Design And Implementation Of IP Facsimile Module In Voice Gateway

Real-time FoIP(Facsimile over IP), born from the combined technology of IP and traditional facsimile communication, with the advantages of real time, easy operation, low cost and so on, has good prospect. Traditionally, the function of FoIP is realized in the voice gateway, which has too many functions to deploy the IP telephony system in large scale. As a result, the idea of gateway separation is presented: Voice gateway is divided into Media Gateway(MG), Media Gateway Controller(MGC) , Signalling Gateway(SG). Based on this separation, next generation network framework with the main technology of Softswitch is generated.Based on the idea of gateway separation mentioned above, Chengdu MP Data Communication Co. has reconstructed the voice gateway Software, which can be adapted to the future Softswitch framework better. The author is responsible for the job of adding IP Facsimile function in the new voice gateway software. The main work concerned includes:1. The protocols used in the Real-time FoIP communication are analysed,and the main job includes: The communication procedures between the facsimile terminal and the gateway based on the recommendation T.30; the communication procedures between gateways based on the recommendation T.38; the call establishment procedures between gateways based on H.323 and the call establishment procedures between gateways based on MGCP (Media Gateway Control Protocol)/H.248 in the Softswitch network.2. The supporting function of DSP to the IP facsimile is analyzed.3. Based on the gateway software framework of the Softswitch system, the designing, coding, and testing are finished, and the details of the job done here include: Adding Facsimile state machine in the call control module to control fax transmission, encoding and decoding T.38 UDPTL(Facsimile UDP Transport Layer) package in the driver module by using DSP voice processor, configuring shell commands relevant to the IP facsimile module.