Dominant Users Grouping Algorithm for Multiple RAUs-UEs Coordination in DAS System

Abstract-This paper concerns the coordinated transmission among multiple remote antenna units (RAUs) and user equipments (UEs) in distributed antenna system (DAS), where instantaneous channel state information (CSI) feedback of multiple links is a big challenge. By exploring the inherent relationship among coordinated UEs, the dominant UEs grouping algorithm is proposed only using long-term CSI in each proportional fairness (PF) scheduling decision. The so-called "dominant" refers to a subgroup of UEs as potential partners with higher probability to coordinate. In the proposed algorithm, each UE only needs to report a single value of large-scale fading (denoted as PL). At the central unit, use weighted PL instead of the resultant throughput to prioritize UEs, set the threshold according to the variance of all UEs' PL, and employ a simple scalar-wise metric for grouping. Performance evaluation shows that in contrast to the conventional methods, the proposed algorithm with twopart scheduling strategy can reduce about 20% of the feedback overhead and improve the UEs fairness. This proposal is more efficient for high-density hotspot areas where a large number of UEs exist to join the coordinated transmission.