79,238 research outputs found
Performance of multiple-input multiple-output wireless communications systems using distributed antennas
In this contribution we propose and investigate a multiple-input multiple-output (MIMO) wireless communications system, where multiple receive antennas are distributed in the area covered by a cellular cell and connected with the base-station (BS). We first analyze the total received power by the BS through the distributed antennas, when assuming that the mobile's signal is transmitted over lognormal shadowed Rayleigh fading channels. Then, the outage probability of the distributed antenna MIMO systems is investigated, when considering various antenna distribution patterns. Furthermore, space-time coding at the mobile transmitter is considered for enhancing the outage performance of the distributed antenna MIMO system. Our study and simulation results show that the outage performance of a distributed antenna MIMO system can be significantly improved, when either increasing the number of distributed receive antennas or increasing the number of mobile transmit antennas
Interface crack between dissimilar one-dimensional hexagonal quasicrystals with piezoelectric effect
Quantum Limits of Interferometer Topologies for Gravitational Radiation Detection
In order to expand the astrophysical reach of gravitational wave detectors,
several interferometer topologies have been proposed to evade the thermodynamic
and quantum mechanical limits in future detectors. In this work, we make a
systematic comparison among them by considering their sensitivities and
complexities. We numerically optimize their sensitivities by introducing a cost
function that tries to maximize the broadband improvement over the sensitivity
of current detectors. We find that frequency-dependent squeezed-light injection
with a hundred-meter scale filter cavity yields a good broadband sensitivity,
with low complexity, and good robustness against optical loss. This study gives
us a guideline for the near-term experimental research programs in enhancing
the performance of future gravitational-wave detectors.Comment: grammar correcte
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