Design And Implementation Of VoIP Billing System Based On SIP

As an important part of NGN (Next Generation Network), VoIP (Voice over IP) is one of the hottest emerging technologies in telecommunication industry, which integrates technologies including voice signal, voice encoding and compression, network transmission, QoS, and real time transmission. Combining voice transmission with IP network, VoIP changes the carrying network and transmission way, greatly influences the traditional telecom market in the world, and challenges the running pattern of voice communication business.According to the signal technology, VoIP can be divided into two systems, i.e., H. 323 and SIP (Session Initial Protocol). SIP takes voice transmission business as a kind of application of IP network, which is simple, low-cost and convenient for business development, and therefore becomes the first choice to establish VoIP system.Currently, since all the technologies of VoIP have become relatively mature, VoIP is on the preparing phase of extension in scale. As one of the most important systems supporting for VoIP running, the status and significance of billing system of VoIP is becoming very crucial.This thesis presents the design and implementation of VoIP billing system based on SIP protocol. The main research is as follows:(1) Considering the special features and current charging status of VoIP billing system, this thesis puts forward a solution of the seamless integration of billing system with SIP system by using charging agent servers, and specifies the function modules and entities for the billing system. As for the special requirements of "one number with multi-terminals", this thesis proposes a way to differentiate different terminals by means of the head segment value at FROM field.(2) By building the third party VoIP testing platform, the thesis analyzes SIP message, and determines the starting and ending points of charge. By help of Visio, the general charging flow chart and thread composition figure of the core charging system and the phone-bar charging system are designed. Moreover, detailed design is made fromtwo aspects, that is, the executing flow chart of thread and the data flow among threads.(3) Based on the detailed design above, the thesis implements the function modules by using the object-oriented method. At this stage, solutions for the key problems are put forward, for example, employing hash-chain-table data structure to meet the demand of the query performance of the session-status table, adopting thread scheduler to improve the management and schedule of multi-thread, and using SIP parser to improve the data-collecting performance.(4) The system test environment is set up by connecting the third-party testing platform with the core billing system and phone-bar billing system, and the detailed testing is carried out on this test environment from such aspects as terminal compatibility, dialing delay and anti-pressure ability, etc.