# Clustering on the Chicago Array of Things: Spotting Anomalies in the Internet of Things Records
## 2 Related Work
### The Chicago AoT, Waggle, Eclipse, and SAGE  
The Waggle project [7] is the hardware platform used by the Chicago AoT. Developed by Argonne National Laboratory, Waggle incorporates a modality of sensors into the Waggle platform. In addition, virtualization of edge functions was added for researchers to perform analysis and management using cloud services. The paper focuses mostly on non-environmental sensing and is more interested in computer vision and counts of pedestrians and vehicles in the wild. This paper goes into detail about the components used in an AoT node. One computer controls the node, including sensor reading, reporting sensor data, data integrity checks, and managing security. This is only managed by system support staff, with the other computer used for edge processing. This computer utilizes the data received by the node to perform analysis. The node controller is in charge of transmitting any analyzed data. The central management server called a beehive, collects the data, registers new nodes, and manages encrypted connections between itself and the nodes. Security is handled by not allowing listening services, making the nodes fully autonomous. The Beehive only receives data from nodes and is available for interaction with system staff. This paper points out the Waggle manager node used for managing the different computers and payloads and its robustness to failure; the AoT nodes stay working despite one or more sensor payload failures. Lastly, this paper emphasizes the need for privacy when collecting sound and video data, mentioning that the AoT nodes preprocess images before the data are sent to a cloud database. The authors of [8] describe the AoT, its development, and the challenges and motivations for its construction. The AOT was developed with three goals in mind: (a) data analysis, (b) R&D for edge computing, and (c) R&D for new embedded hardware. These goals were determined after a series of scientific workshops. Cooperation with a city government and a modular hardware developer was needed. The city of Chicago, IL,USA, was chosen, and collaboration with Waggle, a platform designed for modularity and sensing in remote environments, began. One significant challenge and interest was privacy and usability; for the network to be viable if the Internet was lost and void of privacy issues, AoT needed edge computing capabilities to process data at the node before data were transferred to the cloud. This was performed so that audio and video were not transferred to the cloud; only the desired data from those streams were transferred (sound level and vehicle and person counts, respectively). An interesting thing to note here is that the goal of creating the AoT was not to perform anomaly detection but to provide data for researchers, a key reason for using this dataset in our research. This work also goes into detail about the waggle infrastructure, which is a robust, modular structure allowing local data storage for situations where Internet access is temporarily unavailable, secure encrypted communications between the hardware stack and the cloud, safety management between all components of the system, ensuring the system can run when one or more sensors are down permanently or temporarily, and redundant booting in the case of a system boot failure. Since drift in sensor measurements can occur over time and re-calibration of sensors over the whole network would be costly, measurement corrections were performed on the data. The authors of [9] reference the development of the Chicago AoT. This paper specifies that SAGE is the successor to Chicago AoT, an NSF-funded collaborative project. It further elaborates on the Waggle platform like previous papers have carried out. The work seen in [10] is a similar product to Chicago AoT and another successor project. This paper notes that many air sensors in the AoT dataset were susceptible to hardware failure during transport.