Soft Real-Time Communication with WebSocket and WebRTC Protocols Performance Analysis for Web-based Control Loops

摘要

The web browser has become an access window for content and services. The browser is available on almost any device connected to the network, regardless of its intended use: desktop, mobile device, computing server, e-book reader etc. Browsers are used by people to read news, contact the world, to check a bank account, register a visit at the doctor, watching video content, electronic purchases, using web versions of the office package, etc. Universal availability, uniformity and intuitive handling, independence from hardware and operating systems are advantages over executable programs. Current applications in the field of automation include, for example, the implementation of user interfaces to present the state of the process and to accept operators' instructions in the form of web pages. The article considers network services and web browser as elements of the control loop. At least soft real-time (RT) work is needed for such applications. With the development of network protocols, the issue of providing RT transmission has appeared. There are currently two leading protocols taking into account the time aspects: WebSocket and WebRTC. The article compares their properties (mainly communication delays) in various network configurations and assess their suitability as an infrastructure of control systems. Selected techniques allowing to handle with delays in control loops are presented. Two control loops (simple PID loop and a multidimensional DMC) on web platform case studies are presented.