5 Requirements for Handover

22.1293GPPHandover requirements between UTRAN and GERAN or other radio systemsRelease 17Service aspectsTS

5.1 Handover due to UE Movement

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.

When there is handover to a new cell with different radio conditions and if a PS sessions is unable to maintain the required quality of service, the QoS of the sessions may be modified to lower quality to continue communication.

5.2 Handover due to negotiated service requirement

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

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

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

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:

i The call of teleservice emergency call ;

ii The call of teleservice telephony;

iii The call of any other type according to operator preferences.

Calls that cannot be handed over will be released.

A change in the availability of suitable radio resources may also occur for other reasons in addition to handover.

5.6 Access Rights

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

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

NOTE: Access rights describe which of the candidates for handover a subscriber is allowed to access. The access rights are granted by the home PLMN on a subscriber by subscriber basis.