Min-Max Approach to Arbitrary Unicast Transmission in Multi-Way Relay Network with Up and Downlink CSI Error

摘要

In this paper, we investigate a robust design of multi-way relay precoder for arbitrary unicast transmission (AUT) in the multiple-input multiple-output (MIMO) relay network, where each user having a single antenna communicates with the other user via a relay station (RS) having multiple antennas. We assume that both up and downlink channel state information (CSI) available at the relay is imperfect and the norm of the estimation errors have upper bounds, which are known to the relay. The robust precoder design is formulated as a min-max problem, where the worst case sum mean-square-error (MSE) at the receivers is minimized over the range of CSI errors under the transmit power constraint of the RS. In the worst-case analysis, the intractable optimization problem is transformed into a tractable form by approximating the cost function. On the other hand, the minimization problem can be transformed into a semi-definite program (SDP) with efficient numerical solutions. The robustness of the proposed design is demonstrated via computer simulations.