Abstract
In the emerging framework of visible light communications, the limitation of modulation bandwidth of light emitting diodes (LEDs) transmitters is counterbalanced by the use of red-green-blue (RGB) LEDs since they exhibit higher modulation bandwidth. Using RGB LEDs allows to exploit the spatial multiplexing aspects, that is obtaining parallel channels for transmission. In this context, we used at the receiver RGB-tuned photodiodes (PDs). Hence each PD can, in principle, detect only the information its tuning is matched to. The drawback of increasing spectral efficiency is the presence of cross-talk at the single PD due to the signals emitted by the remaining colors when a perfect color filtering is not applied. In this paper we consider amplitude shift keying (ASK) modulation, investigate the issue of the spatial (color) interference and we present a blind multichannel adaptive equalizer able to mitigate the temporary intersymbol interference (ISI) and also the spatial (color) ISI, this latter partially suppressed using suitable color filters. We analyze also the convergence of the adaptive algorithm and compare its performance with the literature.
Highlights
Visible light communication (VLC) is a complementary technology to radio frequency that is attracting the international research and industrial community interest [1]
In this paper we consider amplitude shift keying (ASK) modulation, investigate the issue of the spatial interference and we present a blind multichannel adaptive equalizer able to mitigate the temporary intersymbol interference (ISI) and the spatial ISI, this latter partially suppressed using suitable color filters
Phospore-based light emitting diodes (LEDs), known as white light LEDs (WLEDs), are used; such LEDs are composed by only one LED chip or multi-colored transmitters, e.g. RedGreen-Blue (RGB) LEDs, which are more complex and expensive but have better illumination quality and higher modulation bandwidth in comparison with WLEDs
Summary
Visible light communication (VLC) is a complementary technology to radio frequency that is attracting the international research and industrial community interest [1]. Another field in the framework of VLC is the camera communication case. Space-time equalization usually aims at taking into account the spatial dimension by avoiding to manage the time aspect due to the relationship between signaling time and delay spread of the channel [12] As it appears clear after a deep literature review, some contributions aim at considering channel equalization techniques that exploit the spatial diversity using WLEDs or the color diversity using RGB LEDs. On the other hand, when WLED are used in Single-Input-Single-Output (SISO) configuration, time equalization is taken into account.
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