TS 22.129
Handover Requirements
between UTRAN and GERAN
or other Radio Systems
V18.0.0 (PDF)
2024/03 … p.
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- Rapporteur:
- Mr. Bleckert, Peter
Ericsson LM
Content for TS 22.129 Word version: 18.0.0
1 Scope
2 References
3 Definitions and Abbreviations
4 General Principles governing service continuity
5 Requirements for Handover
6 Requirements for Handover from UTRAN to GERAN
7 Requirements for Handover from GERAN to UTRAN
8 Cross Phase Compatibility for this release
A Illustration of elements in inter-PLMN handover
B Open Points on Inter-Operator Handover
$ Change history
1 Scope p. 6
The scope of this document includes service requirements for handover maintaining continuity of service to a wireless terminal as it moves between the radio coverage area, or "cells", associated with different base station sites. This functionality is called "handover". Handover can also occur due to change of radio resource providing a service without necessarily any change of the base stations involved. In particular, when the radio resources providing a service change from one of the UTRA radio access modes to the other (UTRA-FDD and UTRA-TDD), this is regarded as handover. Particular emphasis has been placed on the description of requirements for service continuity within UTRAN and between UTRAN and GERAN.
It is a key requirement to allow for dual or multi-mode terminals to handover traffic from UTRAN to GERAN and vice versa. This document describes the service requirements for intra- and inter- system handover.
The following subject areas are within the scope of these service requirements:
- User perceived performance that may be influenced by handover;
- Operational requirements relating to handover;
- Security requirements.
- The requirements are independent of the implementation of the UTRAN;
- The extent to which the requirements are met are in principle verifiable using observables that are not internal to the UTRAN.
1.1 Situations in which Service Requirements apply p. 6
The service requirements in this document are as far as possible independent of the implementation. They therefore apply to situations where handover would occur regardless of how the radio access network is implemented. Situations envisaged are:
- Handover within UTRAN due to change of radio resource caused by UE movement between areas covered by different transmitters;
- Handover within UTRAN due to change of UTRA radio access mode;
- Handover due to change of radio system.
- Where the technical implementation of the UTRAN necessitates handover as a matter of normal operation (i.e. not related to the above situations), then services shall in no way be degraded or adversely affected;
- The service requirements for handover occurring in situations such as O&M activity are outside the scope of this document.
2 References p. 7
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
3 Definitions and Abbreviations p. 7
3.1 Definitions p. 7
In addition to the following, abbreviations used in the present document are listed in TR 21.905.
For the purposes of the present document, the following definitions apply:
Connection mode (for a bearer service):
characterises the type of association between two endpoints as required by the bearer service for the transfer of information. A bearer service is either connection-oriented or connectionless. In a connection oriented mode, a logical association called connection needs to be established between the source and the destination entities before information can be exchanged between them. Connection oriented bearer services lifetime is the period of time between the establishment and the release of the connection.
Connectionless (for a bearer service):
In a connectionless bearer, no connection is established beforehand between the source and the destination entities; the source and destination network addresses need to be specified in each message. Transferred information cannot be guaranteed of ordered delivery. Connectionless bearer services lifetime is reduced to the transport of one message.
GERAN coverage:
an area where mobile cellular services are provided by a GERAN in accordance with GERAN specifications.
UTRAN coverage:
an area where mobile cellular services are provided by a UTRAN in accordance with UTRAN specifications.
Multi mode terminal:
UE that can obtain service from at least one UTRA radio access mode, and one or more different systems such as GERAN bands or possibly other radio systems such IMT-2000 family members.
Handover:
The process in which the radio access network changes the radio transmitters or radio access mode or radio system used to provide the bearer services, while maintaining a defined bearer service QoS.
Intra PLMN handover:
Handover within the same network, i.e. having the same MCC-MNC regardless of radio access system. Note: this includes the case of UTRAN ↔ GERAN handover where MCC-MNC are the same in both cases.
Inter PLMN handover:
Handover between different PLMNs, i.e. having different MCC-MNC.
Inter system handover:
Handover between networks using different radio systems , e.g. UTRAN - GERAN.
UTRA Radio access mode:
the selected UTRA radio access mode i.e. UTRA-FDD; UTRA-TDD.
Radio system:
the selected 2nd or 3rd generation radio access technology.
Service Continuity:
The means for maintaining active services during changes in the coverage areas or their characteristics without, as far as possible, the user noticing. Note that Service Continuity can be achieved by handover, cell re-selection or other mechanisms.
3.2 Abbreviations p. 8
For the purposes of the present document, the following abbreviations apply:
UE
User equipment
4 General Principles governing service continuity p. 8
4.0 General Principles for service continuity p. 8
The general principles for service continuity described in this specification refer to service continuity within the UTRAN, within the GERAN and between the UTRAN and GERAN. As a principle, the requirements on service continuity characteristics should be according to the target network on which the service is maintained.
Service requirements for seamless mobility between multiple heterogeneous access systems beyond only UTRAN and GERAN are contained within TS 22.278.
4.1 Service Continuity Scenarios p. 8
Service continuity shall support the following scenarios:
- Continuity of active CS services when moving within UTRAN, within GERAN and between UTRAN and GERAN coverage areas.
- Continuity of active GPRS sessions when moving within UTRAN, within GERAN and between UTRAN and GERAN coverage areas.
- Continuity of active IM Services when moving within UTRAN, within GERAN and between UTRAN and GERAN coverage areas (that support those IM services).
4.2 Service Continuity requirements p. 8
For all scenarios, the specifications shall cover both service continuity within the same PLMN (intra-PLMN) and between PLMNs (inter-PLMN), including the case where the PLMNs involved are operated by different network operators.
It shall be possible for a user to roam between the different parts of a shared network without requiring any user intervention. The user experience while roaming in a shared network shall be comparable to the user experience while roaming in a non-shared network.
4.2.1 Service continuity for CS p. 8
The scenario numbers in this table refer to the scenarios in clause 4.1.
| To CS services | |||
|---|---|---|---|
| UTRAN | GERAN | ||
| From CS services | UTRAN | Yes - Scenario 1 | Yes - Scenario 1 |
| GERAN | Yes - Scenario 1 | Yes - Scenario 1 | |
4.2.2 Service continuity for GPRS p. 9
Service continuity of GPRS sessions (conversation, streaming, interactive and background) is required within the GERAN, within the UTRAN, and between the UTRAN and GERAN (scenario 2 in clause 4.1 above).
4.2.3 Service continuity for IM Services p. 9
Service continuity of IM services is required within the GERAN, within the UTRAN, and between the UTRAN and GERAN (scenario 3 in clause 4.1 above).
4.3 General Operational Considerations p. 9
4.3.1 Coverage environment p. 9
Mechanisms defined to support service continuity between different radio systems or radio access modes should effectively cope with a number of coverage scenarios:
- Limited coverage in a 'sea' of coverage provided by another radio system or radio access mode, or vice versa;
- Selective operation at a geographical boundary, with extensive UTRAN coverage on one side and extensive coverage from another radio system on the other side;
- Geographically co-located areas of UTRAN coverage and another radio system.
4.3.2 Inter PLMN Handover Issues p. 9
Handovers to support service continuity between PLMNs should remain an optional feature to implement. It is envisaged that handover would take place due to changing radio conditions caused e.g. by movement of the terminal causing it to leave the coverage area of a PLMN.
The following networks may be involved with an inter-PLMN handover procedure. These concepts are illustrated in Annex A:
- The user's home network, i.e. the operator where the user's subscription may be found;
- The user's visited network where the subscriber user is currently registered, i.e. the network where the subscriber user has performed the last successful update location procedure. As long as the subscriber user is roaming within the home network, home and visited network are identical;
- The user's serving network covering the cell that serves the subscriber. After successful completion of the update location update procedure, the serving network is identical with the visited network. After an inter-PLMN handover, the visited network is different from the serving network until a location update procedure has been successfully completed (excepted the case that the subscriber returns into the visited network);
- The target network covering candidate target cell(s) for inter-PLMN handover. The target network has overlapping radio coverage with the serving network but not necessarily with the visited network.
- Continuity of an active call across the handover procedure, where this would be possible for intra-PLMN handover;
- The decision whether the handover request is accepted must be taken by the target network.
4.3.3 Charging and Network Management p. 10
Means shall be standardised which allow charging records to record the time of handover in the case of inter-PLMN operator handover. Charging records must be able to reflect the level of UTRA radio access, operation mode and network type after handover.
A capability to provide network management information relating to frequency of occurrence and type of handover should be defined.
4.3.4 Cost and efficiency p. 10
The UTRAN specifications shall facilitate the cost-effective implementation both on the network and on the terminal side, of multi mode operation between GERAN and UTRAN. Impacts on networks based on earlier releases shall be minimised. Such handover shall not require user intervention.
4.3.5 Security p. 10
Security requirements should embody the principle that handover shall not compromise the security of the network providing the new radio resources; the (possibly different) network providing the original radio resources; and the UE. The security mechanisms should also cater for appropriate authentication processes and meet the requirements of national administrations in terms of lawful interception.
4.4 Performance Requirements p. 10
4.4.1 Temporary degradation of service caused by handover p. 10
During intra UTRAN handover or handover from UTRAN to GERAN, degradation of service shall be no greater than during intra GERAN handover.
The duration of the discontinuity experienced by PS and CS real time services should be shorter than that in the handover of CS speech calls over GERAN.
5 Requirements for Handover p. 10
5.1 Handover due to UE Movement p. 10
It should be possible to provide a technical implementation of handover such that there is no measurable impact on the quality of any service when handover due to UE movement occurs. This does not imply that all handovers will achieve this ideal. However, the specifications shall define at least one UTRA radio access mode in which this is possible given the following:
- UE speed stays within limits for given service;
- UE stays constantly within UTRA coverage of a single UTRAN.
5.2 Handover due to negotiated service requirement p. 11
In order to allow the connection with the negotiated bearer- or teleservice to be established, means shall be defined, which makes it possible for the core network, to recommend to access network to handover the UE to another RAT better suited to support the desired bearer- or teleservice.
5.3 Handover between Radio Access Modes p. 11
The specifications shall permit a technical implementation of handover between radio access modes, although there may be a temporary degradation of QoS on bearer services at the time of handover.
5.4 Cell capacity p. 11
Consideration must be given services such as multimedia, which may involve use of multiple bearers. Due for example to cell loading, it may happen that a target cell cannot support the combination of bearer services provided by the current serving cell. Although all bearer services may not be handed over, the handover to another cell should not be precluded.
5.5 Handover of a Multicall p. 11
The handover event can trigger changes to individual calls in any multicall scenario.
It shall be possible to handover all the calls in a multicall configuration. If the target system is UTRAN and the target cell is not able to accommodate all the calls in a multicall configuration, then the calls that are handed over are selected according to operator preferences. If the target system is GERAN, then the call that is handed over shall be selected in following order:
- The call of teleservice emergency call ;
- The call of teleservice telephony;
- The call of any other type according to operator preferences.
5.6 Access Rights p. 11
It shall be possible to prevent handover to cells to which the UE does not have access rights. In this case, a handover to allowed cells shall be attempted. For this release this requirement only applies for UTRAN to UTRAN and UTRAN to GERAN handover in both A/Gb and Iu mode.
5.7 Handover for shared networks p. 11
Handover shall be supported within a shared network and between a shared network and a non-shared network.
The requirements that apply to inter PLMN handover between non-shared networks shall equally apply to inter PLMN handover between shared networks as well as between a shared and a non-shared network.
The network shall be able to make the decision on the most appropriate candidate for handover based on any combination of the following information:
- type of subscription (e.g. prepay / postpay)
- home network of the subscriber
- access rights
- connected core network
6 Requirements for Handover from UTRAN to GERAN p. 12
6.1 Operational Requirements p. 12
6.1.2 GERAN bands p. 12
The standard shall support handover to any combination of GERAN bands supported by the specifications.
6.2 Performance Requirements p. 12
The following service principles apply to performance requirements:
- When the UE performs handover to GERAN then the service requirements of GERAN that relate to handover between different cells in different location areas is taken as the benchmark. It is not the intention to set more stringent service requirements for UTRAN to GERAN handover than are already commonly accepted for handover within GERAN.
6.2.1 Detection Time of Potential GERAN Handover Candidates p. 12
Means shall be defined which allow the UE to achieve as good detection time performance as the GERAN benchmark: i.e. to behave in such a way as to detect potential handover candidates as quickly as a mobile performing an intra GERAN handover is required to do so.
6.2.2 Number of GERAN handover candidates to detect p. 12
Means shall be available which allow UE to detect an equal number of GERAN handover candidates relative to the GERAN benchmark, i.e. to behave in such a way as to detect as many potential handover candidates as a mobile performing an intra GERAN handover is required to do so.
6.2.3 Probability of Connection Loss p. 12
The service requirement is that it should be possible to hand over to GERAN from UTRAN with a probability of connection loss that fulfils the corresponding service requirement for intra GERAN handover.
6.3 Specific Requirements for Individual Services from UTRAN to GERAN p. 13
6.3.1 Speech p. 13
Handover of a CS Speech teleservice (TS11) from UTRAN to GERANis required. This requirement also applies to emergency calls (TS12):
- Any call based on the default UTRAN speech codec (AMR) shall be mapped to the FR GSM speech codec. In the case the terminal and the GERAN network support AMR and /or EFR and/or HR, it shall be the operators choice to define the appropriate mapping.
6.3.2 Short Message Service p. 13
There are no requirements related to handover for short message service.
6.3.3 Cell Broadcast p. 13
There are no requirements related to handover for cell broadcast.
6.3.4 USSD p. 13
The technical specifications shall provide means to ensure that any handover that occurs during a USSD interaction need no more affect the service than intra-GERAN handover.
6.3.5 Facsimile p. 13
It is not required that a facsimile transmission that is active between UE and network at the time of handover from UTRAN to GERAN completes successfully.
6.3.6 Data Bearer Services p. 13
6.3.6.1 Circuit Switched Data p. 13
Specifications shall be defined to permit the possibility of handover of a UTRAN data bearer service to GERAN
Means shall be defined which make it possible to limit any temporary degradation on handover so it meets the performance specified by GERAN service requirements for data bearer service handover.
6.3.6.2 Packet Switched Data p. 13
It is required to handover a user PS context between GERAN and UTRAN. Independently of the used air interface, the user shall stay connected to an external network (internet, intranet).
6.3.7 Supplementary Services p. 13
Control and use of Supplementary Services should not be effected by a handover to GERAN.
6.4 Requirements on multiple bearer services handover from UTRAN to GERAN p. 13
Consideration must be given to services that may involve multiple bearer services. The mapping between UTRAN bearer services and GERAN bearer services will depend upon many factors such as data rate, delay constraints, error rate etc. In the event certain UTRAN bearer services cannot be handed over to GERAN, the handover of some of the bearers to maintain the service should not be precluded.
In the case where user equipped with a dual mode terminal is in UTRAN coverage and has multiple PDP contexts activated (for instance to support multimedia) then it is preferable to handover one PDP context, rather than dropping all of them.
As a first priority only the PDP contexts which have an associated QoS that can be supported by the GERAN should be candidates for handover.
If there are still multiple PDP contexts as "handover candidates" then it shall be an operator choice which PDP context will be maintained. When roaming this decision shall be taken by the serving network. The operator may choose to either;
- Drop all of the PDP contexts.
- Choose one based upon criteria such as duration, amount of traffic transferred, etc.
7 Requirements for Handover from GERAN to UTRAN p. 14
7.1 Operational Requirements p. 14
7.1.2 GERAN bands p. 14
The standard shall support handover from any combination of GERAN bands supported by the GERAN specifications.
7.2 Performance Requirements p. 14
During handover from GERAN to UTRAN, temporary degradations shall be no greater than for intra-GERAN handovers.
7.3 Specific Requirements for Individual Service Handover from GERAN to UTRAN p. 14
7.3.1 Speech p. 14
AMR, EFR, FR and HR calls shall be mapped to the default UTRAN speech codec.
7.3.2 Short Message Service p. 14
There are no requirements related to handover for short message service.
7.3.3 Cell Broadcast p. 14
There are no requirements related to handover for cell broadcast.
7.3.4 USSD p. 14
The technical specifications shall provide means to ensure that any handover that occurs during a USSD interaction need no more affect the service than intra-GERAN handover.
7.3.5 Facsimile p. 15
It is not required that a facsimile transmission that is active between UE and network at the time of handover from GERAN to UTRAN completes successfully.
7.3.6 Data Bearer Services p. 15
7.3.6.1 Circuit Switched Data p. 15
Specifications shall be defined to permit the possibility of handover of a data bearer from GERAN to UTRAN.
Means shall be defined which make it possible to limit any temporary degradation on handover so it meets the performance specified by GERAN service requirements for circuit switched data handover.
7.3.6.2 Packet Switched Data p. 15
It is required to handover a user context between GERAN and UTRAN. Independently of the used radio interface, the user shall stay connected to an external network (internet, intranet). Any change in the QoS shall be seen at the service access points as a network initiated renegotiation of QoS. If the supported QoS is not acceptable, the UE/user may terminate the connection/context.
Means shall be defined which make it possible to limit any temporary degradation on handover so it meets the performance specified by GERAN service requirements for packet switched data handover.
7.3.7 Supplementary services p. 15
Control and use of Supplementary Services should not be effected by a handover to UTRAN.
7.4 Requirements on multiple bearer services handover from GERAN to UTRAN p. 15
Consideration must be given to services that may involve the use of multiple bearer services. For example Class A GPRS terminals will be capable of simultaneously supporting more than one data bearer services. Means shall be defined to allow handover of several data bearer services from GERAN to UTRAN
8 Cross Phase Compatibility for this release p. 15
This section details the cross phase compatibility requirements relating to the service requirements in this document.
8.1 Compatibility with Existing Specifications p. 15
Where the service and operational requirements in this document relate to a GERAN, compatibility is required with systems conforming to the R99 or later GERAN specifications.
8.2 Compatibility with Future 3GPP specifications p. 15
The specifications that define the technical implementation of this release should be developed in such a way that it is practical to add the requirements in this section in a backward compatible manner.
8.2.1 Requirements for Service Capabilities p. 16
3GPP standardises service capabilities, not services. As part of the service capabilities it is envisaged that applications may wish to respond to events related to handover that either has occurred, is about to occur or could potentially occur. The service capabilities described in this section should be available at least to UE hosted applications.
The following list of uses is provided as an example and is not intended to be exhaustive:
- An application may wish to accept or reject offered QoS;
- An application may wish to cope to the effect that handover has on a service, for example facsimile retransmission;
- An application may wish to preferentially choose radio resources.
8.2.2 Inter PLMN Handover Issues p. 16
The minimum requirements for inter-PLMN HO are:
- The ability to check with the home network whether the user is permitted to handover from the visited network to a target network.
- Invocation of the handover procedure only occurs if the target network provides the radio channel type required for the respective call;
- The avoidance of "network hopping", i.e. successive handover procedures between neighbouring networks for the same call;
- The possibility of user notification of inter-PLMN HO (e.g. possible tariff change) when it occurs.
8.2.3 Handover between Environments p. 16
UMTS is expected to provide coverage in a number of environments including fixed and mobile as described in the table below. The technical specifications should not preclude the possibility of implementing these requirements in a backward compatible manner.
| To | Terrestrial Cellular | Fixed/Cordless | Satellite | |
|---|---|---|---|---|
| From | ||||
| Terrestrial Cellular | Yes (R99) | Yes | Yes | |
| Fixed/Cordless | Yes | Yes | Yes | |
| Satellite | Yes | Yes | No | |
8.3 Support of Multicall with Simultaneous Voice Calls p. 16
In the case where Multicall is used to support multiple voice calls a handover must be attempted for each bearer that is in use. In the case where not all bearers can be supported by the destination network the related voice calls shall be automatically put on hold. After the handover is completed, the subscriber shall be able to retrieve any held voice call by invoking the Call Hold service.
This requirement is dependent on the user subscribing to Call Hold.
This is only required if there is more than one simultaneous speech call and this is therefore not required for this release.
A Illustration of elements in inter-PLMN handover p. 17
Figure 1 illustrates the above definitions taking an example of European GSM networks. The subscriber's home network is France. The visited network where the subscriber is registered in a VLR is Germany. The signalling connection between HLR and VLR is indicated by dotted lines. The calls for the subscriber are controlled by the MSC collocated to the VLR where the subscriber is registered. This MSC is called "anchor MSC".
Handover to a different MSC may occur if the cell serving the subscriber after handover is not controlled by the anchor MSC. This MSC is called the "serving MSC". Even after the call has been handed over to a different MSC, the call control function remains in the anchor MSC. The signalling connection and circuit switched connection established between anchor MSC and serving MSC are indicated by a solid line.
When the French subscriber registered in a German network roams near the border to the Netherlands, inter-PLMN handover may occur. In this case a Dutch network is the target network. After handover, the anchor MSC located in a German network continues to control the call. The German network remains the visited network where the subscriber is registered. The subscriber's location information stored in the HLR remains unchanged. The signalling and circuit switched connections between the anchor MSC and the previously serving MSC in the German network will be released when the User Equipment (UE) is served by a cell within a Dutch network. The Dutch network becomes the serving network. From the Dutch network the subscriber may be handed over to a Belgian network.
B Open Points on Inter-Operator Handover p. 18
The requirements outlined below are likely to need further elaboration, although these may be outside the scope of service requirements.
B.2 Selection of Target Cells for Handover p. 18
A mechanism is envisaged to support the selection of the target cell for handover. The target cell may be part of the serving network or part of another network.
B.3 Network Information Exchange p. 18
A mechanism is envisaged to support the exchange of network information between different operators. Two categories of network information are identified:
- static information, for example, neighbour cell lists, interconnecting traffic and signalling links, etc.;
- dynamic information, for example real-time signalling information related to target cell selection, etc.
B.4 Service Requirements p. 18
FFS.
[There is a need to identify which services can be maintained during handover and the interactions of services across network boundaries]
B.5 Billing, Accounting and Charging Requirements p. 18
FFS.
$ Change history p. 19
