624 research outputs found
Modified Newton's Law of Gravitation Due to Minimal Length in Quantum Gravity
A recent theory about the origin of the gravity suggests that the gravity is
originally an entropic force. In this work, we discuss the effects of
generalized uncertainty principle (GUP) which is proposed by some approaches to
quantum gravity such as string theory, black hole physics and doubly special
relativity theories (DSR), on the area law of the entropy. This leads to a
-type correction to the area law of entropy which imply that the
number of bits is modified. Therefore, we obtain a modified Newton's law of
gravitation. Surprisingly, this modification agrees with different sign with
the prediction of Randall-Sundrum II model which contains one uncompactified
extra dimension. Furthermore, such modification may have observable
consequences at length scales much larger than the Planck scale.Comment: 12 pages, no figures, references adde
Opportunistic Spectrum Sharing using Dumb Basis Patterns: The Line-of-Sight Interference Scenario
We investigate a spectrum-sharing system with non-severely faded mutual
interference links, where both the secondary-to-primary and
primary-to-secondary channels have a Line-of-Sight (LoS) component. Based on a
Rician model for the LoS channels, we show, analytically and numerically, that
LoS interference hinders the achievable secondary user capacity. This is caused
by the poor dynamic range of the interference channels fluctuations when a
dominant LoS component exists. In order to improve the capacity of such system,
we propose the usage of an Electronically Steerable Parasitic Array Radiator
(ESPAR) antenna at the secondary terminals. An ESPAR antenna requires a single
RF chain and has a reconfigurable radiation pattern that is controlled by
assigning arbitrary weights to M orthonormal basis radiation patterns. By
viewing these orthonormal patterns as multiple virtual dumb antennas, we
randomly vary their weights over time creating artificial channel fluctuations
that can perfectly eliminate the undesired impact of LoS interference. Because
the proposed scheme uses a single RF chain, it is well suited for compact and
low cost mobile terminals
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