A Hybrid Approach Combining Non-Regenerative MIMO Two-Way Relaying and Direct Link Transmission

In this paper, two different transmission schemes which are based on the joint consideration of two-way relaying and direct link transmission are proposed. The considered scenario consists of two half-duplex multi-antenna nodes which want to bidirectionally exchange information under asymmetric data rate requirements. To enable the communications, the nodes can either perform transmissions via the direct link or via an intermediate non-regenerative multi-antenna half-duplex relay station, termed RS. To maximize the achievable data rates under asymmetric data rate requirements, a hybrid approach is proposed which combines the transmissions via two-way relaying and via the direct link using two orthogonal time resources. Furthermore, an approach is introduced which performs the transmissions either via two-way relaying or via the direct link depending on the instantaneous channel conditions. Additionally, a joint filter design approach for the spatial filters at the nodes and at RS is presented considering the same number of antennas at both nodes and at RS. The performances of the proposed transmission schemes are investigated by numerical results and it is shown that both schemes achieve higher data rates than conventional approaches which consider pure two-way relaying or pure direct link transmissions.