CSI-RS design for virtualized antenna when LTE and LTE-A efficiently coexisting

In this paper, we newly design a CSI-RS for virtualized antenna system when LTE and LTE-A are efficiently coexisting in Rel-10 and beyond. To this end, we newly insert a small amount of CSI-RS into the locations which is close to the existing CRS positions for legacy LTE as enough as possible. The newly designed CSI-RS modulated by space time coded signal efficiently works well for LTE-A UE channel estimation when the number of antennas involved in LTE-A system is larger than four which are normally used for LTE system as maximal. In such a legacy system with eight physical transmit antennas, eight antenna ports with eight orthogonal CSI-RSs are exploited for LTE-A system while virtualized four antenna ports are for LTE system. The benefit of the proposed solution is to significantly reduce the CSI-RS overhead, compared to the overhead employed in the existing Rel-10 system.