Content for TS 22.101 Word version: 18.6.0
21 Voice Call Continuity
21.1 General
21.2 Support of Supplementary Services
21.2.1 Line Identification Services
21.2.2 All Call Forwardings
21.2.3 Call Waiting
21.2.4 Call Hold
21.2.5 Multiparty
21.2.6 All Call Barrings
21.2.9 All other Supplementary Services
21.3 Quality of Service
21.4 Security
21.5 Emergency calls
21.6 Charging
21.7 VCC Activation
22 IMS Centralized Services
22.1 General
22.2 Service Consistency
22.3 Service Continuity
22.4 IMS Services
22.5 Roaming Support
23 CS IP interconnection requirements
23.1 Introduction
23.2 IP interconnect
23.3 MSC server interconnect
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21 Voice Call Continuity |R7| p. 54
21.1 General p. 54
The 3GPP system shall be able to provide continuity between CS voice services (Teleservice 11 [14]) and the full duplex speech component of IMS multimedia telephony service [40] with no negative impact upon the user's experience of the voice service. This functionality is known as voice call continuity. Voice call continuity shall be executed when continuation of a voice service is required based on operator policy across a change in the connection of the UE to the 3GPP system as the user moves from using the CS domain to using IMS and vice versa.
The user experience shall be unaffected by the transition from a CS voice service to a full duplex speech component of IMS multimedia telephony and vice versa, and the user shall experience no disruption in the voice service provided. The voice service is continued with the same ME.
It shall be possible to support Voice call continuity between IMS and the CS domain belonging to different operators; i.e., when the user's IMS services are under the control of the home IMS and the user is roaming in the coverage of the visited CS network.
It shall be possible for an operator to enable or disable Voice call continuity for a given subscriber e.g. based on roaming conditions, terminal capabilities.
21.2 Support of Supplementary Services p. 54
The voice call continuity user's experience shall be such that, to the greatest degree possible, a consistency of service is provided regardless of the underlying communication infrastructure and technology. With regard to supplementary services, the general principle is that CS-based supplementary services only apply whilst a VCC subscriber is in the CS domain and equivalent services over IMS only apply whilst a VCC subscriber is in the IMS domain, although there are exceptions listed below. It is not required to synchronise the supplementary service settings of the CS domain with the related service settings of the IMS (e.g. different forwarding numbers may apply over CS and over IMS).
The following supplementary services apply. The impact on the supplementary services in case the VCC is executed for the calling party, the called party, or both is described below.
21.2.1 Line Identification Services p. 54
A user who has subscribed to the CLIP Supplementary Service and receives a call shall also receive the line identity or appropriate IMS information of the calling party.
The identity presentation is not changed for the duration of the call regardless of whether the call undergoes VCC.
If the CLIR Supplementary Service or IMS identity restriction is applicable to the call, then at call setup time the called user shall receive an indication that the identity is not available because of restriction.
The indication is not changed for the duration of the call regardless of whether the call undergoes VCC.
If COLP or a corresponding IMS service is applicable to a call the calling subscriber shall receive the connected line identity or appropriate IMS information at call setup time.
The identity presentation is not changed for the duration of the call regardless of whether the call undergoes VCC.
If the COLR Supplementary Service or IMS identity restriction is applicable to the call, then the calling user shall receive an indication at call setup time that the identity of the connected party is not available because of restriction.
The indication is not changed for the duration of the call regardless of whether the call undergoes VCC.
21.2.2 All Call Forwardings p. 54
It shall be possible to perform VCC on a call which was forwarded due to call forwarding supplementary services in the CS or redirecting services in the IMS.
21.2.3 Call Waiting p. 55
The functionality of call waiting supplementary service in the CS domain shall not be affected by the user's ability to undergo VCC.
21.2.4 Call Hold |R8| p. 55
It shall be possible to re-establish a call which has been put on hold before undergoing VCC, after the VCC has been performed.
21.2.5 Multiparty p. 55
It shall be possible for any party in a multiparty call to undergo VCC and to stay in the call. It shall be possible to terminate the entire multiparty call when the served mobile subscriber releases even if she is connected via the IMS after undergoing VCC.
21.2.6 All Call Barrings p. 55
If a call were to undergo VCC and that would result in the call being barred in the target domain/system, it shall be up to the home operator policy whether the call continues in the target domain/system, the call terminates, or VCC is not executed for the call.
21.2.7 Void
21.2.8 Void
21.2.9 All other Supplementary Services p. 55
Other supplementary services are not discussed in this section as they do not apply to calls in progress (i.e. they apply to call set up only) or their support and/or the need for standardised implementation has not been identified as critical for VCC in this Release.
21.3 Quality of Service p. 55
Voice call continuity shall not adversely impact the quality of the voice service experienced by the user.
21.4 Security p. 55
Voice call continuity shall not adversely impact the security of the 3GPP system.
Security mechanisms of the 3GPP system shall be reused for voice call continuity.
21.5 Emergency calls p. 55
Voice call continuity for emergency calls shall be applicable to dual radio and single radio UEs.
Voice call continuity of emergency calls shall only be performed when all the following conditions are met:
- the source network is IMS;
- the target network supports emergency calls;
- the user is moving out of coverage;
- the source and target network belong to the same operator;
- the target network supports voice call continuity.
21.6 Charging p. 56
It shall be possible to indicate in the charging information that a VCC event has occurred (e.g., so that appropriate ratings can be applied for the CS and IMS parts of the continued voice call).
21.7 VCC Activation p. 56
It shall be possible to activate VCC based on operator policies, taking into account any of the following:
- Radio conditions e.g. radio quality thresholds and related hysteresis
- Coverage availability e.g.: Always prefer I-WLAN, if certain SSID are available
22 IMS Centralized Services |R8| p. 57
22.1 General p. 57
The ICS user shall receive both registered and unregistered services in a consistent manner when the user accesses IMS either via the CS or the PS domain (both of which can be supported by 3GPP access networks or non-3GPP access networks). Support of UEs enhanced with ICS capability as well as UEs without ICS capability shall be possible.
22.2 Service Consistency p. 57
Subscribers shall have a consistent user experience regardless of the domain used, subject to the constraints of the UE and access network.
22.3 Service Continuity p. 57
ICS shall support service continuity between CS and PS domains (both of which can be supported by 3GPP access networks or non-3GPP access networks), subject to the constraints of the UE and access networks.
The service continuity shall include:
- Basic services
- Non mid-call services
- Mid-call services
22.4 IMS Services p. 57
The set of IMS services supported by ICS shall include at least the following, subject to the constraints of the UE and access networks:
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IMS Multimedia Telephony services, including:
- speech,
- video,
- fax,
- data (CS),
- Supplementary services defined within [40]; and
- Multimedia priority service.
- IMS emergency calls, including eCall.
22.5 Roaming Support p. 58
An ICS user shall be able to receive full ICS support from the HPLMN while roaming in the VPLMN, subject to the constraints of the VPLMN (e.g. roaming agreements, operator policies).
The Home operator shall be able to control if the UE enhanced with ICS capability shall act without ICS capability while roaming.
23 CS IP interconnection requirements |R8| p. 59
23.1 Introduction p. 59
CS IP interconnect represents the interconnection of MSC Server functionality between 2 CS networks over an underlying IP infrastructure.
23.2 IP interconnect p. 59
The IP connection used for CS IP interconnect shall be generic such that it can support all combinations of core network interconnection. E.g. the IP interconnection shall be shared between the IMS interconnection and the CS IP interconnection.
It shall be possible to handle the inter-connection of all services over this generic IP interface. The handling of security and charging shall also be generic for all IP interconnect scenarios.
23.3 MSC server interconnect p. 59
The following requirements apply at the interconnection point when two PLMNs are interconnected by means of IP transport technology for 2G and 3G CS services.
The system shall support the capability for CS service interoperability and interworking.
It shall be possible to apply operator defined policy at the interconnection point.
The system shall support the capability to control the session resources when two different network domains are connected that may have, for example, different IP addressing schemes.
The system shall support IP inter-connection between core networks either by direct connection or by using an intermediate carrier (e.g. GSMA IPX [43]).
The system shall support both bilateral interconnection between two carriers and multilateral interconnection (e.g. GSMA IPX [43]) by means of intermediate carrier.
The system shall support either
- transparent relay of the IP signalling and traffic;
- service aware interconnection
