Adaptive Feedback for Rician Channels Exploiting Channel Statistic Information

In multi-antenna multiuser downlink systems, an adaptive feedback scheme is proposed which is more efficient in Rician channels. First, a new concept of the angle distance distribution is introduced. Based on this theory and channel statistic information at the transmitter, we propose a limited feedback scheme in which the quantization codebook can be more close to the channel direction for each user. Moreover, without increasing the quantized error of the channel direction, this scheme can adapt the number of feedback bits to the strength of the line-of-sight (LOS) component of channel. The simulation results show that our scheme outperforms the strategies proposed for uncorrelated Rayleigh channels both on increasing throughput and on decreasing feedback overhead in Rician channels.