15,115 research outputs found
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
Constellation Optimization in the Presence of Strong Phase Noise
In this paper, we address the problem of optimizing signal constellations for
strong phase noise. The problem is investigated by considering three
optimization formulations, which provide an analytical framework for
constellation design. In the first formulation, we seek to design
constellations that minimize the symbol error probability (SEP) for an
approximate ML detector in the presence of phase noise. In the second
formulation, we optimize constellations in terms of mutual information (MI) for
the effective discrete channel consisting of phase noise, additive white
Gaussian noise, and the approximate ML detector. To this end, we derive the MI
of this discrete channel. Finally, we optimize constellations in terms of the
MI for the phase noise channel. We give two analytical characterizations of the
MI of this channel, which are shown to be accurate for a wide range of
signal-to-noise ratios and phase noise variances. For each formulation, we
present a detailed analysis of the optimal constellations and their performance
in the presence of strong phase noise. We show that the optimal constellations
significantly outperform conventional constellations and those proposed in the
literature in terms of SEP, error floors, and MI.Comment: 10 page, 10 figures, Accepted to IEEE Trans. Commu
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
Calculation of Mutual Information for Partially Coherent Gaussian Channels with Applications to Fiber Optics
The mutual information between a complex-valued channel input and its
complex-valued output is decomposed into four parts based on polar coordinates:
an amplitude term, a phase term, and two mixed terms. Numerical results for the
additive white Gaussian noise (AWGN) channel with various inputs show that, at
high signal-to-noise ratio (SNR), the amplitude and phase terms dominate the
mixed terms. For the AWGN channel with a Gaussian input, analytical expressions
are derived for high SNR. The decomposition method is applied to partially
coherent channels and a property of such channels called "spectral loss" is
developed. Spectral loss occurs in nonlinear fiber-optic channels and it may be
one effect that needs to be taken into account to explain the behavior of the
capacity of nonlinear fiber-optic channels presented in recent studies.Comment: 30 pages, 9 figures, accepted for publication in IEEE Transactions on
Information Theor
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
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