DocumentCode :
1483661
Title :
Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems
Author :
Karout, Johnny ; Agrell, Erik ; Szczerba, Krzysztof ; Karlsson, Magnus
Author_Institution :
Dept. of Signals & Syst., Chalmers Univ. of Technol., Gothenburg, Sweden
Volume :
58
Issue :
7
fYear :
2012
fDate :
7/1/2012 12:00:00 AM
Firstpage :
4645
Lastpage :
4659
Abstract :
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.
Keywords :
Gaussian channels; Gaussian noise; error correction codes; optical communication; optical modulation; optimisation; Gaussian noise channel; average electrical power gain; average-power limited systems; capacity-achieving error-correcting codes; conical constraint; intensity-modulated direct-detection channel; modulation format evaluation; nonnegative constraint; nonnegative input; optimization criteria; peak-power limited systems; power penalty; power-efficient modulation formats; signal space; single-subcarrier intensity-modulated optical systems; wideband regime; Adaptive optics; Lattices; Optical fiber communication; Optical modulation; Optical noise; Optical receivers; Direct detection; fiber-optical communications; free-space optical communications; infrared communications; intensity modulation; lattice codes; mutual information; noncoherent communications; sphere packing;
fLanguage :
English
Journal_Title :
Information Theory, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9448
Type :
jour
DOI :
10.1109/TIT.2012.2193374
Filename :
6178013
Link To Document :
بازگشت