User-Centric Clustering in Cell-Free Networks with Dynamic TDD

Samuel S Silva, Yuri C. B. Silva, Igor M. Guerreiro, Victor Farias Monteiro, Matheus D. Carneiro, Abraão de Carvalho Albuquerque

DOI: 10.14209/sbrt.2025.1571157298

Evento: XLIII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais (SBrT2025)

Keywords: Cell-Free system MIMO D-TDD

Abstract

This work investigates the performance of a cell-free multiple-input multiple-output (MIMO) system with dynamic time division duplex (D-TDD), in which user-centric clustering algorithms are introduced as an additional stage to dynamically allocate access points (APs) at each time slot. This additional step enables an AP to simultaneously serve multiple user equipment (UEs) transmitting in the same direction. The implementation of these algorithms, incorporating an additional clustering step, is motivated by the fact that assigning an AP to serve multiple UEs does not significantly increase the system's interference levels; however, it can enhance the signal strength received from or by a given UE. The results indicate an advantage in applying an additional clustering step-or, conversely, a disadvantage in maintaining disjoint clusters of UEs transmitting in the same direction. This additional step yields greater performance improvements for uplink (UL) transmissions. This outcome can be explained by the fact that, when an AP is allocated to serve multiple UEs, the resulting increase in interference levels for downlink (DL) UEs is not substantial compared to the gain in received signal strength. In contrast, for UL transmissions, no additional interference is introduced, while the received signal strength increases significantly due to the larger number of antennas available to serve each UE.

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