In the case of a cloud-based remote control system that enables users to control cloud-connected devices from anywhere at any time, costs tend to increase in proportion to the number of devices. Most of the costs are derived from a message broker, a key component of the system that keeps connections from devices and relays messages between users and devices. In this paper, we analyze the costs of the message broker under a typical remote-control workload and reveal that keepalive communication costs account for a non-negligible percentage of the total. Then, we present a novel method to reduce the costs. By using the message broker as an echo back server for NAT timeout measurements initiated from devices, the method allows each device to extend the keep-alive interval adaptively by itself while keeping availability of devices and without customizing the existing message broker. The method also keeps extra resource consumption caused by the measurements under control. Finally, we evaluate our proposal on a public cloud and confirm its cost-effectiveness quantitatively.

This paper presents the system architecture of bidirectional communication for remote control of home devices. The system architecture is designed in view of the requirements such as feasibility for typical home users, scalability, and responsiveness of interactive operations. The proposed architecture, named Mediation architecture, features use of WebSocket and the hosting of connections from a home device and a user application at the same server to achieve low-latency communication. The experimental results obtained in a testbed environment indicate that the proposed system provides low latency that is practical for an actual service.

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This paper presents the system architecture of bidirectional communication for remote control of home devices. For remote control systems, WebSocket is a promising technology since it is feasible for typical home users and enables low-latency communications of interactive operations. However, current WebSocket-based remote control systems do not take into consideration the problems concerning scalability and operational costs that exists in the case of large-scale environments. The proposed architecture, named Mediation architecture, features scalability and the hosting of connections from a home device and a user application at the same server to ensure low-latency communications. We also incorporate an automated scaling mechanism to reduce operational costs. It adaptively adjusts the number of WebSocket servers depending on their load states and automatically configures a newly launched server. The experimental results obtained in a testbed environment indicate that the proposed system provides low latency that is practical for an actual service and that works with moderate resource consumption. We also show that, as expected, the automated scaling mechanism detects the need to launch a new server or to isolate a down server and keeps the normal working state as a whole.

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