4.1 Purpose
Under certain circumstances, it will be desirable to prevent UE users from making access attempts (including emergency call attempts) or responding to pages in specified areas of a PLMN. Such situations may arise during states of emergency, or where 1 of 2 or more co-located PLMNs has failed.
Broadcast messages should be available on a cell by cell basis indicating the class(es) or categories of subscribers barred from network access.
The use of these facilities allows the network operator to prevent overload of the access channel under critical conditions.
It is not intended that access control be used under normal operating conditions.
It should be possible to differentiate access control between CS and PS domains. Details are specified in TS23.122[3] and TS25.304 [10]. Not all RATs need to support this functionality.
4.2 Allocation
All UEs are members of one out of ten randomly allocated mobile populations, defined as Access Classes 0 to 9. The population number is stored in the SIM/USIM. In addition, UEs may be members of one or more out of 5 special categories (Access Classes 11 to 15), also held in the SIM/USIM. These are allocated to specific high priority users as follows. (The enumeration is not meant as a priority sequence):
Class 15 - PLMN Staff;
-"- 14 - Emergency Services;
-"- 13 - Public Utilities (e.g. water/gas suppliers);
-"- 12 - Security Services;
-"- 11 - For PLMN Use.
4.3 Operation
4.3.1 Access Class Barring
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. Additionally, in the case of the access network being UTRAN the serving network can indicate that UEs are allowed to respond to paging and perform location registration (see, sec 3.1), even if their access class is not permitted. Otherwise access attempts are not allowed. Also, the serving network can indicate that UEs are restricted to perform location registration, although common access is permitted. If the UE responded to paging it shall follow the normal defined procedures and react as specified to any network command.
Note: The network operator can take the network load into account when allowing UEs access to the network.
Access Classes are applicable as follows:
Classes 0 - 9 - Home and Visited PLMNs;
Classes 11 and 15 - Home PLMN only if the EHPLMN list is not present or any EHPLMN;
Classes 12, 13, 14 - Home PLMN and visited PLMNs of home country only. For this purpose the home country is defined as the country of the MCC part of the IMSI.
Any number of these classes may be barred at any one time.
The following is the requirements for enhanced Access control on E-UTRAN.
- The serving network shall be able to broadcast mean durations of access control and barring rates (e.g. percentage value) that commonly applied to Access Classes 0-9 to the UE. The same principle as in UMTS is applied for Access Classes 11-15.
- E-UTRAN shall be able to support access control based on the type of access attempt (i.e. mobile originating data or mobile originating signalling), in which indications to the UEs are broadcasted to guide the behaviour of UE. E-UTRAN shall be able to form combinations of access control based on the type of access attempt e.g. mobile originating and mobile terminating, mobile originating, or location registration. The ‘mean duration of access control’ and the barring rate are broadcasted for each type of access attempt (i.e. mobile originating data or mobile originating signalling).
- The UE determines the barring status with the information provided from the serving network, and perform the access attempt accordingly. The UE draws a uniform random number between 0 and 1 when initiating connection establishment and compares with the current barring rate to determine whether it is barred or not. When the uniform random number is less than the current barring rate and the type of access attempt is indicated allowed, then the access attempt is allowed; otherwise, the access attempt is not allowed. If the access attempt is not allowed, further access attempts of the same type are then barred for a time period that is calculated based on the ‘mean duration of access control’ provided by the network and the random number drawn by the UE.
4.3.2 Service Specific Access Control
Additionally to the above requirements in 4.3.1;
- In E-UTRAN it shall be possible to support a capability called Services Specific Access Control (SSAC) to apply independent access control for telephony services (MMTEL) for mobile originating session requests from idle-mode as following:
- EPS shall provide a capability to assign a service probability factor [13] and mean duration of access control for each of MMTEL voice and MMTEL video:
- assign a barring rate (percentage) commonly applicable for Access Classes 0-9
- assign a flag barring status (barred /unbarred) for each Access Class in the range 11-15.
- SSAC shall not apply to Access Class 10.
- SSAC can be provided by the VPLMN based on operator policy without accessing the HPLMN.
- SSAC shall provide mechanisms to minimize service availability degradation (i.e. radio resource shortage) due to the mass simultaneous mobile originating session requests and maximize the availability of the wireless access resources for non-barred services.
- The serving network shall be able to broadcast mean durations of access control, barring rates for Access Classes 0-9, barring status for Access class in the range 11-15 to the UE.
- The UE determines the barring status with the information provided from the serving network, and perform the access attempt accordingly. The UE draws a uniform random number between 0 and 1 when initiating connection establishment and compares with the current barring rate to determine whether it is barred or not. When the uniform random number is less than the current barring rate and the type of access attempt is indicated allowed, then the access attempt is allowed; otherwise, the access attempt is not allowed. If the access attempt is not allowed, further access attempts of the same type are then barred for a time period that is calculated based on the ‘mean duration of access control’ provided by the network and the random number drawn by the UE.
