MultiIoT: Towards Large-scale Multisensory Learning for the Internet of Things

The Internet of Things (IoT), the network integrating billions of smart physical devices embedded with sensors, software, and communication technologies for the purpose of connecting and exchanging data with other devices and systems, is a critical and rapidly expanding component of our modern world. The IoT ecosystem provides a rich source of real-world modalities such as motion, thermal, geolocation, imaging, depth, sensors, video, and audio for prediction tasks involving the pose, gaze, activities, and gestures of humans as well as the touch, contact, pose, 3D of physical objects. Machine learning presents a rich opportunity to automatically process IoT data at scale, enabling efficient inference for impact in understanding human wellbeing, controlling physical devices, and interconnecting smart cities. To develop machine learning technologies for IoT, this paper proposes MultiIoT, the most expansive IoT benchmark to date, encompassing over 1.15 million samples from 12 modalities and 8 tasks. MultiIoT introduces unique challenges involving (1) learning from many sensory modalities, (2) fine-grained interactions across long temporal ranges, and (3) extreme heterogeneity due to unique structure and noise topologies in real-world sensors. We also release a set of strong modeling baselines, spanning modality and task-specific methods to multisensory and multitask models to encourage future research in multisensory representation learning for IoT.

Iterative Refinement of the Approximate Posterior for Directed Belief Networks

Variational methods that rely on a recognition network to approximate the posterior of directed graphical models offer better inference and learning than previous methods. Recent advances that exploit the capacity and flexibility in this approach have expanded what kinds of models can be trained. However, as a proposal for the posterior, the capacity of the recognition network is limited, which can constrain the representational power of the generative model and increase the variance of Monte Carlo estimates. To address these issues, we introduce an iterative refinement procedure for improving the approximate posterior of the recognition network and show that training with the refined posterior is competitive with state-of-the-art methods. The advantages of refinement are further evident in an increased effective sample size, which implies a lower variance of gradient estimates.