4 Description

22.0673GPPenhanced Multi Level Precedence and Pre-emption service (eMLPP)Stage 1TS

a) 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.

b) 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.

c) There are three classes of set‑up time performance and examples of the call set‑up times are:

‑ class 1 fast set‑up 1‑2 s;

‑ 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 3GPP 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.

d) 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.

e) 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.

f) 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.

g) 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.

Table 1: Example on eMLPP service composition

Priority level	Set‑up time	Pre‑emption	Examples
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.

h) In case of pre‑emption the pre‑empted subscriber shall be provided with a suitable indication.

4.1 Applicability to telecommunication services

The applicability of this supplementary service is defined in 3GPP 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.