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A Full-digital M-CAP Receiver with Synchronisation and Adaptive Blind Equalisation for Visible Light Communications

Li, X. ; Ghassemlooy, Z. ; Zvanovec, S. ; Alves, L. ; Figueiredo, M. ; Zhang, M. ; Mana, S. ; Jungnickel, V. ; Chvojka, P.

Journal of Lightwave Technology Vol. 40, Nº 8, pp. 2409 - 2426, April, 2022.

ISSN (print): 0733-8724
ISSN (online):

Scimago Journal Ranking: 1,45 (in 2018)

Digital Object Identifier: 10.1109/JLT.2021.3135468

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Abstract
With an emphasis on the real-time implementation
of a practical carrier-less amplitude and phase (CAP) receiver
for visible light communication (VLC), this paper proposes a full-
digital architecture for the M -CAP receiver with synchronisation
and adaptive blind equalisation. The architecture is mainly based
on the observation that a CAP signal can be demodulated
using a quadrature and amplitude (QAM) receiver with an
added counterclockwise rotation operation. The proposed CAP
receiver employs two digital phase-locked loops (DPLL) to realise
the symbol timing and carrier synchronisation, which are the
most critical issues in practical systems. With the constant-
modulus algorithm (CMA) offering the benefit of decoupling
carrier and symbol timing synchronisation, the receiver can
blindly equalise the distorted signal at the output of symbol
timing synchronisation. Finally, the performance of 4/16/64-CAP
receivers, which are designed using this architecture and operates
at 80/160/240 Mbit/s through a low-pass light-emitting diode
(LED) with a 3-dB bandwidth of 7 MHz cascaded with three
measured optical wireless channels, is evaluated by Monte Carlo
simulations. Results show that the receiver architecture can
successfully solve the symbol timing and carrier synchronisation
problems and mitigate inter-symbol interference caused by LED
and/or wireless channels. The design framework for a full-digital
CAP receiver has been laid out in this pape