Unprecedented traffic growth is expected in future wireless networks and new
technologies will be needed to satisfy demand. Optical wireless (OW) communication offers vast unused spectrum and high area spectral efficiency. In this work, optical
cells are envisioned as supplementary access points within heterogeneous RF/OW networks. These networks opportunistically offload traffic to optical cells while utilizing
the RF cell for highly mobile devices and devices that lack a reliable OW connection.
Visible light communication (VLC) is considered as a potential OW technology due
to the increasing adoption of solid state lighting for indoor illumination.
Results of this work focus on a full system view of RF/OW HetNets with three primary areas of analysis. First, the need for network densication beyond current RF
small cell implementations is evaluated. A media independent model is developed
and results are presented that provide motivation for the adoption of hyper dense
small cells as complementary components within multi-tier networks. Next, the relationships between RF and OW constraints and link characterization parameters are
evaluated in order to define methods for fair comparison when user-centric channel
selection criteria are used. RF and OW noise and interference characterization techniques are compared and common OW characterization models are demonstrated
to show errors in excess of 100x when dominant interferers are present. Finally,
dynamic characteristics of hyper dense OW networks are investigated in order to optimize traffic distribution from a network-centric perspective. A Kalman Filter model
is presented to predict device motion for improved channel selection and a novel OW
range expansion technique is presented that dynamically alters coverage regions of
OW cells by 50%.
In addition to analytical results, the dissertation describes two tools that have
been created for evaluation of RF/OW HetNets. A communication and lighting
simulation toolkit has been developed for modeling and evaluation of environments
with VLC-enabled luminaires. The toolkit enhances an iterative site based impulse
response simulator model to utilize GPU acceleration and achieves 10x speedup over
the previous model. A software defined testbed for OW has also been proposed
and applied. The testbed implements a VLC link and a heterogeneous RF/VLC
connection that demonstrates the RF/OW HetNet concept as proof of concept.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/13681 |
| Date | 28 October 2015 |
| Creators | Rahaim, Michael |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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