Browsing by Subject "wireless sensor networks"

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  • Vallet Garcia, José M. (MDPI, 2020)
    Journal of Sensor and Actuator Networks
    Using the classical received signal strength (RSS)-distance log-normal model in wireless sensor network (WSN) applications poses a series of characteristic challenges derived from (a) the model’s structural limitations when it comes to explaining real observations, (b) the inherent hardware (HW) variability typically encountered in the low-cost nodes of WSNs, and (c) the inhomogeneity of the deployment environment. The main goal of this article is to better characterize how these factors impact the model parameters, an issue that has received little attention in the literature. For that matter, I qualitatively elaborate on their effects and interplay, and present the results of two quantitative empirical studies showing how much the parameters can vary depending on (a) the nodes used in the model identification and their position in the environment, and (b) the antenna directionality. I further show that the path loss exponent and the reference power can be highly correlated. In view of all this, I argue that real WSN deployments are better represented by random model parameters jointly accounting for HW and local environmental characteristics, rather than by deterministic independent ones. I further argue that taking this variability into account results in more realistic models and plausible results derived from their usage. The article contains example values of the mean and standard deviation of the model parameters, and of the correlation between the path loss exponent and the reference power. These can be used as a guideline in other studies. Given the sensitivity of localization algorithms to the proper model selection and identification demonstrated in the literature, the structural limitations of the log-normal model, the variability of its parameters and their interrelation are all relevant aspects that practitioners need to be aware of when devising optimal localization algorithms for real WSNs that rely on this popular model.
  • Poteri, Juho (Helsingin yliopisto, 2020)
    The Internet of Things (IoT) paradigm is seeing rapid adoption across multiple domains—industry, enterprise, agriculture, smart cities, households, only to name a few. IoT applications often require wireless autonomy, thereby placing challenging requirements on communication techniques and power supply methods. Wireless networking using devices with constrained energy, as often is the case in wireless sensor networks (WSN), provokes explicit considerations around the conservation of the supplied power on the one hand and the efficiency of the power drawn and energy used on the other. As radio communications characteristically consume the bulk of all energy in wireless IoT systems, this constrained energy budget combined with aspirations for terminal device lifetime sets requirements for the communications protocols and techniques used. This thesis examines two open architecture low-power wide-area network (LPWAN) standards with mesh networking support, along with their energy consumption profile in the context of power-constrained wireless sensor networks. The introductory section is followed by an overview of IoT and WSN foundations and technologies. The following section describes the IEEE 802.15.4 standard and ecosystem, followed by the Bluetooth LE and Bluetooth Mesh standards. A discussion on these standards' characteristics, behavior, and applicability to power-constrained sensor networks is presented.
  • Suomela, Jukka (Helsingfors universitet, 2005)