  In this letter, we propose two power allocation schemes based on the
statistical channel state information (CSI) and instantaneous s->r CSI at
transmitters respectively for a 2-N-2 cooperative multicast system with
non-regenerative network coding.Then the isolated precoder and the distributed
precoder are respectively applied to the schemes to further improve the system
performance by achieving the full diversity gain. Finally, we demonstrate that
joint instantaneous s->r CSI based power allocation and distributed precoder
design achieve the best performance.
