331 research outputs found
Two-photon detuning and decoherence in cavity electromagnetically induced transparency for quantized fields
The interaction of a quantized field with three-level atoms in
configuration inside a two-mode cavity is analyzed in the small noise
approximation. The atoms are in a two-photon detuning with respect to the
carriers of the field. We calculate the stationary quadrature noise spectrum of
the field outside the cavity in the case where the input probe field is a
squeezed state and the input pump field is a coherent state. The mean value of
the field is unaltered in all the analysis: the atoms shows electromagnetically
induced transparency (EIT). The effect of the atoms' base level decoherence in
the cavity output field is also studied. It is found that the output field is
very sensitive to two-photon detuning.Comment: 8 page
Energy Harvesting Wireless Sensor Networks: Delay Analysis Considering Energy Costs of Sensing and Transmission
Energy harvesting (EH) provides a means of greatly enhancing the lifetime of
wireless sensor nodes. However, the randomness inherent in the EH process may
cause significant delay for performing sensing operation and transmitting the
sensed information to the sink. Unlike most existing studies on the delay
performance of EH sensor networks, where only the energy consumption of
transmission is considered, we consider the energy costs of both sensing and
transmission. Specifically, we consider an EH sensor that monitors some status
environmental property and adopts a harvest-then-use protocol to perform
sensing and transmission. To comprehensively study the delay performance, we
consider two complementary metrics and analytically derive their statistics:
(i) update age - measuring the time taken from when information is obtained by
the sensor to when the sensed information is successfully transmitted to the
sink, i.e., how timely the updated information at the sink is, and (ii) update
cycle - measuring the time duration between two consecutive successful
transmissions, i.e., how frequently the information at the sink is updated. Our
results show that the consideration of sensing energy cost leads to an
important tradeoff between the two metrics: more frequent updates result in
less timely information available at the sink.Comment: submitted for possible journal publicatio
Comments on "Timing Estimation and Resynchronization for Amplify-and-Forward Communication Systems
This correspondence first shows that the Cramer-
Rao lower bound (CRLB) derivations in the above paper are
incorrect. In addition, contrary to the claims in the above
paper, the assumptions of perfect timing offset estimation and
matched-filtering at the relays affect the generality of the
analytical results and cannot be justified assumption
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