Spectral efficiency enhancement in the multi-user MIMO downlink with partial feedback information

In the multi-user multiple-input multiple-output (MIMO) downlink, co-channel interference (CCI) is the dominating impairment of the system performance. When channel state information (CSI) is completely available to the transmitter, a precoder rightly chosen based on the current CSI can effectively suppress CCI, and thus leads to simpler receiver structure. However, design of precoder based on only partial CSI is still an unsolved problem. Focusing on this point, this paper proposes a novel scheme using joint transmission, which completely eliminates CCI for each mobile terminal and thus enables simple and independent single-user signal detection. The proposed scheme requires only the principal right singular vector of each user's channel response matrix as feedback information. With adaptive modulation for each user, the spatial diversity of the MIMO channel can be sufficiently exploited, and therefore higher spectral efficiency attained. Simulation results show that the proposed scheme has better performance for spectral efficiency in either scenario with or without multi-user selection diversity than the existing scheme.