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Resource Allocation in OFDM Based Wireless Relay Networks ...

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1.5 Contribution and Organization of the Thesis<br />

relay transmission. The cognitive radio (CR) has been proposed to improve<br />

spectrum utilization by exploit<strong>in</strong>g the less used spectrum <strong>in</strong> a dynamically chang<strong>in</strong>g<br />

environment. In the proposed algorithms, the secondary user’s throughput is<br />

maximized through the power allocation (at the secondary source node and the<br />

secondary relay node) and the sub-carrier pair<strong>in</strong>g (on two hops of secondary system)<br />

subject to various power constra<strong>in</strong>ts. Meanwhile, the <strong>in</strong>terference from both the<br />

secondary source and the secondary relay node to the primary receiver is kept with<strong>in</strong><br />

an acceptable limit. The numerical examples demonstrate enhanced performance<br />

compared to trivial cognitive relay resource allocation algorithms.<br />

In chapter 7, we conclude our work by highlight<strong>in</strong>g the major contributions of<br />

the thesis. An overview of the thesis organization is shown <strong>in</strong> Fig. 1.4.<br />

14

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