79,134 research outputs found
On the Capacity and Performance of Generalized Spatial Modulation
Generalized spatial modulation (GSM) uses antenna elements but fewer
radio frequency (RF) chains () at the transmitter. Spatial modulation and
spatial multiplexing are special cases of GSM with and ,
respectively. In GSM, apart from conveying information bits through
modulation symbols, information bits are also conveyed through the indices of
the active transmit antennas. In this paper, we derive lower and upper
bounds on the the capacity of a ()-GSM MIMO system, where is the
number of receive antennas. Further, we propose a computationally efficient GSM
encoding (i.e., bits-to-signal mapping) method and a message passing based
low-complexity detection algorithm suited for large-scale GSM-MIMO systems.Comment: Expanded version of the IEEE Communications Letters pape
Generalized Spatial Modulation in Indoor Wireless Visible Light Communication
In this paper, we investigate the performance of generalized spatial
modulation (GSM) in indoor wireless visible light communication (VLC) systems.
GSM uses light emitting diodes (LED), but activates only of them at
a given time. Spatial modulation and spatial multiplexing are special cases of
GSM with and , respectively. We first derive an analytical
upper bound on the bit error rate (BER) for maximum likelihood (ML) detection
of GSM in VLC systems. Analysis and simulation results show that the derived
upper bound is very tight at medium to high signal-to-noise ratios (SNR). The
channel gains and channel correlations influence the GSM performance such that
the best BER is achieved at an optimum LED spacing. Also, for a fixed
transmission efficiency, the performance of GSM in VLC improves as the
half-power semi-angle of the LEDs is decreased. We then compare the performance
of GSM in VLC systems with those of other MIMO schemes such as spatial
multiplexing (SMP), space shift keying (SSK), generalized space shift keying
(GSSK), and spatial modulation (SM). Analysis and simulation results show that
GSM in VLC outperforms the other considered MIMO schemes at moderate to high
SNRs; for example, for 8 bits per channel use, GSM outperforms SMP and GSSK by
about 21 dB, and SM by about 10 dB at BER
On the Capacity of Generalized Quadrature Spatial Modulation
In this letter, the average mutual information (AMI) of generalized
quadrature spatial modulation (GQSM) is first derived for continuous-input
continuous-output channels. Our mathematical analysis shows that the
calculation error induced by Monte Carlo integration increases exponentially
with the signal-to-noise ratio. This nature of GQSM is resolved by deriving a
closed-form expression. The derived AMI is compared with other related SM
schemes and evaluated for different antenna activation patterns. Our results
show that an equiprobable antenna selection method slightly decreases AMI of
symbols, while the method significantly improves AMI in total.Comment: 5 pages, 5 figure
Peregrine comb: multiple compression points for Peregrine rogue waves in periodically modulated nonlinear Schr{\"o}dinger equations
It is shown that sufficiently large periodic modulations in the coefficients
of a nonlinear Schr{\"o}dinger equation can drastically impact the spatial
shape of the Peregrine soliton solutions: they can develop multiple compression
points of the same amplitude, rather than only a single one, as in the
spatially homogeneous focusing nonlinear Schr{\"o}dinger equation. The
additional compression points are generated in pairs forming a comb-like
structure. The number of additional pairs depends on the amplitude of the
modulation but not on its wavelength, which controls their separation distance.
The dynamics and characteristics of these generalized Peregrine soliton are
analytically described in the case of a completely integrable modulation. A
numerical investigation shows that their main properties persist in
nonintegrable situations, where no exact analytical expression of the
generalized Peregrine soliton is available. Our predictions are in good
agreement with numerical findings for an interesting specific case of an
experimentally realizable periodically dispersion modulated photonic crystal
fiber. Our results therefore pave the way for the experimental control and
manipulation of the formation of generalized Peregrine rogue waves in the wide
class of physical systems modeled by the nonlinear Schr{\"o}dinger equation
Generalized Spatial Modulation in Large-Scale Multiuser MIMO Systems
Generalized spatial modulation (GSM) uses transmit antenna elements but
fewer transmit radio frequency (RF) chains, . Spatial modulation (SM)
and spatial multiplexing are special cases of GSM with and
, respectively. In GSM, in addition to conveying information bits
through conventional modulation symbols (for example, QAM), the
indices of the active transmit antennas also convey information bits.
In this paper, we investigate {\em GSM for large-scale multiuser MIMO
communications on the uplink}. Our contributions in this paper include: ()
an average bit error probability (ABEP) analysis for maximum-likelihood
detection in multiuser GSM-MIMO on the uplink, where we derive an upper bound
on the ABEP, and () low-complexity algorithms for GSM-MIMO signal detection
and channel estimation at the base station receiver based on message passing.
The analytical upper bounds on the ABEP are found to be tight at moderate to
high signal-to-noise ratios (SNR). The proposed receiver algorithms are found
to scale very well in complexity while achieving near-optimal performance in
large dimensions. Simulation results show that, for the same spectral
efficiency, multiuser GSM-MIMO can outperform multiuser SM-MIMO as well as
conventional multiuser MIMO, by about 2 to 9 dB at a bit error rate of
. Such SNR gains in GSM-MIMO compared to SM-MIMO and conventional MIMO
can be attributed to the fact that, because of a larger number of spatial index
bits, GSM-MIMO can use a lower-order QAM alphabet which is more power
efficient.Comment: IEEE Trans. on Wireless Communications, accepte
On the Performance of MIMO FSO Communications over Double Generalized Gamma Fading Channels
A major performance degrading factor in free space optical communication
(FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a
promising approach to mitigate turbulence-induced fading. In this paper, we
study the error rate performance of FSO links with spatial diversity over
atmospheric turbulence channels described by the Double Generalized Gamma
distribution which is a new generic statistical model covering all turbulence
conditions. We assume intensity modulation/direct detection with on-off keying
and present the BER performance of single-input multiple-output (SIMO),
multiple-input single-output (MISO) and multiple-input multiple-output (MIMO)
FSO systems over this new channel model.Comment: 6 Pages, 4 figure, IEEE ICC conference 201
Downlink Precoding for Massive MIMO Systems Exploiting Virtual Channel Model Sparsity
In this paper, the problem of designing a forward link linear precoder for
Massive Multiple-Input Multiple-Output (MIMO) systems in conjunction with
Quadrature Amplitude Modulation (QAM) is addressed. First, we employ a novel
and efficient methodology that allows for a sparse representation of multiple
users and groups in a fashion similar to Joint Spatial Division and
Multiplexing. Then, the method is generalized to include Orthogonal Frequency
Division Multiplexing (OFDM) for frequency selective channels, resulting in
Combined Frequency and Spatial Division and Multiplexing, a configuration that
offers high flexibility in Massive MIMO systems. A challenge in such system
design is to consider finite alphabet inputs, especially with larger
constellation sizes such as . The proposed methodology is next
applied jointly with the complexity-reducing Per-Group Processing (PGP)
technique, on a per user group basis, in conjunction with QAM modulation and in
simulations, for constellation size up to . We show by numerical results
that the precoders developed offer significantly better performance than the
configuration with no precoder or the plain beamformer and with
Complex Quadrature Spatial Modulation
In this paper, we propose a spatial modulation (SM) scheme referred to as
complex quadrature spatial modulation (CQSM). In contrast to quadrature spatial
modulation (QSM), CQSM transmits two complex signal constellation symbols on
the real and quadrature spatial dimensions at each channel use, increasing the
spectral efficiency. To this end, signal symbols transmitted at any given time
instant are drawn from two different modulation sets. The first modulation set
is any of the conventional QAM/PSK alphabets, while the second is a rotated
version of it. The optimal rotation angle is obtained through simulations for
several modulation schemes and analytically proven for the case of QPSK, where
both results coincide. Simulation results showed that CQSM outperformed QSM and
generalized SM (GSM) by approximately 5 and 4.5 dB, respectively, for the same
transmission rate. Its performance was similar to that of QSM; however, it
achieved higher transmission rates. It was additionally shown numerically and
analytically that CQSM outperformed QSM for a relatively large number of
transmit antennas.Comment: 11 pages, 3 tables, 11 figures. ETRI Journal, 201
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