Combining interference alignment and two-way relaying in partially connected networks with only local CSI

In this paper, a network consisting of several partially connected subnetworks where each subnetwork includes one relay is considered. “Partially connected” means that not all nodes are connected to all relays. Some nodes may be connected to multiple relays. The entire bidirectional pair-wise communication between the nodes takes place via the intermediate half-duplex amplify-and-forward relays, considering two-way relaying. The algorithm proposed in this paper is a closed-form solution which requires only local channel state information (CSI) to achieve interference alignment. The properness condition for the proposed algorithm is derived. The process of interference alignment is decomposed into signal alignment, channel alignment and transceive zero forcing. It is shown that all subnetworks can be investigated separately. This means the whole problem can be divided into subproblems. The simulation results show that the degrees of freedom increase for the considered partially connected network in comparison with the fully connected version of the considered network.