This paper considers an energy-limited cognitive relay network where asecondary transmitter (ST) assists to forward the traffic from a primarytransmitter (PT) to a primary receiver (PR), in exchange for serving its ownsecondary receiver (SR) in the same frequency. The multiple-antenna ST isassumed to be energy-constrained and powered by both information flow fromsource (PT) and dedicated energy streams from destinations (PR and SR), whichis called destination-aided wireless power transfer (DWPT) scheme. Then, therelay processing matrix, cognitive beamforming vector and power splitter arejointly de- signed to maximize the rate of secondary users under the energycausality constraint and the constraint that the demanded rate of primary usersis satisfied. For the perfect channel information state (CSI) case, by adoptingsemi-definite relax (SDR) technique and Charnes-Cooper transformation, theglobal optimal solution is given. To reduce the complexity, matrixdecomposition, zero forcing (ZF) scheme, and dual method are jointly employedto derive a suboptimal solution. For the imperfect CSI case, S- procedure isused to transform the worst-case robust problem into a tractable semi-definiteprogram (SDP). Simulation results reveal that our proposed DWPT scheme isgreatly preferred for both perfect and imperfect CSI cases when ST is close toPR/SR.
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