3,651 research outputs found
On the genetic optimization of APSK constellations for satellite broadcasting
Both satellite transmissions and DVB applications over satellite present
peculiar characteristics that could be taken into consideration in order to
further exploit the optimality of the transmission. In this paper, starting
from the state-of-the-art, the optimization of the APSK constellation through
asymmetric symbols arrangement is investigated for its use in satellite
communications. In particular, the optimization problem is tackled by means of
Genetic Algorithms that have already been demonstrated to work nicely with
complex non-linear optimization problems like the one presented hereinafter.
This work aims at studying the various parameters involved in the optimization
routine in order to establish those that best fit this case, thus further
enhancing the constellation.Comment: IEEE International Symposium on Broadband Multimedia Systems and
Broadcasting (BMSB), 2014; IEEE proceedings, 201
Design of APSK Constellations for Coherent Optical Channels with Nonlinear Phase Noise
We study the design of amplitude phase-shift keying (APSK) constellations for
a coherent fiber-optical communication system where nonlinear phase noise
(NLPN) is the main system impairment. APSK constellations can be regarded as a
union of phase-shift keying (PSK) signal sets with different amplitude levels.
A practical two-stage (TS) detection scheme is analyzed, which performs close
to optimal detection for high enough input power. We optimize APSK
constellations with 4, 8, and 16 points in terms of symbol error probability
(SEP) under TS detection for several combinations of input power and fiber
length. Our results show that APSK is a promising modulation format in order to
cope with NLPN. As an example, for 16 points, performance gains of 3.2 dB can
be achieved at a SEP of 10^-2 compared to 16-QAM by choosing an optimized APSK
constellation. We also demonstrate that in the presence of severe nonlinear
distortions, it may become beneficial to sacrifice a constellation point or an
entire constellation ring to reduce the average SEP. Finally, we discuss the
problem of selecting a good binary labeling for the found constellations. For
the class of rectangular APSK a labeling design method is proposed, resulting
in near-optimal bit error probability.Comment: Submitted to IEEE Transactions on Communication
Performance Analysis of Physical Layer Network Coding for Two-way Relaying over Non-regenerative Communication Satellites
Two-way relaying is one of the major applications of broadband communication
satellites, for which an efficient technique is Physical Layer Network Coding
(PLNC). Earlier studies have considered satellites employing PLNC with onboard
processing. This paper investigates the performance of PLNC over
non-regenerative satellites, as a majority of the operational and planned
satellites have no onboard processing. Assuming that the channel magnitudes of
the two users are equal, two operating conditions are considered with
uncoded-QPSK relaying. In the first condition, both users are completely
synchronized in phase and transmit power, and in the second condition, phase is
not synchronized. The peak power constraint imposed by the satellite amplifier
is considered and the error performance bounds are derived for both the
conditions. The simulation results for end-to-end Bit Error Rate (BER) and
throughput are provided. These results shall enable communication system
designers to decide system parameters like power and linearity, and perform
tradeoff analysis between different relaying schemes.Comment: 9 pages and 13 figure
On Low Complexity Detection for QAM Isomorphic Constellations
Despite of the known gap from the Shannon's capacity, several standards are
still employing QAM or star shape constellations, mainly due to the existing
low complexity detectors. In this paper, we investigate the low complexity
detection for a family of QAM isomorphic constellations. These constellations
are known to perform very close to the peak-power limited capacity,
outperforming the DVB-S2X standard constellations. The proposed strategy is to
first remap the received signals to the QAM constellation using the existing
isomorphism and then break the log likelihood ratio computations to two one
dimensional PAM constellations. Gains larger than 0.6 dB with respect to QAM
can be obtained over the peak power limited channels without any increase in
detection complexity. Our scheme also provides a systematic way to design
constellations with low complexity one dimensional detectors. Several open
problems are discussed at the end of the paper.Comment: Submitted to IEEE GLOBECOM 201
Capacity of a Nonlinear Optical Channel with Finite Memory
The channel capacity of a nonlinear, dispersive fiber-optic link is
revisited. To this end, the popular Gaussian noise (GN) model is extended with
a parameter to account for the finite memory of realistic fiber channels. This
finite-memory model is harder to analyze mathematically but, in contrast to
previous models, it is valid also for nonstationary or heavy-tailed input
signals. For uncoded transmission and standard modulation formats, the new
model gives the same results as the regular GN model when the memory of the
channel is about 10 symbols or more. These results confirm previous results
that the GN model is accurate for uncoded transmission. However, when coding is
considered, the results obtained using the finite-memory model are very
different from those obtained by previous models, even when the channel memory
is large. In particular, the peaky behavior of the channel capacity, which has
been reported for numerous nonlinear channel models, appears to be an artifact
of applying models derived for independent input in a coded (i.e., dependent)
scenario
Time-Frequency Packing for High Capacity Coherent Optical Links
We consider realistic long-haul optical links, with linear and nonlinear
impairments, and investigate the application of time-frequency packing with
low-order constellations as a possible solution to increase the spectral
efficiency. A detailed comparison with available techniques from the literature
will be also performed. We will see that this technique represents a feasible
solution to overcome the relevant theoretical and technological issues related
to this spectral efficiency increase and could be more effective than the
simple adoption of high-order modulation formats.Comment: 10 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1406.5685 by other author
Constellation Design for Channels Affected by Phase Noise
In this paper we optimize constellation sets to be used for channels affected
by phase noise. The main objective is to maximize the achievable mutual
information of the constellation under a given power constraint. The mutual
information and pragmatic mutual information of a given constellation is
calculated approximately assuming that both the channel and phase noise are
white. Then a simulated annealing algorithm is used to jointly optimize the
constellation and the binary labeling. The performance of optimized
constellations is compared with conventional constellations showing
considerable gains in all system scenarios.Comment: 5 pages, 6 figures, submitted to IEEE Int. Conf. on Communications
(ICC) 201
Improving the Spectral Efficiency of Nonlinear Satellite Systems through Time-Frequency Packing and Advanced Processing
We consider realistic satellite communications systems for broadband and
broadcasting applications, based on frequency-division-multiplexed linear
modulations, where spectral efficiency is one of the main figures of merit. For
these systems, we investigate their ultimate performance limits by using a
framework to compute the spectral efficiency when suboptimal receivers are
adopted and evaluating the performance improvements that can be obtained
through the adoption of the time-frequency packing technique. Our analysis
reveals that introducing controlled interference can significantly increase the
efficiency of these systems. Moreover, if a receiver which is able to account
for the interference and the nonlinear impairments is adopted, rather than a
classical predistorter at the transmitter coupled with a simpler receiver, the
benefits in terms of spectral efficiency can be even larger. Finally, we
consider practical coded schemes and show the potential advantages of the
optimized signaling formats when combined with iterative detection/decoding.Comment: 8 pages, 8 figure
Replacing the Soft FEC Limit Paradigm in the Design of Optical Communication Systems
The FEC limit paradigm is the prevalent practice for designing optical
communication systems to attain a certain bit-error rate (BER) without forward
error correction (FEC). This practice assumes that there is an FEC code that
will reduce the BER after decoding to the desired level. In this paper, we
challenge this practice and show that the concept of a channel-independent FEC
limit is invalid for soft-decision bit-wise decoding. It is shown that for low
code rates and high order modulation formats, the use of the soft FEC limit
paradigm can underestimate the spectral efficiencies by up to 20%. A better
predictor for the BER after decoding is the generalized mutual information,
which is shown to give consistent post-FEC BER predictions across different
channel conditions and modulation formats. Extensive optical full-field
simulations and experiments are carried out in both the linear and nonlinear
transmission regimes to confirm the theoretical analysis
Code Design for Non-Coherent Detection of Frame Headers in Precoded Satellite Systems
In this paper we propose a simple method for generating short-length
rate-compatible codes over that are robust to non-coherent
detection for -PSK constellations. First, a greedy algorithm is used to
construct a family of rotationally invariant codes for a given constellation.
Then, by properly modifying such codes we obtain codes that are robust to
non-coherent detection. We briefly discuss the optimality of the constructed
codes for special cases of BPSK and QPSK constellations. Our method provides an
upper bound for the length of optimal codes with a given desired non-coherent
distance. We also derive a simple asymptotic upper bound on the frame error
rate (FER) of such codes and provide the simulation results for a selected set
of proposed codes. Finally, we briefly discuss the problem of designing binary
codes that are robust to non-coherent detection for QPSK constellation.Comment: 11 pages, 5 figure
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