A Comparative Study of Unipolar OFDM Schemes in Gaussian Optical Intensity Channel

Zhou, Jing; Zhang, Wenyi

doi:10.1109/tcomm.2017.2785766

Cited by 39 publications

(32 citation statements)

References 64 publications

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“…A similar discussion applies to other unipolar OFDM constructions. Reference [27] studies the achievable rates of several unipolar OFDM schemes, and clearly shows a gap between these achievable rates and capacity bounds from [13,30]. Whether this is a limitation of unipolar OFDM in general or a limitation of existing constructions of unipolar OFDM remains to be seen.…”

Section: Discussion and Extensions (A) On Unipolar Ofdm Schemesmentioning

confidence: 99%

Capacity of optical wireless communication channels

Chaaban

Hranilovic

2020

Phil. Trans. R. Soc. A.

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Optical wireless communications are realized by modulating the intensity of a light source and detecting intensity fluctuations at the receiver. This mode of operation, known as intensity modulation and direct detection (IM/DD), is simple to implement in practice. However, computing the channel capacity of the underlying channel is not straightforward because of the amplitude constraints that arise due to IM/DD operation. In particular, the transmit signal must be non-negative, while the peak and average amplitudes are constrained due to practical and safety considerations. Though a closed form for the capacity of IM/DD channels is not known, much work has been done to find capacity bounds and asymptotic capacity expressions. In this paper, a description of the IM/DD channel and its physical constraints is presented, followed by a review of recent progress pertaining to the capacity of IM/DD channels. Additionally, capacity-achieving distributions are discussed along with simple constructions that approach capacity. This article is part of the theme issue ‘Optical wireless communication’.

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Section: Discussion and Extensions (A) On Unipolar Ofdm Schemesmentioning

confidence: 99%

Capacity of optical wireless communication channels

Chaaban

Hranilovic

2020

Phil. Trans. R. Soc. A.

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“…A later paper on the analysis of LACO-OFDM used tone injection to give a further 5-dB reduction in PAPR [53]. Zhou & Zhang [54] have also compared schemes based on the information rate, which assumes unlimited coding to achieve zero error rates, and so is a more fundamental limit. Multilayer schemes were shown to approach the performance limit of intensity-modulated channels to within 0.07 bits for power-limited optical channels.…”

Section: Signal-to-noise Ratio Cost Of Increasing Spectral Efficiencymentioning

confidence: 99%

Spectrally efficient optical orthogonal frequency division multiplexing

Lowery

2020

Phil. Trans. R. Soc. A.

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This paper charts the development of spectrally efficient forms of optical orthogonal frequency division multiplexing (OFDM) that are suited for intensity-modulated direct detection systems, such as wireless optical communications. The journey begins with systems using a DC-bias to ensure that no parts of the signal that modulates the optical source are negative in value, as negative optical intensity is unphysical. As the DC-part of the optical signal carries no information, it is wasteful in energy; thus asymmetrically clipped optical OFDM was developed, removing any negative-going peaks below the mean. Unfortunately, the clipping causes second-order distortion and intermodulation, so some subcarriers appear to be unusable, halving spectral efficiency; this is similar for unipolar and flipped optical OFDM. Thus, a considerable effort has been made to regain spectral efficiency, using layered techniques where the clipping distortion is mostly cancelled at the receiver, from a knowledge of one unpolluted layer, enabling one or more extra ‘layers/paths/depths’ to be received on the previously unusable subcarriers. Importantly, for a given optical power and high-order modulation, layered methods offer the best spectral efficiencies and need the lowest signal-to-noise ratios, especially if diversity combining is used. Thus, they could be important for high-bandwidth optical fibre systems. Efficient methods of generating all layers simultaneously, using fast Fourier transforms with their partial calculations extracted, are discussed, as are experimental demonstrations in both wireless and short-haul communications links. A musical analogy is also provided, which may point to how orchestral and rock music is deciphered in the brain. This article is part of the theme issue ‘Optical wireless communication’.

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“…The capacity bounds for bandlimited optical intensity channels were given in [32]. More recently, Zhou et al derived the continuous-input continuous-output memoryless channel (CCMC) capacity, also known as the unrestricted bound, of LACO-OFDM [33]. Inspired by these advances, in this section we quantify the achievable rate [34] of a LACO-OFDM system relying on different number of layers and different modulation schemes, which has not been studied in the open literature.…”

Section: Achievable Rate Analysismentioning

confidence: 99%

Multi-Class Coded Layered Asymmetrically Clipped Optical OFDM

Zhang

Babar

Zhang

et al. 2019

IEEE Trans. Commun.

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Multi-class channel coded layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) is proposed, where the achievable rate of the system is derived based on our mutual information analysis. We conceive a multi-class channel encoding scheme integrated with the layered transmitter. At the receiver both the coded and uncoded likelihood ratios (LLRs) are extracted for interlayer interference cancellation and symbol detection, respectively. Simulations are conducted and the results show that our design approaches the achievable rate within 1.1 dB for 16QAM 4-layer LACO-OFDM with the aid of a half-rate 8-iteration turbo code at BER = 10 −3 , outperforming its conventional counterpart by about 3.6 dB.Index Terms-Optical communications, forward error correction, layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM), achievable rate.

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A Comparative Study of Unipolar OFDM Schemes in Gaussian Optical Intensity Channel

Cited by 39 publications

References 64 publications

Capacity of optical wireless communication channels

Capacity of optical wireless communication channels

Spectrally efficient optical orthogonal frequency division multiplexing

Multi-Class Coded Layered Asymmetrically Clipped Optical OFDM

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