Riassunto analitico
Visible Light Communication systems are receiving growing attention both in the
research and in the industry fields, since they enable a pervasive networked communication
that relies on low-cost off-the-shelf LEDs. The OpenVLC open-source platform
offers the opportunity to design and study applications and networking concepts
for VLC. This thesis investigates the deployment of OpenVLC to build a Power
efficient and Adaptive Distributed-Multiple-Input-Single-Output (PAD-MISO) environment
for indoor communication, that consists of a system with LEDs distributed
on the ceiling and a single photodetector as receiver. In particular, it focuses on
a study about the system’s synchronization, which is a key element for a reliable
communication. The study has lead to adopt a ’hierarchical synchronization’, which
involves PTP and NTP at network level and an ad-hoc designed algorithm at packet
level. The average delay among two synchronized transmitters is proved to be in
the order of a few s , which is a reduction of at least a factor of forty with respect to
an unsynchronized environment. A further investigation is held to check the propagation
of the delay when transmitting a single packet. The delay in transmitting the
first symbol is below 10 ppm, which is the best result that can been obtained without
hardware modifications, as it will be proved throughout the thesis. In addition to
this, the variation of a symbol’s length throughout a packet has been investigated,
showing a degradation of the length, starting from the middle of the packet and going
through its end. Moreover, a preliminary insight about the optimal sampling
frequency in each point of the environment, lies the basis for the implementation of
an adaptive algorithm to choose the optimum frequency in each point served by the
PAD-MISO system.
|
Abstract
Visible Light Communication systems are receiving growing attention both in the
research and in the industry fields, since they enable a pervasive networked communication
that relies on low-cost off-the-shelf LEDs. The OpenVLC open-source platform
offers the opportunity to design and study applications and networking concepts
for VLC. This thesis investigates the deployment of OpenVLC to build a Power
efficient and Adaptive Distributed-Multiple-Input-Single-Output (PAD-MISO) environment
for indoor communication, that consists of a system with LEDs distributed
on the ceiling and a single photodetector as receiver. In particular, it focuses on
a study about the system’s synchronization, which is a key element for a reliable
communication. The study has lead to adopt a ’hierarchical synchronization’, which
involves PTP and NTP at network level and an ad-hoc designed algorithm at packet
level. The average delay among two synchronized transmitters is proved to be in
the order of a few s , which is a reduction of at least a factor of forty with respect to
an unsynchronized environment. A further investigation is held to check the propagation
of the delay when transmitting a single packet. The delay in transmitting the
first symbol is below 10 ppm, which is the best result that can been obtained without
hardware modifications, as it will be proved throughout the thesis. In addition to
this, the variation of a symbol’s length throughout a packet has been investigated,
showing a degradation of the length, starting from the middle of the packet and going
through its end. Moreover, a preliminary insight about the optimal sampling
frequency in each point of the environment, lies the basis for the implementation of
an adaptive algorithm to choose the optimum frequency in each point served by the
PAD-MISO system.
|
