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Entry type: Product note Entry ID: 48034649, Entry date: 01/25/2011

Conversion from GSM-CSD services by Deutsche Telekom (T-Mobile)

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Deutsche Telekom will convert the CSD service in GSM networks to IP technology. This affects all systems that utilize this service, in particular it affects the data transmission in SINAUT ST1 and ST7 systems.




Deutsche Telekom has announced that it will convert the CSD (Circuit Switched Data) service (data call) in the beginning of 2011. Deutsche Telekom will completely convert CSD (data call) to IP technology in its networks. As a result, it must be expected that the CSD service will require higher latencies or longer round trip times. This can cause problems in applications that use this service. These applications also include SINAUT ST1 and SINAUT ST7 data transmission in the GSM dial-up network. SINAUT ST7, however, offers options for users to respond to the changed runtime behavior, so that SINAUT ST7 systems can continue working properly.

In addition, we recommend that users consider a conversion to GPRS data transmission.

Important: The GPRS service (packet-oriented data service) is NOT affected by this.


Link to the Telekom website:






The conversion of the CSD (Circuit Switched Data) service at Deutsche Telekom will probably result in longer runtimes or round trip times.

The increase in round trip times (latencies or signal delay times) by up to 2 seconds (in the worst-case scenario up to 8 seconds according to Telekom) can have negative effects on GSM connections that are based on the CSD service and are used in a SINAUT system. Generally, it must be expected that data transmission will be slower and that connections must be established for longer periods. In addition, the connection stability might become impaired, i.e. connections are interrupted more frequently then now and must be re-established by the system. This might result in higher connection costs.


Possible solution:

In the SINAUT ST7 system, there is an "additional transmission time" parameter available in the properties of the TIM module (HW Config or NetPro). This property is preset to 1000 ms for GSM applications and should be increased, for example, to 2000 ms.

However, since it is not certain that the announced latencies of 2 seconds will be actually observed, it may be necessary to set an even higher parameter value.


The situation is not as good for the SINAUT ST1 system, since it is not possible to respond to the increased runtimes. The SINAUT ST1 TIM uses a fixed value that cannot be configured. Should the increased runtime cause problems in connection with ST1, this can only be resolved by switching over to ST7.


In general, the CSD service is obsolete. There will be no technical innovations based on CSD (data call). It is more likely that the provider will discontinue the service at some point in time. The obvious trend is that providers are consistently focusing on packet-oriented services (GPRS / UMTS). Therefore, customers should consider a migration to GPRS in the short or medium term.

In many cases, with SINAUT ST7 it is possible to switch from CSD data call to GPRS data transmission without any problems.

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