A Study Of Bearer Independent Call Control

Based on the experiences in the research and development of circuit-switched (CS) domain of 3G core network, this document discussed the problems relevant to the bearer independent call control in soft-switched system, including the architecture and telephony routing of soft-switch network, media gateway (MGW) selection and how to control the MGW to realize the bearer control through MGW control protocol.By introducing Location Server (LS) and the concept of administrator domain into the telecomm network, IETF's TRIP-based architecture and telephony routing strategies of general soft-switch system were promoted. Then, aiming at the network characteristics and the control protocols adopted by the CS domain, the architecture, telephony routing and MGW selection of CS domain were studied. By adopting TRIP protocol in soft-switch system, the network architecture and network operations were simplified, dynamic telephony routing could be implemented, the capabilities of the network were improved and the trend of network convergences could be adapted.As to MGW selection, based on the resource congestion control package and overload control package of H.248 protocol, the call admission control (CAC) of MGW was discussed, and simple OPNET simulation of MGW CAC was described. The result of the simulation indicated that the application of MGW CAC ensured higher call success ratio and better network capability at the same time.In the last part of this document, MGW control was studied, and the way for MSC Server to identify the context and termination in MGW was introduced. By this way, the implementation of extensible, modularization MGW control functions was possible, and the logic of call control could be simplified, and, to some extent, call establishment was accelerated.