The efficiency of the random beamforming technique strongly depends on the number of precoders.
To make the actual channel fading experienced on each PRB to be approximately i.i.d., we can employ random beamforming vectors that are identical within one PRB but independently generated between PRBs, because the random beamforming approach reduces the correlation between PRBs [25].
Specifically, we present and study selfish random beamforming (SRB), interference-aware random beamforming (IA-RB), both of which require no information exchange between cells, and random beamforming with limited coordination (LC-RB), where only the selected beam index is shared among BSs.
Furthermore, the performance of low-complexity random beamforming transmission with user scheduling in the same scenarios is analyzed in[19].
We introduce the zero-forcing beamforming and random beamforming into NOMA downlink multiuser system and give the feedback forms of channel direction information and channel quality indicator, which are transmitted by the candidate users via a limited rate channel.
Random beamforming at the downlink [2] is an attractive solution for spectrally efficient MIMO transmission requiring limited channel knowledge at the transmitter.
In this section, we introduce a random beamforming scheme for the downlink NOMA multiuser system with limited CSI feedback.
Among them, selfish random beamforming and interference-aware random beamforming need no information exchange between cells, while random beamforming with limited coordination (LC-RB) selects the beamforming vector and users with the help of a small amount of overhead signaling.
To be compatible with existing mobile communication systems, we consider two classic beamforming technologies: zero-forcing beamforming (ZFBF), which is a linear precoding and easy to be implemented, and random beamforming (RBF), which is specially designed for the transmitter with limited CSI feedback.
In this paper, we studied the ergodic capacity of dual-cell MISO broadcast channels with low-complexity random beamforming.
