The Design And Implementation Of Train Audio Control System Based On SIP

Passenger Information System (PIS) is an important part of train system, and it is also a key platform for trains to provide passengers with information and service. It can be divided into three parts, broadcasting and intercom system, video surveillance system and passenger information display system. With the rapid development of train communication network, Ethernet-related technology is added to it, which further promotes the development of passenger information system.There are many voice transmission schemes on the aspect of train audio technologies. Using the analog voice transmission scheme in the train still occupies a large market. But gradually some train manufacturers have implemented a single, redundant ethernet network instead of the traditional voice communication technology. The rapid development of Voice over IP (VoIP) promotes flexible and expansive audio control technologies. Among them, Session Initiation Protocol (SIP) is a session control protocol which is widely used.In order to explore the audio application based on ethernet network in the train, some technologies of audio communication are introduced. And then a design scheme of PIS is proposed. In the scheme, an overall PIS architecture and functions of broadcasting and intercom system are introduced. A detailed description of click-to-dial model with SIP and offer/answer model with SDP is presented to illustrate the basic principles of system design better. Based on SIP, some basic models and control processes for the train broadcasting and intercom system are introduced, including driver call, emergency call, manual broadcasting, and digital broadcasting. With understand of the OpenSIPS software structure, a logic control module of B2BUA is designed and implemented. Above the SIPS server, an application responsible for the management of the audio system is designed. And then, the design and implementation of SIP end-devices are introduced.To test the scheme, a PIS platform is built, and the system test shows that the train audio control system can complete all the preset functions well. Now, the system has been used in a prototype system for a metro project in North America.