Dual Transfer Mode
Encyclopedia
Dual Transfer Mode is a protocol based on the GSM standard that allows simultaneous transfer of Circuit switched (CS) voice and Packet switched (PS) data over the same radio channel (ARFCN
). DTM is a 3GPP
baseline R99 feature.
A mobile phone which is DTM capable can be engaged in both CS and PS call and simultaneous voice and packet data connection in GSM/EDGE networks. The DTM Capability and the multislot capability of a mobile phone can be found in its technical specifications.
One common class implemented by mobile phone vendors is the DTM Multislot Class 11. For example, the technical specification of Nokia N95
states a speed of DL/UL 177.6/118.4 kbit/s. In 2010, devices with DTM multislot class 32 such as Nokia N900
are available.
A simultaneous voice and data call implies that a data call might start on an ongoing voice call or a voice call might start on an ongoing data call.
In case a voice is started on a mobile phone that is in Packet Transfer Mode(i.e. in a data call), the procedure takes place in three stages. The TBF's (Data "Call") are released. A dedicated connection for the voice call is initiated. Finally, the mobile phone uses DTM for re-establishing the data connection.
3GPP Release 6 specifies the Enhanced DTM CS Establishment and Enhanced DTM CS Release procedures to enable smooth transitions between the packet transfer and dual transfer modes, without having to release the TBF's. This enables continuous data transfer also when calls are set up and released, as well as reduced load on the common control channels of the GSM network. This technology is not yet supported by any operator.
As a side effect, in a network supporting DTM it is possible to have paging coordination (a service already provided by some operators based on a different network setup) for the GSM/EDGE devices engaged in data transfer. This means that incoming calls can be received also during packet data transfer sessions (be it web browsing, file download, or background services such as email), which is beneficial for both the operator (more calls are established) and the subscriber (calls come through persistently, i.e. also in case the device is engaged in data transfer).
Starting late 2009 or early 2010, Vodafone
has added DTM support in its network in the UK. In addition to enabling simultaneous call and data transfer in 2G network, DTM -capable network can also secure that incoming calls are received by devices that are transferring packet data (depending on the network implementation, this can also apply to devices that do not support the DTM feature).
ARFCN
In GSM cellular networks, an absolute radio-frequency channel number is a code that specifies a pair of physical radio carriers and channels used for transmission and reception on the Um interface, one for the uplink signal and one for the downlink signal. ARFCNs are defined in GSM Specification...
). DTM is a 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...
baseline R99 feature.
A mobile phone which is DTM capable can be engaged in both CS and PS call and simultaneous voice and packet data connection in GSM/EDGE networks. The DTM Capability and the multislot capability of a mobile phone can be found in its technical specifications.
One common class implemented by mobile phone vendors is the DTM Multislot Class 11. For example, the technical specification of Nokia N95
Nokia N95
The Nokia N95 is a smartphone produced by Nokia as part of their Nseries line of portable devices. It was released in 2007. The N95 runs Symbian OS v9.2, with a S60 3rd Edition user interface. The phone has a two-way sliding mechanism, which can be used to access either media playback buttons or...
states a speed of DL/UL 177.6/118.4 kbit/s. In 2010, devices with DTM multislot class 32 such as Nokia N900
Nokia N900
The Nokia N900 is a smartphone made by Nokia. It supersedes the Nokia N810. Its default operating system, Maemo 5, is a Linux-based OS originally developed for the Nokia 770 Internet Tablet. It is the first Nokia device based upon the Texas Instruments OMAP3 microprocessor with the ARM Cortex-A8...
are available.
A simultaneous voice and data call implies that a data call might start on an ongoing voice call or a voice call might start on an ongoing data call.
In case a voice is started on a mobile phone that is in Packet Transfer Mode(i.e. in a data call), the procedure takes place in three stages. The TBF's (Data "Call") are released. A dedicated connection for the voice call is initiated. Finally, the mobile phone uses DTM for re-establishing the data connection.
3GPP Release 6 specifies the Enhanced DTM CS Establishment and Enhanced DTM CS Release procedures to enable smooth transitions between the packet transfer and dual transfer modes, without having to release the TBF's. This enables continuous data transfer also when calls are set up and released, as well as reduced load on the common control channels of the GSM network. This technology is not yet supported by any operator.
As a side effect, in a network supporting DTM it is possible to have paging coordination (a service already provided by some operators based on a different network setup) for the GSM/EDGE devices engaged in data transfer. This means that incoming calls can be received also during packet data transfer sessions (be it web browsing, file download, or background services such as email), which is beneficial for both the operator (more calls are established) and the subscriber (calls come through persistently, i.e. also in case the device is engaged in data transfer).
Starting late 2009 or early 2010, Vodafone
Vodafone
Vodafone Group Plc is a global telecommunications company headquartered in London, United Kingdom. It is the world's largest mobile telecommunications company measured by revenues and the world's second-largest measured by subscribers , with around 341 million proportionate subscribers as of...
has added DTM support in its network in the UK. In addition to enabling simultaneous call and data transfer in 2G network, DTM -capable network can also secure that incoming calls are received by devices that are transferring packet data (depending on the network implementation, this can also apply to devices that do not support the DTM feature).