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Sum Rate Optimization in Multiuser Cognitive Radio Networks
Fanggang WANG Bo AI Zhangdui ZHONG
Publication
IEICE TRANSACTIONS on Communications
Vol.E94B
No.12
pp.35053514 Publication Date: 2011/12/01 Online ISSN: 17451345
DOI: 10.1587/transcom.E94.B.3505 Print ISSN: 09168516 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: cognitive radio, network sum rate, beamforming, power control, convex optimization, robust algorithm,
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Summary:
In multiuser cognitive radio (CR) networks, we address the problem of joint transmit beamforming (BF) and power control (PC) for secondary users (SUs) when they are allowed to transmit simultaneously with primary users (PUs). The objective is to optimize the network sum rate under the interference constraints of PUs, which is a nonconvex problem. Iterative dual subgradient (IDuSuG) algorithm is proposed by iteratively performing BF and PC to optimize the sum rate, among which minimum mean square error (MMSE) or virtual powerweighed projection (VIP^{2}) is used to design beamformers and subgradient method is used to control the power. VIP^{2} algorithm is devised for the case in which the interference caused by MMSE beamformer exceeds the threshold. Moreover, channel uncertainty due to lack of cooperation is considered. A closedform worstcase expression is derived, with which the uncertainty optimization problem is transformed into a certain one. A robust algorithm based on IDuSuG is provided by modifying updates in iterative process. Furthermore, secondorder cone programming approximation (SOCPA) method is proposed as another robust algorithm. Typical network models are approximated to SOCP problems and solved by interiorpoint method. Finally the network sum rates for different PU and SU numbers are assessed for both certainty and uncertainty channel models by simulation.

