OWL: Worker-assisted server bandwidth optimization for efficient communication federated learning

Edge computing in federated learning based on centralized architecture often faces communication constraints in large clusters. Although there have been some efforts like computation-communication overlapping and fine-granularity flow scheduling towards how to reduce the communication cost, this is still a matter of ongoing research. Motivated by the underutilization of bandwidth among workers (edge devices) and the replication of deep neural network (DNN) model distributions in data-parallel federated learning, we propose OWL, a novel worker-assisted server bandwidth optimization method. OWL partitions numerous computation branches into groups based on the model's network topology , allowing for overlapping model distribution and computation among workers, thereby leveraging idle communication resources on the workers to compensate for server bandwidth. To address the issue of model distribution congestion on the server, we formulate group partition as an optimization problem , which proves to be NP-hard. We tackle this problem through a divide-and-conquer approach employing an approximation grouping algorithm and a deploying algorithm. Finally, we evaluate the performance of OWL through simulations and a comprehensive real-world case study involving model training on OWL and deployment on edge systems. Experimental results demonstrate that OWL reduces overall training time by up to 20%-69% and improves scalability by over 9.5% compared to state-of-the-art overlapping approaches. • We make a case on model distribution congestion problem in existing federated learning. • We show that idle bandwidth and non-linear DNNs enable better overlap strategies. • We design two efficient algorithms to schedule parameter communication to further overlap between edge devices. • We use real traces for experiments. • We implement a face-recognized punch clock in real world which is trained by OWL.