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In this paper, we introduce a new technique that allows the coexistence of secondary users (SUs) with a primary user (PU), in the same frequency and time. The proposed technique (i.e., the cluster-based spatial opportunistic spectrum sharing (CB-SOSS) technique) exploits the spatial degrees of freedom resulting from the use of multiple antennas at both the secondary base station (SBS) and SUs; also...
This paper investigates the joint power control and transmit beamforming problem in multiuser cognitive radio systems (CR). Comparing to the conventional downlink transmit problems, joint power management and beamforming schemes in CR systems is more complicated because designers must take the interference to primary users (PUs) into consideration. Assuming perfect channel information to both CR users...
This paper addresses the problem of joint transmit beamforming and power control with receive beamforming for a multigroup multicast MIMO downlink channel. As receive beamformers, we consider the matched-filter beamformers and the optimal MMSE beamformers. We propose two low complexity transmit strategies and compare them with some known approximations of the solutions to certain max-min problems...
Cognitive radio technique has been considered as a strong solution of frequency scarcity due to the limitation of frequency resource. In this paper, we propose an orthogonal beamforming methodology which enables cognitive radio systems to coexist with primary users' systems in the same spectrum and region with no interference to the primary users' systems. The orthogonal beams are obtained using Gram-Schmidt...
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