Mindaugas Žilinskas

Bio: Mindaugas Žilinskas is an academic researcher. The author has contributed to research in topics: Ice crystals & Water vapor. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

Atmospheric Attenuation due to Humidity

Abstract: Humidity remains in the atmosphere even on bright days. Water of all three states can be found naturally in the atmosphere: liquid (rain, fog, and clouds), solid (snowflakes, ice crystals), and gas (water vapour). Water in any state is an obstacle in the link of the electromagnetic wave. When the wave passes through the water particles, a part of its energy is absorbed and a part is scattered. Therefore the electromagnetic wave is attenuated. Prediction of the influence of these factors is very important in radio system design. Attenuation due to rain, fog, and clouds can lead to the perturbations of the wireless, mobile, satellite and other communications. Another problem is the refractive index of the atmosphere, which affects the curvature of the electromagnetic wave path and gives some insight into the fading phenomenon. The anomalous electromagnetic wave propagation can cause disturbances to radar work, because variation of the refractive index of the atmosphere can induce loss of radar coverage. Accurate prediction of losses due to these factors can ensure a reliability of the radio system, decrease an equipment cost, furthermore, the radio systems can become less injurious to health of people. When there are no possibilities to gather data for calculations of the specific attenuation due to rain, clouds and fog, and atmospheric refractive index, the values recommended by the International Communication Union’s Radiocommunication sector (ITU-R) can be used. But the recommended values are not always exact. In design of the radio links, the most desirable operating frequencies are below 10 GHz, because in such cases atmospheric absorption and rainfall loss may generally be neglected (Freeman, 2007). However, in most countries, the frequency-band below 10 GHz is highly congested. In addition, high frequencies provide larger bandwidth, narrower beam width, good resolution and smaller component size (Bhattacharyya et al., 2000). Therefore, the operating frequencies of 10 GHz and above are often used in design of radio systems. The higher the operating frequency, the greater attenuation due to hydrometeors (rain, cloud, fog, snow, and etc.) is observed (Tamosiūnaitė et al., 2010a). In (Ishimaru, 1978), it was mentioned that the electromagnetic wave attenuation due to snow is less than attenuation due to rain, and that the attenuation due to dry snow may be neglected

Real Measurement Study for Rain Rate and Rain Attenuation Conducted Over 26 GHz Microwave 5G Link System in Malaysia

Abstract: In this paper, real measurements were conducted to investigate the impact of rain on the propagation of millimeter waves at 26 GHz. The measurements were accomplished using a microwave fifth generation radio link system with 1.3 km path length implemented at Universiti Teknologi Malaysia Johor Bahru, Malaysia. The implemented system consisted of Ericsson CN500 mini E-link, radio unit, rain gauge, and data logger. The measurements were attained and logged daily for a continuous year, with 1-min time intervals. Next, the MATLAB software was used to process and analyze the annual rain rate and rain attenuation, including for the worst month. From the analyzed results, it was found that at 0.01% percentage of time, the rain rate was 120 mm/hr; while the specific rain attenuation was 26.2 dB/km and the total rain attenuation over 1.3 km was 34 dB. In addition, the statistics acquired from the measurements for the worst month were lower than what was predicted by the international telecommunication union (ITU) model; around 51% and 34% for the rain rate and rain attenuation, respectively. The average percentage of error calculated between the measurements and predicted results for the rain rate and rain attenuation were 143% and 159%, respectively. Thus, it can be concluded that the statistics for the worst month in Malaysia is lower than what was predicted by the ITU model.

Use of WRF model to characterize propagation effects in the troposphere

Abstract: Next generations of satellite communication systems demand the use of high frequency bands and the effect of the troposphere at these frequencies has a major impact in the signal attenuation. In this context, the objective of the work presented in this paper is to take advantage of the Weather Research and Forecasting (WRF) system, capable of providing reanalysis and forecasts at high resolution, to be able to simulate the atmospheric conditions, to finally estimate the signal attenuation for slant path satellite links beyond 10 GHz. This is of paramount importance to effectively supplant the lack of measurements for the design of new satellite systems.

Atmospheric Attenuation of the Terahertz Wireless Networks

Abstract: The increase of data traffic, a demand for high-speed reliable mobile networks and congested frequency bands raised both technological and regulatory challenges. Therefore, the fifth-generation mobile network (5G) is being developed. Recently, researchers have focused on a very promising terahertz (THz) band (frequencies from 100 GHz to 30 THz), which will allow fast transmission of huge amounts of data. However, transmission distance is limited due to atmospheric attenuation, as THz waves undergo significant absorption by water vapor and oxygen molecules in the atmosphere. Moreover, THz waves are very vulnerable by precipitation. Furthermore, the path of the propagating waves changes due to variations of the atmospheric refractive index. Nevertheless, the THz networks could be perfect candidates for fiber-to-THz bridges in difficult-to-access areas. The aim of this chapter is to present the possibilities and challenges of the THz networks from a point of view of atmospheric attenuation. The results show that simulations of the atmospheric attenuation using real-time data are a powerful tool that should complement technological basis, as it will help to foresee possible failures, extend transmission distance and improve reliability of the THz and other high-frequency broadband wireless networks.

A browser-side view of starlink connectivity

Abstract: LEO satellite "mega-constellations" such as SpaceX's Starlink, Amazon's Kuiper, OneWeb are launching thousands of satellites annually, promising high-bandwidth low-latency connectivity. To quantify the achievable performance of such providers, we carry out a measurement study of the spatial and temporal characteristics as well as the geographic variability of the connectivity provided by Starlink, the current leader in this space. We do this by building and deploying a browser extension that provides data about web performance seen by 28 users from 10 cities across the world. We complement this with performance tests run from three measurement nodes hosted by volunteer enthusiasts in the UK, EU and USA. Our findings suggest that although Starlink offers some of the best web performance figures among the ISPs observed, there are important sources of variability in performance such as weather conditions. The bent-pipe connection to a satellite and back to earth also forms a significant component of the observed latency. We also observe frequent and significant packet losses of up to 50% of packets, which appear to be correlated with handovers between satellites. This has an effect on achievable throughput even when using modern congestion control protocols such as BBR or CUBIC.