Research On Railway Mission Critical Video Service Based On LTE-R

Railway mobile communication system is a key infrastructure necessary for the safe operation of high-speed railways,and has played a vital role in many aspects such as railway dispatching,fault monitoring,maintenance and repair,and emergency rescue.As the development direction of intelligent railways becomes more and more clear,the evolution of railway mobile communication system to broadband mobile communication system becomes inevitable.Railway dedicated broadband mobile communication system,LTE-R(Long Term Evolution-Railway)has advantages such as large bandwidth,high speed,and low latency.Therefore,in addition to traditional voice services,LTE-R can also meet the bandwidth requirements of multimedia services such as video and image,which in turn provides more guarantees for railway transportation security,operational efficiency,and service quality.The relevant standardization work around LTE-R services has been launched at home and abroad.However,through the investigation,it can be found that there are still the following limitations in the current research of LTE-R services:(1)The future railway mobile communication system user requirements specification issued by International Union of Railways only defines user requirements,but does not specify system architecture,service procedures and other aspects.(2)The 3rd Generation Partnership Project,3GPP proposes MCC(Mission Critical Communication)mechanism and related protocols,which provides an implementation method of trunking services.However,they are mainly for the scenarios such as public security and fire fighting,which do not meet the trunking service requirements of special scenarios(such as location addressing,functional addressing,etc.).(3)The current research achievements at home and abroad mainly focus on the field of voice communication in the trunking services,and the realization method of the video communication service in the future railway mobile communication system has not yet been clarified.In order to solve the above limitations,this thesis is dedicated to improving the LTER system architecture and designing the implementation scheme of the railway video service based on the LTE-R system.The work in this thesis mainly includes the following:Firstly,the LTE-R system requirement specification and service function requirement specification are analyzed and used as the basis for the scheme design.By comparing and studying 3GPP LTE,e MBMS(Evolved Multimedia Broadcast/ Multicast Services),MCC series protocols and architectures in the public safety system,a complete logical architecture of the LTE-R system based on the MCC mechanism is proposed.This architecture can be used to implement railway special video services,namely railway mission critical video.Then the implementation of the LTE-R-based railway video service is divided into two major steps to solve: The first step is,according to the special application scenarios and requirements of LTE-R services,the services procedures are designed using the timing diagrams.These services include location-based video services,function numberbased video services,and group communication services based on multicast bearers.The second step is to design and develop the application layer function modules MCVideo(Mission Critical Video)service and MCInformation(Mission Critical Information)service of the LTE-R system around the above service design.And the interface between the MCC application system and the multicast system and other interfaces used to support service implementation are designed,including the coding definition of signaling.So that the designed service procedure is implemented in the LTE-R system.Finally,with the LTE-R system and service requirements as the reference basis for the test,the service function,signaling process and performance are tested based on the laboratory LTE-R system test platform.The test results verify the rationality of the functions of the railway mission-critical video service based on the MCC mechanism and the group communication service based on MBMS bearer in LTE-R.In addition,by evaluating the performance,the key performance indicator and service optimization direction of the railway mission critical video service are analyzed and proposed,which are of reference significance for future research of LTE-R.