Analysis and evaluation of in-home networks based on HomePlug-AV power line communications

[ESP] No hace mucho tiempo, las redes in-home (también denominadas redes domésticas) únicamente se utilizaban para interconectar los diferentes ordenadores de una vivienda, de manera que pudieran compartir una impresora entre ellos. Hoy en día, sin embargo, esta definición es mucho más amplia debido a la gran cantidad de dispositivos existentes en la vivienda con capacidad de conectarse a una red para transmitir y recibir información. En una red in-home actual, podemos encontrar desde teléfonos móviles equipados con conectividad WI-FI a dispositivos NAS (Network Attached Storage), utilizados para almacenar información, imágenes o videos en red, que a su vez pueden ser transferidos a televisiones de alta definición u ordenadores. A la hora de instalar una red de comunicaciones en una vivienda, se persiguen principalmente dos objetivos, reducir el coste de instalación y conseguir una gran flexibilidad de cara a futuras ampliaciones. Una red basada en tecnología PLC (Power Line Communications) cumple estos requisitos ya que, al utilizar la infraestructura de cableado eléctrico existente en la vivienda, es muy sencilla y económica de instalar y ampliar. Dentro de la tecnología PLC existen diferentes estándares, siendo HomePlug-AV (HomePlug Audio-Video o simplemente HPAV) el más extendido en la actualidad para la instalación de redes domésticas. Este estándar permite alcanzar velocidades de transmisión de hasta 200Mbps a través de los cables de baja tensión de una vivienda convencional. El objetivo principal de esta tesis doctoral es aportar nuevas ideas que mejoren las prestaciones de las redes in-home basadas en la tecnología PLC, utilizando como base el estándar Homeplug-AV. Estas redes utilizan una arquitectura centralizada, en la que la mayor parte de la inteligencia de red está concentrada en un coordinador central (CCo, por sus siglas en inglés). Por lo tanto, la mayor parte de las modificaciones propuestas irán encaminadas a mejorar dicho dispositivo, que podrá llegar a convertirse en un gestor de red capaz de manejar conjuntamente interfaces de diferentes tecnologías. En primer lugar, se presenta un análisis detallado del comportamiento del estándar en diferentes situaciones que se pueden producir de manera común en una red doméstica. Este análisis se realizó tanto con dispositivos reales como mediante simulación. Para el segundo tipo de medidas, se diseñó un simulador de la tecnología HomePlug que implementa el nivel físico y el nivel MAC de la misma, junto con modelos de los servicios más utilizados en entornos domésticos. Este simulador se utilizó tanto para estas medidas iniciales como para evaluar las diferentes modificaciones del estándar propuestas posteriormente en este trabajo. Este análisis proporcionó dos resultados significativos. En primer lugar, se comprobó que al introducir un modelo real de nivel físico al protocolo CSMA/CA utilizado a nivel MAC se producían resultados muy diferentes a los presentados en los modelos publicados hasta ese momento. Por ello, se propuso un modelo matemático que incorporaba dichos efectos. En segundo lugar, se identificaron diferentes áreas de la tecnología que eran susceptibles de mejora. El resto de la tesis se centró entonces en la mejora de dichos puntos débiles. El primero de estos puntos débiles está relacionado con las transmisión de datos unicast. El medio PLC es selectivo en frecuencia y muy dependiente del tiempo y de la localización de las estaciones. Incluso es posible que, en un mismo enlace, la capacidad de los enlaces ascendente y descendente sea distinta. En estos entornos, la utilización del protocolo de transporte TCP presenta serios problemas, ya que define gran parte de sus parámetros en función del Round Trip time (RTT) del enlace. Como alternativa se pensó en los códigos Fountain. Este tipo de codificación de fuente permite realizar transmisiones fiables de datos sin necesidad de utilizar un canal de retorno, evitando de esta forma los problemas derivados de las asimetrías de la red. Se realizaron varios experimentos comparando ambas soluciones, y se comprobó que las prestaciones de este tipo de codificaciones superan al protocolo TCP a la hora de transmitir ficheros de manera fiable a través de las redes PLC. Además, los códigos Fountain también se utilizaron para el diseño de otra aplicación. Es muy común que en un escenario doméstico haya disponible más de una tecnología (Wi-Fi, Ethernet, PLC, etc). Tenemos por tanto que una aplicación capaz de integrar interfaces de diferentes tecnologías podría ser muy útil en estos entornos, ya que se podría conseguir un mayor ancho de banda, mayor tolerancia a errores, balanceo de carga, etc. El kernel de Linux dispone de un módulo denominado Bonding que permite agrupar diferentes interfaces Ethernet. Sin embargo, no está preparado para agrupar interfaces de diferentes tecnologías, y mucho menos para tecnologás de capacidad variable como es el caso de PLC o de las comunicaciones inalámbricas. Por ello, se realizó una modificación de dicho driver utilizando para ello los códigos Fountain, que solucionan los problemas que se pueden producir debido a las variaciones de capacidad. Por otra parte, con la actual versión del estándar HomePlug AV, las comunicaciones multicast presentan unas prestaciones muy pobres. Esto es debido a que, a pesar de que el canal PLC es broadcast, la naturaleza de la modulación OFDM (Ortogonal Frequency Division Multiplexing) que se utiliza a nivel físico es punto a punto. Esto hace que las transmisiones simultáneas a un grupo de receptores se traduzcan automáticamente en sucesivas transmisiones punto a punto a los diferentes miembros del grupo. Con esta técnica, la capacidad efectiva de transmisión multicast disminuye de manera muy importante a medida que aumenta el número de receptores. En este trabajo se han propuesto dos técnicas alternativas. La primera consiste en la utilización de un mapa de tonos común para todos los miembros del grupo multicast, asignado a estas comunicaciones los parámetros de modulación del cliente con las peores condiciones de canal. Este algoritmo ha sido tradicionalmente descartado en los sistemas OFDM por sus bajas prestaciones. Sin embargo, la correlación existente entre los diferentes canales de una red PLC hace que su comportamiento sea mucho mejor. Además, se propuso un segundo algoritmo que utilizaba técnicas de optimización para maximizar la tasa de comunicación multicast, obteniendo un mejor comportamiento cuando el número de clientes es elevado. Por último, en redes de capacidad física variable, como es el caso de las redes PLC, las técnicas cross-layer están despertando un gran interés. Este tipo de algoritmos están basado en la compartición de información entre diferentes capas de la estructura OSI para mejorar el comportamiento del sistema. En este trabajo se ha propuesto un algoritmo que modifica los parámetros del protocolo CSMA/CA de nivel MAC utilizando información de nivel físico y los requerimientos de QoS del servicio de niveles superiores. De esta forma se consigue dar prioridad en el acceso al medio a los clientes con problemas de QoS, mejorando de esta forma del comportamiento de la red. Este algoritmo ha sido evaluado mediante simulación en un escenario doméstico típico, comprobando que ofrece unos resultados muy prometedores. [ENG] Not very long time ago, in-home networks (also called domestic networks) were only used to share a printer between a number of computers. Nowadays, however, due to the huge amount of devices present at home with communication capabilities, this definition has become much wider. In a current in-home network we can find, from mobile phones with wireless connectivity, or NAS (Network Attached Storage) devices sharing multimedia content with high-definition televisions or computers. When installing a communications network in a home, two objectives are mainly pursued: Reducing cost and high flexibility in supporting future network requirements. A network based on Power Line Communications (PLC) technology is able to fulfill these objectives, since as it uses the low voltage wiring already available at home, it is very easy to install and expand, providing a cost-effective solution for home environments. There are different PLC standards, being HomePlug-AV (HomePlug Audio-Video, or simply HPAV) the most widely used nowadays. This standard is able to achieve transmission rates up to 200 Mpbs through the electrical wiring of a typical home. The main objective of this thesis is to provide new ideas to improve the performance of PLC technology based in-home networks, using as starting point the HPAV standard. A network based on this technology uses a centralized architecture, in which the most important part of the network intelligence is concentrated in a single device, the Central Coordinator (CCo). Hence, most of the modifications proposed in this work will try to improve this particular device, which can even become a multi-technology central manager, able to combine interfaces of different technologies to improve the network performance. Initially, it is presented a detailed analysis of HPAV performance in some scenarios typically found in a home environment. It was done through simulation and by experimentation using real devices. To obtain the former results, it was designed a HPAV simulator which implements the physical (PHY) and medium access control (MAC) layers of the standard, together with a traffic modeling module which implements the services most commonly found in a home network. This simulation tool was used both in these initial measurements and to evaluate the standard modifications that are proposed in this work. This analysis provides two main results. Firstly, it was found that when a real PHY model is used together with the CSMA/CA MAC protocol the simulation results were very different to those obtained with previously presented mathematical models of this protocol. Hence, it was proposed a new model that considers these effects. Next, some areas of the technology which could be improved were identified. The rest of the thesis was then centered around proposing solutions to these weaknesses. The first weakness solved is related to unicast data transmission. PLC medium is frequency selective and time variant, and it presents a remarkable variation among locations or depending on the connected loads. Even in a single link, the channel capacities between transmitter and receiver can be very asymmetric. In such environments, the use of TCP as transport protocol presents serious problems, since it defines some of its parameters according to the Round Trip Time (RTT). Alternatively, the use of Fountain codes for reliable data transmission in these environments was proposed. These codes allow to transmit information without a feedback channel, overcoming in this way the problems related to the variability of the channel. Different experiments were performed comparing both solutions, concluding that in PLC based networks the performance achieved by Fountain codes outperforms the results obtained with a TCP-based application. In addition, Fountain codes were also used for another application. In home environments, it is very common to find more than one available technology to deploy a network (Wi-Fi, Ethernet, PLC, etc). Therefore, an application that makes possible the aggregation of different interfaces would be very useful, as it will provide higher bandwidth, fault tolerance and load balancing. The Linux Kernel contains a driver (Bonding) which allows Ethernet interfaces aggregation. However, it is not prepared for asymmetric interfaces aggregation and even less for variable capacity technologies like PLC or Wi-Fi. In this work, it is presented a modification of this driver which uses Fountain codes to solve the problems that may arise when asymmetric interfaces are aggregated. On another note, multicast communications in the actual HPAV standard versions presents serious problems. This is because, although PLC medium is broadcast by nature, the Orthogonal Frequency Division Multiplexing (OFDM) modulation used at PHY layer is always point to point. Therefore, multicast communications are carried out as successive point-to-point transmissions to the different members of the group. This technique clearly degrades the performance of multicast services as the number of receivers increases. In this work, they have been proposed two alternative algorithms. The first one consists of using a common tone map for all the multicast group members. This tone map corresponds to the modulation parameters obtained for the client with the worst channel conditions. This algorithm has been traditionally discarded in OFDM systems because of its poor performance. However, in contrast to other technologies (like wireless for example), channel responses in a given PLC network exhibit significant correlation among them. This reduces the differences among the users, improving the performance of this algorithm. In addition, another technique which uses an optimization algorithm to maximize the multicast bit rate is also evaluated, obtaining that its use can be suitable when the number of multicast clients is high. Finally, due to the properties of PLC medium, cross-layer technique are eliciting a big interest. These algorithms are based in the information sharing between adjacent layers in the OSI model to improve the system behavior. In this work, it has been proposed an extension of the HPAV CSMA/CA algorithm which modifies the protocol parameters using PHY layer information and the QoS requirements of the upper-layer services. In this way, priority access to the channel can be provided to the nodes with QoS problems, improving the whole network performance. This algorithm has been evaluated through simulation in a typical home environment with very promising results.Universidad Politécnica de Cartagen

Energy-Efficient Vector OFDM PLC Systems with Dynamic Peak-Based Threshold Estimation

© 2013 IEEE. Power line communication (PLC) has made remarkable strides to become a key enabler of smart grid and its applications. Existing PLC systems are based on orthogonal frequency division multiplexing (OFDM), which has a high peak-to-average power ratio (PAPR). This paper presents vector OFDM (VOFDM) with advanced signal processing at the receiver to improve the energy efficiency of the PLC system. Results show that, due to its low PAPR properties, VOFDM is less sensitive to impulsive noise and provides a reduction of 5.8 dB in transmit power requirement relative to conventional OFDM. Furthermore, unlike the existing impulsive noise cancellation methods, the adopted signal processing technique also improves the SNR at the receiver by 2.1 dB, which further reduces the power requirement of the PLC transceiver. Together, these can simplify design, reduce cost, and improve energy efficiency of future PLC transceivers

POWER LINE COMMUNICATIONS FOR SMART HOME NETWORKS: MODELING, SIMULATION AND OPTIMIZATION

In recent years, research and development efforts are devoted to the deployment of information and communication technology (ICT) within residential buildings and houses, in order to provide services that will increase the quality of life. Although this trend is originated in the late 60’s as a result of the application of industrial automation to residential buildings and houses, i.e., home automation, nowadays, further services are offered to the final users, i.e., home networking and energy management. In fact, a lot of effort is put on the joint delivery of these services in order to make the home, namely the smart home (SH), an integral part of the future smart grid (SG). The concept of SH can be described as a house equipped with electronic systems and appliances, namely, “smart” appliances, which are able to exchange information by means of a communication network. However, these systems are characterized by a broad variety of communication technologies, standards and protocols, so that they often cannot interconnect, and/or interoperate and in some cases even coexist. In our opinion, coexistence, interconnection and interoperability problems represents the bottleneck to a pervasive deployment of smart appliances and systems within residential buildings and houses. To this respect, the first topic that we consider in this thesis is the definition of the SH network architecture and devices, which allows to obtain convergence among smart appliances. To this aim, a survey of the communication technologies, standards, protocols and also media, which can be used for SH applications, is necessary in order to define a network topology that is able to be scalable, extensible, and rather reliable. Moreover, in order to achieve interconnectivity among “smart” appliances, we define a shared common layer that is able to manage heterogeneous lower layers allowing network convergence. Once defined the SH network architecture and its network devices, we focus on power line communication (PLC) technologies and we implement a network testbed in order to evaluate some of the functionalities of the SH network within real environments. From the analysis of field trial data, we are able to highlight performances and disadvantages of two representative narrow band PLC (NB-PLC) solutions. Furthermore, exploiting the network testbed where broadband PLC (BB-PLC) technology is used to provide an Ethernet backbone for NB-PLC devices, we achieve interconnectivity between heterogeneous devices and we observe a significant improvement of the performances. Although NB-PLC technologies have been conceived for the development of low data rate applications and, in particular, for automatic meter reading (AMR), we focus our attention on the G3-PLC technology, for which we propose enhancements at the medium access control (MAC) sub-layer to allow the implementation of SH applications that could potentially require higher data rate than AMR. The G3-PLC technology has been taken into account since (i) it has been used as baseline technology for the development of popular communication standards for SG applications, and (ii) we have found, from the field trials, that the performance of NB-PLC may be poor in large houses where the signal is strongly attenuated because it spans large distances and crosses different circuit breakers (CBs), e.g., in multi-floor houses. Furthermore, an innovative cross-platform simulator that allows to realistically simulate the G3-PLC technology up to the network layer is presented. The proposed cross-platform consists of two different simulators jointly connected: one for the physical (PHY) layer and one for the data link layer (DLL)/network layer (NL). The PHY layer simulator is implemented in MATLAB, while the DLL/network simulator in OMNeT++. A convergent network architecture that permits the integration of the G3-PLC technology within a switched Ethernet network is also presented with the aim of improving the G3-PLC performance in large scale houses/buildings. The performance of the considered communication technology are presented through extensive numerical results for the in-home application scenario. Finally, the cross-platform simulator is used to evaluate G3-PLC systems for SG applications in the access network scenario. This is fundamental since the interaction of the outside world, i.e., the access network, with the SH is mandatory in order to achieve and exploit the SG concept. Moreover, to improve the performance and coverage of G3-PLC, a simple adaptive tone mapping algorithm together with a routing algorithm are also presented.Ricerca condotta all'interno del WiPLi Lab/Wireless and Power Line Communications LaboratoryopenDottorato di ricerca in Ingegneria industriale e dell'informazioneopenDI BERT, Luc

Impact of modern lighting technology on the power line communications channel

Abstract: In this study, we look at the impact of modern lighting technology on Power Line Communications (PLC). Power Line Communications has become important due to the Smart Grid and Internet of Things (IoT) development. Modern lighting technology has been developed to make efficient use of electric energy. This technology uses power converters to enable the use of different lighting sources. A byproduct of this conversion process is electronic noise. This noise can interfere with the PLC channel. In this study, different lighting technologies are investigated from a noise standpoint and compared to PLC signal levels. Both narrowband and broadband PLC frequency ranges are investigated. This study shows that the influence of noise on the PLC channel depends predominantly on the conversion topology as well as whether filters have been used. The measurement results show that the influence on data communication system can vary in impact from low to severe. Results were obtained for low energy, high energy, indoor and outdoor lighting sources. A common front end topology encounted is the bridge rectifier and high frequency DC-DC converter combination. These topologies are investigated in details. The study presented here shows that lighting technology (causing interference) needs special consideration when designing PLC systems. Of particular importance is the use of filters which ensure compliance with interference standards and limit the noise effects on the PLC signal.D.Ing. (Electrical and Electronic Engineering Science

Enhanced Amplify-and-Forward Relaying in Non-Gaussian PLC Networks

Relaying over power line communication (PLC) channels has the potential to improve the reliability and robustness of many PLC-based applications. In particular, this paper proposes to enhance the energy efficiency (EE) of a dual-hop relaying PLC system in the presence of impulsive noise by considering energy-harvesting (EH) at the relaying modem. Amplify-and-forward (AF) relaying and time-switching relaying EH protocols are deployed in this paper. The PLC modems are assumed to have the capability to go on low-power consumption sleep mode when they are neither transmitting nor receiving. The system performance is evaluated in terms of EE and average outage probability for which analytical expressions are derived. Using the derived expressions, several system parameters are investigated, such as the channel gain, which is related to the number of network branches, EH time factor and impulsive noise characteristics. Particularly, the optimization problem of the EH time is addressed thoroughly in order to maximize the achievable gains. Results reveal that the proposed system can offer considerable improvements compared with the conventional AF relaying scheme

Designing the Undersea Internet of Things (IoT) and Machine-to-Machine (M2M) Communications Using UnderWater Acoustic MIMO Networks

This review paper tries to assess the spectral-efficient (SE) and energy-efficient (EE) performance of underwater acoustic multiple-input multiple-output (UWA/MIMO) networks. Since UWA/MIMO networks define the cutting-edge communications platform of the future’s undersea IoT and M2M networks, the factors that influence their SE and EE performance are thoroughly examined in this paper.The contribution of this paper is three-fold. First, the performance of UWA/MIMO networks is studied with regard to appropriate transmission, SE and EE metrics. The SE and EE performance of these networks drastically depends on the used frequency band, the transmitted power, the MIMO scheme properties, the power consumption profile of the deployed UWA system equipment and the topological characteristics of MIMO configurations. In order to achieve the transition from traditional UWA single-input single-output (UWA/SISO) networks to UWA/MIMO networks, a new singular value decomposition MIMO (SVD/MIMO) module, which also permits the theoretical computation of the aforementioned transmission, SE and EE metrics in UWA networks, is first presented. Second, based on the aforementioned transmission, SE and EE metrics, a SE/EE trade-off relation is proposed in order to investigate the combined SE and EE performance of UWA/MIMO networks. On the basis of this SE/EE trade-off relation, it is first revealed that today’s UWA system equipment cannot support the further IoT broadband exploitation with satisfactory EE performance. Third, the concepts of multi-hop UWA communications and standard UWA topologies are outlined and promoted so that further SE and EE improvement can concurrently occur. These concepts are quantitatively validated by the SE and EE metrics as well as the SE/EE trade-off curves.Based on the findings of this paper, suitable transmitted power levels and better design of UWA/MIMO configurations are promoted so that: (i) SE and EE requirements can be satisfied at will; and (ii) EE-oriented high-bitrate M2M communications network design can be established.Citation: Lazaropoulos, A. G. (2016). "Designing the Undersea Internet of Things (IoT) and Machine-to-Machine (M2M) Communications Using UnderWater Acoustic MIMO Networks." Trends in Renewable Energy, 2(1), 13-50. DOI: 10.17737/tre.2016.2.1.001

Opportunistic Routing with Network Coding in Powerline Communications

Opportunistic Routing (OR) can be used as an alternative to the legacy routing (LR) protocols in networks with a broadcast lossy channel and possibility of overhearing the signal. The power line medium creates such an environment. OR can better exploit the channel than LR because it allows the cooperation of all nodes that receive any data. With LR, only a chain of nodes is selected for communication. Other nodes drop the received information. We investigate OR for the one-source one-destination scenario with one traffic flow. First, we evaluate the upper bound on the achievable data rate and advocate the decentralized algorithm for its calculation. This knowledge is used in the design of Basic Routing Rules (BRR). They use the link quality metric that equals the upper bound on the achievable data rate between the given node and the destination. We call it the node priority. It considers the possibility of multi-path communication and the packet loss correlation. BRR allows achieving the optimal data rate pertaining certain theoretical assumptions. The Extended BRR (BRR-E) are free of them. The major difference between BRR and BRR-E lies in the usage of Network Coding (NC) for prognosis of the feedback. In this way, the protocol overhead can be severely reduced. We also study Automatic Repeat-reQuest (ARQ) mechanism that is applicable with OR. It differs to ARQ with LR in that each sender has several sinks and none of the sinks except destination require the full recovery of the original message. Using BRR-E, ARQ and other services like network initialization and link state control, we design the Advanced Network Coding based Opportunistic Routing protocol (ANChOR). With the analytic and simulation results we demonstrate the near optimum performance of ANChOR. For the triangular topology, the achievable data rate is just 2% away from the theoretical maximum and it is up to 90% higher than it is possible to achieve with LR. Using the G.hn standard, we also show the full protocol stack simulation results (including IP/UDP and realistic channel model). In this simulation we revealed that the gain of OR to LR can be even more increased by reducing the head-of-the-line problem in ARQ. Even considering the ANChOR overhead through additional headers and feedbacks, it outperforms the original G.hn setup in data rate up to 40% and in latency up to 60%.:1 Introduction 2 1.1 Intra-flow Network Coding 6 1.2 Random Linear Network Coding (RLNC) 7 2 Performance Limits of Routing Protocols in PowerLine Communications (PLC) 13 2.1 System model 14 2.2 Channel model 14 2.3 Upper bound on the achievable data rate 16 2.4 Achieving the upper bound data rate 17 2.5 Potential gain of Opportunistic Routing Protocol (ORP) over Common Single-path Routing Protocol (CSPR) 19 2.6 Evaluation of ORP potential 19 3 Opportunistic Routing: Realizations and Challenges 24 3.1 Vertex priority and cooperation group 26 3.2 Transmission policy in idealized network 34 3.2.1 Basic Routing Rules (BRR) 36 3.3 Transmission policy in real network 40 3.3.1 Purpose of Network Coding (NC) in ORP 41 3.3.2 Extended Basic Routing Rules (BRR) (BRR-E) 43 3.4 Automatic ReQuest reply (ARQ) 50 3.4.1 Retransmission request message contents 51 3.4.2 Retransmission Request (RR) origination and forwarding 66 3.4.3 Retransmission response 67 3.5 Congestion control 68 3.5.1 Congestion control in our work 70 3.6 Network initialization 74 3.7 Formation of the cooperation groups (coalitions) 76 3.8 Advanced Network Coding based Opportunistic Routing protocol (ANChOR) header 77 3.9 Communication of protocol information 77 3.10 ANChOR simulation . .79 3.10.1 ANChOR information in real time .80 3.10.2 Selection of the coding rate 87 3.10.3 Routing Protocol Information (RPI) broadcasting frequency 89 3.10.4 RR contents 91 3.10.5 Selection of RR forwarder 92 3.10.6 ANChOR stability 92 3.11 Summary 95 4 ANChOR in the Gigabit Home Network (G.hn) Protocol 97 4.1 Compatibility with the PLC protocol stack 99 4.2 Channel and noise model 101 4.2.1 In-home scenario 102 4.2.2 Access network scenario 102 4.3 Physical layer (PHY) layer implementation 102 4.3.1 Bit Allocation Algorithm (BAA) 103 4.4 Multiple Access Control layer (MAC) layer 109 4.5 Logical Link Control layer (LLC) layer 111 4.5.1 Reference Automatic Repeat reQuest (ARQ) 111 4.5.2 Hybrid Automatic Repeat reQuest (HARQ) in ANChOR 114 4.5.3 Modeling Protocol Data Unit (PDU) erasures on LLC 116 4.6 Summary 117 5 Study of G.hn with ANChOR 119 5.1 ARQ analysis 119 5.2 Medium and PHY requirements for “good” cooperation 125 5.3 Access network scenario 128 5.4 In-home scenario 135 5.4.1 Modeling packet erasures 136 5.4.2 Linear Dependence Ratio (LDR) 139 5.4.3 Worst case scenario 143 5.4.4 Analysis of in-home topologies 145 6 Conclusions . . . . . . . . . . . . . . . 154 A Proof of the neccessity of the exclusion rule 160 B Gain of ORPs to CSRPs 163 C Broadcasting rule 165 D Proof of optimality of BRR for triangular topology 167 E Reducing the retransmission probability 168 F Calculation of Expected Average number of transmissions (EAX) for topologies with bi-directional links 170 G Feedback overhead of full coding matrices 174 H Block diagram of G.hn physical layer in ns-3 model 175 I PER to BER mapping 17

Power line communications: an implementation of a real time control architecture for smart grid

Negli ultimi anni è aumentata la presenza di risorse energetiche distribuite (DERs) nella rete elettrica. La visione della ``rete intelligente'' (Smart Grid) cerca di introdurre un'infrastruttura di controllo e di comunicazione di tipo distribuito in modo da sfruttare le potenzialità delle DERs e quindi potenziare e modernizzare la rete di distribuzione attuale. Applicandolo alle reti a bassa tensione, la cosiddetta ``Smart Microgrids'', si è sviluppato un banco di prova (testbed) che permette di dimostrare tecniche di riduzione delle perdite di distribuzione. La soluzione adottata bilancia localmente la potenza reattiva della microgrid attraverso il controllo delle risorse locali ottenendo una riduzione della corrente necessaria per alimentare la rete. Inoltre, vengono analizzati i vantaggi nell'usare la linea elettrica come mezzo di comunicazione e vengono evidenziati alcuni standard di comunicazion