Digital Pre-Equalization for OFDM-Based VLC Systems: Centralized or Distributed?

Chen, Chen; Nie, Yungui; Liu, Min; Du, Ye; Liu, Ruisi; Wei, Zixian; Fu, H. Y.; Zhu, Binbin

doi:10.1109/lpt.2021.3104618

Cited by 30 publications

(14 citation statements)

References 14 publications

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“…The CP with the ratio of 1/64 is adopted for mitigating ISI. In addition, we choose DC = 0.4 and f 0 = 20 MHz for a LED model in (4). For an empty room scenario, the indoor VLC channel following the model in [39] is used for training.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…It has many advantages such as high anti-electromagnetic interference, low cost, good safety, and a rich and license-free spectrum. Compared with the single carrier modulation schemes, the optical orthogonal frequency division multiplexing (O-OFDM), which has a higher spectral efficiency and system capacity, attracted more and more attention from scholars [3][4][5]. Combining the low-cost structure of intensity modulation and direct detection (IM/DD), the direct current-biased (DC) O-OFDM has been widely deployed in the VLC system to achieve a high-speed rate [6], where the Hermitian symmetry is adopted to provide the real-valued signal and the DC bias is used to ensure the non-negativity constraint of light-emitting diode (LED).…”

Section: Introductionmentioning

confidence: 99%

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Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems

et al. 2021

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The inherent impairments of visible light communication (VLC) in terms of nonlinearity of light-emitting diode (LED) and the optical multipath restrict bit error rate (BER) performance. In this paper, a model-driven deep learning (DL) equalization scheme is proposed to deal with the severe channel impairments. By imitating the block-by-block signal processing block in orthogonal frequency division multiplexing (OFDM) communication, the proposed scheme employs two subnets to replace the signal demodulation module in traditional system for learning the channel nonlinearity and the symbol de-mapping relationship from the training data. In addition, the conventional solution and algorithm are also incorporated into the system architecture to accelerate the convergence speed. After an efficient training, the distorted symbols can be implicitly equalized into the binary bits directly. The results demonstrate that the proposed scheme can address the overall channel impairments efficiently and can recover the original symbols with better BER performance. Moreover, it can still work robustly when the system is complicated by serious distortions and interference, which demonstrates the superiority and validity of the proposed scheme in channel equalization.

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Section: Simulation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems

et al. 2021

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“…However, this has not been studied in a broader range of input electrical powers. In [58] the authors propose to split the pre-emphasis into two separate sub-bands to avoid excessive DRAFT March 21, 2023 power loss associated with boosting high-frequency signal components. However, this technique could be interpreted as a coarse bit and power loading, which is since long ago known to be a successful strategy.…”

Section: B Transmitter Pre-emphasismentioning

confidence: 99%

A Behavioral Model of the Light Emitting Diode Nonlinearity

Bojarczuk¹,

Marzęcki²,

Sun³

et al. 2023

Preprint

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<p>Correct modeling of light emitting diode (LED) nonlinearity is vital for evaluating the performance of advanced modulation formats and nonlinear distortion mitigation methods in visible light communication systems. In this paper, we review the existing simplified nonlinear LED models: static polynomial, Wiener and Hammerstein and provide strong experimental evidence against their even coarse correctness. Instead, we propose an evenly uncomplicated model of LED, which is based on rigorous factorization of the Volterra 2nd order kernel stemming from the recombination rate equations of the LED. We further experimentally validate this model in four different LEDs by: (i) finding that linear transmitter pre-emphasis, against the results of the communications theory in a linear, bandlimited channel, can at very high input powers improve the transmission perfromance compared to linear equalization at the receiver, which is explained in our model by a reduction of the nonlinear distortion by the pre-emphasis; (ii) by comparing the measured 2nd order quadratic kernels of LEDs in regular form and with the constraints of our model. Finally, we propose a two-parameter calibration method of our model, which requires measurement of the LED bandwidth and 2nd order harmonic distortion at a single frequency. Excellent convergence of the signal transmitted in the calibrated model to the rate equation model and to the measurement is observed.</p>

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“…Moreover, these methods can be applied in two different ways: digital or analog. On one hand, digital pre-equalizer methods have been developed through the different types of techniques, such as adding weights to subcarriers, or the use of finite impulse response (FIR) filters [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Besides, analog pre-equalizer methods have been developed using techniques, such as the cascaded constant-resonance amplitude equalizer and the multiple-resonant-driving equalization technique [ 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Modelling and Design of Pre-Equalizers for a Fully Operational Visible Light Communication System

Bostanoglu,

Dalveren,

Catak

et al. 2023

Sensors

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Nowadays, Visible Light Communication (VLC) has gained much attention due to the significant advancements in Light Emitting Diode (LED) technology. However, the bandwidth of LEDs is one of the important concerns that limits the transmission rates in a VLC system. In order to eliminate this limitation, various types of equalization methods are employed. Among these, using digital pre-equalizers can be a good choice because of their simple and reusable structure. Therefore, several digital pre-equalizer methods have been proposed for VLC systems in the literature. Yet, there is no study in the literature that examines the implementation of digital pre-equalizers in a realistic VLC system based on the IEEE 802.15.13 standard. Hence, the purpose of this study is to propose digital pre-equalizers for VLC systems based on the IEEE 802.15.13 standard. For this purpose, firstly, a realistic channel model is built by collecting the signal recordings from a real 802.15.13-compliant VLC system. Then, the channel model is integrated into a VLC system modeled in MATLAB. This is followed by the design of two different digital pre-equalizers. Next, simulations are conducted to evaluate their feasibility in terms of the system’s BER performance under bandwidth-efficient modulation schemes, such as 64-QAM and 256-QAM. Results show that, although the second pre-equalizer provides lower BERs, its design and implementation might be costly. Nevertheless, the first design can be selected as a low-cost alternative to be used in the VLC system.

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Digital Pre-Equalization for OFDM-Based VLC Systems: Centralized or Distributed?

Cited by 30 publications

References 14 publications

Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems

Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems

A Behavioral Model of the Light Emitting Diode Nonlinearity

Modelling and Design of Pre-Equalizers for a Fully Operational Visible Light Communication System

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