Askari, Elaheh
(2013).
Access control in full-duplex wireless networks.
Mémoire.
Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 105 p.
Résumé
Single-channel full-duplexing is a new concept that enables wireless stations to
transmit and receive simultaneously over the same frequency channel. This concept
has recently found practical aspects with the introduction of innovative antenna design
approaches and implementation of signal processing methods that finally led to
the fabrication of few prototypes. As has been anticipated by the theory, the empirical
results have confirmed that full-duplexing (FD) can indeed enhance the network
throughput and capacity as well as combat the hidden terminal problem. Moreover,
the biggest potential of the FD technology would be in the area of cognitive radio
networks where it enables the cognitive stations to sense (receive) and transmit concurrently
without needing to dedicate separate sensing intervals to serve this purpose.
This can not only reduce the vulnerability of primary users (PUs) to the interference
that secondary users(SUs) can generate but it also allows the SUs to increase their
channel utilization and throughput.
This fundamental change reveals the need of discovering suitable higher-layer protocols
and mechanisms in the protocol stack, at the very bottom of which the FD
technology is laid. In particular, the medium access layer (MAC) should be adapted
properly to efficiently distribute the resources offered by the underneath layer and
handle the FD related tasks that do not exist in the standard half duplexing (HD)
mode. Moreover, in order to extend the advantages promised by FD to the network
level, building well-tailored routing protocols that can take the most out of this powerful
technology is essential, as most of the these protocols have been designed for the
HD mode of operation. Certainly, the medium access layer must be the cornerstone
of these efforts. In order to fill in these existing gaps, the contribution of this thesis
is structured in two parts.
In the first part, we evaluate the performance of SUs in a cognitive setting when
the cognitive nodes are enabled with FD technology. To that end, we compare the
performance of such a system over an HD system and we demonstrate the superiority
of the former over the latter. Even though the exploitation of FD improves the
bandwidth efficiency and allows SUs to discover the transmission opportunities more
quickly, a support from higher layers is needed. To this end, we propose progressive
communication by the implementation of packet fragmentation at the MAC layer.
In particular, we show that by dividing the packet into smaller, but independent,
segments, the system performance, in terms of key performance metrics such as successful
transmission probability and system reliability, get improved considerably. As
the first study to unify the FD and packet fragmentation in cognitive radio networks,
we compare the performance of FD, HD and fragmentation-enabled FD, and also
identify the conditions under which the proposed method is superior.
In the second part, we propose a MAC protocol that leverages the advantages of
FD by considering the issues that have been left unaddressed in previous studies. This
protocol, which works based on the concepts of worm-hole routing and uncontended
access in distributed access settings, can combat the hidden terminal problem in the
network. Moreover, the proposed protocol is capable of forwarding the packets in
a route for an arbitrary number of hops, which is an efficient approach to take full
advantage of the opportunities that the single-channel FD opens up for having higher
spectral efficiency.
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