AI/ML for Mobile Networks: Release 19 Status and Future Challenges
Artificial intelligence (AI) and machine learning (ML) have become essential drivers of sixth-generation (6G) mobile networks. Unlike earlier surveys that mainly review high-level standardization progress, this paper focuses on the practical deployment barriers that remain after Release 19. We identify three open problems: dataset construction under 3GPP guidelines, cross-scenario and cross-simulator generalization, and baseline selection under joint performance-cost KPIs. These problems are examined through a CSI-feedback case study that uses both DeepMIMO (outdoor/indoor, ray-tracing) and QuaDRiGa (indoor-factory/highway, geometry-based stochastic) channel models. It reveals pronounced generalization challenges in zero-shot transfer, especially when models move across different simulators. A clear mismatch exists between deterministic ray-tracing and stochastic geometry-based modeling paradigms and leads to dramatic performance degradation. In contrast, pre-training on a source simulator followed by targeted fine-tuning on the target domain substantially mitigates these cross-simulator difficulties, and markedly outperforms zero-shot transfer. Attention-based models generalize better across the two physics regimes while keeping computational cost moderate. These results explain why the fine-tuning and LCM procedures already partially standardized in Release 19 are necessary, and they point to concrete next steps for scalable LCM, wider use cases, and multi-task learning.