A novel signaling for communication on MIMO Y channel: Signal space alignment for network coding

In this paper, we study a new network information flow for a multiple-input multiple-output (MIMO) wireless network system with three users and a single intermediate relay which of each is equipped with multiple antennas. In this system, each user wants to convey independent messages for different two users via the intermediate relay while receiving two independent messages from the other two users by using only two time slots. This network information flow is a generalized version of the two-way relay channel for more than two users case. We will call this network information flow as a dasiaMIMO Y channel.psila To achieve much higher multiplexing gain in the MIMO Y channel, we propose two novel signaling techniques, which are signal space alignment for network coding during the first time slot and network coding based interference nulling beamforming during the second time slot. By evaluating the multiplexing gain it is shown that the proposed signaling scheme significantly outperforms the conventional time division multiple access and multi-user MIMO schemes.