| 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 a cellular fax call over the cellular communications channel from that portion of the cellular fax call through the PSTN. Fax information is transmitted over the PSTN-portion of the cellular fax call using a "1-D" fax compression scheme. However, fax information is transmitted over the cellular-portion of the cellular fax call using a "2-D" fax compression scheme and a data modulation as specified in AT & T Paradyne's "Enhanced Throughput Cellular" (ETC) Protocol. The fax terminal equipment at the cellular end of the cellular fax call is configured to perform fax compression/decompression using the "2-D" fax compression scheme. The PSTN-side modem of the cellular modem pool performs the translation between the "2-D" and "1-D" fax compression schemes transmitted on the cellular-side and PSTN-side, respectively. |
