Large scale circulation patterns associated to seasonal dry and wet conditions over the Czech Republic

Ponencia presentada en: VIII Congreso de la Asociación Española de Climatología celebrado en Salamanca entre el 25 y el 28 de septiembre de 2012.[ES]Este trabajo analiza la relación entre las condiciones estaciónales extremadamente secas y húmedas en la República Checa y los patrones de circulación de gran escala. El índice estandarizado de precipitación y evapotranspiración (SPEI) se utiliza para cuantificar las condiciones de humedad. El SPEI fue calculado a partir de los registros mensuales de temperatura media y precipitación total de una densa red de 184 estaciones climatológicas para el período 1961-2010 en la escala temporal de un mes.[EN]This paper analyzes the link between the extremely dry and wet conditions over the Czech Republic and the large scale circulation patterns, at seasonal scale. The Standardized Precipitation Evapotranspiration Index (SPEI) is used to quantify the moisture conditions. The SPEI for one month lag was calculated from monthly records of mean air temperature and precipitation totals using a dense network of 184 climatological stations for the period 1961-2010.The research on drought conditions in the Czech Republic was supported by S grant of MSMT CR and projects 6046070901 and OC10010

Optimizing NB-IoT Communication Patterns for Permanently Connected mMTC Devices

The new types of industry-driven applications that need to be supported by low-power wide-area networks (LP-WANs), such as remote control or metering of devices within the massive machine-type infrastructures (e.g., Smart Grids), require a permanent connection to the remote server. In addition, there is also a shift in the communication paradigm, as the user equipment (UE) nodes are queried in regular and frequent intervals. Notably, the presence of this type of traffic may drastically deteriorate the performance of LPWAN technologies initially developed to support conventional use-cases characterized by non-synchronized transmissions. Though none of the LPWAN technologies is inherently designed to handle such demanding communication patterns, the narrowband Internet of things (NB-IoT) still stands for the best candidate as it operates within the license frequency spectrum. To optimize the delay performance of both types of traffic coexisting at the NB-IoT air interface, we propose an approach based on spreading the message transmission time instants of regular and stochastic traffic. We show an optimal value of the spreading interval minimizing the message transmission delay of regular traffic and propose a mathematical model to estimate its value. By parameterizing the model using a detailed measurements campaign of NB-IoT, we show that the optimal value of spreading interval and associated mean message delay is a linear function of the number of UEs. We report these values for a wide range of UEs in the coverage area of the NB-IoT base station and show that conventional stochastic traffic does not influence regular traffic performance.acceptedVersionPeer reviewe

Experimental Quality Assessment of Cellular Networks and their Utilization for UAV Services

Unmanned aerial vehicles (UAVs) have attracted significant attention. Many potential applications are predicted to bring abundant business opportunities in the next decade thanks to the ubiquitous connectivity of the 4G and 5G cellular networks. Unlike terrestrial deployments, airborne infrastructures have diverse attributes, e.g., increased deployment flexibility, line-of-sight (LoS) connections, and controlled mobility. These attributes bring new research questions and challenges, including LoS dominant ground channels together with increased aerial-terrestrial network interference, the exploitation of the degree of freedom (DoF) provided by the UAV mobility, and the different and tighter quality of service (QoS) requirements for purposes of unmanned traffic management (UTM). Further challenges stem from existing infrastructure oriented towards service availability in low altitudes and low data transfer costs. A key challenge in this context is to achieve and guarantee sufficient service reliability in all altitudes where UTM is planned to be used. Obtained results from the measurement campaign at Twente airport indicate the performance of the 4G cellular network is stable and equals the terrestrial use cases up to 60 m of altitude. However, if the altitude increases more, the network performance degrades significantly. In detail, the analysis revealed the fact the performance drop is significant, especially for downlink transmissions (from ground to UAVs), as the strong interference and connection outages were observed in increased numbers.Peer reviewe

Exploiting NB-IoT Network Performance and Capacity for Smart-Metering Use-Cases

The requirements introduced in directive 2019/944 of the European Parliament for the smart metering scenarios, which differ from the ones defined in ITU-R M.2410, accelerated the integration of cellular technologies for the Internet of Things (IoT). Requiring a permanent connection to the cellular network (radio resource control in a connected state) and more synchronous-oriented data transmissions led to selecting the Narrowband IoT (NB-IoT) technology as the main enabler for the secured data transmissions. This paper focuses on the features in- troduced by 3GPP in Release 13, i.e., user plane and control plane optimization, and Release 15 early data transmissions (EDT) for the smart metering scenarios. Our simulation results confirm that EDT is a powerful feature for decreasing transmission delay and improving spectrum efficiency with reduced overheads. Our results show that the transmission delay is reduced by over 50 %. Notably, the data indicates EDT significantly improves latency for smaller messages (for Release 13, less than 97 B in uplink and 57 B in downlink). Finally, the results confirm that an NB-IoT network (3GPP Release. 13; NB1) can manage 1000 smart meters per single base station communicating in a 15 minutes window.Peer reviewe

Performance Analysis of Different LoRaWAN Frequency Bands for mMTC Scenarios

The possibility of utilizing different frequencies for the LoRaWAN is a key component which, together with the other parameters, i.e., (i) bandwidth, (ii) spreading factor, (iii) coding rate, and (iv) transmission power, defines the communication performance. In this paper, we present the substantive im- provements for both the end devices and the radio access network (gateways) to enhance the data rates and decrease the communication latency. The implementation changes were made for the publicly available LoRaWAN module “signetlabdei” for Network Simulator 3. Utilizing the frequency 2.4GHz, the transmission time in the LoRaWAN network has improved by 80 % decreasing from 75 ms to 14 ms. The frequency 2.4 GHz for the EU region also showed the best performance due to the extended bandwidth (transmission success above 90%) in the case of the mMTC scenario with thousands of devices deployed. Together with the updated LoRaWAN module, the reported results are expected to serve as a building block for mMTC- oriented simulation scenarios.acceptedVersionPeer reviewe

LWM2M for Cellular IoT : Protocol Implementation and Performance Evaluation

With the growing number of IoT devices, numerous IoT protocols are being developed to provide the market with options based on product requirements. With the release of cellular IoT (CIoT) technologies in the Czech Republic, recently LTE Cat-M, the focus shifts towards not only satisfying the requirements of the device application but also minimizing the generated traffic and overall co-existence of many devices under one cell. It led to the modification of the existing and the creation of new IoT protocols designed to generate as little overhead traffic as possible while adopting the existing well- known communication schemes. Namely, the new UDP-based protocol for IoT, LWM2M strives to be the alternative to the well-established IoT protocols used outside of CIoT. This paper explains the communication principles and capabilities of the well-established IoT protocols with a heavy focus on the LWM2M protocol. Further, it describes difficulties during user implementation of the LWM2M protocol. Furthermore, two carefully designed scenarios are used to compare the differences among these protocols, focusing on generated overhead as it is subject to a fee paid to the network operators within the CIoT networks.Peer reviewe

Morphogenesis, volume and number of hop (Humulus lupulus L.) glandular trichomes, and their influence on alpha-acid accumulation in fresh bracts of hop cones

The ESEM investigations revealed the morphogenesis of peltate glandular trichomes, which was divided into five phases. In phase one, new peltate glandular trichomes were initiated; in phase two, they were differentiated; in phase three trichomes grew vigorously; in phase four they were determined; in the fifth and final phase they came to maturity. Volume of glandular trichome during the different phases of morphogenesis varied from 0.25 ´ 10–2mm3 in phase 1, to 1.95 ´ 10–2mm3 in phase 5. More glandular trichomes are placed on the base of the adaxial side of bracts (average 7 mm–2) than on the base of abaxial side (average 5.8 mm–2). In this research, positive spearman\u27s rank order correlations were found between the average number of glandular trichomes and content of a-acids as well as between the average volume of glandular trichomes and content of a- acids

Priority questions in multidisciplinary drought research

Addressing timely and relevant questions across a multitude of spatio-temporal scales, state-of-the-art interdisciplinary drought research will likely increase in importance under projected climate change. Given the complexity of the various direct and indirect causes and consequences of a drier world, scientific tasks need to be coordinated efficiently. Drought-related research endeavors ranging from individual projects to global initiatives therefore require prioritization. Here, we present 60 priority questions for optimizing future drought research. This topical catalogue reflects the experience of 65 scholars from 21 countries and almost 20 fields of research in both natural sciences and the humanities. The set of drought-related questions primarily covers drought monitoring, impacts, forecasting, climatology, adaptation, as well as planning and policy. The questions highlight the increasingly important role of remote sensing techniques in drought monitoring, importance of drought forecasting and understanding the relationships between drought parameters and drought impacts, but also challenges of drought adaptation and preparedness policies