55 research outputs found
Designing Power-Efficient Modulation Formats for Noncoherent Optical Systems
We optimize modulation formats for the additive white Gaussian noise channel
with a nonnegative input constraint, also known as the intensity-modulated
direct detection channel, with and without confining them to a lattice
structure. Our optimization criteria are the average electrical and optical
power. The nonnegativity input signal constraint is translated into a conical
constraint in signal space, and modulation formats are designed by sphere
packing inside this cone. Some remarkably dense packings are found, which yield
more power-efficient modulation formats than previously known. For example, at
a spectral efficiency of 1 bit/s/Hz, the obtained modulation format offers a
0.86 dB average electrical power gain and 0.43 dB average optical power gain
over the previously best known modulation formats to achieve a symbol error
rate of 10^-6. This modulation turns out to have a lattice-based structure. At
a spectral efficiency of 3/2 bits/s/Hz and to achieve a symbol error rate of
10^-6, the modulation format obtained for optimizing the average electrical
power offers a 0.58 dB average electrical power gain over the best
lattice-based modulation and 2.55 dB gain over the best previously known
format. However, the modulation format optimized for average optical power
offers a 0.46 dB average optical power gain over the best lattice-based
modulation and 1.35 dB gain over the best previously known format.Comment: Submitted to Globecom 201
Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems
We optimize modulation formats for the additive white Gaussian noise channel
with nonnegative input, also known as the intensity-modulated direct-detection
channel, with and without confining them to a lattice structure. Our
optimization criteria are the average electrical, average optical, and peak
power. The nonnegative constraint on the input to the channel is translated
into a conical constraint in signal space, and modulation formats are designed
by sphere packing inside this cone. Some dense packings are found, which yield
more power-efficient modulation formats than previously known. For example, at
a spectral efficiency of 1.5 bit/s/Hz, the modulation format optimized for
average electrical power has a 2.55 dB average electrical power gain over the
best known format to achieve a symbol error rate of 10^-6. The corresponding
gains for formats optimized for average and peak optical power are 1.35 and
1.72 dB, respectively. Using modulation formats optimized for peak power in
average-power limited systems results in a smaller power penalty than when
using formats optimized for average power in peak-power limited systems. We
also evaluate the modulation formats in terms of their mutual information to
predict their performance in the presence of capacity-achieving error-
correcting codes, and finally show numerically and analytically that the
optimal modulation formats for reliable transmission in the wideband regime
have only one nonzero point.Comment: submitted to IEEE Transactions on Information Theory, June 201
Error control techniques for satellite and space communications
The results included in the Ph.D. dissertation of Dr. Fu Quan Wang, who was supported by the grant as a Research Assistant from January 1989 through December 1992 are discussed. The sections contain a brief summary of the important aspects of this dissertation, which include: (1) erasurefree sequential decoding of trellis codes; (2) probabilistic construction of trellis codes; (3) construction of robustly good trellis codes; and (4) the separability of shaping and coding
Hierarchical Distribution Matching for Probabilistically Shaped Coded Modulation
The implementation difficulties of combining distribution matching (DM) and
dematching (invDM) for probabilistic shaping (PS) with soft-decision forward
error correction (FEC) coding can be relaxed by reverse concatenation, for
which the FEC coding and decoding lies inside the shaping algorithms. PS can
seemingly achieve performance close to the Shannon limit, although there are
practical implementation challenges that need to be carefully addressed. We
propose a hierarchical DM (HiDM) scheme, having fully parallelized input/output
interfaces and a pipelined architecture that can efficiently perform the
DM/invDM without the complex operations of previously proposed methods such as
constant composition DM (CCDM). Furthermore, HiDM can operate at a
significantly larger post-FEC bit error rate (BER) for the same post-invDM BER
performance, which facilitates simulations. These benefits come at the cost of
a slightly larger rate loss and required signal-to-noise ratio at a given
post-FEC BER.Comment: 11 pages, 7 figure
On Product Codes with Probabilistic Amplitude Shaping for High-Throughput Fiber-Optic Systems
Probabilistic amplitude shaping (PAS) can flexibly vary the spectral
efficiency (SE) of fiber-optic systems. In this paper, we demonstrate the
application of PAS to bit-wise hard decision decoding (HDD) of product codes
(PCs) by finding the necessary conditions to select the PC component codes. We
show that PAS with PCs and HDD yields gains up to dB and SE improvement
up to approximately bit/channel use compared to using PCs with uniform
signaling and HDD. Furthermore, we employ the recently introduced iterative
bounded distance decoding with combined reliability of PCs to improve
performance of PAS with PCs and HDD.Comment: Accepted for publication in IEEE Communications Letter
Designing Voronoi Constellations to Minimize Bit Error Rate
In a classical 1983 paper, Conway and Sloane presented fast encoding and decoding algorithms for a special case of Voronoi constellations (VCs), for which the shaping lattice is a scaled copy of the coding lattice. Feng generalized their encoding and decoding methods to arbitrary VCs. Less general algorithms were also proposed by Kurkoski and Ferdinand, respectively, for VCs with some constraints on their coding and shaping lattices. In this work, we design VCs with a cubic coding lattice based on Kurkoski\u27s encoding and decoding algorithms. The designed VCs achieve up to 1.03 dB shaping gains with a lower complexity than Conway and Sloane\u27s scaled VCs. To minimize the bit error rate (BER), pseudo-Gray labeling of constellation points is applied. In uncoded systems, the designed VCs reduce the required SNR by up to 1.1 dB at the same BER, compared with the same VCs using Feng\u27s and Ferdinand\u27s algorithms. In coded systems, the designed VCs are able to achieve lower BER than the scaled VCs at the same SNR. In addition, a Gray penalty estimation method for such VCs of very large size is introduced
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