Method and System for Implementing Single Radio Voice Call Continuity

[0051]The inventive concept of the present invention is as follows: after having received an available resource query message from a mobility management and control function (MMCF) entity, a resource and admission control function (RACF) entity of a visited network acquires degrade information of the current service of a user from a resource and admission control platform, and according to a candidate access network list in the available resource query message, checks the availability of the current resource of each candidate access network in the candidate access network list, so as to obtain the resource availability information of each candidate access network; and the RACF entity of the visited network carries out resource decision according to the degrade information, resource availability information and user information of the user.

[0052]As to those users with the QoS or priority thereof being degraded, the RACF of the visited network carries out resource decision thereon with r