Enhanced cognitive radio with energy harvesting and non-ortohogonal multiple access
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Date
2019-04-10
Authors
Arzykulov, Sultangali
Journal Title
Journal ISSN
Volume Title
Publisher
Nazarbayev University School of Engineering and Digital Sciences
Abstract
The increasing demand for wireless applications is making radio spectrum scarce. Meantime, studies show that the assigned spectrum is not thoroughly utilized. The cognitive
radio (CR) technology is proposed as a feasible key technology to solve issues related
to the spectrum scarcity. CR can improve the spectrum utilization by reusing the unused
spectrum occupied by licensed users. Introduction of CR networks produces two kinds
of interference: interference from the CR network (secondary network) to the primary
network (PN) and the interference among secondary users. All unwanted interference
should be adequately managed in order not to jeopardize the performance of the PN and
at the same time improve the performance of CR systems. Interference alignment (IA) is
a promising technique that can efficiently manage interference. One of the aims of this
thesis is to mitigate the interference by deploying multiple antennas at both transmitter
and receiver sides in order to improve the performance of CR networks.
The rapid growth of data-hungry wireless applications is forcing us to perform energy
harvesting (EH) from external power sources for the next-generation of wireless communication systems. Especially, CR networks, where receiver nodes need advanced hardware
to process a large amount of data, require higher energy consumption. Thus, another goal
of the current thesis is to investigate simultaneous wireless information and power transfer (SWIPT) in CR networks in the presence of intra- and inter-network interference over
various channel state conditions.
Firstly, a cooperative CR network is investigated over the general α−µ fading channel.
The contribution of this study is mainly described by the exact closed-form expression
for the outage probability (OP) of secondary users, which clearly shows how the outage
saturation paradigm appears when the interference level at primary receiver is applied.
Secondly, the proposed cooperative CR is extended by applying multiple-input multiple out (MIMO) antennas and an IA technique to deal with intra- and inter-network
interference. The negative effect of interference at both primary and secondary receivers
is mitigated by using precoding and interference suppression beamforming matrices. The
management of interference at primary receivers allows secondary transmitters to increase the transmit power level. Moreover, the instantaneous capacity performance is
assessed for the same CR system by applying two EH methods, i.e., time-switching (TS)
and power-splitting (PS). Then, the optimal values of TS and PS portions are determined
for different channel state information (CSI) scenarios. In addition, the effect of imperfect
CSI on bit error rate and capacity performance is provided.
Finally, we jointly study a cooperative CR and non-orthogonal multiple access (NOMA),
where we derive closed-form expressions for the OP of NOMA secondary destination
users for detect-and-forward and amplify-and-forward relaying techniques. Furthermore,
power allocation factors for different distances of secondary NOMA users are found to
satisfy OP fairness for all users. In addition, the proposed CR-NOMA network model is
further studied with enabled SWIPT technology.
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Citation
Arzykulov, Sultangali (2019). Enhanced cognitive radio with energy harvesting and non-ortohogonal multiple access. Nazarbayev University School of Engineering