Multiparty SS¶

The multi-party supplementary service builds on top of the Call Hold (HOLD) supplementary service.

A precondition for the multi-party service is that the served mobile subscriber is in control of one active call and one call on hold, both calls having been answered. In this situation the served mobile subscriber can request the network to begin the multiParty service.

Once a multiParty call is active, remote parties may be added, disconnected or separated (i.e. removed from the multiParty call but remain connected to the served mobile subscriber).

The maximum number of remote parties is 5.

Relevant Specifications¶

• 3GPP TS 22.084: Multi Party (MPTY) supplementary service; Stage 1
  • high-level description + definition
• 3GPP TS 23.084: Multi Party (MPTY) supplementary service; Stage 2
  • contains SDL state diagrams for VLR and MSC
• 3GPP TS 24.010: Supplementary services specification
• 3GPP TS 24.080: supplementary services specification; Formats and coding
• 3GPP TS 24.084: Multi Party (MPTY) supplementary service; Stage 3

Notes¶

• the previously held party will get notification by means of a single SS Facility with two components:
  • Invoke/NotifySS/CallRetrieved
  • Invoke/NotifySS/MPTYindicator
• the previously active party will receive
  • Invoke/NotifySS/MPTYindicator

Putting MPTY call on hold¶

this is typically done to do another call?

• Facility/Invoke/HoldMPTY

Splitting MPTY call to have a private conversation with one participant¶

• Facility/Invoke/SplitMPTY

Call termination¶

• simply use normal call clearing using the TI of the specific call

Retrieving a MPTY call¶

• Facility/Invoke/RetrieveMPTY
  • no call retrieved notification is sent to remote parties

SIP translation¶

• https://tools.ietf.org/html/rfc5850
• TS 23.231 Section 13.7 refers heavily on TS 23.205 sub-clause 13.7 but also shows an example message sequence chart
• TS 29.235 Section 7.7.5 refers heavily to TS 29.163