Synchronization in Visible Light Communication for Smart Cities

The rapid deployment of light emitting diodes and the prominence of facilitating simultaneous illumination and communication have driven Visible Light Communication (VLC) to gain enormous prevalence in the recent times. This expedited VLC to become amalgamated with many smart city applications in pa...

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Bibliographic Details
Published in:IEEE sensors journal 2018-03, Vol.18 (5), p.1877-1886
Main Authors: Vappangi, Suseela, Vakamulla, Venkata Mani
Format: Article
Language:English
Subjects:
Amalgamation
carrier frequency offset
Communication
CRLB
DCO-OFDM
Illumination
Light emitting diodes
Lighting
Lower bounds
Mathematical analysis
OFDM
Optical communication
Optical modulation
Organic light emitting diodes
Orthogonal Frequency Division Multiplexing
Orthogonality
Parameter estimation
Radio frequency
Smart cities
symbol time offset
Synchronism
Synchronization
VLC
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Summary:The rapid deployment of light emitting diodes and the prominence of facilitating simultaneous illumination and communication have driven Visible Light Communication (VLC) to gain enormous prevalence in the recent times. This expedited VLC to become amalgamated with many smart city applications in particular, with the lighting infrastructure to enable seamless connectivity. The underlying challenge of this technology is to assure high data rate communication while fulfilling illumination requirements in smart cities. In this regard, optical orthogonal frequency division multiplexing (OOFDM) compatible with intensity modulated/direct detection (IM/DD) system can be exploited for VLC. Where, IM and DD is one approach of envisioning VLC. DC biased Optical OFDM (DCO-OFDM), the earliest variant of OFDM for VLC is employed in this paper. It is apparent that, the advantages of OOFDM cannot be utilized if its orthogonality is destroyed by any means. The striking difference between RF-based OFDM and OOFDM is that, OOFDM necessitates the transmitted time-domain signal to be both real and unipolar. Hence, the synchronization techniques existing for RF cannot be directly applied for VLC and consequently must be revisited. This paper analyzes the effects of carrier frequency offset (CFO) and symbol time offset (STO) in DCO-OFDM over VLC channel. Here, mathematical analysis is performed showing the effects of CFO and STO in OOFDM. Synchronization algorithms, such as Moose, Classen and Training Symbol assisted are revisited. Detailed analysis of Cramer Rao lower bound is carried out considering the joint parameter estimation of both CFO and channel estimation error.
ISSN:1530-437X
1558-1748
DOI:10.1109/JSEN.2017.2777998