Dual Transfer Mode

Last updated: December 9, 2008

This section is only applicable to the lab applications, and to mobile stations that support Dual Transfer Mode operation.

This section details the following:

Dual Transfer Mode (DTM) Overview

Dual Transfer Mode (DTM) operation is a simultaneous CS (circuit switched) voice call and PS (packet switched) session on the same ARFCN.

See Dual Transfer Mode Concepts for more information.

Receiver Measurements

The GSM Bit Error (BER) measurement or Fast Bit Error (FBER) measurement can be run on a circuit switched timeslot during a dual transfer mode. Likewise, the GPRS BER and Block Error (BLER) measurements can be run simultaneous provided the connection type is set to ETSI Type B (Ack or Unack) or BLER. Other measurements available in DTM are GPRS BLER and the In-Band Frame Error (IFER).

Transmitter Measurements

All transmitter measurements are available during a DTM session. Transmitter measurements are restricted to a maximum of two uplinks. Therefore, transmitter measurements are not available for the 2x3 DTM multislot configuration.

Non-enhanced DTM

Once the Non-enhanced DTM is enabled, the test set allows a DTM session to be established if a CS connection (CS Voice Call) or a PS session has been established first. However, the PS session is aborted if a CS voice call is established while the PS session is active. see DTM Enable .

NOTE

CS data calls are not supported by the test set in conjunction with DTM in the test set.

Scenario 1: CS -> CS + MO PS

In this scenario a voice call (MO or MT) has been established and the MS requests a PS session. A DTM assignment message is used by the test set to request the MS to move the existing TCH to a timeslot specified by DTM Multislot Configuration and DTM CS Timeslot Position . DTM parameters are used to configure the CS voice call and PS session. Some TCH and PDTCH based parameters will have no effect during a DTM session. Once the voice call is dropped, the DTM connection is effectively finished and the TCH and PDTCH will revert to using their own configuration settings as normal.

Scenario 2: CS -> CS + MT PS

Establishing a mobile terminated PS session when a CS connection exists is similar to establishing a mobile originated PS session. The difference is that when establishing a mobile terminated PS session, there is no DTM Request message sent, because the data is sent from the test set.

Scenario 3: PS -> CS + PS

When a PS session exists and a mobile terminated or mobile originated CS voice call is attempted, the test set aborts the PS session before initiating the CS connection. Once the DCCH has been established for the CS voice call, the DUT may request the re-establishment of the packet resources by sending a DTM Request message. When a PS session is re-established, the TCP recovers and resends any lost IP data rather than recover the aborted downlink TBF. DTM parameters are used to configure the CS voice call and PS session. Some TCH and PDTCH based parameters will have no effect during a DTM session. Once the voice call is dropped, the DTM connection is effectively finished and the TCH and PDTCH will revert to using their own configuration settings as normal.

Scenario 4: Handover in a DTM session

Once a DTM session has been established, some Handover Setup parameters become inaccessible and will only become available again upon the release of the CS call. If a handover occurs, the deferred DTM parameters are used to configure the CS + PS session. See Immediate and Deferred Parameters for more information.

Enhanced DTM

The only difference between Non-enhanced DTM and Enhanced DTM is the behavior in the PS <-> PS + CS scenario, Enhanced DTM allows a CS voice call to be established without aborting the PS session, the test set can also delay the release of the CS connection until sufficient Packet System Information messages have been received by the MS so that the PS can be maintained without the presence of the CS connection. see Enhanced DTM Enable .

Operating Considerations

DTM capability is available in the following operating modes: Active Cell (GPRS), Active Cell (EGPRS), GPRS BCH+PDTCH+TCH , and EGPRS BCH + PDTCH + TCH .

DTM capability is available in the following connection types: ETSI Type A, ETSI Type B (Unack), ETSI Type B (Ack), BLER, Auto, and SRB Loopback.

If the mobile station requests a DTM session while on a circuit switched data call, a warning will be generated and the DTM Request will be rejected.

If the mobile station is not capable of DTM operation, it enters GPRS Suspend state after establishing the CS connection, which inhibits the test set from attempting any DTM procedures.

The test set does not support DTM operation while the Destination Channel is set to SDCCH. If a DTM session is in progress and a channel assignment occurs (that is, the Destination Channel and the Assignment Channel settings are changed to SDCCH), the DTM session is aborted prior to applying the change.

The PS data can not be sent on the timeslot used by the CS connection in the test set.

Configurable Parameters

Immediate and Deferred Parameters

Some of the DTM parameters have two styles: Immediate and Deferred. The Immediate DTM parameters are used when an attempt to establish DTM occurs and after DTM is triggered. The related PDTCH parameters revert after the DTM session has been released. This also holds true for some TCH and PDTCH Handover Setup parameters. The deferred DTM parameters are used instead when the handover occurs during a DTM session.

Selection of DTM vs. PDTCH Parameters

The table below shows the various connection transitions and how these transitions affect the DTM trigger status and the parameters selected for channel assignment.


Current Channel Configuration	Destination Channel Configuration	Current DTM Trigger Status	Resultant DTM Trigger Status	Parameters selected for channel assignment
None	*	Not Triggered	Not Triggered	N/A
CS	None	Not Triggered	Not Triggered	N/A
CS	CS	Not Triggered	Not Triggered	N/A
CS	PS	Not Triggered	Not Triggered	PDTCH
CS	CS+PS	Not Triggered	Triggered	DTM
PS	None	Not Triggered	Not Triggered	N/A
PS	CS	Not Triggered	Not Triggered	N/A
PS	PS	Not Triggered	Not Triggered	PDTCH
PS	CS+PS	Not Triggered	Triggered	DTM
CS+PS	None	Triggered	Not Triggered	N/A
CS+PS	CS	Triggered	Triggered	N/A
CS+PS	PS	Triggered	Not Triggered	PDTCH
CS+PS	CS+PS	Triggered	Triggered	DTM

* indicates any Channel Configuration.

DTM Enable
The operating mode must be set to Cell Off in order to change the state of DTM. DTM must be enabled in the test set in order to have simultaneous circuit switched voice and packet switched data connection. see Non-enhanced DTM for more information.

The command to enable DTM is CALL[:CELL]:DTMode .
Enhanced DTM Enable
The operating mode must be set to Cell Off in order to change the state of Enhanced DTM. Enhanced DTM must be enabled if you do not want to abort the PS session when an attempt to establish a simultaneous CS voice call is made. See Enhanced DTM for more information

The command to enable DTM is CALL[:CELL]:DTMode:ENHanced .
DTM CS Timeslot Position
This parameter allows you to set the timeslot position to be used within the DTM Multislot Configuration that the CS timeslot occupies. Valid CS timeslot positions vary depending on the selected multislot configuration. Also, the test set allows you to set the deferred timeslot position to be used within the deferred DTM Multislot Configuration that the CS timeslot will occupy following a handover execution. Valid deferred CS timeslot positions vary depending on the selected deferred DTM Multislot Configuration. See DTM Multislot Configuration for more information.

The command to set the immediate CS timeslot position is CALL:(PDTCH|PDTChannel):DTMode:CSWitched:TSLot . The command to set the deferred CS timeslot position is CALL:SETup:DTMode:CSWitched:TSLot . For instructions on how to manually set the CS timeslot position see Configure DTM CS Timeslot Position .
DTM CS Half Rate Sub Channel
This parameter indicates whether or not the half-rate subchannel is used for the CS connection while DTM is triggered. Note that the value will only have an effect when the current speech channel mode uses a Half Rate TCH channel (i.e. AHS and HS).

The command to set the immediate CS Half Rate Sub Channel is CALL:(PDTCH|PDTChannel):DTMode:CSWitched:HRSPeech:SCHannel . The command to set the deferred CS Half Rate Sub Channel is CALL:SETup:DTMode:CSWitched:HRSPeech:SCHannel . For instructions on how to manually set the CS Half Rate Sub Channel, see Configure DTM CS Half Rate Sub Channel .
DTM Multislot Configuration
You can set the DTM Multislot Configuration that is used when an attempt to establish DTM occurs and after DTM is triggered.

When the DTM is enabled, if a CS connection is active and an attempt is made to start a PS session while the multislot configuration for the PS session is DTM Invalid. the DTM attempt is rejected and a warning indicating an invalid DTM multislot configuration is generated.When the Enhanced DTM is enabled, if a PS session is active and an CS connection establishment is attempted whist the multislot configuration for the PS session is DTM Invalid, an encapsulated immediate assignment is sent to the DUT, causing the PS session to abort and the CS connection to establish. A warning is generated indicating an invalid DTM multislot configuration is being used.The PDTCH multislot configuration reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.

The command to set the immediate DTM Multislot Configuration is CALL:(PDTCH|PDTChannel):DTMode:MSLot:CONFig . The command to set the deferred DTM Multislot Configuration is CALL:SETup:DTMode:MSLot:CONFig . For instructions on how to manually set the DTM Multislot Configuration see Configure DTM Multislot Configuration .

You are allowed to position timeslots within the TDMA frame as much flexibility as possible. See Flexible Timeslot . To customized the DTM multislot configuration, use the GPIB command CALL:(PDTCH|PDTChannel):DTMode:MSLot:CONFig to set the multislot configuration to `Custom' , then use the GPIB command CALL:(PDTCH|PDTChannel):DTMode:MSLot:CONFig:CUSTom:TSLots to customize the multislot combination as your requirement. Note that all the timeslots in DTM custom multislot configuration must be contiguous.
DTM Traffic Band
The test set allows you to set the destination Band to be used in DTM-based channel assignment (or reassignment). Also, the test set allows you to set the deferred DTM Traffic Band to be used following a handover execution.

The command to set the immediate DTM Traffic Band is CALL:(PDTCH|PDTChannel):DTMode:BAND . The command to set the deferred DTM Traffic Band is CALL:SETup:DTMode:BAND . For instructions on how to manually set the DTM Traffic Band see Configure DTM Traffic Band .
DTM Traffic Channel
The test set allows you to set the destination Traffic Channel to be used in the DTM-based channel assignment (or reassignment). Also, the test set allows you to set the deferred DTM Traffic Channel to be used following a handover execution.

The command to set the immediate DTM Traffic Channel is CALL:(PDTCH|PDTChannel):DTMode:ARFCn[:SELected] . The command to set the deferred DTM Traffic Channel is CALL:SETup:DTMode:ARFCn[:SELected] . For instructions on how to manually set the DTM Traffic Channel see Configure DTM Traffic Channel .
DTM Frequency Hopping
The test set allows you to set whether the destination DTM channel assignment (or reassignment) implements frequency hopping or not. Also, the test set allows you to set the deferred DTM Frequency Hopping to be used following a handover execution. The PDTCH MA table is used for DTM Frequency Hopping, indexed by the DTM Band.

The command to set the immediate DTM Frequency Hopping is CALL:(PDTCH|PDTChannel):DTMode:FHOPping[:STATe] . The command to set the deferred DTM Frequency Hopping is CALL:SETup:DTMode:FHOPping[:STATe] . For instructions on how to manually set the DTM Frequency Hopping see Configure DTM Frequency Hopping .

The PDTCH Frequency Hopping reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
DTM Coding Schemes
The test set allows you to set the coding scheme for GPRS to use after the DTM channel assignment (or reassignment). Also, the test set allows you to set the deferred DTM Coding Schemes to be used following a handover execution.

The command to set the immediate DTM Coding Schemes is CALL:(PDTCH|PDTChannel):DTMode:CSCHeme:UPLink . The command to set the deferred DTM Coding Schemes is CALL:SETup:DTMode:CSCHeme . For instructions on how to manually set the DTM Coding Schemes see Configure DTM Coding Scheme .

The PDTCH Coding Schemes reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
DTM MS Tx Levels
When the MS Output Power Selection Mode is selected in either MS TX Lev mode or Alpha Gamma mode, the DTM Parameter and the DTM Handover Setup are changed to either MS TX Lev mode or Alpha Gamma mode followed.
- MS TX lev
  The test set allows you to set the ordered MS transmit power level for the individual bursts of the DTM session. Also, the test set allows you to set the deferred DTM MS Tx Levels to be used following a handover execution.
  
  The command to set the immediate DTM MS Tx Levels is CALL:(PDTCH|PDTChannel):DTMode:MS:TXLevel[:SELected]:BURSt<[1]|2|3|4|5> . The command to set the deferred DTM MS Tx Levels is CALL:SETup:DTMode:MS:TXLevel[:SELected]:BURSt<[1]|2|3|4|5> . For instructions on how to manually set the DTM MS Tx Levels see Configure DTM MS Tx Levels .
  
  The PDTCH MS Tx Levels reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
- Alpha and Gamma The test set allows you to set the power control power parameters alpha and gamma for the individual bursts of the DTM session. Also, the test set allows you to set the deferred DTM Gamma and DTM CS Gamma to be used following a handover execution.
  The GPIB command to set the DTM Gamma Burst parameter is CALL:(PDTCH|PDTChannel):DTMode:MS:GAMMa:BURSt<[1]|2|3|4>[:SELected] . The GPIB command to set the Deferred DTM Gamma Burst parameter is CALL:SETup:DTMode:MS:GAMMa:BURSt<[1]|2|3|4>[:SELected] . See MS Output Power for more information.
DTM Power Reduction Reference
The test set allows you to modify the downlink power reduction reference level of the bursts present in the DTM session. Also, the test set allows you to set the deferred DTM Power Reduction Reference to be used following a handover execution.

The command to set the immediate DTM Power Reduction Reference is CALL:(PDTCH|PDTChannel):DTMode:PZERo:LEVel . The command to set the deferred DTM Power Reduction Reference is CALL:SETup:DTMode:PZERo:LEVel . For instructions on how to manually set the DTM Power Reduction Reference see Configure DTM Power Reduction Reference .

The PDTCH Power Reduction Reference reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
DTM Measured Burst
The test set allows you to set the burst to be measured in the DTM session.

The command to set the DTM Measured Burst is CALL:(PDTCH|PDTChannel):DTMode:MSLot:MEASurement:BURSt . For instructions on how to manually set the DTM Measured Burst see Configure DTM Measured Burst .

The PDTCH Measured Burst reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
DTM Uplink State Flag
The test set allows you to modify the assigned uplink state flag for TBF use in the DTM session. Also, the test set allows you to set the deferred DTM Uplink State Flag to be used following a handover execution.

The command to set the immediate DTM Uplink State Flag is CALL:(PDTCH|PDTChannel):DTMode:USFLag[:ASSigned] . The command to set the deferred DTM Uplink State Flag is CALL:SETup:DTMode:USFLag[:ASSigned] . For instructions on how to manually set the DTM Uplink State Flag see Configure DTM Uplink State Flag .

The PDTCH Uplink State Flag reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
DTM Manual Unassigned USF
The test set allows you to modify the manual unassigned uplink state flag value for TBF use in the DTM session.

The command to set the DTM Manual Unassigned USF is CALL:(PDTCH|PDTChannel):DTMode:USFLag:UNASsigned[:MANual] . For instructions on how to manually set the DTM Manual Unassigned USF see Configure DTM Manual Unassigned USF .

The PDTCH Manual Unassigned USF reverts after the DTM session is released. See Selection of DTM vs. PDTCH Parameters for more information.
Operating Mode
There are two test mode operating modes that are offered specifically to support DTM in addition to the Active Cell operating mode (serving cell GPRS or EGPRS). See Operating Considerations details.

The command to set the operating mode is CALL:OPERating:MODE .

Reported Parameters

Additional mobile station parameters are available via GPIB and reported on the Call Setup screen. These parameters consist of the following:

DTM Class

The supported GPRS and EGPRS DTM Class are displayed on the Call Setup screen for the selected cell band, however you may query which GPRS DTM Class the mobile station supports for any of the following bands: PGSM, EGSM, DCS, PCS, RGSM, T-GSM810, GSM450, GSM480, GSM750, GSM850. In addition to which DTM class the mobile station supports for GPRS and EGPRS, the test set also displays if the class reported by the mobile station provides support for half rate DTM operation.

Note: The test set reports whether or not the mobile station can support half rate operation. However, the test set does not support half rate operation in DTM and so will not establish a half rate DTM connection.

Supported DTM Multislot Classes


DTM GPRS/EGPRS Multislot Class	1	2	3	4	5	5	6	7	8	9	9	10	11	12	30	31	32	33
Half-Rate Supported	No	Yes	Yes	Yes	No	Yes	Yes	Yes	*	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

*DTM GPRS/EGPRS Multislot Class 8 is not used. It is interpreted as Multislot Class 5.

The command to query the GPRS DTM Class is CALL:MS:REPorted:DTMClass:GPRS[:SELected]? .

The command to query the EGPRS DTM Class is CALL:MS:REPorted:DTMClass:EGPRs[:SELected]? .

Connection Status
The Connection Status of the CS voice and the packet switched data connection states are simultaneously displayed and updated when DTM is enabled.

The GPRS Suspended connection status is included in the packet switched state reported by the test set. GPRS Suspended is displayed when a GPRS mobile station suspends packet switched data transfer in order to transfer CS traffic rather than establish a DTM connection. Note: If your existing GPIB code queries the connection status, it must be updated to accept the new GPRS Suspended parameter.

The command to query the voice connection status is CALL:STATus[:STATe][:VOICe]? . The command to query the data connection status is CALL:STATus[:STATe]:DATA?

Dual Transfer Mode