Fountain codes have recently gained wide attention in the communications research
community due to their capacity-approaching performance and rateless properties
that allow them to seamlessly adapt to unknown channel statistics. This thesis of
fers two key contributions. For the first, we consider the problem of low complexity
decoding of Luby Transform (LT) and Raptor codes, which are classes of Fountain
codes. We introduce a decoding method which has a significantly reduced compu
tational load compared to the commonly used alternative of message-reset decoding
with a flooding schedule. This method combines the recently proposed technique of
informed dynamic scheduling combined with incremental decoding. Simulation re
sults for the example of the binary symmetric channel show complexity reductions
(in terms of the total required number of decoding iterations) by 87% compared to
conventional message-passing decoding and 54% compared to a recently proposed
incremental decoding scheme for Raptor codes.
Having proposed our novel decoding method, we then focus on applying rateless
codes to free-space optical (FSO) transmission systems. FSO systems enable high
speed communication with relatively small deployment costs. However, FSO systems
suffer a critical disadvantage, namely susceptibility to fog, smoke, and similar con
ditions. A possible solution to this dilemma is the use of hybrid systems employing
FSO and radio frequency (RF) transmission. As for the second contribution of this
thesis, we propose the application of rateless coding for such hybrid FSO/RF sys
tems. The advantages of our approach are (i) the full utilization of available FSO
and RF channel resources at any time and (ii) very little feedback from the receiver.
In order to substantiate these claims, we establish the pertinent capacity limits for
hybrid FSO/RF transmission and present simulation results for transmission with
off-the-shelf Raptor codes, which achieve realized rates close to these limits under a
wide range of channel conditions.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU./4064 |
| Date | 11 1900 |
| Creators | AbdulHussein, Ali |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | 1418117 bytes, application/pdf |
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