Filter design with optimized numbers of data streams for multi-pair two-way relaying under asymmetric rate requirements

A multi-pair two-way relaying scenario with multi-antenna nodes is considered. The bidirectional communications between the nodes are supported by an intermediate non-regenerative multi-antenna relay station. It is assumed that the nodes can subtract the back-propagated self-interference. In such a scenario, the required data rates for each direction of transmission are typically different which is considered by introducing asymmetric rate requirements. To maximize the achievable sum rate under asymmetric rate requirements, a strategy to optimize the number of simultaneously transmitted data streams of each node is presented. Furthermore, a weighted self-interference aware relay transceive filter as well as transmit and receive filters at the nodes are proposed. Additionally, the transmit powers of the nodes are optimized with respect to the transceive filter at the relay station and the asymmetric rate requirements. The aforementioned approach achieves higher sum rates compared to conventional approaches which do not optimize the number of simultaneously transmitted data streams of each node.