Multi-Input Physical Layer Network Coding in Wireless Two-Way Relay Networks

In this paper, we propose multi-input physical layer network coding (multi-input PLNC) for high speed wireless communication in two-dimensional multi-hop networks. In the proposed PLNC, all the terminals send their packets simultaneously for the neighboring relays to maximize the network throughput in the first slot, as well as the relays doing for the terminals in the second slot, which causes multiple signals to be received at the relays and the terminals. We propose linear precoding techniques that transform the multiple signal reception channel into parallel channels, in each of which the two-input XOR-physical layer network coding (XOR-PLNC) can be applied. The proposed precoding enables a simple XOR-PLNC decoder to be used at the relays and the terminals, even though all the terminals or the relays transmit their packets simultaneously. The proposed multi-input PLNC makes all the terminals exchange their packets to the neighboring terminals in only two time slots. The proposed multi-input PLNC makes more than 6-stream spatial multiplexing possible in spite of the number of antennas on the relay and the terminal. The performance of the proposed multi-input PLNC is confirmed by computer simulation. Because more than 6 antennas spatial multiplexing is performed by the proposed multi-input PLNC, the proposed PLNC achieves better transmission performance as more than 6 antennas are placed on the relay and the terminal in a two-dimensional network just like cellular networks.