What is GSM CSD Service ?

Applies to the UMG8900 , Optional software feature for Circuit Switch Data (bearer/Fax)

The GSM circuit-switched data (CSD) services are basic telecommunication services that the UMG8900 supports. They are classified into bearer service and fax service.

• Bearer service

  Bearer services provide subscribers with the capability to transmit appropriate signals between access points. The services are lower-layer services which correspond to the physical layer, data link layer, and network layer. Bearer services are a prerequisite for a mobile telecommunication system to provide data services.

  In the Global System for Mobile Communications (GSM) CS domain, the UMG8900 supports BS20 asynchronous transparent bearer service and asynchronous non-transparent bearer service. In the Universal Mobile Telecommunications System (UMTS) CS domain, the UMG8900 supports the BS20 asynchronous non-transparent bearer service and BS30 synchronous transparent bearer service. Those bearer services differ in bearer capabilities.

• Fax service

  The fax service is a type of terminal services. It provides the complete service capability between the public land mobile network (PLMN) side and the public switched telephone network (PSTN), integrated services digital network (ISDN), or PLMN side. The fax service provides not only bearer capability for fax data but also fax service management.

  At present, the GSM and UMTS networks support the following fax services:

  • TS61: voice-to-fax services. A mobile subscriber provided with the TS61 service can switch the current voice call to a fax call at any moment during the conversation. If the subscriber wants to switch back to the voice call, the subscriber can do the switchover only after the fax transmission or one-page transmission is complete.
  • TS62: direct data services. A mobile subscriber provided with the TS62 service can set the fax machine to automatically initiate a call or answer a call.

This feature requires the cooperation of the media gateway (MGW), media gateway controller (MGC), and interworking function (IWF).