Simple Digital Pre-equalization of VLC Links

Surampudi, Atchutananda; Collins, Steve

doi:10.1109/ipc47351.2020.9252332

Cited by 6 publications

(7 citation statements)

References 4 publications

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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%

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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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Section: Introductionmentioning

confidence: 99%

“…In the literature, several digital pre-equalizer methods have been proposed for VLC systems [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In [ 13 ], in order to improve the modulation speed of 1 MHz bandwidth white LED communication, digital FIR and matched filters were used.…”

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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“…Among them, there are equalizers based on the general Hammerstein model [6], decision feedback equalizer (DFE) with static nonlinearity compensation [8], equalizers based on the Volterra and Wiener approach [4,5], devices based on neural networks [7], and others [9]. Usually, the equalizer is employed at the receiver side (post-equalizer), but there are solutions that insert the compensating device at the transmitter (pre-equalizer) [10,11]. Immediately, a question arises as to which solution (pre-or post-equalization) is better.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Nonlinear Dynamic Pre- and Post-LED Equalization

Siuzdak

2022

Sensors

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Visible Light Communications (VLC) have gained much popularity lately. In such a system, a white LED (Light-Emitting Diode) plays a double role as a light source and a transmitter. The main problem here is that the LED exhibits a low bandwidth and high nonlinearity, so the equalization of the LED nonlinear dynamic response is necessary. For this, various equalizers are used. This paper compares the pre- and post-equalizer performance in terms of the received signal quality for a channel that includes a nonlinear element of limited bandwidth, such as an LED. Multilevel Pulse Amplitude Modulation (PAM) was selected as the signal format, as well as a variant of the Volterra series equalizer as the compensating element. The results obtained may be used for the correction of the dynamic characteristics of LEDs applied in VLC systems. For the sake of comparison, we used Modulation Error Ratio (MER) values at the receiver output. The dynamic nonlinear behavior was modeled by a Wiener–Hammerstein device, whereas the post/pre-equalizer was based on the dynamic deviation reduction-based Volterra series. The obtained results indicate that the post- and pre-equalizer performed comparably for the linear/moderately nonlinear channels and for a high noise level. In the case of high nonlinearity and a large SNR (Signal–to–Noise Ratio) values, the post-equalizer performed somewhat better in terms of MER by a few dB at maximum.

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“…However, the variety of preequalizers that can be created using analogue circuits is limited by the frequency responses of analogue circuits. In contrast, their programmability means that digital methods can be used to create a wide range of preequalizers, including equalizers that would be difficult to fabricate over cascading analog circuits for links whose response isn't a product of a few single poles [9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The pre-equalization of OOK pulses results in overshoots at the bit transition edges. It has been shown that in a digital implementation, these overshoots need to be appropriately represented by the number of samples (or points) per bit Nppb [10]. This is because a more precise construction results in a better representation of the overshoot and therefore compensation for the low-pass response of the link.…”

Section: Introductionmentioning

confidence: 99%

Raised Cosine Pulse Shaping for Pre-equalized Optical Wireless Links

Surampudi

Singh

Faulkner

et al. 2021

IEEE Photon. Technol. Lett.

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Their programmability means that digital preequalization techniques are more flexible than analog circuit equalizers. However, their performance depends on the number of samples per data symbol needed to accurately represent the pre-equalized time domain pulse. This requirement limits the maximum data rate that can be generated by a digital-to-analog converter (DAC). Another challenge when pre-equalizing the signal applied to a transmitter is the need to restrict the maximum voltage applied to the transmitter. Given these challenges, this paper demonstrates the benefits of constructing digitally pre-equalized On-Off Keying (OOK) symbols with raised cosine pulses. In addition, results are presented which show that each symbol can be represented with as few as 5 samples per bit. The performance of the proposed equalization method is investigated using an off-the-shelf LED-based optical wireless communication (OWC) link. Using equalization, the bandwidth of the link is increased by a factor of 10 to 100 MHz. Consequently, the data rate achievable with a 2 GSa/s DAC is 400 Mb/s.

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Simple Digital Pre-equalization of VLC Links

Cited by 6 publications

References 4 publications

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

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

Comparison of the Nonlinear Dynamic Pre- and Post-LED Equalization

Raised Cosine Pulse Shaping for Pre-equalized Optical Wireless Links

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