Srs Limited User Grouping Scheduling Algorithm For Downlink Massive Mimo Systems

In the time division duplex (TDD) communication system, the sounding reference signal (SRS) is used for uplink channel estimation and we can eventually obtain the downlink channel depending on the channel reciprocity. However, the limited SRS makes it impossible to estimate the channels of all users simultaneously if there are numerous users in a cell. This can degrade the performance of multi-user (MU) grouping and scheduling. In this paper, we present a user grouping scheduling scheme for TDD massive MIMO system under the SRS limited condition. The algorithm alliances several consecutive time and frequency domain resources to form a resource block group (RBG) set. The users are grouped and assigned to one RBG in a RBG set for channel estimation and scheduling, according to the approximate correlation through the channel information obtained by users in RBG. Under the SRS limited situation, simulation results show that the proposed scheme can increase the throughput of the system compared to the schemes without considering this impact.