Robust cooperative beamforming for MIMO decode-and-forward one-way relay networks

Relays play a pivotal role in extending the service quality at the cell edges of LTE/LTE-A networks. In this letter, a one-way relay channel with a direct link which is equipped with multiple antennas at the source and relay nodes, acting in a half-duplex regime is investigated. To best design the precoder of the source and relay nodes, the channel state information (CSI) of both links are required. Usually, this information is not perfectly known. To overcome this limitation, a worst-case robust design is proposed in this paper. We assume that the CSI is known to conform to a ball-shaped uncertainty set. The design problem is formulated to maximize the achievable rate of the whole system while maintaining the regulatory constraints on the transmit power limits. The aforementioned design problem is formulated as a semi-definite programming problem, and two approximate convex counterparts are proposed. Finally, we numerically compare the data rates of both designs using extensive simulations. (C) 2019 Elsevier B.V. All rights reserved.