Content for TS 22.067 Word version: 17.0.0
The present document specifies the stage 1 description of the enhanced Multi Level Precedence and Pre emption Service (eMLPP). This service has two parts: precedence and pre emption. Precedence involves assigning a priority level to a call in combination with fast call set up. Pre emption involves the seizing of resources, which are in use by a call of a lower precedence, by a higher level precedence call in the absence of idle resources. Pre emption can also involve the disconnection of an on going call of lower precedence to accept an incoming call of higher precedence.
The eMLPP service is provided as a network operator's option to a domain of a network. The domain can be the whole network or a subset of the network. The eMLPP service applies to all network resources in the domain that is in common use. The eMLPP service is applicable to all mobile stations in the domain with all or some mobile stations having a respective subscription assigning precedence according to the eMLPP service.
eMLPP is a supplementary service and shall be provided to a subscriber for all basic services subscribed to and for which eMLPP applies.
The service is described from the service subscriber's and user's point of view, in particular:
the procedure for normal operation with successful outcome;
the action to be taken in exceptional circumstances;
the interaction with other services and features.
The present document does not deal with the Man Machine Interface (MMI) requirements, but makes reference to the appropriate specifications.
The present document is applicable to teleservices 1x and 6x and to all bearer services used in a mobile network if eMLPP is provided. Any interaction with other services and/or networks not dealt with in clauses 8 or 9 are outside the scope of the present document.
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.
: "Vocabulary for 3GPP Specifications".
: "General on supplementary services".
: "Description of Charge Advice Information (CAI)".
: "Voice Group Call Service (VGCS) Stage 1".
: "Voice Broadcast Service (VBS) Stage 1".
: "Technical performance objectives".
ITU-T Recommendation I.255.3: "ISDN Multi Level Precedence and Pre emption (MLPP) stage 1".
For the purposes of the present document, the following definitions apply:
Termination of a call to a particular user when a higher priority call is directed towards that specific user. Called party pre-emption is decided by the User Equipment without interaction of the user.
Service subscriber which invokes the eMLPP service.
Entity which provides the network operating elements and resources for the execution of the enhanced Multi Level Precedence and Pre emption service (eMLPP).
Precedence is the priority associated with a call.
Entity which offers the eMLPP service for subscription. The network operator may be the service provider.
Mobile subscriber which subscribes to the eMLPP service. In principle, if a network provides eMLPP service, all users are able to subscribe to this service.
For the purposes of the present document, the following abbreviations apply, in addition to those listed in GSM 01.04 and TR 21.905
enhanced Multi Level Precedence and Pre emption
The enhanced Multi Level Precedence and Pre emption service (eMLPP) provides different levels of precedence for call set up and for call continuity in case of handover.
eMLPP shall be applicable also in case of roaming if supported by the related networks.
The maximum precedence level of a subscriber is set at the subscription time by the service provider, based on the subscriber's need. The subscriber may select a precedence level up to and including the maximum precedence level subscribed to, on a per call basis.
There are at maximum 7 priority levels. The highest level (A) is reserved for network internal use, e.g. for emergency calls or the network related service configurations for specific voice broadcast or voice group call services. The second highest level (B) may be used for network internal use or, optionally, depending on regional requirements, for subscription. These two levels (A and B) may only be used locally, i.e. in the domain of one MSC. The other five priority levels are offered for subscription and may be applied globally, e.g. on inter switch trunks, if supported by all related network elements, and also for interworking with ISDN networks providing the MLPP service.
The seven priority levels are defined as follows:
A (highest, for network internal use).
B (for network internal use or, optionally, for subscription).
0 (for subscription).
1 (for subscription).
2 (for subscription).
3 (for subscription).
4 (lowest, for subscription).
Levels A and B shall be mapped to level 0 for priority treatment outside of the MSC area in which they are applied.
Priorities shall be treated in the network as defined for the following call scenarios:
Mobile originated calls:
The priority level depends on the calling subscriber.
If the user has no eMLPP subscription, the call shall have a default priority level defined in the network.
If the user has an eMLPP subscription, the call shall have the priority level selected by the user at set up or the priority level predefined by the subscriber as default priority level by registration.
Mobile terminated calls:
The priority level depends on the calling party. For this, interworking with the ISDN MLPP (Multi Level Precedence and Pre emption) service is required.
If the call is not an ISDN MLPP call, i.e. no priority level is received for the calling party, then the call shall be treated in the terminating mobile network with a default priority level defined in the terminating mobile network, or as an operator option may be treated with the priority level predefined by the called party subscriber as default priority level by registration.
If the call is an ISDN MLPP call, the call shall be treated with the priority level provided by the interfacing network.
Mobile to mobile calls in case of roaming:
The priority shall be treated for the calling subscriber as for mobile originated calls and for the called subscriber as for mobile terminated calls.
Mobile to mobile calls in one network:
The priority shall be treated for the calling subscriber as for mobile originated calls and for the called subscriber as for mobile terminated calls.
Voice broadcast (VBS) and voice group calls (VGCS):
At the first instances of the voice broadcast or voice group call, when there is only a link between the calling mobile station and the network, the call shall be treated at the defined priority level of this voice broadcast or voice group call if this information is available. If the information is not available the call shall be treated as defined for mobile originated calls. Then, for the set up of the voice broadcast or voice group call links in the related cells, the call shall have the priority level as defined for this voice broadcast or voice group call in the network.
There are three classes of set up time performance and examples of the call set up times are:
class 1 fast set up
class 2 normal set up
< 5 s;
class 3 slow set up
< 10 s.
The achievement of the set up times depends on technical realizations and network planning. Mechanisms shall be implemented to provide the performance defined by the service provider under normal circumstances (no congestion). They do not include any allowance for user reaction times. The call set up time is considered to be the time from pressing the "send" button to the point at which the called party, or at least one called party in the case of a multi party, voice group or voice broadcast call, can receive information.
The class 1 figures depend on the required connection type and service and will have to be considered accordingly. It is assumed that for calls which originate or terminate in external networks, 25 % of the set up time is spent in these external networks. The procedures assume normal operating conditions apply, e.g. reference loads as defined in TS 43.005
, the mobile station is in an area of sufficient coverage, the mobile station is not busy, no call redirection is in place, etc.
Calls with a high priority requiring a class 1 set up may not require authentication at call set up nor confidentiality on the radio link.
For precedence calls, the network shall have the possibility to pre empt on going calls with lower priority, in ascending order of priority, in case of congestion at set up on the radio interface or the core network side, respectively, or at handover of the precedence call to a congested cell. In case of necessary pre emption of another on going call at set up, the successful call set up may exceed the set up time performance defined under c) but shall be completed as soon as possible.
A call can be pre empted any time after the precedence level of the call has been established and before call clearing has begun.
Pre emption shall only be performed to provide precedence for those priority levels which have a pre emption capability allocated by the network operator. Priority levels with no pre emption capability allocated shall only have queuing priority.
A subscriber shall be able to set her mobile station to automatic answer a call if the incoming call is of or exceeds a defined priority level, respectively.
In case of called mobile subscriber busy, the on going call shall be pre empted (or set automatically on call hold by the mobile station in case of telephony and if the subscriber is entitled to call hold services) to accept the incoming call with the priority defined for automatic answering. If the on going call is a point to point call, this function is only possible if the subscriber has a subscription for Call Waiting (CW).
In public networks the capability to pre empt an on going TS12 call (emergency call) shall be subject to national regulations.
The definition of the priority level which shall cause automatic answering of an incoming call or pre emption of another on going call shall be stored in the mobile station and can be changed by the subscriber.
If a mobile station does not automatically accept an incoming call while being idle and the user does not accept the call, the call may be forwarded to another party if Call Forwarding on No Reply (CFNRy) applies.
If a mobile station does not pre empt an on going point to point call to accept an incoming call of higher priority, the call is indicated by CW and the user may still accept the incoming call. It the user rejects CW, the call may be forwarded to another party if Call Forwarding on mobile station Busy (CFB) applies.
If the mobile station does not pre empt an on going voice broadcast or voice group call to accept an incoming call of higher priority, the call may be forwarded to another party if CFNRy applies.
The network operator can allocate set up classes and resource pre emption capabilities to each priority level. Table 1 presents an example for the assignment of priority levels and the corresponding parameters.
||Set up time
|A||class 1||yes||VBS/VGCS emergency applications|
|B||class 2||yes||Operators calls|
|0||class 2||yes||TS12 Emergency calls |
|1||class 3||yes||Premium rate calls|
|2||class 3||no||Standard rate calls|
|3||class 3||no||Default for no eMLPP subscription|
|4||class 3||no||Low tariff calls|
Network operators which provide the eMLPP service for subscription need to consider the interrelation of the number of subscriptions offered (possibly restricted for particular users), the technical performance and the network planning issues in order to guarantee the service performance for the subscriber.
In case of pre emption the pre empted subscriber shall be provided with a suitable indication.
The applicability of this supplementary service is defined in TS 22.004
The effects of the eMLPP service are applicable, potentially, to all subscribers in a network, should a precedence call set up or handover occur and pre emption be necessary.
A maximum authorized precedence level is provided to a service subscriber after prior arrangements with the service provider. Service subscribers without an eMLPP subscription are assigned to a default priority level (in case of emergency calls, TS12, exceptions shall be possible).
The maximum authorized precedence level can be changed or the complete eMLPP service withdrawn at the subscriber's request or for administrative reasons.
The definition of the priority level to be used as default level at mobile originated call establishment shall be registered in the network. This default level will be used if a subscriber has a subscription for a priority level higher than the lowest priority level and has not selected a priority level at call set up.
Registration can take place either by the service provider or with an appropriate control procedure by the subscriber.
If the subscriber requests a priority level higher than the maximum entitled one then the network shall reject this registration with an appropriate indication to the subscriber.
Erasure of a default priority level is done as a result of a new registration overruling, and thus effectively erasing the previous registration.
The allocation of eMLPP priority levels to the call set up classes and the possibility of pre emption of on going calls in case of congestion will be arranged by the network operator for a specific composition of the eMLPP service in a network. This is not related to one specific service subscriber.
An example is given in table 1 of clause 4
The eMLPP shall be invoked automatically by the network at call set up.
The precedence level may be selected by the user on a per call basis. The user may select any precedence level up to and including her maximum authorized precedence level. The maximum authorized precedence level shall be stored on the SIM/USIM and the mobile station shall check that only an authorized level is used for set up. In addition, it shall be possible to verify in the network the level used at set up against the maximum authorized level.
If the user has not selected a precedence level at set up, the network shall apply the subscriber specific default precedence level.
If the user has selected a precedence level higher than the maximum authorized level, the maximum authorized precedence level shall be applied for the call.
At invocation of the eMLPP on a call set up, the network notes the call priority related to the call and decides on the respective actions to be taken, i.e. on queuing priority, fast call set up procedures and possibly pre emption in case of congestion of network resources. In case of pre emption the network shall release the lowest lower priority call and seize the necessary resources that are required to set up the higher priority call.
Once set for a call, the precedence level cannot be changed.
In the case of automatic answering of an incoming call with a sufficient priority level, the alerting indication to the calling party may not be provided in order shorten the set up time. In case of called mobile subscriber busy, the on going call shall be released if automatic answering applies (or set on call hold in case of a telephony call) to accept an incoming call of higher priority.
When pre emption applies, at handover to a congested cell, higher priority calls shall replace those of the lowest priority. The pre empted user shall receive an indication for congestion as defined in TS 22.001
A service subscriber may interrogate the range of priority levels he can use and the default priority level used for mobile originated call establishment.
The utilized precedence level shall be able to be extracted from the event records if different from the default precedence level.
When a service subscriber makes a call, he expects the network to automatically invoke the eMLPP service according to her subscription. If the network cannot provide the service for some reason an indication shall be provided to the service subscriber to notify her of the absence or modification of the priority handling.
Exceptional procedures for voice group call and voice broadcast call establishment durations exceeding the specified times are given in TS 42.068
and TS 42.069
The CFU service takes precedence over the eMLPP service. The precedence level of calls shall be preserved during the forwarding process.
No interaction except for voice broadcast and voice group calls (see the respective stage 1 descriptions TS 42.069
and -3GPP TS42.068 ).
An incoming call with higher priority level shall override CFB in case of CW (see item f of clause 4
If the mobile station does not pre empt the on going call of lower priority and the user rejects the CW, the call may be forwarded to another party if CFB applies.
If a mobile station does not automatically accept an incoming call while being idle and the user does not accept the call, the call may be forwarded to another party if CFNRy applies.
Pre emption of on going point to point calls to accept incoming calls of higher priority is only possible if the subscriber has a CW subscription.
The CW indication to the mobile station shall imply the precedence level in order to enable the mobile station to decide on automatic accepting of the waiting call.
A held call may be pre empted due to lack of network resources. The call is cleared and the pre empted user shall receive an appropriate indication.
eMLPP shall apply to the different call legs of a MPTY as for other calls.
No interaction. eMLPP shall not override CUG restrictions, except high priority calls shall override CUG restrictions as a network option.
High priority calls shall override BAOC as a network option.
High priority calls shall override BOIC as a network option.
High priority calls shall override BOIC exHC as a network option.
An incoming high priority call shall override BAIC as a network option.
For a normal call transfer, the precedence level of calls is preserved during the transfer process.
Interworking of the eMLPP service with other networks shall be provided based on the MLPP service specified in ITU-T Recommendation I.255.3 or a possibly future EN related to MLPP.
For this interworking it shall be considered that:
precedence levels A and B shall be mapped to precedence level 0 (see clause 4);
pre emption of network resources and on going calls in the interfacing network will be performed according to the MLPP service, i.e. pre emption will only affect other MLPP subscribers;
other details in the treatment of precedence calls as specified for MLPP which are different to eMLPP.
The precedence level of a call except levels A and B shall not be changed when interworking with networks providing MLPP.