Device Grouping for Fast and Efficient Channel Access in IEEE 802.11ah based IoT Networks

The recent advances in Internet of Things (IoT) have led to numerous emerging applications ranging from eHealthcare to industrial control, which often demand stringent Quality of Service (QoS) requirements such as low-latency and high system reliability. However, the ever-increasing number of connected devices in ultra-dense IoT networks and the dynamic traffic patterns increase the channel access delay and packet collision rate. In this regard, this paper proposes a sector-based device grouping scheme for fast and efficient channel access in IEEE 802.11ah based IoT networks such that the total number of the connected devices within each sector is dramatically reduced. In the proposed framework, the Access Point (AP) divides its coverage area into different sectors, and then each sector is further divided into distinct groups based on the number of devices and their location information available from the cloud-center. Subsequently, individual groups within a sector are assigned to specific Random Access Window (RAW) slots, and the devices within distinct groups in different sectors access the allocated RAW slots by employing a spatial orthogonal access mechanism. The performance of the proposed sectorized device grouping scheme has been analyzed in terms of system delay and network throughput. Our simulation results show that the proposed scheme can significantly enhance the network throughput while simultaneously decreasing the system delay as compared to the conventional Distributed Coordination Function (DCF) and IEEE 802.11ah grouping scheme

Optimal Policy Derivation for Transmission Duty-Cycle Constrained LPWAN

Low-power wide-area network (LPWAN) technologies enable Internet of Things (IoT) devices to efficiently and robustly communicate over long distances, thus making them especially suited for industrial environments. However, the stringent regulations on the usage of certain industrial, scientific, and medical bands in many countries in which LPWAN operate limit the amount of time IoT motes can occupy the shared bands. This is particularly challenging in industrial scenarios, where not being able to report some detected events might result in the failure of critical assets. To alleviate this, and by mathematically modeling LPWAN-based IoT motes, we have derived optimal transmission policies that maximize the number of reported events (prioritized by their importance) while still complying with current regulations. The proposed solution has been customized for two widely known LPWAN technologies: 1) LoRa and 2) Sigfox. Analytical results reveal that our solution is feasible and performs remarkably close to the theoretical limit for a wide range of network activity patterns

Sub-GHz Wrist-Worn Antennas for Wireless Sensing Applications: A Review

With recent advances in wearable wrist-worn wireless sensing applications, the demand for smartwatches and wristbands is rapidly increasing due to their widespread adoption in applications such as smart health monitoring, security, and fitness tracking. Currently, these devices primarily operate in the 2.45 GHz band, leveraging the availability of Bluetooth and Wi-Fi wireless technologies. However, the use of Sub-GHz frequencies (e.g., 433 MHz, 868 MHz, 915 MHz, 923 MHz) for wearable systems has also gained interest due to the emergence of wireless technologies like long-range wide area network (LoRaWAN), narrowband-IoT (NB-IoT) and Sigfox, which offer the potential for long-range wireless communications and sensing applications. In recent times, there has been a notable surge in the commercial production of a variety of Sub-GHz wrist-worn wireless sensing devices for health monitoring and tracking applications. Nevertheless, communications at Sub-GHz frequencies present significant challenges in antenna design, primarily due to the practical size constraints of wrist-worn devices and the necessity for using electrically small antennas. This paper meticulously reviews wrist-worn Sub-GHz antennas reported in the literature, analyzing key antenna parameters such as antenna topology, size, impedance bandwidth, peak realized gain, radiation efficiency, and specific absorption rate (SAR). Additionally, it underlines antenna design challenges, limitations, current trends, and presents potential future perspectives. To the best of the author’s knowledge, there is currently no existing literature comprehensively reviewing Sub-GHz wrist-worn antennas. Therefore, this paper represents the inaugural effort to provide a comprehensive review in this specific domain

5G Cellular Networks

Tématem této bakalářské práce byly mobilní sítě 5. generace spolu se zaměřením na jednotlivá vylepšení stávající 4. generace. V úvodu práce byl rozebrán systém 4. generace mobilních sítí EPS spolu s popisem jednotlivých prvků. V další části je popisována 5. generace mobilních sítí, jako například její požadavky a směr vývoje, rádiové rozhraní, architektura nebo Internet věcí. Dále je zde řešena D2D komunikace, zvláště pak technologie LTE Direct a Wi-Fi Direct. Pozornost je zde také věnována agregátorům dat, které se uplatní ve spolupráci s Internetem věcí a budou schopny operovat na standardu IEEE 802.11 nebo IEEE 802.15.x. Na závěr teoretické části je zde popsána heterogenní rádiová síť a zejména vzájemná integrace buňkové a Wi-Fi sítě. V první části praktické části byly měřeny parametry Wi-Fi sítě při komunikaci klientserver. V druhé části byla testována agregace dat dvou zařízení na experimentální síti na Ústavu telekomunikací.The subject of the bachelor’s thesis is mobile communication network of 5𝑡ℎ generation with focus on improvements from current 4𝑡ℎ generation. At the beginning of my work I summarized the system of 4𝑡ℎ generation mobile network EPS including description of individual parts. Next section pays attention to 5𝑡ℎ generation mobile communication network in context of network demands and future development, radio interface, network architecture or Internet of Things. Next follows solution of D2D communication especially LTE Direct and Wi-Fi Direct technologies. Here I paid attention to data agregation used in conjunction with Internet of Things enabling usage of IEEE 802.11 or IEEE 802.15.x standards. In closing part I described heterogeneous radio network and in particular mutual integration of cellular and Wi-Fi networks. In the first practical part of my bachelor’s thesis I measured parameters of Wi-Fi network during client-server communication. In the second practical part I tested data agregation of two devices using experimental network at Institute of communication.

Contribution to the integration, performance improvement, and smart management of data and resources in the Internet of Things

[SPA] Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones.[ENG] This doctoral dissertation has been presented in the form of thesis by publication. The IoT has seen a tremendous growth in the last few years. Not only due to its potential to transform societies, but also as an enabling technology for many other technological advances. Unfortunately, the IoT is a relatively recent paradigm that lacks the maturity of other well-established (not so recent) revolutions like the internet itself or Wireless Sensor Networks; upon which the IoT is built. The presented Thesis contributes to this maturation process by researching on the underlying communication mechanisms that enable a truly ubiquitous and effective IoT. As a Thesis by compilation, 5 relevant articles are introduced and discussed. Each of such articles delve into different key aspects that, in their own way, help closing the gap between what the IoT is expected to bring and what the IoT actually brings. As thoroughly commented throughout the main text, the comprehensive approach taken in this Thesis ensures that multiple angles of the same plane --the communication plane-- are analyzed and studied. From the mathematical analysis of how electromagnetic waves propagate through complex environments to the utilization of recent Machine Learning techniques, this Thesis explore a wide range of scientific and researching tools that are shown to improve the final performance of the IoT. In the first three chapters of this document, the reader will be introduced to the current context and state-of-the-art of the IoT while, at the same time, the formal objectives of this Thesis are outlined and set into such a global context. In the next five chapters, the five corresponding articles are presented and commented. For each and every of these articles: a brief abstract, a methodology summary, a highlight on the results and contributions and final conclusions are also added. Lastly, in the two last chapters, the final conclusions and future lines of this Thesis are commented.Los artículos que componen la tesis son los siguientes: 1. R. M. Sandoval, A.-J. J. Garcia-Sanchez, F. Garcia-Sanchez, and J. Garcia-Haro, \Evaluating the More Suitable ISM Frequency Band for IoT-Based Smart Grids: A Quantitative Study of 915 MHz vs. 2400 MHz," Sensors, vol. 17, no. 1, p. 76, Dec. 2016. 2. R. M. Sandoval, A.-J. J. Garcia-Sanchez, J.-M. M. Molina-Garcia-Pardo, F. Garcia-Sanchez, and J. Garcia-Haro, \Radio-Channel Characterization of Smart Grid Substations in the 2.4-GHz ISM Band," IEEE Trans. Wirel. Commun., vol. 16, no. 2, pp. 1294{1307, Feb. 2017. 3. R. M. Sandoval, A. J. Garcia-Sanchez, and J. Garcia-Haro, \Improving RSSI-based path-loss models accuracy for critical infrastructures: A smart grid substation case-study," IEEE Trans. Ind. Informatics, vol. 14, no. 5, pp. 2230{2240, 2018. 4. R. M. Sandoval, A.-J. Garcia-Sanchez, J. Garcia-Haro, and T. M. Chen, \Optimal policy derivation for Transmission Duty-Cycle constrained LPWAN," IEEE Internet Things J., vol. 5, no. 4, pp. 1{1, Aug. 2018. 5. R. M. Sandoval, S. Canovas-Carrasco, A. Garcia-Sanchez, and J. Garcia-Haro, \Smart Usage of Multiple RAT in IoT-oriented 5G Networks: A Reinforcement Learning Approach," in 2018 ITU Kaleidoscope: Machine Learning for a 5G Future (ITU K), 2018, pp. 1-8.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado en Tecnologías de la Información y las Comunicaciones por la Universidad Politécnica de Cartagen