Spectrum sharing with limited feedback in cognitive radio networks

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Copyright: Wang, Zhe
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Abstract
With the rapid growth of wireless applications and services in recent decades, huge demands of radio spectrum are created. Traditional approach of spectrum management which allocates fixed spectrum to licensed users leaves most of the spectrum underutilized. To overcome spectrum scarcity and improve spectrum utilization efficiency, cognitive radio was recently proposed as a promising technology that allows secondary users to share the underutilized licensed spectrum while not causing harmful interference to primary users. To better protect primary system and fully utilize secondary transmission opportunities, perfect channel state information is required at secondary user. Limited feedback is a practical approach by sending a few bits of channel state information from receiver to transmitter. This thesis studies the spectrum sharing designs with limited feedback in the point-to-point, broadcast scheduling and Poisson cognitive radio networks. The design aim is to optimally allocate the secondary resources so as to improve the throughput of secondary users while maintaining a certain quality of service of primary users. Firstly, three spectrum sharing schemes are proposed in a point-to-point system when various side information of primary user and interference channel is available at the secondary user. Differential Evolution algorithm is employed to provide global optimal solutions of secondary quantization thresholds and power allocation. Numerical results show that more secondary feedback bits or more side information may result in better secondary system performance. Secondly, a spectrum sharing scheme is proposed in a broadcast scheduling system where the user scheduling and power allocation are based on the limited feedback. The optimal secondary quantization thresholds and power allocation are derived analytically via Karush-Kuhn-Tucker conditions. It shows that the average throughput of the secondary user grows double logarithmically with the increase of the number of users. Thirdly, two spectrum sharing schemes are proposed in a Poisson cognitive radio network without and with the primary exclusion regions, respectively. The optimal node density which maximizes the secondary area spectral efficiency is derived analytically using stochastic geometry theory. Numerical results show that the secondary throughput benefits from the primary exclusion region if the secondary outage constraint is relatively loose. Otherwise, no primary exclusion region is preferable.
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Author(s)
Wang, Zhe
Supervisor(s)
Zhang, Wei
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Publication Year
2014
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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