Power Efficient Subcarrier Modulation for Intensity Modulated Channels

Karout, Johnny; Agrell, Erik; Karlsson, Magnus

doi:10.1364/oe.18.017913

Cited by 12 publications

(26 citation statements)

References 23 publications

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“…The nonnegativity constraint, x(t) ≥ 0 for all t ∈ R, is fulfilled by choosing µ in (1) sufficiently large, see Sec. V. This DC bias is added equally to each symbol to maintain a strictly bandlimited signal x(t), in contrast to works like [25], [27], [28] in which the bias is allowed to vary with time. The bandwidth constraint is fulfilled by choosing the pulse q(t) such that…”

Section: System Modelmentioning

confidence: 99%

Bandlimited Intensity Modulation

Tavan

Agrell

Karout

2012

IEEE Trans. Commun.

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In this paper, the design and analysis of a new bandwidth-efficient signaling method over the bandlimited intensity-modulated direct-detection (IM/DD) channel is presented. The channel can be modeled as a bandlimited channel with nonnegative input and additive white Gaussian noise (AWGN).Due to the nonnegativity constraint, standard methods for coherent bandlimited channels cannot be applied here. Previously established techniques for the IM/DD channel require bandwidth twice the required bandwidth over the conventional coherent channel. We propose a method to transmit without intersymbol interference in a bandwidth no larger than the bit rate. This is done by combining Nyquist or root-Nyquist pulses with a constant bias and using higher-order modulation formats. In fact, we can transmit with a bandwidth equal to that of coherent transmission. A trade-off between the required average optical power and the bandwidth is investigated. Depending on the bandwidth required, the most power-efficient transmission is obtained by the parametric linear pulse, the so-called "better than Nyquist" pulse, or the root-raised cosine pulse. Index TermsIntensity-modulated direct-detection (IM/DD), strictly bandlimited signaling.

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Section: System Modelmentioning

confidence: 99%

Bandlimited Intensity Modulation

Tavan

Agrell

Karout

2012

IEEE Trans. Commun.

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“…In addition, it helps in quantifying the impact of relative intensity noise (RIN) in fiberoptical links [35], and in assessing the power consumption of optical systems [34]. In [30],P e was used as a performance measure for comparing different intensity modulation formats. The second measure is the average optical powerP o , which has been studied in [1], [2], [6]- [8] for the wireless optical channel.…”

Section: A Performance Measuresmentioning

confidence: 99%

“…At the same symbol rate, modulation formats such as OOK and M -PAM have W = R s , whereas the modulation formats belonging to the single-subcarrier family occupy W = 2R s ; this is due to the intermediate step of modulating the information onto an electrical subcarrier before modulating the optical carrier [1, Ch. 5], [30]. We now describe explicitly the admissible region Υ for single-subcarrier modulation formats [3, Fig.…”

Section: B Single-subcarrier Modulation Formatsmentioning

confidence: 99%

“…In this work, we address this question by optimizing singlesubcarrier modulation formats for uncoded IM/DD systems, with and without confining them to a lattice structure. We choose a uniform probability distribution over constellation points as in [1]- [3], [7], [15], [16], [23], [30]- [32]. We propose a set of 4-, 8-, and 16-level single-subcarrier modulation formats which are optimized for average electrical, average optical, and peak power.…”

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confidence: 99%

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Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems

Karout

Agrell

Szczerba

et al. 2012

IEEE Trans. Inform. Theory

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We optimize modulation formats for the additive white Gaussian noise channel with nonnegative input, also known as the intensity-modulated direct-detection channel, with and without confining them to a lattice structure. Our optimization criteria are the average electrical, average optical, and peak power. The nonnegative constraint on the input to the channel is translated into a conical constraint in signal space, and modulation formats are designed by sphere packing inside this cone. Some dense packings are found, which yield more power-efficient modulation formats than previously known. For example, at a spectral efficiency of 1.5 bit/s/Hz, the modulation format optimized for average electrical power has a 2.55 dB average electrical power gain over the best known format to achieve a symbol error rate of 10 −6 . The corresponding gains for formats optimized for average and peak optical power are 1.35 and 1.72 dB, respectively. Using modulation formats optimized for peak power in average-power limited systems results in a smaller power penalty than when using formats optimized for average power in peak-power limited systems. We also evaluate the modulation formats in terms of their mutual information to predict their performance in the presence of capacity-achieving errorcorrecting codes, and finally show numerically and analytically that the optimal modulation formats for reliable transmission in the wideband regime have only one nonzero point.

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“…It was shown that the ultimate shaping gain is 1.53 dB as N → ∞ and can be approached when the 1-dimensional constituent constellation follows a truncated half-Gaussian distribution. Karout et al proposed a novel quaternary subcarrier modulation format for IM/DD systems which is a hybrid between OOK and ternary PSK [28]. It was shown that a 0.6 dB average optical power gain over OOK can be obtained at asymptotically high signal-to-noise ratio (SNR).…”

Section: Previous Workmentioning

confidence: 99%

Bandlimited Optical Intensity Modulation Under Average and Peak Power Constraints

Zhang

Hranilovic

2016

IEEE Trans. Commun.

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Bandlimited optical intensity channels, arising in applications such as indoor infrared communications and visible light communications (VLC), require that all signals satisfy a bandwidth constraint as well as average, peak and non-negative amplitude constraints. However, the signaling designed for conventional radio frequency (RF) electrical channels cannot be applied directly, since they take energy constraints into consideration instead of amplitude constraints. In addition, conventional transmission techniques optimized for broad-band optical channels such as fiber optics, terrestrial/satellite-to-satellite free-space optical (FSO) communications are typically not bandwidth efficient.In this thesis, a two-dimensional signal space for bandlimited optical intensity channels is presented. A novel feature of this model is that the non-negativity and peak amplitude constraints are relaxed. The signal space parameterizes the likelihood of a negative or peak amplitude excursions in the output. Although the intensity channel only supports non-negative amplitudes, the impact of clipping on system performance is shown to be negligible if the likelihood of negative amplitude excursion is small enough. For a given signal space, a tractable approximation approach using a finite series is applied to accurately compute the likelihood of clipping under average and peak optical power constraints. The uncoded asymptotic optical power and iv spectral efficiencies using two-dimensional lattice constellations are computed. The Monte-Carlo (MC) simulation results show that for a given average or peak optical power, schemes designed in the presented signal space haver higher spectral efficiency than M -ary pulse amplitude modulation (PAM) using previously established tech- g 1 (t) first branch receive filterg 2 (t) second branch receive filterh(t) channel response I(t) instantaneous optical intensity n(t) channel noise n 1,i output sample noise after filter g 1 (t) at i-th symbol interval n 2,i output sample noise after filter g 2 (t) at i-th symbol interval n c,1,i clipping distortion after filter g 1 (t) at i-th symbol interval n c,2,i clipping distortion after filter g 2 (t) at i-th symbol interval q variable defined as the ratio of t to symbol period T Q(·) tail probability of the standard normal distribution R residual sum r 1 (t) output waveform of filter g 1 (t)

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Power Efficient Subcarrier Modulation for Intensity Modulated Channels

Cited by 12 publications

References 23 publications

Bandlimited Intensity Modulation

Bandlimited Intensity Modulation

Optimizing Constellations for Single-Subcarrier Intensity-Modulated Optical Systems

Bandlimited Optical Intensity Modulation Under Average and Peak Power Constraints

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