| 1. |
- Cai, Xuesong, et al.
(författare)
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Characterizing the Small-Scale Fading for Low Altitude UAV Channels
- 2021
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Ingår i: ICWMC 2021 : The Seventeenth International Conference on Wireless and Mobile Communications - The Seventeenth International Conference on Wireless and Mobile Communications. - 9781612088785 ; , s. 16-19
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Konferensbidrag (refereegranskat)abstract
- In this contribution, a recently conducted measurement campaign in a suburban scenario for the Unmanned Aerial Vehicle (UAV) Air-to-Ground (A2G) radio channel is introduced.The downlink signals in an in-service Long Term Evolution (LTE) network were collected and utilized to extract the Channel Impulse Responses (CIRs). A high-resolution parameter estimation algorithm derived based on the Space-Alternating Generalized Expectation-maximization (SAGE) principle is applied to estimate the delays, Doppler frequencies and complex amplitudes of Multi Path Components (MPCs) from the CIRs. Based on the MPC estimation results, fast fading characteristics of the A2G channels are investigated. It is found that the Rician distribution models the fast fading the best compared to Nakagami, Lognormal and Rayleigh distributions. Rician K factors are also calculated for the A2G channels.
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| 2. |
- Cai, Xuesong, et al.
(författare)
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Empirical Low-Altitude Air-to-Ground Spatial Channel Characterization for Cellular Networks Connectivity
- 2021
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Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716. ; 39:10, s. 2975-2991
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Tidskriftsartikel (refereegranskat)abstract
- Cellular-connected unmanned aerial vehicles (UAVs) have recently attracted a surge of interest in both academia and industry. Understanding the air-to-ground (A2G) propagation channels is essential to enable reliable and/or high-throughput communications for UAVs and protect the ground user equipments (UEs). In this contribution, a recently conducted measurement campaign for the A2G channels is introduced. A uniform circular array (UCA) with 16 antenna elements was employed to collect the downlink signals of two different Long Term Evolution (LTE) networks, at the heights of 0-40m in three different, namely rural, urban and industrial scenarios. The channel impulse responses (CIRs) have been extracted from the received data, and the spatial, including angular, parameters of the multipath components in individual channels were estimated according to a high-resolution-parameter-estimation (HRPE) principle. Based on the HRPE results, clusters of multipath components were further identified. Finally, comprehensive spatial channel characteristics were investigated in the composite and cluster levels at different heights in the three scenarios.
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| 3. |
- Ehrencrona, Erik, et al.
(författare)
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The IgGFc-binding protein FCGBP is secreted with all GDPH sequences cleaved but maintained by interfragment disulfide bonds
- 2021
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Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258. ; 297:1
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Tidskriftsartikel (refereegranskat)abstract
- Mucus forms an important protective barrier that minimizes bacterial contact with the colonic epithelium. Intestinal mucus is organized in a complex network with several specific proteins, including the mucin-2 (MUC2) and the abundant IgGFc-binding protein, FCGBP. FCGBP is expressed in all intestinal goblet cells and is secreted into the mucus. It is comprised of repeated von Willebrand D (vWD) domain assemblies, most of which have a GDPH amino acid sequence that can be autocatalytically cleaved, as previously observed in the mucins MUC2 and mucin-5AC. However, the functions of FCGBP in the mucus are not understood. We show that all vWD domains of FCGBP with a GDPH sequence are cleaved and that these cleavages occur early during biosynthesis in the endoplasmic reticulum. All cleaved fragments, however, remain connected via a disulfide bond within each vWD domain. This cleavage generates a C-terminal-reactive Asp-anhydride that could react with other molecules, such as MUC2, but this was not observed. Quantitative analyses by MS showed that FCGBP was mainly soluble in chaotropic solutions, whereas MUC2 was insoluble, and most of the secreted FCGBP was not covalently bound to MUC2. Although FCGBP has been suggested to bind immunoglobulin G, we were unable to reproduce this binding in vitro using purified proteins. In conclusion, while the function of FCGBP is still unknown, our results suggest that it does not contribute to covalent crosslinking in the mucus, nor incorporate immunoglobulin G into mucus, instead the single disulfide bond linking each fragment could mediate controlled dissociation.
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| 4. |
- Zhu, Hong, et al.
(författare)
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Affordable Quality of Service Assessment for Cellular-Connected UAV Communications
- 2021
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Ingår i: ICWMC 2021 : The Seventeenth International Conference on Wireless and Mobile Communications - The Seventeenth International Conference on Wireless and Mobile Communications. - 9781612088785
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Konferensbidrag (refereegranskat)abstract
- In recent years, Unmanned Aerial Vehicles (UAVs)have been used extensively in military and civilian fields, making the research on cellular-connected UAVs a popular topic forFifth Generation (5G) and beyond communications. In order to support the increasing amount of applications, it is essential to evaluate the performance of UAV communications. In this work, the end-to-end delay, packet success rate, and through put of Air-to-Ground (A2G) communications are evaluated based on a realistic channel model obtained from measurements. The measurement campaign, conducted in a suburban environment, includes both Line-of-Sight (LoS) and Obstructed Line-of-Sight(OLoS) scenarios. From the results, it can be seen that architectural elements close to the flight route can severely decrease the communications performance even when the visibility between the Base Station (BS) and the UAV is permanently ensured. Moreover, we have shown that the Quality of Service (QoS) requirements for critical communications proposed by 3rd Generation Partnership Project (3GPP) can be fulfilled by establishing a threshold on the received Signal to Interference and Noise Ratio (SINR). This way, the SINR can be used as a condense dperformance metric for the design of safe flight routes for critical communications for UAVs.
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