6 User plane interworking
29.2923GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem (IMS) and MSC Server for IMS Centralized Services (ICS)Release 17TS
6.1 General
The following subclauses define the interworking performed by the CS-MGW between the IM CN subsystem and CS domain access. The interworking between the Mb reference point and the user plane portions of the IuCS and A reference points is specified.
6.2 IuCS to Mb interworking
6.2.1 Interworking with transcoding
Figure 6.2.1.1 shows the user plane protocol stacks for the IuCS and IM CN subsystem interworking when transcoding is required.
Figure 6.2.1.1: IuCS to Mb protocol stack (transcoding)
IuFP is defined is defined in 3GPP TS 25.415 [16]. IuCS layer 2 and layer 3 are defined in 3GPP TS 25.414 [15]. The IuCS layer 1 is defined in 3GPP TS 25.411 [17].
6.2.2 Transcoder-less interworking
Figure 6.2.2.1 shows the user plane protocol stacks for the interworking when the same codec configuration is used on the IuCS and Mb reference points and transcoding is not required.
Figure 6.2.2.1: IuCS to Mb protocol stack (no transcoding)
If no transcoder is inserted, the CS-MGW shall interwork procedures between the IuCS and Mb reference points as specified in 3GPP TS 29.414 [18] clause 7.4.
6.3 TDM-based A-interface to Mb interworking
6.3.1 Interworking with transcoding
Figure 6.3.1.1 shows the user plane protocol stacks for the TDM-based A and Mb reference point interworking when transcoding is required.
Figure 6.3.1.1: TDM-based A to Mb protocol stack (transcoding)
Layer 1 for the TDM-based A-interface is defined in 3GPP TS 48.004 [19].
6.3.2 Transcoder-less interworking
Figure 6.3.2.1 shows the user plane protocol stacks for the interworking when the same codec is used on the TDM-based A and Mb reference points and transcoding is not required.
Figure 6.3.2.1: TDM-based A to Mb protocol stack (no transcoding)
6.4 IP-based A-interface to Mb interworking
6.4.1 Interworking with transcoding
Figure 6.4.1.1 shows the user plane protocol stacks for the IP-based A and Mb reference point interworking when transcoding is required.
Figure 6.4.1.1: IP-based A to Mb protocol stack (transcoding)
The IP-based A-interface user plane transport is defined in 3GPP TS 48.103 [38].
6.4.2 Transcoder-less interworking
Figure 6.4.2.1 shows the user plane protocol stacks for the interworking when the same codec is used on the IP-based A and Mb reference points and transcoding is not required.
Figure 6.4.2.1: IP-based A to Mb protocol stack (no transcoding)
The IP-based A-interface user plane transport is defined in 3GPP TS 48.103 [38].