An OFDM based cognitive radio (CR) network is considered in this paper. The goal is to maximize the total sum rate of the CR system while ensuring that no excessive interference is induced to the primary system. The optimal scheme adopts the dual decomposition technique and in order to reduce the computational complexity of the optimal scheme, a greedy suboptimal algorithm is proposed. Selected numerical results is discussed to reveal the near-optimal performance of the suboptimal scheme and the superiority of the proposed algorithm over the random and the signal-to-noise ratio (SNR) based schemes.
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