1 research outputs found
Cooperative Beamforming for Cognitive Radio-Based Broadcasting Systems with Asynchronous Interferences
In order to address the asynchronous interference issue for a generalized
scenario with multiple primary and multiple secondary receivers, in this paper,
we propose an innovative cooperative beamforming technique. In particular, the
cooperative beamforming design is formulated as an optimization problem that
maximizes the weighted sum achievable transmission rate of secondary
destinations while it maintains the asynchronous interferences at the primary
receivers below their target thresholds. In light of the intractability of the
problem, we propose a two-phase suboptimal cooperative beamforming technique.
First, it finds the beamforming directions corresponding to different secondary
destinations. Second, it allocates the power among different beamforming
directions. Due to the multiple interference constraints corresponding to
multiple primary receivers, the power allocation scheme in the second phase is
still complex. Therefore, we also propose a low complex power allocation
algorithm. The proposed beamforming technique is extended for the cases, when
cooperating CR nodes (CCRNs) have statistical or erroneous channel knowledge of
the primary receivers. We also investigate the performance of joint CCRN
selection and beamforming technique. The presented numerical results show that
the proposed beamforming technique can significantly reduce the asynchronous
interference signals at the primary receivers and increase the sum transmission
rate of secondary destinations compared to the well known zero-forcing
beamforming (ZFBF) technique.Comment: Submitted to the IEEE Transactions on Wireless Communication