  Due to the rapid growth of IoT and artificial intelligence, deploying neural
networks on IoT devices is becoming increasingly crucial for edge intelligence.
Federated learning (FL) facilitates the management of edge devices to
collaboratively train a shared model while maintaining training data local and
private. However, a general assumption in FL is that all edge devices are
trained on the same machine learning model, which may be impractical
considering diverse device capabilities. For instance, less capable devices may
slow down the updating process because they struggle to handle large models
appropriate for ordinary devices. In this paper, we propose a novel data-free
FL method that supports heterogeneous client models by managing features and
logits, called Felo; and its extension with a conditional VAE deployed in the
server, called Velo. Felo averages the mid-level features and logits from the
clients at the server based on their class labels to provide the average
features and logits, which are utilized for further training the client models.
Unlike Felo, the server has a conditional VAE in Velo, which is used for
training mid-level features and generating synthetic features according to the
labels. The clients optimize their models based on the synthetic features and
the average logits. We conduct experiments on two datasets and show
satisfactory performances of our methods compared with the state-of-the-art
methods.
