The following clauses specify procedures, information flows and APIs about SEALDD enabled data transmission for XR application, including the SEALDD facilate PDU set handling.
Figure 9.12.2.1.2-1 illustrate the procedure for establishing XR data transmission connection, and the SEALDD facilitates the XR application to transmit its data between the VAL client and VAL server with RTP packetilization and PDU set inclusion.
Pre-condition:
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The VAL server can discover and select the SEALDD server by CAPIF functions.
Step 1.
The VAL server decides to use SEALDD service for XR traffic transfer and allocates address/port as SEALDD-S Data transmission connection information for receiving the data packets from SEALDD server. The VAL server sends Sdd_XRTransmission request to the SEALDD server discovered by CAPIF. The service request includes UE ID/address, VAL server ID, VAL service ID, SEALDD-S Data transmission connection information of the VAL server side, and optionally, the protocol description, the QoS information for the application traffic, e.g. QoS requirements.
Step 2.
Same as step 2 of
clause 9.2.2.2. For application multi-modal service, the SEALDD server derives PDU Set related assistance information based on received VAL service ID and/or VAL server ID, and protocol description for interacting with NEF/PCF.
Step 3-5.
Step 6.
The SEALDD client establishes XR transmission connection with the SEALDD server. The request includes the SEALDD client ID, VAL user/UE ID, VAL server ID, VAL service ID, SEALDD-UU flow IDs, and traffic descriptors for the multiple flows from the SEALDD client side. The SEALDD server sends the SEALDD traffic descriptors for multiple flows from SEALDD server side (e.g. address/port for multiple SEALDD-UU flow) to the SEALDD client, and may send the protocol description (UL related info) received from the VAL server to the SEALDD client in the XR transmission connection response. The response also includes a multi-modal SEALDD-UU flow ID which the SEALDD server allocates.
Step 7-8.
The XR application traffic is exchanged between VAL client and VAL server via SEALDD layer as described in
clause 9.2.2.2. If packetization indication indicates that SEALDD layer needs to perform packetization, the SEALDD server performs packetization and sends streaming data (e.g. RTP packet) via SEALDD-UU user plane (e.g. SEALDD/UDP/IP) to the SEALDD client for downlink application traffic. Similarly, the SEALDD client performs packetization and sends streaming data (e.g. RTP packet) via SEALDD-UU user plane (e.g. SEALDD/UDP/IP) to the SEALDD server for uplink application traffic. The SEALDD server and client also perform PDU Set inclusion (e.g. in RTP extension as defined in
TS 26.522), and if needed, stream session and transport management (e.g. RTCP, RTSP).