Abstract
This paper proposes a method that selects a set of transmission reception points (TRPs), a TRP group, to be connected for each user equipment (UE) to maximize the system throughput defined based on the generalized mean of the user throughput in a downlink distributed multi-input multi-output (MIMO) system. As a realistic assumption, the TRP groups to be selected are pre-determined by the system. We assume an overlapped TRP group (OTG) configuration where some TRPs can belong to multiple adjacent TRP groups. The OTG configuration improves the transmission quality for UEs positioned at the coverage-area border of adjacent TRP groups. The proposed method is actualized through autonomous decentralized control among UEs and TRP groups, which is favorable for implementation in a large-scale network. In the proposed method, each TRP group independently informs all UEs of supplementary information regarding the bandwidth allocated to newly connected UEs. Based on this information, each UE calculates a metric for selecting a TRP group and feeds back the metric value to the best TRP group showing the highest metric. Finally, each TRP group determines the UE to be newly connected, i.e., the one to be handed over from other TRP groups, based on the metrics reported by multiple UEs. Furthermore, to utilize fully the OTG configuration, quasi-optimal bandwidth splitting for the transmission of multiple TRP groups at the overlapping TRP is processed in a decentralized manner for given TRP-group-selection results after the update of TRP group selection. By repeating the above process, TRP group selection for all UEs that maximizes the system throughput is achieved. Computer simulations show the effectiveness of the proposed bandwidth splitting among TRP groups and the TRP group selection method in the OTG configuration compared to the conventional method based on the received signal power.
