联合随机波束成形与迫零预编码的多波束选择

随机波束成形(RBF)在系统用户足够多时，具有与最优预编码方案相同的容量尺度，当系统用户少时，性能却下降严重。针对该问题，提出了联合RBF和迫零波束成形(ZFBF)的广播信道预编码方案。该方案利用RBF实现用户的初步调度，然后要求初选用户附加反馈量化的信道方向信息(CDI)和信道质量信息(CQI)，在基站根据CDI和CQI反馈完成最终波束选择和ZFBF预编码。仿真结果表明，所提出的预编码方案，与现有的增强型RBF相比，在基本不增加上行链路反馈量的前提下，可明显提高系统和容量。

Selection scheme for multi-beam by using random beamforming and zero-forcing precoding

Random beamforming (RBF) can yield the same capacity scaling as the optimal precoding scheme, in the large number of users regime. Unfortunately, for more practically low to moderate users, RBF yields degraded performance. We present a combined RBF and zero-forcing beamforming (ZFBF) precoding scheme for MIMO broadcast channels. Based on RBF, the initial scheduling is achieved, and then the selected users are requested additional feedback on quantified channel direction information (CDI) and channel quality information (CQI). The second user selection is implemented to maximize the achievable sum rate at the base station, and then we obtain the final precoding design by using ZFBF. Numerical results show that the presented precoding strategy significantly improve sum-rate performance, compared to the existing enhanced RBF scenario for systems with the not so large number of users, without increasing feedback bits.