Technique for sending faxes over cellular communications channels

摘要

A Mobile Switching Center (MSC) includes a cellular modem pool that comprises a number of pairs of modems in which the data terminal equipment (DTE) ports of each modem pair are cross-connected in a "back-to-back" fashion. This allows the two modems of each pair to interchange data via their DTE ports and thereby isolate that portion of the cellular fax call over the cellular communications channel from that portion of the cellular fax call through the public-switched telephone network (PSTN). Fax information is transmitted over both the PSTN-portion of the cellular fax call and the cellular portion of the cellular fax call using standard fax modulation techniques. The cellular-side modem of each modem pair is adapted to recover fax handshaking and data signaling from the received-fax modulated-signal and translate the recovered fax information into non-modulated signals (e.g. AT commands) for application to the corresponding PSTN-side modem of the modem pair. The PSTN-side modem, in a similar fashion, is adapted to recover fax handshaking and data signaling from the received-fax modulated-signal and translate the recovered fax information into non-modulated signals for application to the corresponding cellular-side modem.