| The IMS media transmission adopts the single-path transmission mode which entirely depends on the bearer network,which is difficult to meet the development needs of IMS services due to the disadvantages of the transmission mode,such as difficulty of guarantying end-to-end QoS,prominent effect of bandwidth bottlenecks,low transmission efficiency,etc,which also has seriously hamperd the IMS business development.Multipath transmission can help to overcome bandwidth bottlenecks and improve the quality of transmission by distributing load to subflows,and it is an important direction of network transmission technology.Multipath transmission of realtime media is still in the primary stage and there is no available scheme at present,especially in the aspect of related transmission control mechanism.The RFC draft,draft-leiwm-tsvwq-mpts-ar,submitted by our laboratory,puts forward a framework of multipath transport system based on application-level relay which build a new mode of the IMS media transmission based on application-layer relay network.In compliance with the principle of IMS architecture,"Signaling control,QoS guarantees",to improve the efficiency of IMS media transmission through the means of multipath transmission.In the proposed framework,endpoints are allowed to use multiple paths,including relay paths and the default IP path,to transport data stream in a single session.A relay path may via one or more application-level relays which provide application-level relay services for endpoints.Multipath relay transmission system framework is based on IP network,which is a universal business independent multipath transmission scheme,and can be combined with many kinds of application systems,such as streaming media system,SIP system,file sharing system,etc.The IMS multipath transmission system proposed and designed by our laboratory is to apply the framework to IMS,which helps to promote the innovation of the high bandwidth business.This thesis designs a media session negotiation mechanism which support IMS media multipath relay transmission,and implements multipath nogotiation between network entities on signaling layer and relay-path-information's request and release.The main research contents and obtained achievements in the thesis are as follows.1)Session initial protocol and session description protocol extension methods supporting IMS media multipath negotiation are proposed and designed,the relevant signaling message process is designed.2)A design scheme that extend a function entity,MTCF,in IMS core network element,P-CSCF,to control multipath negotiation is designed,and the MTCF internal function entities supporting IMS multipath session negotiation are implemented.3)Multipath interaction interfaces between MTCF and relay controller,MTCF and P-CSCF,are designed,and the interface logic functions are implemented.4)In IMS multipath relay transmission system,cooperate with the user terminals and other functional entities in the system,verify the correctness of the signal extension MTCF multipath consultation control performance,and verify the feasibility of the media session negotiation solution that support IMS media multipath relay transmission.Results of the tests show that the design of IMS multipath relay transmission media session consultation mechanism that is applied to the IMS multipath transmission system meet the design requirement. |
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