Design And Implementation Of Embedded Service Logic Subsystem On Softswitch

The evolution of PSTN to NGN requires softswitch to provide or support the original supplementary services of PSTN. The Embedded Service Logic Subsystem (ESL) is a module of softswitch system software, which is used to provide supplementary services for the softswitch. Currently, the Embedded Service Logic Subsystems of some of the soft switches have the following problems:one is that the coupling degree of the Embedded Service Logic Subsystem and the Call Control System is too high; the other problem is that the newly added services are not flexible enough. However, the Embedded Service Logic Subsystem designed by this paper has effectively avoided the above problems.This paper firstly analyzes and introduces the NGN, softswitch and intelligent network which is relative to the design and realization of ESL subsystem; then it specifically explains the design of the ESL, specially focusing on the frame construction, key processing and specific service logic design of ESL; when explaining the realization of ESL, the paper focuses on the calculation and flow of message processing conducted according to different message sources and types; at last, it introduce the testing of the ESL subsystem, focusing on the functional test.The idea of design of this paper has already been put into practice and proved to be clear with reasonable partition of the system modules, and to be good for the update of system and the add of the new services, and to be able to well instruct the R&D work. The high cohesion low coupling design of the system modules has made the partition and encoding of the system convenient and improves the R&D efficiency. In addition, through the classification of the messages into several processing modes according to different sources and types, the difficulty and complexity of system realization have been greatly simplified. The plug-in design of SL has made the adding and deletion of services more flexible.The Embedded Service Logic Subsystem presented by this paper also has some limits. When adding new services, although it is convenient for expansion, it is required to compile program again after the development of new services. Thus the next step work is how to load logic control script of new service to achieve adding new service without compiling program again.