On the Achievable Rate of MISO Fading Channels With Instantaneous CSI Only at the Transmitter

We investigate Multiple-Input Single-Output (MISO) fading channels with perfect instantaneous Channel State Information (CSI) at the transmitter and with statistical average CSI at the receiver. We outline achievable rates for maximum ratio transmission and show that the rate loss of not having instantaneous CSI at the receiver behaves like an additional noise term whose variance is equal to one fourth of the transmit power. Similar results are obtained for equal gain transmission. The simulation results are in agreement with the theoretical bounds and indicate that requirement of instantaneous CSI at the receiver becomes obsolete up to a certain transmit power.