LoRa is a chirp spread-spectrum modulation developed for the Internet of Things (IoT). In this work, we examine the performance of LoRa in the presence of both additive white Gaussian noise and interference from another LoRa user. To this end, we extend an existing interference model, which assumes perfect alignment of the signal of interest and the interference, to the more realistic case where the interfering user is neither chip- nor phase-aligned with the signal of interest and we derive an expression for the error rate. We show that the existing aligned interference model overestimates the effect of interference on the error rate. Moreover, we prove two symmetries in the interfering signal and we derive low-complexity approximate formulas that can significantly reduce the complexity of computing the symbol and frame error rates compared to the complete expression. Finally, we provide numerical simulations to corroborate the theoretical analysis and to verify the accuracy of our proposed approximations.

On the Error Rate of the LoRa Modulation With Interference

Energy efficiency in multihop cooperative power-line communication (PLC) systems has recently received considerable attention in the literature. In order to make such systems more energy efficient, this paper proposes a relaying technique equipped with energy-harvesting capabilities. More specifically, we consider a dual-hop decode-and-forward (DF) broadband PLC relaying system in which the relay exploits the high noise inherent in PLC channels to further enhance energy efficiency; this system will be referred to as DF with energy harvesting (DF-EH). This study deploys, particularly, the time-switching relaying protocol for energy harvesting. An accurate analytical expression for the energy efficiency and a closed-form expression for the average outage probability of the proposed system are derived and then verified with Monte Carlo simulations. For the sake of comparison and to highlight the achievable gains, we also analyze the energy-efficiency performances and the average outage probabilities of the conventional DF relaying system, i.e., without energy harvesting, as well as that of the direct-link approach. Furthermore, various frequency selection and power allocation strategies, namely, optimal frequency selection, random frequency selection, and equal power allocation, exploiting the multiple power cables, are studied. Then, the impact of several system parameters such as the energy-harvesting time factor, various idle power consumption profiles, relay location, power allocation as well as different noise scenarios are examined. The results reveal that the proposed DF-EH system is able to provide energy efficiency improvements of more than 30% compared to the conventional DF relaying scheme. It is also shown that the proposed system with optimal frequency selection performs better at low SNR, whereas at high SNR the equal power allocation based system will have the best performance.

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For More Energy-Efficient Dual-Hop DF Relaying Power-Line Communication Systems

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.

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

Power line communication (PLC) technology offers a promising platform for numerous communication applications. The power lines however can significantly attenuate communication signals operating in high frequency band. For this reason, multi-hop PLC systems become desirable. In this paper, we investigates the effect of multi-hop relaying on the power line channel transfer function. Measured results are compared with results obtained from sumulations in Matlab. Results show that the presence of relays between a transmitting and a receiving PLC nodes can intensify the attenuation and frequency selectivity. Measurements show that maximum attenuation increases with number of relays.

/pdf/channel-characterisation-of-cooperative-relaying-power-line-5f1ukrrjxv.pdf

Channel characterisation of cooperative relaying power line communication systems

Energy efficiency (EE) in multi-hop cooperative communication systems, both wireless and wired, is increasingly becoming more and more critical. This has recently been extended to include power line communications (PLC). In this respect, we propose in this paper to enhance the EE of a dual-hop amplify-and-forward (AF) cooperative relaying PLC system by considering energy-harvesting (EH) at the relay node. The energy harvester exploits the high noisy PLC channel feature as well as the transmitted signal power to forward the source information. In light of this, we derive an analytical expression for the EE and verify it with Monte Carlo simulations. The performance of the conventional relaying system, i.e. without any EH, is also considered to clearly quantify the achievable gains. The results show that the proposed system can considerably improve the EE of PLC systems and that increasing the channel variance will always make the proposed system more energy-efficient.

/pdf/improving-energy-efficiency-in-dual-hop-cooperative-plc-1n9p2ugpa5.pdf

Improving energy efficiency in dual-hop cooperative PLC relaying systems

This paper addresses the problem of estimating the location of Internet of Things (IoT) Long Range Wide Area Networks (LoRaWAN) devices from time of arrival differences measured at gateways. An Extended Kalman Filter (EKF) based approach is considered to aggregate the measurements obtained at different time instants. Particular attention is paid to the processing of outliers. Based on experimental data obtained from field measurements conducted on a real LoRaWAN™ network an insight into the realistic localization accuracy of the considered localization approach is provided.

Kalman filter-based localization for Internet of Things LoRaWAN™ end points

In this paper a detailed measurements-based analysis of the energy consumption of commercial broadband PLC modems is reported. Energy consumption measurements are carried out on the basis of pairs of many commercial PLC modems. Ethernet frames with variable sizes and bit/frame rates are sent on a modem, and received on the other modem. An analytic linear model that quantifies the energy consumption associated to Ethernet frames and PLC Physical Blocks (PBs) processing is proposed for a pair of PLC modems.

/pdf/a-measurement-based-model-of-energy-consumption-for-plc-39afdeughj.pdf

A measurement-based model of energy consumption for PLC modems

In this paper a simulations-based evaluation of the energy efficiency performance of relay Power Line Communication (PLC) networks is reported. Our system model is based on two PLC modems as source/destination and one relay modem with time division Decode-and-Forward (DF) scheme. In addition to the transmission power, we consider the static power of PLC modems in our energy consumption model and find the best energy efficiency performance for DF strategy by optimizing the transmission time of each link. Through extensive numerical results and two representative scenarios, we show that the use of PLC relaying with optimal time allocation allows for better performance than direct transmission, yet achieving the same rate of the direct transmission.

Energy efficiency performance of relay-assisted Power-Line Communication networks

In this paper, we investigate the energy efficiency performance of Multiple-Input-Multiple-Output (MIMO) relay-assisted Power Line Communication (PLC) networks. We consider a half-duplex Decode and Forward (DF) relay system and compare its performance for both uniform time allocation and optimized time allocation strategies. Based on realistic MIMO PLC channels, obtained from the European Telecommunications Standards Institute (ETSI) Specialist Task Force (STF) 410 field measurement campaign that was performed in six European countries, we show that depending on the idle power consumption of MIMO PLC modems in the relay network, possible energy saving gain can be obtained by using DF MIMO PLC relays.

Energy efficiency performance of decode and forward MIMO relay PLC systems

The COVID-19 pandemic has spurred a large amount of experimental and observational studies reporting clear correlation between the risk of developing severe COVID-19 (or dying from it) and whether the individual is male or female. This paper is an attempt to explain the supposed male vulnerability to COVID-19 using a causal approach. We proceed by identifying a set of confounding and mediating factors, based on the review of epidemiological literature and analysis of sex-dis-aggregated data. Those factors are then taken into consideration to produce explainable and fair prediction and decision models from observational data. The paper outlines how non-causal models can motivate discriminatory policies such as biased allocation of the limited resources in intensive care units (ICUs). The objective is to anticipate and avoid disparate impact and discrimination, by considering causal knowledge and causal-based techniques to compliment the collection and analysis of observational big-data. The hope is to contribute to more careful use of health related information access systems for developing fair and robust predictive models. 

https://doi.org/10.1016/j.ipm.2023.103276

Wafae Bakkali

Papers

Kalman filter-based localization for Internet of Things LoRaWAN™ end points

A measurement-based model of energy consumption for PLC modems

Energy efficiency performance of relay-assisted Power-Line Communication networks

Energy efficiency performance of decode and forward MIMO relay PLC systems

Gender and sex bias in COVID-19 epidemiological data through the lens of causality