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Spectrum Sharing Algorithm for Downlink Cognitive Radio Systems |
Zhang Ran-ran; Liu Si-yang; Xie Gang; Liu Yuan-an |
Key Lab of Universal Wireless Communications, Ministry of Education,
Beijing University of Posts and Telecommunications, Beijing 100876, China |
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Abstract A spectrum sharing algorithm for downlink cognitive radio systems is proposed to maximize the system capacity under total transmission power and interference constraints. Interference to the licensed users is analyzed, and a method to set interference constraint is given accordingly. Based on the interference constraint, the maximum system capacity is achieved by two steps: first the optimal subcarrier allocation is derived by the maximum channel signal to interference plus noise ratio rule; then transmission power is optimally allocated by the proposed double water-filling method. Simulation results show this algorithm can provide significant capacity gain comparing with the conventional spectrum sharing algorithms.
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Received: 18 March 2008
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