5,041 research outputs found
Low-Latency Millimeter-Wave Communications: Traffic Dispersion or Network Densification?
This paper investigates two strategies to reduce the communication delay in
future wireless networks: traffic dispersion and network densification. A
hybrid scheme that combines these two strategies is also considered. The
probabilistic delay and effective capacity are used to evaluate performance.
For probabilistic delay, the violation probability of delay, i.e., the
probability that the delay exceeds a given tolerance level, is characterized in
terms of upper bounds, which are derived by applying stochastic network
calculus theory. In addition, to characterize the maximum affordable arrival
traffic for mmWave systems, the effective capacity, i.e., the service
capability with a given quality-of-service (QoS) requirement, is studied. The
derived bounds on the probabilistic delay and effective capacity are validated
through simulations. These numerical results show that, for a given average
system gain, traffic dispersion, network densification, and the hybrid scheme
exhibit different potentials to reduce the end-to-end communication delay. For
instance, traffic dispersion outperforms network densification, given high
average system gain and arrival rate, while it could be the worst option,
otherwise. Furthermore, it is revealed that, increasing the number of
independent paths and/or relay density is always beneficial, while the
performance gain is related to the arrival rate and average system gain,
jointly. Therefore, a proper transmission scheme should be selected to optimize
the delay performance, according to the given conditions on arrival traffic and
system service capability
On the scalar nonet in the extended Nambu Jona-Lasinio model
We discuss the lightest scalar resonances, , ,
and in the extended Nambu Jona-Lasinio model. We find
that the model parameters can be tuned, but unnaturally, to accommodate for
those scalars except the . We also discuss problems encountered in
the K Matrix unitarization approximation by using counting technique.Comment: 23 pages 3 eps figures, To appear in Nucl. Phys.
Beamforming Design for Active RIS-Aided Over-the-Air Computation
Over-the-air computation (AirComp) is emerging as a promising technology for
wireless data aggregation. However, its performance is hampered by users with
poor channel conditions. To mitigate such a performance bottleneck, this paper
introduces an active reconfigurable intelligence surface (RIS) into the AirComp
system. Specifically, we begin by exploring the ideal RIS model and propose a
joint optimization of the transceiver design and RIS configuration to minimize
the mean squared error (MSE) between the target and estimated function values.
To manage the resultant tri-convex optimization problem, we employ the
alternating optimization (AO) technique to decompose it into three convex
subproblems, each solvable optimally. Subsequently, we investigate two specific
cases and analyze their respective asymptotic performance to reveal the
superiority of the active RIS in mitigating the MSE relative to its passive
counterpart. Lastly, we adapt our transceiver and RIS configuration design to
account for the self-interference of the active RIS. To handle the resultant
highly non-convex problem, we further devise a two-layer AO framework.
Simulation results demonstrate the superiority of the active RIS in enhancing
AirComp performance compared to its passive counterpart
Hierarchy of measurement-induced Fisher information for composite states
Quantum Fisher information, as an intrinsic quantity for quantum states, is a
central concept in quantum detection and estimation. When quantum measurements
are performed on quantum states, classical probability distributions arise,
which in turn lead to classical Fisher information. In this article, we exploit
the classical Fisher information induced by quantum measurements, and reveal a
rich hierarchical structure of such measurement-induced Fisher information. We
establish a general framework for the distribution and transfer of the Fisher
information. In particular, we illustrate three extremal distribution types of
the Fisher information: the locally owned type, the locally inaccessible type,
and the fully shared type. Furthermore, we indicate the significant role played
by the distribution and flow of the Fisher information in some physical
problems, e.g., the non-Markovianity of open quantum processes, the
environment-assisted metrology, the cloning and broadcasting, etc.Comment: 6 page
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