DocumentCode :
266146
Title :
Hadamard coded modulation: An alternative to OFDM for wireless optical communications
Author :
Noshad, Mohammad ; Brandt-Pearce, Maite
Author_Institution :
Charles L. Brown Dept. of Electr. & Comput. Eng., Univ. of Virginia Charlottesville, Charlottesville, VA, USA
fYear :
2014
fDate :
8-12 Dec. 2014
Firstpage :
2102
Lastpage :
2107
Abstract :
Orthogonal frequency division multiplexing (OFDM) is a modulation technique susceptible to source, channel and amplifier nonlinearities because of its high peak-to-average ratio (PAPR). The distortion gets worse by increasing the average power of the OFDM signals since larger portion of the signals are affected by nonlinearity. In this paper we introduce Hadamard coded modulation (HCM) that uses the fast Walsh-Hadamard transform (FWHT) to modulate data as an alternative technique to OFDM in direct-detection wireless optical systems. This technique is shown to have a better performance for high average optical power scenarios because of its small PAPR, and can be used instead of OFDM in two scenarios: 1) in optical systems that require high average optical powers such as visible light communications (VLC), and 2) in optical wireless systems unconstrained by average power, for which HCM achieves a lower bit error rate (BER) compared to OFDM. The power efficiency of HCM can be improved by removing a part of the signal´s DC bias without losing any information. In this way, the amplitude of the transmitted signal is decreased and the signals become less susceptible to nonlinearity. Interleaving can be applied on HCM to make the resulting signals résistent against inter-symbol interference (ISI) effects in dispersive channels by uniformly distributing the interference over all symbols.
Keywords :
Hadamard codes; Hadamard transforms; Walsh functions; dispersive channels; error statistics; intersymbol interference; modulation coding; optical communication; BER; FWHT; HCM; Hadamard coded modulation; ISI effect; OFDM signals; PAPR; VLC; amplifier nonlinearity; bit error rate; channel nonlinearity; direct-detection wireless optical systems; dispersive channels; fast Walsh-Hadamard transform; high-average optical power scenario; intersymbol interference effect; modulation technique; orthogonal frequency division multiplexing; peak-to-average ratio; power efficiency; signal DC bias; source nonlinearity; transmitted signal amplitude; visible light communications; wireless optical communications; Adaptive optics; Bit error rate; Nonlinear optics; OFDM; Optical distortion; Optical modulation; Optical receivers; Walsh-Hadamard transform; Wireless optical communications; nonlinear systems; orthogonal frequency division multiplexing (OFDM); peak-to-average power ratio (PAPR);
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Global Communications Conference (GLOBECOM), 2014 IEEE
Conference_Location :
Austin, TX
Type :
conf
DOI :
10.1109/GLOCOM.2014.7037118
Filename :
7037118
Link To Document :
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