6.2 Release

3GPP43.055Dual Transfer Mode (DTM)Release 17Stage 2TS

6.2.1 Release of packet resources

The release of a TBF shall follow the current procedures in 3GPP TS 44.060 [5]. The use of the main DCCH as a packet resource is stopped when the signalling connection is cleared (during a handover or assignment procedure) or when the mobile station enters the dual transfer mode.

6.2.2 Release of CS resources

In the case of the release of the CS connection while in dual transfer mode, the mobile station may abandon the packet resources.

Before the re-establishment of the packet resources, the mobile station may need to read all the relevant information contained in the SI messages that was not sent in the SACCH or the PACCH while in DTM. In order to reduce the interruption of the GPRS session at call release, the network sends a new message (PSI 14) on the PACCH when the mobile station is in dual transfer mode. This message contains

– most of the information in SI 13, if the PBCCH is not allocated; or

– the location of the PBCCH, if this is present.

If both the mobile station and the network support enhanced CS release, the network may delay the release of the CS connection until the mobile station has received the needed system information, in order to maintain the packet resources after release of the CS connection. The network shall initiate enhanced CS release by sending PACKET CS RELEASE INDICATION message. System information is provided to the mobile station with PACKET SERVING CELL SI message on the PACCH. Packet system information messages can also be sent as such on PACCH. The MS shall use PACKET SI STATUS or PACKET PSI STATUS message to indicate which messages have been received correctly. When the mobile station has received the required set of a system information it informs the network which in turn sends a CS connection release message to the mobile station. Upon release of the CS connection the mobile station enters packet transfer mode.

If the network is not able to use enhanced CS release (e.g. due to scarce radio resources, no support for enhanced CS release or no possibility to send missing system information) it shall send a CS connection release message to the mobile station indicating the mobile station shall abandon the packet resources after the release of the CS connection.

Figure 10c shows the exchange of messages when a CS connection is released and the MS maintains PS resources.

Figure 10c: Release of CS connection and maintaining PS resources