,” International Symposium on Power Line Communications and its Applications, Tokyo, Japan, pp. 229-237, March 24-26, 1998.
This paper is a pioneering work concerned with indoor PLC channels for broadband applications. It presents interesting measurements results about important characteristics of the transmission channel: the input impedance, frequency response, impulse response, and noise power spectral density. These measurements cover the frequency band up to 30 MHz and are registered at different locations: apartments, detached-houses and university buildings. Different sources of noise are also identified, and their influence on the channel behavior is also briefly discussed. Based on the measurement results, a simple model for the channel is suggested: a linear time-invariant filter plus some additive noise components. This work mainly presents a qualitative analysis of indoor PLC channels behavior.

O.G. Hooijen, “A channel model for the residential power circuit used as a digital communications medium,” IEEE Transactions on Electromagnetic Compatibility, vol. 40, no. 4, pp. 331-336, Nov. 1998.
Another pioneering work, which discusses the main features of the power line channel at low frequencies. It focuses on distribution networks in urban, suburban and rural areas. Measurements for noise power spectral density, network impedance and the attenuation and phase shift that signals experience in the band from 9-95kHz are discussed. A first classification of noise components is also presented, with four categories: background noise, single event impulse noise, noise synchronous to the mains frequency and narrow-band noise.

D. Liu, E. Flint, B. Gaucher, and Y. Kwark, “Wideband AC power line characterization,” IEEE Transactions on Consumer Electronics, vol. 45, no. 4, pp. 1087-1097, Nov. 1999.
This paper provides quantitative information about channel parameters useful for PLC system design. It presents a characterization of indoor power line channels by measuring multiple links, selected among the available outlets at four houses. The measurements are for channel transfer functions and noise power spectral density, considering the frequency range up to 60MHz. A statistical analysis of the mean attenuation and the delay spread is given, and the noise power spectral density for some particular appliances and at several outlets are estimated. Furthermore, the evolution of some of these parameters along a day is shown.

M. Zimmermann and K. Dostert, “A multipath model for the power line channel,” IEEE Transactions on Communications, vol. 50, no. 4, pp. 553-559, April 2002.
This is a seminal work introducing the parametric multipath channel model for broadband PLC applications. The proposed model has received wide acceptance in the research community, evidenced by a considerable citation index. In detail, the paper presents an analytical model of the complex transfer functions of typical PLC networks in the frequency range from 500 kHz to 20 MHz. The main advantage of the model is that it covers fundamental effects with a small set of parameters. The accuracy of the model has been verified in a variety of environments. The sophisticated strategy to estimate the model parameters has proven to be highly effective and easy to use. Due to its overall conciseness and convincing results, the model has been used to define reference channels, e.g. within the European OPERA project, being important for a standardized evaluation of PLC system performance.

T. Esmailian, F.R. Kschischang, and P.G. Gulak, "In-building power lines as high-speed communication channels: channel characterization and a test-channel ensemble," International Journal of Communication Systems, vol. 16, no. 5, pp. 381-400, June 2003.
This paper describes one of the very first attempts to define a PLC statistical channel model. The approach followed in this model is a hybrid approach where deterministic channel models based on transmission-line theory are coupled with Monte Carlo simulations. The proposed modeling requires the generation of random in-home topologies using the US National Electric Code to set constraints on the topologies in terms of number of outlets per branch, wire gauges, inter-outlet spacing, etc. Then, for each generated topology, the transfer function is calculated using classical transmission line theory tools. Although the generalization of this approach requires the knowledge of the electric codes of every country, this paper represents an important step forward in the definition of a statistical PLC channel model.

F. J. Cañete, J. A. Cortés, L. Díez, and J. T. Entrambasaguas, “Analysis of the cyclic short-term variation of indoor power line channels,” IEEE Journal on Selected Areas in Communications, vol. 24, no. 7, pp. 1327-1338, July 2006.
This paper explains and models the periodically time-varying behavior of the channel transfer function in PLC systems due to the mains voltage cycle in AC power networks. Measurements carried out at different locations are discussed and employed to characterize the behavior of some loads, the time-varying channel response, and non-stationary received disturbances. Furthermore, a statistical analysis of parameters related to the time variation is presented. Finally, a channel model is proposed, composed of a linear periodically time-varying (LPTV) filter plus some cyclostationary noise, where the periodicity is synchronized with the mains cycle. This work is useful to evaluate the influence that channel time variation may have on the performance of PLC systems.

S. Galli and T.C. Banwell, “A deterministic frequency-domain model for the indoor power line transfer function,” IEEE Journal on Selected Areas in Communications, vol. 24, no. 7, pp. 1304-1316, July 2006.
This paper contains a wide introduction to channel modeling strategies in PLC, covering both the multi-path models and models based on transmission line theory. The author addresses the issue of grounding and its effect on the communications channel. For the first time, an accurate communication channel model based on multi-conductor transmission line (MTL) theory and modal decomposition is set forth. The proposed modeling approach allows treating both grounded and ungrounded PLC links under the same formalism of cascaded transmission matrices. Together with companion papers published in the IEEE Trans. Power Del. in 2005, the author shows that, if properly modeled, the PLC channel exhibits more determinism than what was commonly believed. The IEEE 1901 Broadband over Power Lines Standard references this work in Annex G.

T. Sartenaer and P. Delogne, "Deterministic modeling of the (shielded) outdoor power line channel based on the multiconductor transmission line equations," IEEE Journal on Selected Areas in Communications, vol. 24, no.7, pp. 1277-1291, July 2006.
This paper applies multiconductor transmission line theory for accurate deterministic modeling of the channel transfer functions for PLC access networks using underground cables. The multidimensional scattering matrix formalism is applied to PLC networks including multiconductor cable segments, derivation points, and termination loads. Examples of outdoor PLC networks with different types of cables are presented and the proposed modeling is tested by analyzing the obtained impulse responses.

M. Tlich, A. Zeddam, F. Moulin, and F. Gauthier, ”Indoor power line communications channel characterization up to 100 MHz - part I: one-parameter deterministic model” and "Part II: time-frequency analysis," IEEE Transactions Power Delivery, vol. 23, no. 3, pp. 1392-1409, July 2008.
These two papers characterize indoor power line channels in the frequency range from 30 kHz to 100 MHz. In Part I measurements of channel transfer functions from different sites are presented. Based on these results, a channel classification according to channel capacity is performed and an approximated deterministic channel model for every class is given. Furthermore a detailed observation of peaks and notches of the transfer function is documented, and a statistical model is devised. Finally a multipath channel generator is proposed, taking the statistical behavior of magnitude and group delay into account. Part II focuses on time-frequency analysis based on the measurement results from Part I. Time delay spread and coherence bandwidth are determined and significant changes of these parameters in dependence of frequency range are discussed. The relation between time delay parameters and the channel classification presented in Part I is outlined as well as the relation between coherence bandwidth and delay spread for the frequency range from 2 MHz to 100 MHz. The importance of these two papers is mainly given by the fact that an extended frequency range of up to 100 MHz is covered. Thus they can be considered as primers to prepare the way for the next generation of high speed PLC systems aiming at data rates up to 1 Gbit/s.

S. Galli, "A simplified model for the indoor power line channel," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Dresden, Germany, March 29 - April 1, 2009.
This paper reports for the first time some important properties of the power line channel. First, it presents correct values of the Root-Mean-Square Delay Spread (RMS-DS) of the PLC channel pointing out that what has been usually reported in the PLC literature is duration of the impulse response and not the RMS-DS. Then, the paper confirms that channel gains and RMS-DS of indoor PLC channels are lognormally distributed on the basis of several statistical tests. Finally, the paper also reports that channel gains and RMS-DS of indoor PLC channels are negatively correlated, thus suggesting that channels that introduce severe multipath are also characterized by large attenuation. These results are important building blocks for defining statistical channel models and for the correct interpretation of the performances of ISI mitigation techniques. Subsequent work by the author found that these properties can also be extended to other wireline channels (see the paper in press, http://arxiv.org/abs/1101.1915).

A. M. Tonello and F. Versolatto, “Bottom-up statistical PLC channel modeling - Part I: topology model and efficient transfer function computation,” IEEE Transactions Power Delivery, in press. A. M. Tonello and F. Versolatto, “Bottom-up statistical PLC channel modeling - part II: inferring the statistics,” IEEE Transactions Power Delivery, vol. 25, no. 4, pp. 2356–2363, Oct. 2010.
A comprehensive analysis of the in-home PLC channel statistics and their dependency from the topological information, as for instance, the layout area, the loads intensity, the wiring structure, is reported in these two papers. The study is carried out with the use of a bottom up channel generator that exploits a structured description of topologies derived from the observation of wiring practices and norms in Europe. The convergence of the results obtained with the channel simulation tool and those from experimental data is also shown.

Noise environment

M. Zimmermann and K. Dostert, “Analysis and modeling of impulsive noise in broadband power line communications,“ IEEE Transactions on Electromagnetic Compatibility, vol. 44, no. 1, pp. 249-258, Feb. 2002.
This work is an important contribution toward simulation and emulation of PLC noise, helping the PLC system designer to reduce or mitigate the impact of challenging disturbances. The authors elaborate on the fundamental basics toward analysis and modeling of impulsive noise within power line channels in the frequency range from 200 kHz to 20 MHz. Based on measurements at various locations like apartments and transformer substations, both in rural and industrial areas with an overall observation time of nearly 90 hours, five general classes of noise are defined: colored background noise, narrow-band noise, periodic impulsive noise asynchronous to the mains frequency, periodic impulsive noise synchronous to the mains frequency, and asynchronous impulsive noise. Characteristic parameters of impulses, such as impulse rate, disturbance ratio, impulse width and amplitude, 'inter-arrival' time and burst events, are examined and statistically evaluated in the time domain. A detailed analysis enables the concise modeling of realistic noise scenarios. The proposed classification of noise from this paper has been widely accepted in the PLC community, so that it is now a common base for the description of noise in different PLC environments.

V. Degardin, M. Lienard, A. Zeddam, F. Gauthier, and P. Degauquel, “Classification and characterization of impulsive noise on indoor power lines used for data communications,” IEEE Transactions on Consumer Electronics, vol. 48, no. 4, pp. 913-918, Nov. 2002.
This paper investigates the statistics of impulsive noise for broadband indoor PLC. From measurements over two days in a house with a large number of appliances connected to the power lines about 1700 waveforms of impulses were collected. These impulses have been analyzed both in time and frequency domain, and categorized into five classes. Probability distributions for pseudo frequencies, inter-arrival time, pulse duration, and peak value are presented with additional discussions on pulse statistics.

A. Kawaguchi, H. Okada, T. Yamazato, and M. Katayama, "Correlations of noise waveforms at different outlets in a power-line network," IEEE International Symposium on Power Line Communications and Its Applications, pp. 92-97, March 2006.
This manuscript shows a unique facet of PLC noise, namely that the noise realizations observed at different receivers are not always independent. Based on measurements of noise waveforms at different outlets in a power line network, it is found that the instantaneous noise voltages at two different outlets show strong correlations if the outlets are connected to the same live conductor. In addition, it is also pointed out that the evolution of instantaneous/cyclic-averaged noise powers exhibit large correlations, even at outlets connected to different live conductors of the network. These features imply that PLC noise being present at a certain location can be predicted accurately from observations made at another point of the same network, and that adaptation to a receivers' noise scenario is possible at a transmitter. (The authors have published an extended version of this work in the IEICE Trans. on Fundamentals, vol. J90-A, no.11, pp 851-860, 2007, in Japanese language).

M. Katayama, T. Yamazato, and H. Okada, “A mathematical model of noise in narrowband power line communication systems,” IEEE Journal on Selected Areas in Communications, vol. 24, no. 7, pp. 1267-1276, July 2006.
This paper focuses on the non-stationary features of PLC noise. All results are based on measurements of narrow-band indoor noise. Evaluating these measurements, it is shown that PLC noise can be modeled as a colored Gaussian random process whose variance is a periodic function synchronous to the absolute value of the mains voltage. A simple expression of the instantaneous variance with a small set of parameters is introduced. With the proposed model, PLC noise can be described concisely with a few parameters, so that noise waveforms can easily be generated, enabling benchmarking for design and evaluation of PLC systems.

J. A. Cortés, L. Díez, F. J. Cañete, and J. J Sánchez-Martínez, "Analysis of the indoor broadband power line noise scenario,” IEEE Transactions on Electromagnetic Compatibility, vol. 52, no. 4, pp. 849-858, Nov. 2010.
This paper presents a detailed analysis of indoor broadband power line disturbances, namely background noise, impulsive noise and narrow-band interference. The study is based on the results of a measurement campaign at different locations. The used methodology combines time-domain techniques with signal processing algorithms that capture the cyclostationary nature of most noise terms. Particular attention is devoted to impulsive noise, revealing aspects of its behavior that were not covered in previous works. Illustrative noise waveforms are shown and also statistical parameters are extracted.

H.-K Podszeck, Carrier Communication over Power Lines, 4th Edition, New York: Springer-Verlag, Section 3.1, pp. 15-45, 1972.
This book shortly discusses the historical development of MV and HV coupling (which progressed from antenna coupling to high-voltage capacitors for direct connection to the HV grid). Resonant ‘wave traps’ are also discussed which ‘blocks off’ certain sections of the grid, preventing the communication signal from entering. Lastly, in order to effectively propagate the signal past substations, bypass circuits are considered.

IEEE Guide for Power-Line Carrier Applications, IEEE Std 643-2004 (Revision of IEEE Std 643-1980), June 2005.
This section of the IEEE standard deals with traditional MV and HV coupling components and strategies. Various types of (series-connected) de-coupling ‘line traps’ are discussed. Coupling capacitor selection is mentioned, after which inductive ‘line tuners’ are discussed. These are chosen for series resonance with the coupling capacitor for optimized band-pass filtering. Finally, bypassing as well as instrumentation cabling are also covered.

P. A. Janse van Rensburg and H. C. Ferreira, “Coupling circuitry: understanding the functions of different components,” International Symposium on Power Line Communications and Its Applications, Kyoto, Japan, pp. 204-209, 2003.
An introductory paper to the concepts of filtering and LV power-line coupling. The band-pass filtering mechanism of a typical capacitor-transformer coupler is explained, showing how the capacitor effects the left-side slope of the pass-band, while the leakage inductance of the coupling transformer affects the right-side slope of the pass-band.

P. A. Janse van Rensburg and H. C. Ferreira, “Design of a bidirectional impedance-adapting transformer coupling circuit for low-voltage power-line communications,” IEEE Transactions on Power Delivery, vol. 20, no. 1, Jan. 2005, pp. 64-70.
This paper describes in detail the design of an LV narrowband capacitive coupler that facilitates bidirectional coupling with the aid of an impedance-adapting coupling transformer. Much attention is given to the design of the coupling transformer, and bidirectional functionality of the coupler is shown. The danger of coupling transformer saturation and its prevention is presented. Finally, the impact of fluctuating power-line impedance levels on the coupler bandwidth is discussed.

P. A. Janse van Rensburg and H. C. Ferreira, “Coupler winding ratio selection for effective narrow-band power-line communications,” IEEE Transactions on Power Delivery, vol. 23, no. 1, Jan. 2008, ISSN 0885-8977, pp. 140-149.
This paper is about LV impedance adaptation by means of varying the coupling transformer’s winding ratio. The PLC channel is modeled as a simple T-structure to include series impedances (cables) and parallel impedances (dominating loads). Classification of series (cable) and parallel (load) impedances, is further demonstrated to facilitate the deployment of optimized winding ratios for impedance adaptation.

A. Kosonen and J. Ahola, “Comparison of signal coupling methods for power line communication between a motor and an inverter,” IET Electric Power Applications, vol. 4, no. 6, 2010, pp. 431-440.
The performance of a capacitive coupler compared to an inductive coupler is studied in this paper for the HomePlug 1.0 specification and frequency band (< 21 MHz). Circuit diagrams and component values are given for both couplers, however analysis and design of said couplers are not discussed. Data throughput rates were measured for the two kinds of coupling, in a setup utilizing LV PLC between a variable-speed drive and its motor. Certain pro’s and con’s of the two couplers are also discussed qualitatively.

Tutorial

E. Biglieri, "Coding and modulation for a horrible channel," IEEE Communications Magazine, vol.41 , no. 5, pp. 92-98, May 2003.
This tutorial paper is well suited for the reader who wishes to get acquainted with PLC. It provides a brief overview of the technical challenges for PLC at the physical layer. It describes relevant channel models and main impairments for reliable communication, and it reviews modulation techniques at large, including spread spectrum, single carrier and multi-carrier, as well as their adaptive realizations and relevant coding schemes.

Modulation

T. Schaub, “Spread frequency shift keying,” IEEE Transactions on Communications, vol. 42, no. 2/3/4, pp. 1056-1064, Feb./March/April 1994.
Frequency shift keying (FSK) is an attractive modulation scheme for the narrowband low data-rate PLC applications. However, the transmission at only one frequency per symbol duration is susceptible to strongly colored background noise and narrowband interferences as experienced in PLC. This article presents a spread-FSK (S-FSK) modulation and demodulation technique, which enables reliable communication even in the presence of the narrowband interferences. The two frequencies of the binary S-FSK are chosen relatively far apart such that narrowband interference only destroys one of the two transmission frequencies and demodulation can still take place using the undisturbed channel on an on-off keying (OOK) basis.

L. Lampe and J. B. Huber, “Bandwidth efficient power line communications based on OFDM,” AEÜ International Journal of Electronics and Communications, vol. 54, no. 1, pp. 2–12, 2000.
One of the earlier papers about coding and modulation with OFDM for PLC. The paper infers the capacity achievable with OFDM using a stochastic representation of the channel transfer function. The combination of a large signal constellation and low rate codes in order to obtain a fixed target rate proves to be advantageous both for coherent and bandwidth efficient noncoherent transmission over power lines.

M. Crusiere, J-Y. Baudais, and J.F. Hélard, “Adaptive spread spectrum multicarrier multiple-access over wireline,” IEEE Journal on Selected Areas in Communications, vol. 24, no. 7, pp. 1377-1389, July 2006.
The resource allocation, i.e., bit and power loading, in multicarrier PLC is important to maximize data throughput. In this paper the resource allocation problem is addressed for the multiuser case in a system that combines OFDM with linear precoding. The proposed algorithm realizes user multiplexing together with the dynamic allocation of subcarriers, codes, bits, and power.

L. Lampe, R. Schober, and S. Yiu, “Distributed space–time coding for multihop transmission in power line communication networks,” IEEE Journal on Selected Areas in Communications, vol. 24, no. 7, pp. 1389-1400, July 2006.
Multihop transmission (or the use of repeaters/relays) is attractive for PLC to bridge large distances and/or achieve high data rates. This paper is one of the earliest works considering the use of space-time coding techniques, developed for wireless communications, in the PLC setting. Using statistical indoor channel models for PLC, it is demonstrated that so-called distributed space-time block codes, which enable relaying without centralized resource allocation, lead to improved transmission range/reliability and delay.

A. M. Tonello, “Wide band impulse modulation and receiver algorithms for multiuser power line communications," EURASIP Journal on Advances in Signal Processing - Special Issue on "Advanced signal processing and computational intelligence techniques for power line communications,” vol. 2007, art. id. 96747, 2007.
This is the first paper, among very few, that considers impulsive ultra wide band (UWB) modulation for PLC. A simple modulation scheme that, when combined with code division multiple access and bit-interleaved coding, provides robust performance in the presence of severe channel frequency selectivity and impulsive noise. This is the result of spreading the symbol energy both in frequency (through the wideband pulse) and in time (through the spreading code and the bit-interleaved convolutional code). Several novel frequency domain algorithms are proposed for detection in the presence of impulsive noise and multiple access interference. In addition, a novel statistical broadband PLC channel model is described.

A. M. Tonello and F. Pecile, “Efficient architectures for multiuser FMT systems and application to power line communications," IEEE Transactions on Communications, vol. 57, no. 5, pp. 1275-1279, May 2009.
To provide better spectrum notching capability and robustness to narrow band interference, which allows better coexistence between PLC and radio systems, filter bank modulation schemes can be used. In this paper, filtered multitone modulation (FMT) for broadband multiuser PLC is considered. Compared to conventional OFDM, or pulse shaped OFDM, that privileges the sub-channel time confinement, FMT privileges the sub-channel frequency confinement. An important issue is the implementation complexity of FMT. The paper proposes a novel efficient digital implementation of both the synthesis and the analysis filter banks, and the performance is evaluated in typical PLC channels.

Coding & Impulse noise analysis/mitigation

S. Miyamoto, M. Katayama, and N. Morinaga, ”Performance analysis of QAM systems under class A impulsive noise environment," IEEE Transactions Electromagnetic Compatibility, vol. 37, no. 2, pp. 260-267, May 1995.
In many communication channels, interference produced by man-made machinery are much more structured (or impulsive) than AWGN. In PLC, the noise includes both background and impulsive components. Effects of background noise on the communication systems are well understood. Designing reliable communication under impulsive noise, however, is still a challenge. This article expands our knowledge by investigating the transmission quality of QAM systems under the influence of class-A impulsive noise. It is first presented that the real and the imaginary parts of the complex impulsive noise samples are dependent. The numerical results show that the receiver performance in an impulsive noise channel is much worse than that achieved in a Gaussian noise channel. The design of a reliable receiver structure is also presented.

J. Haering and A. J. H. Vinck, “OFDM transmission corrupted by impulsive noise," International Symposium on Power Line Communications and Its Applications (ISPLC), Limerick, Ireland, April 2000, pp. 9-14.
OFDM is an attractive modulation scheme for the high data rate PLC applications. However, the reliability of OFDM transmission is strongly influenced by impulse noise, experienced in PLC. This paper studies the influence of the impulse noise on the transmission capacity. By presenting the enormous loss in the achievable rate when using a conventional receiver, the authors stress the importance of designing a receiver matched to impulse noise. This paper is one of the earliest works proposing a simple iterative impulsive noise suppression algorithm, which exploits the noise structure in the time and frequency domain. It is shown that the error rate performance can be significantly improved.

S. V. Zhidkov, “Analysis and comparison of several simple impulsive noise mitigation schemes for OFDM receivers,” IEEE Transactions on Communications, vol. 56, no. 1, pp. 5-9, Jan. 2008.
In PLC, the reliability of transmission is strongly influenced by the impulse noise. Due to its simplicity, clipping or blanking techniques are often used in practical applications. This paper demonstrates how to improve transmission reliability by applying simple impulse noise mitigation techniques at the receiver. One important point is the application of clipping and blanking (nulling) techniques together. The results presented for the communication under impulsive noise show that the joint clipping-blanking technique outperforms pure blanking and clipping techniques.

R. Pighi, M. Franceschini, G. Ferrari, and R. Raheli, “Fundamental performance limits of communications systems impaired by impulse noise,” in IEEE Transactions on Communications, vol. 57, pp. 171-182, Jan. 2009.
It has commonly been assumed that multi-carrier (MC) schemes are more robust to impulse noise, typical of PLC systems, than single-carrier (SC) ones. This paper questions and complements this belief showing that, while it is indeed correct for encoded modulations, conventional coded MC schemes operating at typical rates may be significantly more sensitive to impulse noise than SC ones. The analysis considers the impact of impulse noise on the performance limits of SC and MC communication and is mainly based on the information rate achievable by standard linear modulations with interleaved coding.

D. Fertonani and G. Colavolpe, “On reliable communications over channels impaired by impulse noise,” IEEE Transaction on Communications, vol. 57, no. 7, pp. 2024-2030, July 2009.
While most impulse noise models used for performance analysis and system design are inherently memoryless, actual PLC channels are characterized by the occurrence of impulse bursts. Based on a simple two-state Markov-chain model, this paper addresses the achievable information rate of systems impacted by bursty impulse noise. It also proposes detection schemes to account for the memory induced by the noise bursts and analyzes their performance for representative systems employing low-density parity-check (LDPC) codes. The analysis shows that non negligible performance improvements are indeed achievable.

H. Hrasnica, A. Haidine, and R. Lehnert, "Broadband Powerline Communications Networks: Network Design," John Wiley & Sons Inc., UK, June 2004.
This book covers design, modeling, and performance aspects of broadband PLC systems and especially PLC access networks. Particular attention is given to the specifics of the PLC MAC layer and its protocols.

S. Katar, B. Mashburn, K. Afkhamie, H. Latchman, and R. Newman,"Channel adaptation based on cyclo-stationary noise characteristics in PLC systems," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Orlando, FL, USA, Oct. 2006.
One peculiar characteristic of the PLC channel is the cyclic variation of the noise power with the phase of the underlying AC line cycle. This is one of the earliest papers that proposes a channel adaptation mechanism exploiting the cyclic variation of the power line noise and that reports the achieved performance enhancements.

A. M. Tonello, J. A. Cortés, and S. D'Alessandro, "Optimal time slot design in an OFDM-TDMA system over power-line time-variant channels," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Dresden, Germany, March-April 2009.
The idea of exploiting the cyclostationary noise and the cyclic variations of the channel response is used in this paper to design a MAC scheme with contention and adaptive TDMA regions, similar to the one of the HomePlug AV system. The paper focuses on the optimization of the TDMA region and describes an optimal scheduling scheme with adaptation of the slot duration in the relevant multiuser downlink context.

A. Abdelfatteh and R. Lehnert, "Analysis of the channel allocation problem in broadband power line communications access networks," IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Jeju-Island, Korea, April 2008.
The solution of the PLC channel allocation problem for low voltage networks is of high importance. This paper formulates it as a multiobjective combinatorial optimization (MOO) problem and metaheuristics based on evolutionary search are used to solve it. In detail, the solution is found either converting the MOO problem into a single-objective optimization problem (classical approach) or using multiobjective optimization algorithms.

G. Bumiller, L. Lampe, and H. Hrasnica, "Power line communication networks for large scale control and automation systems," IEEE Communications Magazine, vol. 48, no. 4, pp. 106-113, April 2010.
This paper provides a very readable account of a number of previous works proposing single-frequency networking for PLC when used for control and automation applications such as envisaged for Smart Grid. The requirements on PLC networks comprising many nodes spread over relatively wide areas supporting mentioned applications are discussed, based on which a hybrid medium access protocol and single-frequency networking repeater concepts are advocated.