Open AccessOptimal DCO-OFDM signal shaping with double-sided clipping in visible light communications
Author(s) -
Xintong Ling,
Shuo Li,
Pengfei Ge,
Jiaheng Wang,
Nan Chi,
Xiqi Gao
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.402749
Subject(s) - visible light communication , clipping (morphology) , orthogonal frequency division multiplexing , computer science , signal (programming language) , distortion (music) , time domain , modulation (music) , optics , pulse shaping , dynamic range , transmission (telecommunications) , telecommunications , electronic engineering , intensity modulation , optical power , multiplexing , light emitting diode , physics , channel (broadcasting) , bandwidth (computing) , phase noise , acoustics , phase modulation , engineering , laser , amplifier , philosophy , linguistics , computer vision , programming language
Direct-current-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) is widely used in high-speed visible light communication (VLC). Due to the limited dynamic range of light-emitting diode (LED) and the unipolarity for the intensity modulation (IM), double-sided clipping is inevitably imposed on the time-domain signal in VLC OFDM systems. Consequently, it calls for proper DCO-OFDM signal shaping by selecting an appropriate bias and time-domain signal power to reduce the clipping distortion and achieve a higher transmission rate. In this paper, we deep dive into the signal shaping design problem for double-sided clipping DCO-OFDM over both flat and dispersive channels. We derive the optimal bias for flat and dispersive channels, and explain its optimality from the perspectives of effective signal-to-noise ratio (SNR) and information theory. We then analytically characterize the optimal power for flat channels and propose a useful algorithm for dispersive channels enlightened by the optimal solution to the flat case. Furthermore, we uncover an inherent relationship between the considered double-sided clipping and the downside-clipping only DCO-OFDM regarding signal shaping optimization, and develop an in-depth understanding of the impact of top clipping based on the established connection. Practical simulations are provided to validate the superiority of our proposed signal shaping over the existing shaping schemes.