User Handover Aware Hierarchical Federated Learning for Open RAN-Based Next-Generation Mobile Networks

The Open Radio Access Network (O-RAN) architecture, enhanced by its AI-enabled Radio Intelligent Controllers (RIC), offers a more flexible and intelligent solution to optimize next generation networks compared to traditional mobile network architectures. By leveraging its distributed structure, which aligns seamlessly with O-RAN’s disaggregated design, Federated Learning (FL), particularly Hierarchical FL, facilitates decentralized AI model training, improving network performance, reducing resource costs, and safeguarding user privacy. However, the dynamic nature of mobile networks, particularly the frequent handovers of User Equipment (UE) between base stations, poses significant challenges for FL model training. These challenges include managing continuously changing device sets and mitigating the impact of handover delays on global model convergence. To address these challenges, we propose MHORANFed, a novel optimization algorithm tailored to minimize learning time and resource usage costs while preserving model performance within a mobility-aware hierarchical FL framework for O-RAN. Firstly, MHORANFed simplifies the upper layer of the HFL training at edge aggregate servers, which reduces the model complexity and thereby improves the learning time and the resource usage cost. Secondly, it uses jointly optimized bandwidth resource allocation and handed over local trainers’ participation to mitigate the UE handover delay in each global round. Through a rigorous convergence analysis and extensive simulation results, this work demonstrates its superiority over existing state-of-the-art methods. Furthermore, our findings underscore significant improvements in FL training efficiency, paving the way for advanced applications such as autonomous driving and augmented reality in 5G and next-generation O-RAN networks.