Worst-case robust MIMO relay precoding in cognitive two-way relay networks

In this paper, we investigate robust precoding for two-way relay cognitive networks consisting of a pair of cognitive transceiver users equipped with Multiple Input Multiple Output (MIMO) antenna communicating with each other through a common multi-antenna relay and sharing the same spectrum with primary users (PU). The uncertainty set in this CSI model is defined as Norm Bounded Error (NBE) model. We consider the Mean Squared Error (MSE) constraint at two secondary users (SU) and Interference Temperature (IT) at PU receiver that minimize the relay transmit power under multi CSI errors. We combine the semi-definite items and then transform the non-convex robust precoding problem into a Semidefinite Programming (SDP). This problem is solved efficiently using the numerical solver package CVX. Simulation results show the superior performance of proposed robust precoding design.