Abstract
Low-density parity-check (LDPC) coded optical orthogonal frequency division multiplexing (OFDM) is shown to significantly outperform LDPC coded on-off keying (OOK) over the atmospheric turbulence channel in terms of both coding gain and spectral efficiency. In the regime of strong turbulence at a bit-error rate of 10(-5), the coding gain improvement of the LDPC coded single-side band unclipped-OFDM system with 64 sub-carriers is larger than the coding gain of the LDPC coded OOK system by 20.2 dB for quadrature-phase-shift keying (QPSK) and by 23.4 dB for binary-phase-shift keying (BPSK).
Highlights
Due to the high-complexity associated with coherent detection, current free-space optical (FSO) communication systems [1,2,3,4,5] employ intensity modulation with direct detection (IM/DD)
In this paper we show that orthogonal frequency division multiplexing (OFDM) combined with error control coding is a very good modulation format for FSO IM/DD systems
For binary-phase-shift keying (BPSK) and quadrature-phase-shift keying (QPSK), the coding gain improvement of an Low-density parity-check (LDPC) encoded FSO-OFDM system over an LDPC encoded on-off keying (OOK) FSO system increases as the turbulence strength increases
Summary
Due to the high-complexity associated with coherent detection, current free-space optical (FSO) communication systems [1,2,3,4,5] employ intensity modulation with direct detection (IM/DD). At bit-error rate (BER) below 10-6 both MLSD and PSP require the electrical signal to noise ratio larger than 20 dB even in the weak turbulence regime Such signal powers are unacceptably high for many applications, and novel modulation techniques for IM/DD FSO systems are needed. OFDM [6,7,8,9] is a special case of a multicarrier transmission in which a single informationbearing stream is transmitted over many lower rate subchannels It has been used for digital audio broadcasting [6], high-definition television (HDTV) terrestrial broadcasting [7], in digital subscriber line (DSL) systems [6], in IEEE 802.11, in high-performance LAN type 2 (HIPERLAN/2) and multimedia mobile access communication wireless LANs [6], and has been studied for use in lightwave hybrid AM/OFDM cable systems [8], and in radio over fiber-based networks [9,10].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
