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Distributed beamforming in cognitive relay networks with partial channel state information

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2 Author(s)
Piltan, A. ; Fac. of Electr. & Comput. Eng., K.N. Toosi Univ. of Technol., Tehran, Iran ; Salari, S.

In this study, the authors consider the problem of distributed relay beamforming in an underlay-based cognitive relay network in which a secondary network transmits its data using multiple relays under an amplify-and-forward protocol simultaneously with a primary network over the same spectrum. For such a network, assuming that the partial channel state information (CSI) is available, the authors study two different beamforming approaches to improve performance of the secondary transmissions while ensuring the quality-of-service of the primary transmissions. In the first approach, the authors obtain the beamforming weights as well as the transmit power of the secondary source such that the signal-to-interference plus noise ratio (SINR) at the secondary destination is maximised whereas the interference power from the secondary to the primary network is kept below a predefined threshold. In the second approach, the beamforming weights are obtained through minimising the received interference power at the primary receiver subject to a constraint on SINR at the secondary destination. The authors prove that both proposed approaches result in closed-form solutions. Simulation results show that as the uncertainty in CSI decreases, the proposed schemes achieve better performances. In addition, increasing the number of relays improves the overall system performance.

Published in:

Communications, IET  (Volume:6 ,  Issue: 9 )