21,025 research outputs found
Massive MIMO Full-Duplex Relaying with Optimal Power Allocation for Independent Multipairs
With the help of an in-band full-duplex relay station, it is possible to
simultaneously transmit and receive signals from multiple users. The
performance of such system can be greatly increased when the relay station is
equipped with a large number of antennas on both transmitter and receiver
sides. In this paper, we exploit the use of massive arrays to effectively
suppress the loopback interference (LI) of a decode-and-forward relay (DF) and
evaluate the performance of the end-to-end (e2e) transmission. This paper
assumes imperfect channel state information is available at the relay and
designs a minimum mean-square error (MMSE) filter to mitigate the interference.
Subsequently, we adopt zero-forcing (ZF) filters for both detection and
beamforming. The performance of such system is evaluated in terms of bit error
rate (BER) at both relay and destinations, and an optimal choice for the
transmission power at the relay is shown. We then propose a complexity
efficient optimal power allocation (OPA) algorithm that, using the channel
statistics, computes the minimum power that satisfies the rate constraints of
each pair. The results obtained via simulation show that when both MMSE
filtering and OPA method are used, better values for the energy efficiency are
attained.Comment: Accepted to the 16th IEEE International Workshop on Signal Processing
Advances in Wireless Communications - SPAWC, Stockholm, Sweden 201
Stability of a two-sublattice spin-glass model
We study the stability of the replica-symmetric solution of a two-sublattice
infinite-range spin-glass model, which can describe the transition from
antiferromagnetic to spin glass state. The eigenvalues associated with
replica-symmetric perturbations are in general complex. The natural
generalization of the usual stability condition is to require the real part of
these eigenvalues to be positive. The necessary and sufficient conditions for
all the roots of the secular equation to have positive real parts is given by
the Hurwitz criterion. The generalized stability condition allows a consistent
analysis of the phase diagram within the replica-symmetric approximation.Comment: 21 pages, 5 figure
Effect of inelasticity on the phase transitions of a thin vibrated granular layer
We describe an experimental and computational investigation of the ordered
and disordered phases of a vibrating thin, dense granular layer composed of
identical metal spheres. We compare the results from spheres with different
amounts of inelasticity and show that inelasticity has a strong effect on the
phase diagram. We also report the melting of an ordered phase to a homogeneous
disordered liquid phase at high vibration amplitude or at large inelasticities.
Our results show that dissipation has a strong effect on ordering and that in
this system ordered phases are absent entirely in highly inelastic materials.Comment: 5 pages, 5 figures, published in Physical Review E. Title of first
version slightly change
Full-Duplex Relaying in MIMO-OFDM Frequency-Selective Channels with Optimal Adaptive Filtering
In-band full-duplex transmission allows a relay station to theoretically
double its spectral efficiency by simultaneously receiving and transmitting in
the same frequency band, when compared to the traditional half-duplex or
out-of-band full-duplex counterpart. Consequently, the induced
self-interference suffered by the relay may reach considerable power levels,
which decreases the signal-to-interference-plus-noise ratio (SINR) in a
decode-and-forward (DF) relay, leading to a degradation of the relay
performance. This paper presents a technique to cope with the problem of
self-interference in broadband multiple-input multiple-output (MIMO) relays.
The proposed method uses a time-domain cancellation in a DF relay, where a
replica of the interfering signal is created with the help of a recursive least
squares (RLS) algorithm that estimates the interference frequency-selective
channel. Its convergence mean time is shown to be negligible by simulation
results, when compared to the length of a typical orthogonal-frequency division
multiplexing (OFDM) sequences. Moreover, the bit-error-rate (BER) and the SINR
in a OFDM transmission are evaluated, confirming that the proposed method
extends significantly the range of self-interference power to which the relay
is resilient to, when compared with other mitigation schemes
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