Salvatore D'Alessandro

GREEND: An energy consumption dataset of households in Italy and Austria

Home energy management systems can be used to monitor and optimize consumption and local production from renewable energy. To assess solutions before their deployment, researchers and designers of those systems demand for energy consumption datasets. In this paper, we present the GREEND dataset, containing detailed power usage information obtained through a measurement campaign in households in Austria and Italy. We provide a description of consumption scenarios and discuss design choices for the sensing infrastructure. Finally, we benchmark the dataset with state-of-the-art techniques in load disaggregation, occupancy detection and appliance usage mining.

Opportunistic Relaying in In-Home PLC Networks

We consider the use of a relay to provide capacity improvements and range extension for in-home power line communication networks. In particular, we focus on opportunistic relaying where the relay is exploited only if it provides improved capacity w.r.t. the use of direct transmission between the source and the destination. The relay applies a decode and forward scheme and the channel is shared in a time division multiple access mode. The performance is studied in statistically representative in-home power line communication (PLC) networks via the use of a statistical topology model together with the application of transmission line theory for the computation of the channel transfer function among network nodes. The statistical topology model allows determining the capacity improvements as a function of the relay position. Furthermore, we determine the optimal time slot duration for each considered relay configuration, as well as we propose the use of a globally optimal time slot duration that maximizes the average network capacity. The numerical results show that significant capacity improvement can be obtained via opportunistic relaying in in-home PLC networks. The gains are more significant for low SNR scenarios and for networks composed by sub-networks each connected to the main panel via a circuit breaker that introduces signal attenuation.

Adaptive pulse-shaped OFDM with application to in-home power line communications

We propose an adaptive pulse-shaped orthogonal frequency division multiplexing (OFDM) scheme where the overhead and active sub-channels are adapted to jointly maximize capacity and fulfill the notching mask for coexistence with other devices operating in the same spectrum. The overhead includes the guard interval to partly compensate the channel dispersion, and the roll-off factor used by the shaping window. We show that significant gains are obtained compared to the case of using a fixed guard interval and roll-off factor. To simplify the implementation complexity we also propose to limit the amount of adaptation by deploying a finite set of overhead parameters. Numerical results are reported for typical wideband power line communication indoor channels.

Bit, tone and cyclic prefix allocation in OFDM with application to In-Home PLC

We propose to maximize achievable rate in OFDM systems via the adaptation of the cyclic prefix (CP) length jointly with tone and bit loading. We show that significant gains are obtained compared to the case of using a fixed CP with duration equal to the channel. Several metrics for the CP design are described. They tradeoff between performance and complexity. Both single user and multiuser OFDM are considered. Numerical results are reported for typical power line communication indoor channels.

Optimal time slot design in an OFDM-TDMA system over power-line time-variant channels

This paper analyzes the resource allocation problem in an indoor PLC system with a physical (PHY) layer based on OFDM and a medium access control (MAC) scheme with contention and adaptive TDMA regions, similar to the one of the HomePlug AV specification. In particular, this work focuses in the optimization of the TDMA region. By taking into account both the cyclostationary noise and the cyclic variations of the channel response, the optimal time slot duration in a multi-user scenario is determined for various amounts of overhead required by the PHY layer. Hence, the presented results can be used in practical systems to perform a fast real-time time slot length selection and scheduling as a function of the number of active users.

On power allocation in adaptive cyclic prefix OFDM

We consider the problem of the joint allocation of power and cyclic prefix (CP) duration to maximize the system capacity in orthogonal frequency division multiplexing (OFDM). A closed form solution to the problem does not exist and the exhaustive search of the optimal values is practically unfeasible. Therefore, we propose a sub-optimal iterative power allocation algorithm jointly with the CP adaptation to see whether capacity improvements can be obtained w.r.t. the conventional choice of a uniform power distribution over the sub-channels and a predetermined long CP value. Numerical results show that via power and CP adaptation significant improvements can be obtained.

Improving WLAN capacity via OFDMA and cyclic prefix adaptation

We study capacity improvements in WLAN technology that uses orthogonal frequency division multiplexing (OFDM) and, conventionally, time division multiple access (TDMA) to deliver high quality of service (QoS) traffic. We show that improvements are attainable via the adaptation of the cyclic prefix to the channel conditions w.r.t. the baseline system that uses a fixed value of CP. Furthermore, we compare TDMA with orthogonal frequency division multiple access (OFDMA) and we show that the latter scheme provides large capacity gains w.r.t. TDMA both with and without CP adaptation. To simplify complexity and lower the amount of feedback, we propose to adapat over a finite set of pre-determined CP values. These values are computed using a method that is based on the analysis of the distribution of the capacity-optimal CP. For the numerical results, we have used the widely adopted channel model of the IEEE 802.11 standard, and we have found that a single value of CP for each channel class of this model is sufficient to achieve nearly optimal capacity for a wide range of distances.

Power savings with opportunistic decode and forward over in-home PLC networks

We consider a cooperative system to provide power saving, quality of service, and coverage extension over in-home power line communications (PLC) networks. We focus on a cooperative relay scheme, where the communication between source and destination nodes follows an opportunistic time division decode and forward (ODF) protocol. At the physical layer we assume the use of a multi-carrier scheme. We show that the joint problem of power and time slot allocation for the multi-carrier time division decode and forward (DF) protocol is not convex. To reduce the complexity, we propose an heuristic algorithm that considers two convex sub-problems. The validation of the algorithm is done over statistically representative in-home PLC networks. Through extensive numerical results, we show that the use of relaying allows for saving several dBs of transmitted power, yet achieving the same rate of the direct transmission. Furthermore, over multiple sub-topologies networks interconnected through circuit breakers, e.g., a multi-floor house, the relay increases the network coverage.

Home energy management systems: Design guidelines for the communication infrastructure

Households account for a notable amount of overall energy consumption, thus they represent a field where it is possible to potentially obtain great energy savings. Energy management systems (EMSs) can be used to this end. They allow for monitoring and managing energy consumption of household appliances or renewable energy sources, as well as making users aware of their energy consumptions. User awareness has been shown to yield up to 20% of energy savings. In this paper, we propose a design procedure for the communication network of a home energy management system (HEMS). We discuss design choices of a HEMS which is currently under development within the MONERGY project, an initiative aiming at boosting the energy awareness of households in two regions: Carinthia (Austria) and Friuli-Venezia Giulia (Italy). Although the system is tailored to the peculiarities of the regions, we believe that the proposed design guidelines can be of help for engineers of EMSs. In particular, the work addresses key issues of the communication network requirements such as coverage, topology, number of nodes, metering resolution and communication technologies. Furthermore, real world tests of wireless and power line communication (PLC) technologies are carried out to see whether existing HEMSs satisfy the communication network requirements.

Strategies for domestic energy conservation in Carinthia and Friuli-Venezia Giulia

Households account for a significant fraction of overall energy consumption. Energy usage can be reduced by improving the efficiency of devices and optimizing their use as well as by encouraging people to change their behaviour towards a more sustainable lifestyle. In this study, we investigate patterns of domestic energy use in Carinthia (Austria) and Friuli-Venezia Giulia (Italy). In particular, we report the results of an online survey about electrical devices and their use in households. We outline typical scenarios in the two regions and discuss possible strategies to reduce the consumption of energy in these regions.