PAM-DMT for Intensity-Modulated and Direct-Detection Optical Communication Systems

Lee, S.C.J.; Randel, S.; Breyer, F.; Koonen, Ton

doi:10.1109/lpt.2009.2032663

Cited by 208 publications

(135 citation statements)

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“…The optimum bias levels for 64-QAM, 256-QAM and 1024-QAM DCO-OFDM are estimated using Monte Carlo simulations and are set at 9.5 dB, 11 dB and 13 dB, respectively. sizes M = [2,4,8,16] as a function of the electrical SNR. For U-OFDM, an actual constellation size of M 2 is used for each respective value of M, so that equal spectral efficiency can be achieved by the three schemes.…”

Section: Resultsmentioning

confidence: 99%

“…The concepts of U-OFDM and Flip-OFDM have been developed in parallel completely independently from each other and broadly within the same time period. It is interesting to note that all four approaches -ACO-OFDM, PAM-DMT, Flip-OFDM and U-OFDM -achieve the same performance in both a linear and a non-linear additive white Gaussian noise (AWGN) channel as will be illustrated later in the context of this work [3][4][5][6][7][8]. For an equivalent M-QAM/M-PAM modulation order, the spectral efficiency of each of these four methods is halved in comparison to DCO-OFDM.…”

mentioning

confidence: 84%

“…In PAM-DMT, all subcarriers are modulated with imaginary symbols from an M-PAM scheme as described in [4,8]. If the interference over a single PAM-DMT frame duration possesses a Hermitian symmetry in the time-domain, then its frequency profile is a real signal.…”

Section: Conceptmentioning

confidence: 99%

“…Hence, researchers have explored alternative methods for the generation of unipolar signals. This has lead to the introduction of new inherently non-negative modulation schemes such as asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) [3] and pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) [4]. These modulation techniques exploit the properties of the fast Fourier transform (FFT) and the OFDM frame structure in order to create a 12 OFDM-based Visible Light Communications 3 symmetric time-domain signal.…”

Section: Introductionmentioning

confidence: 99%

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OFDM-Based Visible Light Communications

Tsonev

Islim

Haas

2016

Optical Wireless Communications

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This chapter provides an overview of latest enhancements of the orthogonal frequency division multiplexing (OFDM) based visible light communications. The principals of OFDM techniques for intensity modulation and direct detection (IM/DD) systems are explained in details in [1]. A number of inherently unipolar OFDM techniques were recently proposed as power efficient alternatives to the widely deployed direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM). The unipolar orthogonal frequency division multiplexing (U-OFDM) technique achieves higher power efficiency compared to DCO-OFDM. However, due to the spectral efficiency loss of U-OFDM technique, the power efficiency advantage over DCO-OFDM starts to decrease as the spectral efficiency increases. Multiple U-OFDM streams are superimposed in enhanced unipolar orthogonal frequency division multiplexing (eU-OFDM) to double the spectral efficiency of U-OFDM technique. For the first time, the novel eU-OFDM allows unipolar OFDM techniques to have same spectral efficiency of DCO-OFDM. In this chapter, the concept of eU-OFDM is generalized to GeneRalizEd ENhancEd UnipolaR OFDM (GREENER-OFDM), and extended to other unipolar OFDM schemes (asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and pulse-amplitude-modulated discrete multitone modulation (PAM-DMT)). IntroductionThe physical properties of commercially available light emitting diodes (LEDs) and photodiodes (PDs), which are the foremost candidates for low-cost front-end devices in optical wireless communications (OWC), allow OWC to be realised as Dobroslav Tsonev · Mohamed Sufyan Islim · Harald Haas Li-Fi Research and Development Centre, The University of Edinburgh, Edinburgh EH9 3JL, http://www.lifi-centre.com e-mail: h.haas@ed.ac.uk 1 2 Dobroslav Tsonev, Mohamed Sufyan Islim, and Harald Haas intensity modulation and direct detection (IM/DD) systems only. This is because light emitted by of-the-shelf LEDs is incoherent and so information can be reliably encoded only in the signal intensity. The phase and the amplitude of the light wave cannot be modulated or detected with LEDs and PDs. This limits the set of conventional modulation schemes that can be adopted from the field of radio frequency (RF) communications and directly translated into OWC. Signal modulation techniques such as on-off keying (OOK), pulse-position modulation (PPM), and M-ary pulse-amplitude modulation (M-PAM) are relatively straightforward to implement as they provide real signals that can be directly mapped to light intensity. However, as transmission rates increase, the limited modulation bandwidth of the front-end devices and the limited bandwidth of the OWC channel lead to intersymbol interference (ISI) in the time-domain modulation signal. Hence, a technique such as orthogonal frequency division multiplexing (OFDM) becomes more appropriate as a modulation scheme. OFDM enables simple cost-effective equalisation with single-tap equalisers in the frequency-domain. In add...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 84%

Section: Conceptmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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OFDM-Based Visible Light Communications

Tsonev

Islim

Haas

2016

Optical Wireless Communications

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“…Since intensity modulation with direct detection is utilized in VLC for low-cost implementation, the signals modulated on the light-emitting diodes (LEDs) should be real-valued and nonnegative [2]. Therefore, various optical OFDM schemes have been proposed to satisfy these constraints, namely DC-biased optical OFDM (DCO-OFDM) [3], asymmetrically clipped optical OFDM (ACO-OFDM) [4], pulse-amplitude-modulated discrete multi-tone (PAM-DMT) [5], unipolar OFDM (U-OFDM) [6], and Flip OFDM [7]. In all these optical OFDM schemes, Hermitian symmetry is utilized on the OFDM subcarriers before inverse fast Fourier transform (IFFT), so that the time-domain signals are real-valued.…”

Section: Introductionmentioning

confidence: 99%

Index Modulation-Aided OFDM for Visible Light Communications

Wang¹,

Mao²,

Hanzo³

2017

Visible Light Communications

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Index modulation-aided orthogonal frequency-division multiplexing(IM-OFDM) is a promising modulation technique to achieve high spectral and energy efficiency. In this chapter, the conventional optical OFDM schemes are firstly reviewed, followed by the principles of IM-OFDM. The application of IM-OFDM in visible light communication (VLC) systems is introduced, and its performance is compared with conventional optical OFDM, which verifies its superiority. Finally, the challenges and opportunities of IM-OFDM are discussed for the VLC applications.

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