The capability of Access Control prevents UE from any access attempts (including emergency call attempts) and from responding to pages in specified areas.
Under certain circumstance, the traffic volume exceeds the one that network is capable to handle. Use of access control prevents this overload and provides a mechanism with an aim to maximize the use of communication network resources.
Access restriction information is grouped into two, namely cell access restriction and domain specific access restriction. Followings are the brief introduction of current capability.
Cell access restriction:
If the UE is a member of at least one Access Class which corresponds to the permitted classes as signalled over the air interface, and the Access Class is applicable in the serving network, access attempts are allowed. Otherwise access attempts are not allowed. The Access control with cell access restriction utilizes the Access Classes defined in TS 22.101
and presented in following Table.
Domain specific access restriction (optional):
Optionally, a network configures with domain specific access control scheme where the network performs access control based on the domain. The detail procedure is defined in TS 24.008
, and the Access control with domain specific restriction utilizes the domain specific access restriction information element defined in TS 25.331
and presented in following Table.
Current Service Accessibility prevents a UE to respond to paging signal while the UE is under the influence of access class control as it is described in clause 5
. Sharing the exactly same consequences of this constraint among services provided in this TR (e.g. Priority service, Emergency call, and so on) where call origination does not reach to terminating side, the new capabilities in terms of service accessibility are the followings.
The UE.should be able to respond to a paging request even when it is under class access barring.
The UE should also be able to respond to specific paging requests
In addition to above, current Service Accessibility prevents location registration. Without location registration, the network may not be able to send paging request to UE correctly in the following cases
The mobile reachable timer (network timer for periodic registration) is expired, and the UE is implicitly detached, and UE can not perform the registration procedure because of access control.
The registration area changes, but UE can not perform the registration procedure because of access control.
To provision the successful terminated call with PPAC capability, it is required for UE to perform location registration when the network indicates UE so.
The capability of queuing and pre-emption is supported by two basic schemes, namely eMLPP and Priority Service.
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 provides Precedence and Pre-emption mechanism for prioritization of resource allocation. The Precedence involves assigning a priority level to a call in combination with fast call set-up. A network operator can allocate set-up classes and resource pre-emption capabilities to each priority level. The seven priority levels are defined in TS 22.067
and shown in following Table.
The calling subscriber priority levels are used in both the originating and the terminating networks. The highest level (A) is used for network internal use (e.g. emergency calls) and the second highest level (B) is also used for the same manner, but also used for subscription basis depends on regional requirements. The other five priority levels are reserved for subscription, and if commonly acknowledged priority levels are supported by all related network elements and the assigned priority level is presumably transparent from call origination to termination, it may be applied globally.
The default priority level is registered by the service provider or with an appropriate control procedure by the subscriber. While the user may select any priority level up to and including her maximum authorized priority level, the maximum authorized priority level shall be stored on the SIM/USIM and it is the mobile station to check that only an authorized level is used for set-up.
For a network to actually act on precedence resource allocation such as seizing of resources (e.g. wireless channel), the pre-emption makes the resource available for precedence call of higher priority. A network shall have the possibility to pre-empt ongoing calls with lower priority at radio interface or the core network side, or at handover of the precedence call to a congested cell. Pre-emption shall be performed only if a network operator allocates the priority level with pre-emption capability.
The eMLPP shall be invoked automatically by the network at call set-up while the precedence level may be provided by the user on a per call basis.
The Priority Service shares the most of the capability with eMLPP as it is analysed in TR 22.950
. The capability of Priority Service is to allow an authorised user to obtain priority access to the next available radio (voice or data traffic) channels during situations when PLMN congestion is blocking call attempts. In addition, Priority Service supports priority call progression and call completion to support an "end-to-end"
priority call, see TR 22.950
The capability targets a call origination, a call termination, and a call progression of both non-roaming case and roaming case with applicability of voice and date telecommunication services. The basic mechanisms are specified as follows. Priority Service capability is invoked only when requested originating channel is not available, and in such case, priority call has radio resource queuing and trunk queuing precedence over normal call with numerically assigned priority level where 1 is the highest priority level. It is employed with handover capability and charging capability.
Priority call is authorized based on originating subscription; moreover, it provides manual request of Priority Service by adding service code to origination request.
Optionally, Priority service coexists with eMLPP.
The capability of prioritization in resource allocation is already provided with eMLPP and Priority Service. With the new capability described in the aspect of service accessibility, there is no reasonable justification of introducing a new capability (e.g. prioritization of paging request) in terms of resource allocation and precedence relation. Therefore, no new capability shall be provided.