CSI-RS Based Joint Grouping and Scheduling Scheme with Limited SRS Resources

In time-division duplex (TDD) massive MIMO systems, multi-user (MU) grouping and scheduling is a key technology to improve spectral efficiency. However, in practice limited sounding reference signals (SRS) restrict the channel information acquired by base station (BS), which degrades the performance of MU grouping. To solve this problem, a joint grouping and scheduling scheme based on channel state information reference signal (CSI-RS) is proposed. Our scheme includes two processes. In the first process, we propose a metric to measure the channel accuracy of users estimated several periods before with the aid of un-precoded and beamformed CSI-RS. In the second process, a joint grouping and scheduling algorithm is implemented to distribute low-correlation users with acceptable channel accuracy into one group. Both low-speed and medium-speed circumstances are considered in our simulation using 3D MIMO channel model. In the cases of limited SRS resources, compared to the schemes that do not consider this impact, results show our proposed scheme can enhance the performance of users with low throughputs. Further, a better system sum rate can be reached at the same time.