526 research outputs found
Census Tract License Areas: Disincentive for Sharing the 3.5GHz band?
Flexible licensing model is a necessary enabler of the technical and
procedural complexities of Spectrum Access System (SAS)-based sharing
framework. The purpose of this study is to explore the effectiveness of 3.5GHz
Licensing Framework - based on census tracts as area units, areas whose main
characteristic is population. As such, the boundary of census tract does not
follow the edge of wireless network coverage. We demonstrate why census tracts
are not suitable for small cell networks licensing, by (1) gathering and
analysing the official census data, (2) exploring the boundaries of census
tracts which are in the shape of nonconvex polygons and (3) giving a measure of
effectiveness of the licensing scheme through metrics of area loss and the
number of people per census tract with access to spectrum. Results show that
census tracts severely impact the effectiveness of the licensing framework
since almost entire strategically important cities in the U.S. will not avail
from spectrum use in 3.5GHz band. Our paper does not seek to challenge the core
notion of geographic licensing concept, but seeks a corrective that addresses
the way the license is issued for a certain area of operation. The effects that
inappropriate size of the license has on spectrum assignments lead to spectrum
being simply wasted in geography, time and frequency or not being assigned in a
fair manner. The corrective is necessary since the main goal of promoting
innovative sharing in 3.5 GHz band is to put spectrum to more efficient use.Comment: 7 pages, 5 figures, conferenc
Applications of Cognitive Radio Networks
The term cognitive radio (CR), originally coined in the late 1990s, envisaged a radio that is aware of its operational environment so that it can dynamically and autonomously adjust its radio-operating parameters to accordingly adapt to the different situations. Cognition is achieved through the so-called cognitive cycle, consisting of the observation of the environment, the orientation and planning that leads to making appropriate decisions in accordance with specific operation goals, and finally, the execution of these decisions (e.g., access to the appropriate channel). Decisions can be reinforced by learning procedures based on the past observations and the corresponding results of prior actuations
A Stochastic Geometry Framework for LOS/NLOS Propagation in Dense Small Cell Networks
The need to carry out analytical studies of wireless systems often motivates
the usage of simplified models which, despite their tractability, can easily
lead to an overestimation of the achievable performance. In the case of dense
small cells networks, the standard single slope path-loss model has been shown
to provide interesting, but supposedly too optimistic, properties such as the
invariance of the outage/coverage probability and of the spectral efficiency to
the base station density. This paper seeks to explore the performance of dense
small cells networks when a more accurate path-loss model is taken into
account. We first propose a stochastic geometry based framework for small cell
networks where the signal propagation accounts for both the Line-of-Sight (LOS)
and Non-Line-Of-Sight (NLOS) components, such as the model provided by the 3GPP
for evaluation of pico-cells in Heterogeneous Networks. We then study the
performance of these networks and we show the dependency of some metrics such
as the outage/coverage probability, the spectral efficiency and Area Spectral
Efficiency (ASE) on the base station density and on the LOS likelihood of the
propagation environment. Specifically, we show that, with LOS/NLOS propagation,
dense networks still achieve large ASE gain but, at the same time, suffer from
high outage probability.Comment: Typo corrected in eq. (3); Typo corrected in legend of Fig. 1-2;
Typos corrected and definitions of some variables added in Section III.E;
Final result unchanged; Paper accepted to IEEE ICC 201
Filter Bank Multicarrier for Massive MIMO
This paper introduces filter bank multicarrier (FBMC) as a potential
candidate in the application of massive MIMO communication. It also points out
the advantages of FBMC over OFDM (orthogonal frequency division multiplexing)
in the application of massive MIMO. The absence of cyclic prefix in FBMC
increases the bandwidth efficiency. In addition, FBMC allows carrier
aggregation straightforwardly. Self-equalization, a property of FBMC in massive
MIMO that is introduced in this paper, has the impact of reducing (i)
complexity; (ii) sensitivity to carrier frequency offset (CFO); (iii)
peak-to-average power ratio (PAPR); (iv) system latency; and (v) increasing
bandwidth efficiency. The numerical results that corroborate these claims are
presented.Comment: 7 pages, 6 figure
An investigation of structure-reactivity relationships of d-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines
Thermal reactions of C-aryl d-alkenyl oximes give N-unsubstituted bicylic lactone, lactam and pyrrolidine
fused isoxazolidines by an intramolecular oxime olefin cycloaddition pathway (IOOC) and/or cyclic nitrones
by an azaprotio cyclotransfer (APT) route; a number of factors, including the nature of the aryl
group, the oxime geometry and the structure of the linker between the oxime and the terminal alkene,
contribute to the competition
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