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In this paper, we study the robust relay selection and power allocation problems for orthogonal frequency division multiplexing (OFDM) based cooperative cognitive radio networks (CRNs) with channel uncertainties. The objective is to maximize the capacity of the cooperative CRN, which is subject to the interference threshold constraints of primary users (PUs) and the total transmit power limitation...
Orthogonal frequency division multiplexing (OFD-M)based cognitive radio networks (CRNs) is a promising paradigm to increase spectrum efficiency and achieve flexible resource allocation. However, previous works either lack the consideration of channel uncertainties or ignore the effect of imperfect spectrum sensing. In this paper, we focus on the power control for a downlink OFDM-based CRN with the...
Traditional spectrum allocation policies may result in temporarily unused radio spectrum. Cognitive radio (CR) has emerged as a promising technology to exploit the radio spectrum in a more efficient manner by allowing spectrum sharing between secondary users (SUs) and primary users (PUs). Power control and beamforming are two key techniques in CR design used to maximize the benefits of SUs, yet to...
Subspace methods have been widely used in blind channel estimation of MIMO-OFDM system. However, direct subspace decomposition suffers from heavy computation complexity of o(N)³. In this paper, a new data projection method (DPM) based principal and minor subspace tracking algorithm is presented by exploiting a novel orthonormalization matrix. The new algorithm exhibits good numerical stability and...
Multiantenna wireless systems have been well studied in achieving high data rates. In this paper, we improve a subspace-based blind channel estimation technique for multi- input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) approach based on tracking the subspace recursively. The recursive subspace algorithm has a computational complexity of O(J2) , where the J is the input...
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