102 research outputs found
Convolutive superposition for multicarrier cognitive radio systems
Recently, we proposed a spectrum-sharing paradigm for single-carrier
cognitive radio (CR) networks, where a secondary user (SU) is able to maintain
or even improve the performance of a primary user (PU) transmission, while also
obtaining a low-data rate channel for its own communication. According to such
a scheme, a simple multiplication is used to superimpose one SU symbol on a
block of multiple PU symbols.The scope of this paper is to extend such a
paradigm to a multicarrier CR network, where the PU employs an orthogonal
frequency-division multiplexing (OFDM) modulation scheme. To improve its
achievable data rate, besides transmitting over the subcarriers unused by the
PU, the SU is also allowed to transmit multiple block-precoded symbols in
parallel over the OFDM subcarriers used by the primary system. Specifically,
the SU convolves its block-precoded symbols with the received PU data in the
time-domain, which gives rise to the term convolutive superposition. An
information-theoretic analysis of the proposed scheme is developed, which
considers different amounts of network state information at the secondary
transmitter, as well as different precoding strategies for the SU. Extensive
simulations illustrate the merits of our analysis and designs, in comparison
with conventional CR schemes, by considering as performance indicators the
ergodic capacity of the considered systems.Comment: 29 pages, 8 figure
Equalization Techniques of Control and Non-Payload Communication Links for Unmanned Aerial Vehicles
In the next years, several new applications involving unmanned aerial vehicles (UAVs) for public and commercial uses are envisaged. In such developments, since UAVs are expected to operate within the public airspace, a key issue is the design of reliable control and non-payload communication (CNPC) links connecting the ground control station to the UAV. At the physical layer, CNPC design must cope with time- and frequency-selectivity (so-called double selectivity) of the wireless channel, due to lowaltitude operation and flight dynamics of the UAV. In this paper, we consider the transmission of continuous phase modulated (CPM) signals for UAV CNPC links operating over doubly-selective channels. Leveraging on the Laurent representation for a CPM signal, we design a two-stage receiver: the first one is a linear time-varying (LTV) equalizer, synthesized under either the zero-forcing (ZF) or minimum mean-square error (MMSE) criterion; the second one recovers the transmitted symbols from the pseudo-symbols of the Laurent representation in a simple recursive manner. In addition to LTV-ZF and LTV-MMSE equalizers, their widely-linear versions are also developed, to take into account the possible noncircular features of the CPM signal. Moreover, relying on a basis expansion model (BEM) of the doubly-selective channel, we derive frequency-shift versions of the proposed equalizers, by discussing their complexity issues and proposing simplified implementations. Monte Carlo numerical simulations show that the proposed receiving structures are able to satisfactorily equalize the doubly-selective channel in typical UAV scenarios
Toksikološko istraživanje divlje populacije srne (Capreolus capreolus) i jelena (Cervus elaphus) ispitivanjem zuba
Heavy metal content was evaluated in the teeth of roe deer and red deer. No differences in heavy metal concentrations between sampling areas or species were observed. A similar deposition process can be considered for the two species, as well as a similar chronic exposure levels.U zubima srne i jelena mjeren je sadržaj teških metala. Nije primijećena razlika u koncentracijama metala ni između različitih područja prikupljanja uzoraka, niti između vrsta. Za obje vrste može se pretpostaviti sličan proces taloženja metala, kao i slična razina kronične ekspozicije
Enabling and Emerging Sensing Technologies for Crowd Management in Public Transportation Systems: A Review
Management of crowd information in public transportation (PT) systems is
crucial to foster sustainable mobility, by increasing the user's comfort and
satisfaction during normal operation, as well as to cope with emergency
situations, such as pandemic crises, as recently experienced with COVID-19
limitations. This paper presents a taxonomy and review of sensing technologies
based on Internet of Things (IoT) for real-time crowd analysis, which can be
adopted in various segments of the PT system (buses/trams/trains,
railway/subway stations, and bus stops). To discuss such technologies in a
clear systematic perspective, we introduce a reference architecture for crowd
management, which employs modern information and communication technologies
(ICT) in order to: (i) monitor and predict crowding events; (ii) adapt in
real-time PT system operations, by modifying service frequency, timetables,
routes, and so on; (iii) inform in realtime the users of the crowding status of
the PT system, by means of electronic displays installed inside vehicles or at
bus stops/stations, and/or by mobile transport applications. It is envisioned
that the innovative crowd management functionalities enabled by ICT/IoT sensing
technologies can be incrementally implemented as an add-on to traditional
intelligent transportation system (ITS) platforms, which are already in use by
major PT companies operating in urban areas. Moreover, it is argued that, in
this new framework, additional services can be delivered, such as, e.g.,
on-line ticketing, vehicle access control and reservation in severely crowded
situations, and evolved crowd-aware route planning.Comment: 15 pages, 2 figures, 2 tables, submitted to IEEE Sensors Journa
Modeling and performance analysis of wireless networks with ambient backscatter devices
Ambient backscatter is an intriguing wireless communication paradigm that allows small devices to compute and communicate by using only the power they harvest from far-field radio-frequency (RF) signals in the air. Ambient backscattering devices reflect RF signals emitted by existing or legacy communications
systems, such as digital TV broadcasting, cellular, or Wi-Fi ones, which are designed for transporting information and are not intended for RF energy transfer. This paper deals with mathematical modeling and performance analysis of wireless broadband networks operating over fading channels with ambient backscatter devices. After introducing a detailed signal model of the relevant communication links, we study the influence of physical parameters on the capacity of both legacy and backscatter channels, by considering different receiver architectures. We analytically show that, under reasonable operative conditions, a legacy system—employing an orthogonal frequencydivision multiplexing (OFDM) modulation scheme—can turn the RF interference arising from the backscatter process into a
form of multipath diversity that can be exploited to increase its performance. Moreover, our analysis proves that a backscatter system—transmitting one symbol per OFDM symbol of the legacy system—can achieve satisfactory data rates over relatively short distances, especially when the intended recipient of the
backscatter signal is co-located with the legacy transmitter, i.e., they are on the same device
REVERSEBLE IMMOBILIZATION OF ASIATIC BLACK BEAR (URSUS THIBETANUS)WITH DETOMIDINE-TILETAMINE-ZOLAZEPAN AND ATIPAMEZOLO
Abstract: Chemical immobilization of free-ranging and captive wildlife is often required in many clinical situations.
In this trial, tiletamine-zolazepam was combined with the 2-agonist, detomidine, in order to use the least amount of
anesthetic drug possible to achieve a rapid immobilization; to ensure safety for animals and operators; and to be easily
reversible with specific antagonists for a fast recovery. Twelve captive Asiatic black bears were anesthetized for clinical
procedures, including clinical examination and blood sample collection, and for electrocardiographic and echocardiographic
procedures. The combination detomidine-tiletamine-zolazepam, at the dosages of 0.03 mg/kg for detomidine
and 1.5 mg/kg for tiletamine-zolazepam, proved to be reliable and effective in immobilizing Asiatic black bears for a
1-hr handling period for routine clinical procedures. Minimal or no respiratory and/or cardiopulmonary adverse side
effects were observed, even with dosages calculated on the basis of an estimated body weight. The respiratory rate,
pulse rate, and hemoglobin-oxygen saturation remained stable for the entire duration of anesthesia. Cardiac rhythm
was always sinusal in all animals. Small injection volumes and darts for blowpipe use were utilized to minimize tissue
damage at the site of injection. Induction and recovery were smooth and predictable, and provided for the safety of
operators who could observe the bears\u2019 activities from a safe distance. Furthermore, the availability of the 2-antagonist
atipamezole to counteract the effects of detomidine made this anesthetic regimen easily controllable and reversible.
Moreover, the recovery time can be shortened by intravenous administration of this antagonist drug
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