看36211协议,里边讲的挺清楚的:
Cell-specific reference signals aretransmitted on one or several of antenna ports 0 to 3.
MBSFN reference signals shall betransmitted only when the PMCH is transmitted. MBSFN reference signals aretransmitted on antenna port 4.
UE-specific reference signals are supported for single-antenna-porttransmission of PDSCH and are transmitted on antenna port 5, 7, or 8.
Positioning reference signals aretransmitted on antenna port 6.