Cognitive Multiple Access for Cooperative Communications and Networking
Cognitive Multiple Access for Cooperative Communications and Networking
Files
Publication or External Link
Date
2009
Authors
El Sherif, Amr
Advisor
Liu, K. J. Ray
Citation
DRUM DOI
Abstract
In cooperative communications different network nodes share their
antennas and resources to form a virtual antenna array and improve
their performance through spatial diversity. This thesis contributes
to the advancement of cooperative communications by developing and
analyzing new multiple access cooperation protocols that leverage
the benefits of cooperation to upper network layers.
For speech communications networks, we propose a cooperative
multiple access protocol that exploits inherent characteristics of
speech signals, namely, long periods of silence, to enable
cooperation without incurring bandwidth efficiency losses. Using
analytical and simulation results we show that the proposed protocol
achieves significant increase in network throughput, reduction in
delay, and improved perceptual speech quality.
In TDMA networks, we investigate the problem of sharing idle time
slots between a group of cooperative cognitive relays helping
primary users, and a group of cognitive secondary users. Analytical
results reveal that, despite the apparent competition between relays
and secondary users, and even in case of mutual interference between
the two groups, both primary and secondary users will significantly
benefit in terms of maximum stable throughput from the presence of
relays.
For random access networks, we find a solution to the problem of
achieving cooperation gains without suffering from increased
collision probability due to relay transmissions. A novel
cooperation protocol is developed and analyzed for that purpose.
Analytical and simulation results reveal significant improvements in
terms of throughput and delay performance of the network. Moreover,
collision probability is decreased.
Finally, in the framework of a cognitive radio network, we study the
negative effects of spectrum sensing errors on the performance of
both primary and secondary networks. To alleviate those negative
effects, we propose a novel joint design of the spectrum sensing and
channel access mechanisms. Results show significant performance
improvement in the maximum stable throughput region of both
networks.