OMA PoC and PDP Context Establishment

The set of OMA PoC specifications do not specify when resource reservations (e.g. setting up a PDP context for the media) should be done. The reason for this is that OMA develop services for general IP access. Instead it is the responsibility of the organizations developing the underlying access to specify if resources need to be reserved and in that case how and when resources are reserved for the service. The 3GPP developed a technical report (see 3GPP TR23.979 [2]) that addresses the issue of how resource reservation for PoC should be done.

Care was taken to avoid unnecessary delays in the PoC session setup for the establishment of the media bearer. According to the 3GPP proposal, the media bearer setup should start when the PoC session setup is completed and the PoC client starts to either send or receive the first media in the PoC session. Figure 8.10 shows the 3GPP proposal for the on-demand confirmed indication case. This means that in the typical case a part of the media in the first talk burst needs to be sent over either the bearer that the SIP signaling uses or a generalpurpose bearer that is available in parallel with the bearer used for SIP signaling. Thereafter the media will be transferred over the media bearer for the duration of the PoC session. To insure that this method works with acceptable quality for the PoC users, it is important that the switch of the media stream to the media PDP context is made seamless.

PoC Client A home network

PoC Client B home network

PoC Client A

PoC user A

PoC Server A| (Controlling & Participating)

PoC Server B (Participating)

PoC Client B

PoC Client A home network

PoC Client B home network

PoC Client A

PoC user A

PoC Server A| (Controlling & Participating)

PoC Server B (Participating)

PoC Client B

IMS Core A

MS Core B

Ims Session Establishment

Figure 8.10: Establishment of PDP context in an on-demand session using unconfirmed indication.

IMS Core A

MS Core B

Figure 8.10: Establishment of PDP context in an on-demand session using unconfirmed indication.

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