Real-Time Facsimile Communication Implementation In SIP UA

With its fast development during these years, the TCP/IP protocols based Internet has been the biggest network, carrying biggest scale of service and reaching every corner in the world. For its advantage of high efficiency in bandwidth use and low running cost, to transmit facsimile over IP network is becoming a new generation e-business service.On the other hand, for its versatility and flexibility, SIP (Sesssion Initialization protocol) has become the main stream among all the VoIP signaling protocols.Combining fax communication standards and SIP, this dissertation gives a new model of real time fax communication. In this model the standard SIP entity, the user agent is extended in function. The resulting SIP UA can inter-operate with Group 3 facsimile equipment, sending and receiving image documents real-timely. All fax functions are implemented in computer software, and no extra hardware is needed to make a fax call. Considering the current situation of fax technology and products, to achieve higher applicability of our system, we build a virtual class 1 modem interface based on the SIP session control function and on the implemented fax communication routines. This interface receives class 1 modem AT commands, maps them to corresponding SIP requests, and sends them out through the IP work. The presence of this interface makes old fax software whose operation was dependent upon modem device applicable today.This dissertation summarizes the real time fax communication technology, including the procedures of communication between group 3 fax devices, as well as analyzes and compares the relative merits of two IP fax communication technologies: pass-through and T.38 relay. After analyzing the signaling flow of fax session setup using SIP, we put forward a method of implementing real time fax communication capability in a SIP UA. In order to present the system design and implementation methods, we first give the general architecture, and more detailed depiction is covered in later chapters. According to the test results on the implemented prototype system, the system can be of practical value by given more optimizations.