Towards Context-aware Distributed Learning for CNN in Mobile Applications

Intelligent mobile applications have been ubiquitous on mobile devices. These applications keep collecting new and sensitive data from different users while being expected to have the ability to continually adapt the embedded machine learning model to these newly collected data. To improve the quality of service while protecting users’ privacy, distributed mobile learning (e.g., Federated Learning (FedAvg) [1]) has been proposed to offload model training from the cloud to the mobile devices, which enables multiple devices collaboratively train a shared model without leaking the data to the cloud. However, this design becomes impracticable when training the machine learning model (e.g., Convolutional Neural Network (CNN)) on mobile devices with diverse application context. For example, in conventional distributed training schemes, different devices are assumed to have integrated training datasets and train identical CNN model structures. Distributed collaboration between devices is implemented by a straightforward weight average of each identical local models. While, in mobile image classification tasks, different mobile applications have dedicated classification targets depending on individual users’ preference and application specificity. Therefore, directly averaging the model weight of each local model will result in a significant reduction of the test accuracy. To solve this problem, we proposed CAD: a context-aware distributed learning framework for mobile applications, where each mobile device is deployed with a context-adaptive submodel structure instead of the entire global model structure.