An Overloaded MIMO 2-Hop Network With Physical Layer Network Coding

This paper proposes an overloaded multiple-input-multiple-output (MIMO) 2-hop network with physical layer network coding for high speed wireless communications. The number of the spatial multiplexed signal streams can be raised to that of the transmit antennas in the proposed network even where the number of antennas on the relay is less than that on the terminals. The proposed overloaded MIMO network applies precoding and relay filtering to reduce computational complexity. Furthermore, we propose a technique to select the best filter among candidates relay filters. The performance of the proposed network is evaluated by computer simulation. The proposed filter selection technique attains a gain of about 1.5dB at the BER of $10 ^{-5}$ in the network where 2 antennas and 4 antennas are placed on the relay and the terminal, respectively. This paper shows that 6-stream spatial multiplexing can be exchanged between the terminals via the relay with 2 antennas.