Softswitch and IMS in NGN

Currently,softswitch and IMS become two important directions of the next generation network convergence.IP is their both carrier,and they both have the idea of separation of call control and carrier.But as a result of their system structure and trait,softswitch can become smooth transition of the old telephone network,and IMS has more flexibility in service application if compared with softswitch.In this paper,the concept of NGN,softswitch and IMS are introduced,also,the softswitch and IMS are simply compared,at last the opinion about the direction of network convergence is given.