CoAP and MQTT Measurements over LoRaWAN

Abstract. Internet of Things (IoT) enables the system of interrelated computing devices such as sensors and actuators. Thus, IoT faces few challenges to execute predefined functionalities during device-to-device communication. Low latency, high bandwidth, privacy, security, reliability, resource and energy efficiency are key challenges in the IoT paradigm. The fundamental requirement includes uninterrupted secure and reliable services. The challenges become even more controversial for low powered IoT devices during information over the long-distance (measured in kilometer) especially when the bandwidth is subject to free of cost. Different network layer supports are required for present Internet of Things (IoT) solutions — from applications at a higher level to media-based support at a lower level. The interoperability of the fragmented IoT solutions are being enabled by various emerging integration platforms. However, Long-Range Wireless Area Network (LoRaWAN) is used to exchange small data packet in such long distance. On the other hand, IoT required suitable communication protocols for power critical IoT devices. Many studies show the possibility of using Message Queue Telemetry Transport (MQTT) and Constrained Application Protocol (CoAP) as two major enabling IoT communication protocols to act as middleware to obtain low power consumption, sporadic transmission, and robustness to interference. The main basis of the thesis work is to measure and analysis the performance of the MQTT protocol over LoRaWAN. To implement the analytical approach, MQTT and CoAP protocols are used as a transport vehicle or interoperability middleware on a full TCP/IP-stack to connect end devices, and data transmit over the LoRaWAN. This thesis performed the analytical performance for different Spreading Factors (SF) or Data Rates (DR) along with different payload sizes (the message length) over LoRaWAN by using MQTT and CoAP protocols. In LoRaWAN, the Receive_Delay1 and Receive_Delay2, the minimum time duration needed to establish an MQTT connection is one second for Receive_Delay1, while the maximum is two seconds for Receive_Delay2. The analysis shows for uplink and downlink time and proposes various important facts for future aspects

Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO3_3

Improvement in magnetic and electrical properties of multiferroic BiFeO$_3$ in conjunction with their dependence on particle size is crucial due to its potential applications in multifunctional miniaturized devices. In this investigation, we report a study on particle size dependent structural, magnetic and electrical properties of sol-gel derived Bi$_{0.9}$Ba$_{0.1}$FeO$_3$ nanoparticles of different sizes ranging from $\sim$ 12 to 49 nm. The substitution of Bi by Ba significantly suppresses oxygen vacancies, reduces leakage current density and Fe$^{2+}$ state. An improvement in both magnetic and electrical properties is observed for 10 % Ba-doped BiFeO$_3$ nanoparticles compared to its undoped counterpart. The saturation magnetization of Bi$_{0.9}$Ba$_{0.1}$FeO$_3$ nanoparticles increase with reducing particle size in contrast with a decreasing trend of ferroelectric polarization. Moreover, a first order metamagnetic transition is noticed for $\sim$ 49 nm Bi$_{0.9}$Ba$_{0.1}$FeO$_3$ nanoparticles which disappeared with decreasing particle size. The observed strong size dependent multiferroic properties are attributed to the complex interaction between vacancy induced crystallographic defects, multiple valence states of Fe, uncompensated surface spins, crystallographic distortion and suppression of spiral spin cycloid of BiFeO$_3$.Comment: