Precoder Design For The MIMO-Y Channel

In a MIMO-Y channel, three users communicate with each other through one relay node and it can be seen as a generalized network model of the two-way relay channel. In this paper, we studied, when the relays work at amplify-and-forward mode, the degrees of freedom of the MIMO-Y channel, analysis the achievable sum rate and introduce a precoding method to improve the sum rate.We first introduce the current development of the study for the MIMO-Y channel. Specially, this paper gives a detail description of the transmission strategy with two time slots and introduce the key concepts of the signal space alignment and the network-coding-based interference nulling beamforming when the relay works at decode-and-forward mode.In chapter three, a novel two time slots transmission strategy is proposed when the relay works at amplify-and-forward mode. The analysis shows that, when each user equipped with M antennas, the relay equipped with N antennas, and N≥[3M/2], 3M degrees of freedom can be reached, which is much better than conventional schemes.Chapter four considers the precoder design in user nodes and the relay node, and provides three algorithms to optimize the precoders of the relay or the user nodes. At the end of this paper, the simulation results show that the proposed precoding scheme can achieve significant improvement in sum rate performance with equal power allocation, compared with that of the without precoding case. Further more, the sum rate performance of the system can be further improved through the optimization.