2,617 research outputs found
Nonregenerative MIMO Relaying with Optimal Transmit Antenna Selection
We derive optimal SNR-based transmit antenna selection rules at the source
and relay for the nonregenerative half duplex MIMO relay channel. While antenna
selection is a suboptimal form of beamforming, it has the advantage that the
optimization is tractable and can be implemented with only a few bits of
feedback from the destination to the source and relay. We compare the bit error
rate of optimal antenna selection at both the source and relay to other
proposed beamforming techniques and propose methods for performing the
necessary limited feedback
Half-filled Hubbard Model on a Bethe lattice with next-nearest neighbor hopping
We study the interplay between N\'eel-antiferromagnetism and the paramagnetic
metal-insulator-transition (PMIT) on a Bethe lattice with nearest and
next-nearest eighbor hopping and . We concentrate in this paper on
the situation at half-filling. For the PMIT outgrows the
antiferromagnetic phase and shows a scenario similar to VO. In this
parameter regime we also observe a novel magnetic phase.Comment: 8 pages, 10 figure
The Practical Challenges of Interference Alignment
Interference alignment (IA) is a revolutionary wireless transmission strategy
that reduces the impact of interference. The idea of interference alignment is
to coordinate multiple transmitters so that their mutual interference aligns at
the receivers, facilitating simple interference cancellation techniques. Since
IA's inception, researchers have investigated its performance and proposed
improvements, verifying IA's ability to achieve the maximum degrees of freedom
(an approximation of sum capacity) in a variety of settings, developing
algorithms for determining alignment solutions, and generalizing transmission
strategies that relax the need for perfect alignment but yield better
performance. This article provides an overview of the concept of interference
alignment as well as an assessment of practical issues including performance in
realistic propagation environments, the role of channel state information at
the transmitter, and the practicality of interference alignment in large
networks.Comment: submitted to IEEE Wireless Communications Magazin
Location Spoofing Detection for VANETs by a Single Base Station in Rician Fading Channels
In this work we examine the performance of a Location Spoofing Detection
System (LSDS) for vehicular networks in the realistic setting of Rician fading
channels. In the LSDS, an authorized Base Station (BS) equipped with multiple
antennas utilizes channel observations to identify a malicious vehicle, also
equipped with multiple antennas, that is spoofing its location. After deriving
the optimal transmit power and the optimal directional beamformer of a
potentially malicious vehicle, robust theoretical analysis and detailed
simulations are conducted in order to determine the impact of key system
parameters on the LSDS performance. Our analysis shows how LSDS performance
increases as the Rician K-factor of the channel between the BS and legitimate
vehicles increases, or as the number of antennas at the BS or legitimate
vehicle increases. We also obtain the counter-intuitive result that the
malicious vehicle's optimal number of antennas conditioned on its optimal
directional beamformer is equal to the legitimate vehicle's number of antennas.
The results we provide here are important for the verification of location
information reported in IEEE 1609.2 safety messages.Comment: 6 pages, 5 figures, Added further clarification on constraints
imposed on the detection minimization strategy. Minor typos fixe
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