Asghari, Vahid Reza
Approaches for Adaptive Resource Allocation in
Cognitive Radio Networks.
Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 246 p.
Proposing efficient spectrum utilization techniques to alleviate spectrum congestion is
one of the most important challenges in wireless communication technologies operating at
specific spectrum bands. In fact, the growth of wireless application demands has caused
the frequency allocation table for wireless services to become over congested. On the other
hand, recent measurement studies have shown that the radio frequency spectrum in its current
shape is inefficiently utilized. Hence, for the purpose of alleviating the long-standing
problem of spectrum congestion, the federal communication commission (FCC) is actively
revising the traditional spectrum allocation policies and moving towards the adoption of
opportunistic spectrum-sharing techniques using cognitive radio. Cognitive radio (CR) is
a technology that has the ability of sensing the environment in which it operates and adapting
to its changes. For instance, through sensing, CR detects the portions of the spectrum
that are un-occupied (also referred to as spectrum holes) at a specific location or time.
One of the most efficient ways to identify spectrum holes is to sense the activity of the
primary users operating within the secondary users' (cognitive user) range of communication.
In this dissertation, we study different approaches for adaptive resource allocation in
spectrum-sharing CR networks. In this context, we propose utilizing spectrum sensing information
about the primary users' activity and secondary channel knowledge to adaptively
adjust the secondary transmission parameters such as time, power and rate while adhering
to the generated interference at the primary receivers. In this case, a proper resource management
is needed so as to maximize the throughput performance of the secondary users
and avoid performance degradation for the primary users. The existence and specification
of such resource allocation are necessary issues and will be investigated in this dissertation
for different operating scenarios. We also propose adopting cooperative relaying
techniques in spectrum-sharing CR systems to more effectively and efficiently utilize the
available transmission resources while adhering to the quality of service requirements of
the primary (licensed) users of the shared spectrum band. In particular, while the moment
generating function approach is commonly used to evaluate the performance analysis of
cooperative relaying systems, we propose a unified framework which relies on the first-order
statistics and convolutional methods to investigate the end-to-end performance of
cooperative relaying spectrum-sharing systems. Furthermore, we quantify the advantages
of utilizing relaying transmissions in spectrum-sharing CR networks for different operating
scenarios and conditions.
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