37 research outputs found
Millimeter-Wave Massive MU-MIMO Performance Analysis for Private Underground Mine Communications
In this article, a performance analysis of millimeter wave (mmWave) massive multiuser multiple-input and multiple-output (MU-MIMO) channel within an underground mine is performed. The analysis is based on channel measurements conducted at 28 GHz using a base station of 64 virtual antenna elements serving multiple users. Channel characteristics such as large-scale path loss, time dispersion, coherence bandwidth and sum-rate capacity are reported and evaluated. The results indicate that multislope path loss model is better suited for precise prediction of path loss across various propagation segments within the mining gallery. The time dispersion analysis reveals that the underground mine channel does not cause significant time dispersion, as 90% of the root-mean-square (rms) delay spreads are below 4 ns. In addition, it was found that the rms delay spread is not dependent on the propagation distance. The study on sum-rate capacity highlights the potential of employing massive MIMO technology to improve the channel’s spectral efficiency. The analysis reveals that the capacity, with eight active users, can reach up to 33.54 bit/s/Hz. The outcomes of this article offer valuable insights into the propagation properties of underground mine environment, which is characterized by rich-scattering and irregular topology
5G-PPP Technology Board:Delivery of 5G Services Indoors - the wireless wire challenge and solutions
The 5G Public Private Partnership (5G PPP) has focused its research and innovation activities mainly on outdoor use cases and supporting the user and its applications while on the move. However, many use cases inherently apply in indoor environments whereas their requirements are not always properly reflected by the requirements eminent for outdoor applications. The best example for indoor applications can be found is the Industry 4.0 vertical, in which most described use cases are occurring in a manufacturing hall. Other environments exhibit similar characteristics such as commercial spaces in offices, shopping malls and commercial buildings. We can find further similar environments in the media & entertainment sector, culture sector with museums and the transportation sector with metro tunnels. Finally in the residential space we can observe a strong trend for wireless connectivity of appliances and devices in the home. Some of these spaces are exhibiting very high requirements among others in terms of device density, high-accuracy localisation, reliability, latency, time sensitivity, coverage and service continuity. The delivery of 5G services to these spaces has to consider the specificities of the indoor environments, in which the radio propagation characteristics are different and in the case of deep indoor scenarios, external radio signals cannot penetrate building construction materials. Furthermore, these spaces are usually “polluted” by existing wireless technologies, causing a multitude of interreference issues with 5G radio technologies. Nevertheless, there exist cases in which the co-existence of 5G new radio and other radio technologies may be sensible, such as for offloading local traffic. In any case the deployment of networks indoors is advised to consider and be planned along existing infrastructure, like powerlines and available shafts for other utilities. Finally indoor environments expose administrative cross-domain issues, and in some cases so called non-public networks, foreseen by 3GPP, could be an attractive deployment model for the owner/tenant of a private space and for the mobile network operators serving the area. Technology-wise there exist a number of solutions for indoor RAN deployment, ranging from small cell architectures, optical wireless/visual light communication, and THz communication utilising reconfigurable intelligent surfaces. For service delivery the concept of multi-access edge computing is well tailored to host virtual network functions needed in the indoor environment, including but not limited to functions supporting localisation, security, load balancing, video optimisation and multi-source streaming. Measurements of key performance indicators in indoor environments indicate that with proper planning and consideration of the environment characteristics, available solutions can deliver on the expectations. Measurements have been conducted regarding throughput and reliability in the mmWave and optical wireless communication cases, electric and magnetic field measurements, round trip latency measurements, as well as high-accuracy positioning in laboratory environment. Overall, the results so far are encouraging and indicate that 5G and beyond networks must advance further in order to meet the demands of future emerging intelligent automation systems in the next 10 years. Highly advanced industrial environments present challenges for 5G specifications, spanning congestion, interference, security and safety concerns, high power consumption, restricted propagation and poor location accuracy within the radio and core backbone communication networks for the massive IoT use cases, especially inside buildings. 6G and beyond 5G deployments for industrial networks will be increasingly denser, heterogeneous and dynamic, posing stricter performance requirements on the network. The large volume of data generated by future connected devices will put a strain on networks. It is therefore fundamental to discriminate the value of information to maximize the utility for the end users with limited network resources
Intra- and Out-of-Vehicle Channel Measurements and Modeling
DisertaÄŤnĂ práce je zaměřena na měřenĂ a modelovánĂ kanálu uvnitĹ™ a vnÄ› vozidla pro komunikaci a lokalizaci. Pro účely vytvoĹ™enĂ integrovanĂ©ho inteligentnĂho dopravnĂho systĂ©mu ITS (Intelligent transportation system) je dĹŻleĹľitĂ˝ odhad vlastnosti kanálĹŻ pro vnitĹ™nĂ a venkovnĂ scĂ©náře. Za tĂmto účelem je vhodnĂ© provĂ©st Ĺ™adu ÄŤinnostĂ, kterĂ© jsou obsahem disertaÄŤnĂ práce: Simulace fyzickĂ© vrstvy 802.11p, jejĂ srovnávánĂ s 802.11a, měřenĂ kanálu pro rĹŻznĂ© scĂ©náře pro 802.11p a pro širokopásmovĂ˝ systĂ©m (UWB), vytvoĹ™enĂ modelĹŻ kanálĹŻ pro 802.11p a UWB a vĂ˝zkum vlastnostĂ lokalizace zaloĹľenĂ© na měřenĂ v pásmu UWB. VĂ˝zkum komunikace vozidla s okolĂm zaloĹľená na IEEE 802.11p standardu. JednĂm z cĂlĹŻ disertaÄŤnĂ práce je ukázat rozdĂly mezi standardy fyzickĂ© vrstvy IEEE 802.11a a IEEE 802.11p prostĹ™ednictvĂm simulace s pouĹľitĂm modelu kanálu HIPERPLAN/2. V práci je uvedena simulace pĹ™enosu signálu 802.11p kanálem ITU-R M.1225 s odlišnĂ˝m zpoĹľdÄ›nĂm a stĹ™ednĂm vĂ˝konem (pro chodce a vozidla). Vliv kanálu na signál je analyzován za pouĹľitĂ simulace v prostĹ™edĂ MATLABu pomocĂ vyhodnocenĂ chybovosti. UrÄŤenĂ vlastnostĂ kanálĹŻ v kmitoÄŤtovĂ©m pásmu 5,8 GHz pro standard IEEE 802.11p a UWB. Experimenty byly provádÄ›ny pro vnitĹ™nĂ a vnÄ›jšà prostĹ™edĂ vozidla. Bylo zjištÄ›no, Ĺľe pro protokol 802.11p mĹŻĹľe bĂ˝t trend (dlouhodobĂ˝ vĂ˝voj) profilu PDP (power delay profile) nejlĂ©pe aproximován pomocĂ modelu obsahujĂcĂho dvÄ› klesajĂcĂ exponenciálnĂ funkce, na rozdĂl od Saleh-Valenzuelova (S-V) modelu, kterĂ˝ je vĂce vhodnĂ˝ pro UWB systĂ©my pracujĂcĂ v pásmu 3 aĹľ 11 GHz. VytvoĹ™enĂ odpovĂdajĂcĂ impulznĂ odezvy (CIR) s vyuĹľitĂm trendu PDP. Informace o CIR byla pouĹľita pro simulaci 802.11p za účelem vyhodnocenĂ chybovosti pĹ™i pouĹľitĂ Ricianova modelu. VĂ˝sledky odhadu BER ukazujĂ vhodnost protokolu pro vnitĹ™nĂ a vnÄ›jšà prostĹ™edĂ bezdrátovĂ˝ch aplikacĂ. VĂ˝sledky simulacĂ dále ukazujĂ, Ĺľe se chybovost zásadnÄ› nemÄ›nĂ a proto je moĹľnĂ© urÄŤit stĹ™ednĂ kĹ™ivku BER pro celou sadu změřenĂ˝ch dat. UrÄŤenĂ vlivu malĂ© zmÄ›ny polohy antĂ©ny na vlastnosti kanálu. Práce ukazuje náhodnost parametrĹŻ UWB kanálu pro malĂ© zmÄ›ny polohy antĂ©ny okolo vozidla, zaparkovanĂ©ho v podzemnĂ garáži. Ztráty šĂĹ™enĂm jsou monotĂłnnÄ› rostoucĂ se vzdálenostĂ, avšak náhodnÄ› se mÄ›nĂ v závislosti na Ăşhlu a výšce antĂ©n, a proto je vyhodnocenĂ vzdálenosti pomocĂ sĂly signálu pro tyto scĂ©náře nevhodnĂ©. Na druhĂ© stranÄ› mĹŻĹľe bĂ˝t pro spolehlivĂ© urÄŤenĂ vzdálenosti bez ohledu na Ăşhel nebo výšku antĂ©ny pouĹľita doba pĹ™Ăchodu prvnĂho svazku. OvěřenĂ vlivu zmÄ›n konfigurace kanálu na parametry S-V modelu. Práce demonstruje závislost parametrĹŻ Saleh-Valenzuela modelu v na vzdálenosti a výšce antĂ©n, avšak ukazuje, Ĺľe jejich prĹŻmÄ›rnĂ© hodnoty jsou blĂzkĂ© IEEE 802.15.3 standardu. OvěřenĂ moĹľnosti lokalizace pomocĂ metody TOA (time of arrival). Vzdálenost mezi antĂ©nami byla urÄŤena z profilu PDP s vyuĹľitĂm lineárnĂ závislosti vzdálenosti na zpoĹľdÄ›nĂ. SouĹ™adnice vysĂlacĂ antĂ©ny byly nalezeny pomocĂ dvou pĹ™ijĂmacĂch antĂ©n pomocĂ 2-D lokalizaÄŤnĂ techniky TOA. PorovnánĂ vypoÄŤtenĂ˝ch souĹ™adnic s pĹŻvodnĂmi vykazuje chybu menšà neĹľ 6%, coĹľ ukazuje vhodnost navrĹľenĂ©ho pĹ™Ăstupu pro lokalizaci vozidel.The dissertation is focused on channel measurements and modeling for vehicle-to-X communication and on localization. In order to realize an integrated intelligent transportation system (ITS), it is important to estimate channel features for intra-vehicle and out-of-vehicle scenarios. For this propose the following activities are carried out: simulation of the 802.11p PHY; comparison with 802.11a; channel measurements for different scenarios based on the 802.11p and ultra-wideband (UWB); creating channel models for 802.11p and UWB; UWB measurements to assess performance of localization. The vehicle-to-X communication is supposed on the IEEE 802.11p standard. The dissertation presents the differences between IEEE 802.11a and IEEE 802.11p physical layer standards through the simulation results of the transmission over a HIPERPLAN/2 channel. Further, the simulation of the 802.11p signal transmission over ITU-R M.1225 channel, which includes pedestrian and vehicle models with different relative delays and average power, is presented. The influence of the channel on the signal is analyzed using MATLAB simulation in terms of bit error rate (BER). The dissertation reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard and for UWB (3-11 GHz). Experiments for both intra-vehicle and out-of-vehicle environments are carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best approximated through a two-term exponential decay model for the 802.11p protocol, in contrast to the Saleh-Valenzuela (S-V) model which is suitable for UWB systems. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR). Next, the CIR is used in 802.11p simulation to evaluate the BER performance, following a Rician model. The results of the BER simulation shows the suitability of the protocol for in-car as well as out-of-car wireless applications. The simulation for out-of-car parameters indicate that the error performances do not vary much and it is possible to determine an average BER curve for the whole set of data. The randomness in UWB channel for small positional variations around a car, parked in an underground garage, is reported. The path loss (PL) is found to be monotonically increasing with distance but varies randomly with angle and height and thereby renders signal strength based ranging inaccurate for such scenarios. On the other hand, arrival time of the first ray can be used for reliable estimation of distance, independent on transmitter angle or height. The number of clusters in the PDP is reduced with distance but the nature of the profile remains fairly consistent with angle. The S-V model parameters also vary with distance and height but their average values are close to the IEEE 802.15.3 recommended channel model. For localization applications the distance between the antennas is calculated exploiting the linear dependence of distance on delay from PDP. The coordinates of a transmitting antenna are found with the help of two receiving antennas following a two-dimensional (2-D) time-of-arrival (TOA) based localization technique. A comparison of the calculated coordinates with the original ones exhibits an error of less than 6% which supports the suitability of the proposed approach for localization of the cars.
Smart Sensor Technologies for IoT
The recent development in wireless networks and devices has led to novel services that will utilize wireless communication on a new level. Much effort and resources have been dedicated to establishing new communication networks that will support machine-to-machine communication and the Internet of Things (IoT). In these systems, various smart and sensory devices are deployed and connected, enabling large amounts of data to be streamed. Smart services represent new trends in mobile services, i.e., a completely new spectrum of context-aware, personalized, and intelligent services and applications. A variety of existing services utilize information about the position of the user or mobile device. The position of mobile devices is often achieved using the Global Navigation Satellite System (GNSS) chips that are integrated into all modern mobile devices (smartphones). However, GNSS is not always a reliable source of position estimates due to multipath propagation and signal blockage. Moreover, integrating GNSS chips into all devices might have a negative impact on the battery life of future IoT applications. Therefore, alternative solutions to position estimation should be investigated and implemented in IoT applications. This Special Issue, “Smart Sensor Technologies for IoT” aims to report on some of the recent research efforts on this increasingly important topic. The twelve accepted papers in this issue cover various aspects of Smart Sensor Technologies for IoT
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion
Science at the environmental research station Schneefernerhaus / Zugspitze
Das Buch enthält 22 Aufsätze, in denen die in der Forschungsstation Schneefernerhaus / Zugspitze aktiven Forscherinnen und Forscher ihre Arbeitsgebiete und bisherige Ergebnisse vorstellen. Die Aufsätze sind dabei so konzipiert, dass das Buch auch für die universitäre Lehre eingesetzt werden kann
Large scale dynamics of the atmosphere: Planetary waves
Planetary waves (PW) are global scale waves in the atmosphere, which are known to considerably impact weather patterns in the midlatitudes in the troposphere and the ozone distribution in the stratosphere. PW play an important role in coupling middle atmosphere dynamics. Due to the fact that climate change causes a decrease of the meridional temperature gradient, the strength of the zonal wind might decrease. This should, in turn, change the planetary wave activity (PWA).
In order to quantify possible changes in the PWA we analyze ERA–Interim temperature data (10 m to 65 km height) on the Northern Hemisphere and calculate the so-called dynamical activity index (DAI) as measure for the PWA. We analyze the PWA to find indications for PWA changes and variability. We also use rotational temperature data from hydroxyl airglow measurements at UFS Schneefernerhaus (Germany) embedded in the international Network for the Detection of Mesospheric Change (NDMC) in the upper mesosphere/lower thermosphere (UMLT).
We find an indication for a significant increase of the PWA in the stratosphere. The change of the PWA with higher zonal wavenumbers turns out to be strongest. This finding is in agreement with the expectation that a weakening of the meridional temperature gradient leads to improved vertical propagation conditions for planetary waves. With the empirical mode decomposition (EMD) we are able to extract non-stationary signals of the PWA time series. We further find that longer-term oscillations (QBO, ENSO and solar cycles) have a noticeable impact on the PW variability in all considered heights. Next to the 11-year cycle that is related to the sunspot-cycle in many studies, we also find a pronounced quasi-22-year signal. We tentatively interpret this signal as being due to the solar-magnetic-field (“Hale cycle”)
Propagation at mmW Band in Metropolitan Railway Tunnels
The next generation of mobile communications, 5G, will provide a wideband network based on microwave and millimeter-wave (mmW) communication radio links with the goal of fulfilling the strict and severe requirements of the future test cases. In particular, this paper research is focused on mmW bands in metropolitan railway tunnels. For that purpose, a propagation measurement campaign was performed at 24 GHz band in a passenger train on a realist subway environment, and these results were combined with simulations ad hoc for tunnels and a theoretical modal propagation model. A narrowband and a wideband study have been conducted with the aim of obtaining the path loss, fading, power-delay profile, and angle of arrival, taking into consideration horizontal and vertical polarization in the receiving and transmitting antennas. This validation can be used to design and deploy wideband mobile communication networks at mmW bands in railway scenarios