Abstract
The recent advancement in digital technology has paved the way for present and future
research in the field of telecommunications. Recent work has shown that the telecommunication
industry can significantly benefit from the amalgamation of the Power Line
Communication (PLC) and Visible Light Communication (VLC) systems. The cascaded
PLC–VLC systems have proven to be a conducive candidate or alternative for data transmission
to the already existing Radio Frequency (RF) spectrum. The RF spectrum suffers
from congested bandwidth as well as difficulties in reaching nodes in areas where there
are higher signal interference levels. One of the motivations that has orchestrated the
research of alternative communication systems other than those that utilises the RF spectrum
is the need for more bandwidth which has been diminished as a result of increased
number of electronic devices that require connectivity. The hybrid PLC-VLC systems
have become well known in the field of telecommunications owing to the vast amount of
bandwidth and guaranteed data security at its disposal.
This thesis aims to investigate and provide analysis on the performance of the hybrid
PLC-VLC system with blanking non-linearity. The Asymmetrically Clipped Optical-
Orthogonal Frequency Division Multiplexing (ACO-OFDM) and DC biased Optical -
OFDM (DCO-OFDM) modulations techniques will be utilised to integrate the PLC and
VLC technologies. We also determine the influence of the channel noise to the performance
of the bit error rate (BER) versus signal to noise ratio (SNR) curves as well as
deriving the BER function that best describes the theoretical performance of the system
under different simulation conditions.
This work also aims to provide analysis on the performance of hybrid PLC-VLC system
by deriving an expression of the SNR output of the blanking non-linearity. To reduce
the impact of impulsive noise on the systems’ performance, we apply the blanking method
at the receiver. Due to its effectiveness and simplicity in use, the blanking non-linearity
method is widely employed in impulsive noise communication situations to reduce such
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Abstract
noise. The blanking process identifies data samples containing impulsive noise and clips
them to zero, removing the impulsive noise from the system and enhancing system performance.
In this regard, this work examines the performance of hybrid PLC-VLC systems
with blanking nonlinearity. The SNR at the output of the blanking device is deduced
using a closed-form analytical expression.
This thesis further provides a comparative study on the efficiency of the blanking and
clipping techniques on the proposed hybrid system. These two noise cancellation methods
are applied to the system and the obtained plots were compared to determine which
method performed better. The simulation findings obtained in this thesis show that if
there are enough OFDM sub-carriers, there is good agreement between simulation results
and theory. The results also demonstrated that choosing an appropriate blanking threshold
is crucial for achieving the greatest performance. The derived theoretical expressions
were in perfect agreement with the simulated results which validated our findings. The
analysis in this study gives us additional knowledge on the behaviour of hybrid PLC-VLC
systems under various channel scenarios, which is very helpful for future designs of hybrid
PLC-VLC systems in their pursuit of applications for the fourth industrial revolution.
Furthermore, we investigate the performance of hybrid PLC-VLC in the context of
IoT application in a hostile environment, more specifically, for monitoring applications
in underground environments. The considered system will utilise the existing PLC channels
and VLC technology to communicate the data collected underground to the overground
gateways. To further enhance the performance of the proposed system, we implement
preprocessing at the transmitting node so that the signal detection at the receiving
node becomes more efficient. The proposed hybrid PLC-VLC network system will utilise
the selective mapping method (SLM) for peak-to-average power (PAPR) reduction and
ACO-OFDM. Closed-form analytical expressions for three different performance metrics,
namely, probably of blanking error, probably of successful detection and output SNR, will
be derived and validated with computer simulations.