Investigation into MU-MISO transmission with limited feedback

Downlink multiuser transmission techniques that can serve several users simultaneously in frequency and time have been recently recognized as a promising means to significantly increase system capacity. A disadvantage of these techniques is that accurate channel state information at the transmitter (CSIT) is essential for their proper operation. In practice however perfect CSIT is hard to obtain. In this paper multi-user multiple-input single-output (MU-MISO) transmission with limited feedback is investigated. In particular two feedback design strategies are introduced. One allows users to cooperate in the sense that they can do feedback jointly, which is unrealistic but may serve as an upper-bound of achievable performance of a realistic system. The other is non-cooperative where each user feeds back its CSI in an independent manner. Simulation results show that multi-user transmission needs much more accurate CSI to perform well compared to single-user transmission even when cooperation between users is allowed