Group 3 facsimile transmission over digital satellite land mobile networks

The main characteristics of a real-time bandwidth reduction approach are described whereby facsimile signals are demodulated and their associated protocols are converted by a facsimile interface unit (FIU) to a format suitable for transmission over Inmarsat-M digital satellite channels. The Inmarsat-M system is designed to serve land mobile customers, however, it is also readily used for maritime communications. The FIU concept was developed to allow off-the-shelf facsimile terminals to be interconnected via the PSTN through Inmarsat´s satellite networks and to permit the provision of enhanced user services by converting Group 3 facsimile protocols to broadcast operation. In addition, the FIU concept is designed to compensate for the longer access and transport link delays encountered in mobile satellite systems, and to permit facsimile call recovery procedures to be successfully concatenated with satellite channel error detection and recovery mechanisms