Link-Level Evaluation of Uplink Cell-Free MIMO in 5G NR over Frequency-Selective Channels

Cell-free (CF) MIMO has emerged as a promising next-generation technology, primarily due to its ability to provide uniformly high-quality service to all user equipments (UEs), regardless of their location. While existing research has extensively explored various aspects of CF systems—such as scalability, clustering strategies, power control, and precoding designs—there remains a notable gap in the literature concerning the physical layer performance of 5G New Radio (NR) within CF architectures. This paper addresses this gap by focusing on the Physical Uplink Shared Channel (PUSCH) transmission over frequency-selective channels. A comprehensive, 3GPP-compliant link-level simulator is developed to evaluate the performance of CF MIMO under realistic propagation conditions. Key physical layer parameters—such as subcarrier spacing (SCS), modulation and coding schemes (MCS) ranging from QPSK to 256-QAM, and the number of distributed radio units (RUs)—are systematically evaluated using Block Error Rate (BLER) as the primary performance metric. The analysis reveals that increasing the number of RUs significantly improves BLER due to greater spatial diversity and reduced UE-RU path loss. Additionally, the study shows that employing higher SCS values can effectively exploit frequency diversity, especially when the signal bandwidth exceeds the channel’s coherence bandwidth. By incorporating realistic channel estimation techniques, the analysis captures practical impairments and validates the robustness of the proposed system. The findings offer insights into spatial and frequency resource interactions in CF 5G NR, while guiding MCS selection for target BLER-SNR levels and supporting scheduler design and PHY abstraction in link-level simulators.