For the purposes of the present document, the terms and definitions given in TS 21.905 and the following apply. PoC session: Right to Speak:

For the purposes of the present document, the following abbreviations apply: AMR AS BER CCF CN CS CSCF DL DTM ECF FBC GERAN GGSN GPRS I-CSCF IE IM IMS IP ISC NAS OCS OMA P-CSCF PCO PDP PoC PS PSI QoS RAB RB RD RL RLC RRC RTP RtS S-CSCF SBLP SDP SDU SGSN SIP SMS TBF TCP UDP UE UMTS UTRAN XDMS

The 3GPP system shall provide the capabilities to support the PoC service architecture as specified in OMA. It is assumed that the PoC architecture makes use of the following IMS capabilities in the 3GPP system, which are described in TS 23.228 and TS 23.141:

• Registration;
• IMS routing capabilities, including discovery and address resolution;
• IMS security including authentication and authorization;
• IMS charging;
• SIP compression;
• IMS group management;
• Public service identities;
• Presence Service.

Commonality and differences with IMS conferencing require further study.

In order for 3GPP system to support services like PoC, certain PoC requirements will require additional analysis within 3GPP in order to determine that all necessary architectural support is in place via capabilities provided by the GERAN/UTRAN, GPRS and IMS. This clause captures the possible relevant requirements for the purposes of additional evaluation to ensure proper support is in place within 3GPP infrastructure:

• The PoC service entity may provide the originating user with an early indication to start to speak even before invited users accept the call.
• If the above condition is applied then the initiating PoC subscriber shall receive an indication if no participants receive the talk burst.
• The originating subscriber receives 'right-to-speak' (RtS) indication after certain time depending on the answer mode setting of the target PoC subscriber.
• Depending on the setting by the PoC subscriber, the right-to-speak indication can be given to the originating PoC subscriber before the target PoC subscriber is reached or at least one of the target PoC subscribers has to accept the PoC session before the 'right-to-speak' indication is given to the originating PoC subscriber.
• During the PoC session, the PoC service entity provides 'right-to-speak' indication to a PoC subscriber requesting to speak.
• In case of a chat group session, the communication between chat group participants shall be possible at the time the PoC chat group session is established, that is at least one participant has joined the chat session.
• The timing requirements for capabilities such as RtS shall be taken into account within 3GPP as specified in OMA PoC RD [7].
• Charging architecture requirements shall be taken into account as specified in OMA PoC AD [6].
• The user equipment, depending on its capabilities, shall support notification of incoming CS call during an ongoing PoC session as well as a notification of an incoming PoC session set up during an ongoing CS call.