MIMO Physical Layer Network Coding Based on VBLAST Detection
  For MIMO two-way relay channel, this paper proposes a novel scheme, VBLAST-PNC, to transform the two superimposed packets received by the relay to their network coding form. Different from traditional schemes, which tries to detect each packet before network coding them, VBLAST-PNC detects the summation of the two packets before network coding. In particular, after firstly detecting the second layer signal in 2-by-2 MIMO system with VBLAST, we only cancel part of the detected signal, rather than canceling all the components, from the first layer. Then we directly map the obtained signal, summation of the first layer and the second layer, to their network coding form. With such partial interference cancellation, the error propagation effect is mitigated and the performance is thus improved as shown in simulations. 
Shengli Zhang, Canping Nie, Liya Lu, and Gongbin Qian
cs.IT math.IT