Achievable Rate of Multi-relay Cognitive Radio MIMO Channel with Space Alignment

Conference paper
Part of the Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering book series (LNICST, volume 156)


We study the impact of multiple relays on the primary user (PU) and secondary user (SU) rates of underlay MIMO cognitive radio. Both users exploit amplify-and-forward relays to communicate with the destination. A space alignment technique and a special linear precoding and decoding scheme are applied to allow the SU to use the resulting free eigenmodes. In addition, the SU can communicate over the used eigenmodes under the condition of respecting an interference constraint tolerated by the PU. At the destination, a successive interference cancellation (SIC) is performed to estimate the secondary signal. We present the explicit expressions of the optimal PU and SU powers that maximize their achievable rates. In the numerical results, we show that our scheme provides cognitive rate gain even in absence of tolerated interference. In addition, we show that increasing the number of relays enhances the PU and SU rates at low power regime and/or when the relays power is sufficiently high.


Underlay cognitive radio MIMO space alignment Amplify-and-forward multiple-relay 


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Copyright information

© Institute for Computer Science, Social Informatics and Telecommunications Engineering 2015

Authors and Affiliations

  1. 1.Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) DivisionKing Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia

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