Content for  TR 22.806  Word version:  13.1.0

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0  Introductionp. 6

UEs on which user can easily download applications from web sites are rapidly increasing in the world and a wide variety of applications are constantly created and installed on the UEs. Specific applications can (intentionally or unintentionally) cause congestion over RAN/CN. While network is congested, it is not desirable to allow these applications to access the network in order to protect the network resources. Several SDOs identified key issues related to network inefficiencies caused by such UEs and by the variety of applications.
On the other hand, for example in Japan, after the severe earthquake on March 11th, 2011, the packet based communication applications that users can invoke to confirm the safety of their relatives are recognized as important applications (e.g. Disaster Message Board (DMB) service, Disaster voice messaging service) when disaster occurs. Therefore, Japanese government strongly expects Japanese operators to provide the connectivity at least for such services even when the network is highly congested, while other services are barred to free up the resources for important services.

1  Scopep. 7

The present document provides a study on Application specific Congestion control for Data Communication (ACDC). This Study investigates the following aspects:
  • Identify the use cases and potential requirements to allow/restrict the communication initiation of particular applications defined by operator, subject to regional regulations;
  • Gap analysis with existing access control mechanisms.

2  Referencesp. 7

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.
TR 21.905: "Vocabulary for 3GPP Specifications".
TS 22.011: "Service accessibility".
TR 36.848: "Study on smart congestion mitigation in E-UTRAN".
S1-135073: "ACDC (for information): "Disaster Message Services", observed in the web site of Japan's Ministry of Internal Affairs and Communication", NTT DOCOMO.
TR 22.805: "Feasibility study on user plane congestion management".
TR 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
TR 22.801: "Study on non-MTC Mobile Data Applications impacts".

3  Definitions and abbreviationsp. 7

3.1  Definitionsp. 7

For the purposes of the present document, the terms and definitions given in TR 21.905 apply.
A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

3.2  Abbreviationsp. 7

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply.
An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Access Class Barring
Application specific Congestion control for Data Communication
Domain Specific Access Control
Extended Access Barring
Multimedia Telephony Service for IMS
Service Specific Access Control

4  Overviewp. 8

4.1  Brief description of existing access control mechanismsp. 8

Access Control is described in TS 22.011, clause 4. The various existing mechanisms can be briefly summarized as follows:
ACB: Access Class Barring
ACB classes can be grouped into three categories:
  • Ordinary: Classes 0 ~ 9 are randomly spread amongst UEs;
  • Emergency Calling: Class 10 is to be used for Emergency Calling (e.g. 911 in North America and 112 in Europe);
  • Special Classes: Classes 11 ~ 15 require subscription and are for special purposes such as MPS. They are generally higher priority classes.
Each UE is allocated one Ordinary Class. A UE with special subscription may be additionally allocated at least one Special Class. Emergency Class is not permanently allocated to a UE, but access may be separately controlled if a UE is attempting an emergency call.
Access for each of these classes can be independently controlled via broadcast control messages, which may indicate:
  • barring (no access allowed for a class), or
  • deferring (access allowed, but only upon a randomly determined delay for each UE of that class that wants to attempt access; the average delay varies depending on severity of network congestion, which is indicated in broadcast control messages)
The latter method of stochastic access control is used in EUTRAN (see bottom of clause 4.3.1 of TS 22.011), and is considered superior to the older open/close access of 10 ordinary classes. The 10 access classes are controlled with the common SIB broadcast by the network, but it has much finer granularity and range of control due to exponential control function rule.
SSAC: Service Specific Access Control
SSAC provides an additional independent access control applicable when UE is attempting MMTEL service origination from idle mode. The control method is stochastic algorithm, identical to the aforementioned paragraph of clause 4.3.1 in TS 22.011, though a separate control SIB is used.
The purpose of SSAC is to provide a balance of available network resources between MMTEL vs. other types of services, without having to disallow MMTEL services on an individual attempt basis, which could potentially unproductively consume network resources in situations when MMTEL service attempt arrive in overwhelmingly large numbers.
CSFB Access Control
Access for multi-mode UEs may be controlled by EUTRAN when UE performs CSFB to a network supporting circuit-switched services. Here too, the control method is stochastic algorithm, identical to the aforementioned paragraph of clause 4.3.1 in TS 22.011, though a separate control SIB is used.
The purpose of CSFB access control is to prevent dual-mode UEs from effectively being exempt from associated CS network access control. Though the specification does not go into operational details, CSFB access control on EUTRAN should reflect access control restrictions currently imposed on the associated CS network.
EAB: Extended Access Barring
EAB was designed for UEs more tolerant to access restrictions, such as limited functionality UEs for MTC (e.g. utility meters). EAB access controls have the following features:
  • Black-and-white (open/closed access) controls are applicable for each of 10 ordinary ACB classes
  • Separate controls are specified for three roaming-driven categories
  • When EAB access is open, the UE is still subject to ACB controls (i.e., EAB can only restrict access)
PMOC: Prevention of Mobile Originated Communication
The intent of PMOC is to extend access controls normally applicable when UE is in idle mode to situations when UE is about to initiate an application, but it is in connected mode. The need for this extension arose as a result of connected mode timer extensions implemented to combat excessive UE state control signalling, causing much undesirable traffic, which reduces radio access usable capacity (see MODAI Feasibility Study TR 22.801).

4.2  Envisioned role of ACDCp. 9

ACDC: Application specific Congestion control for Data Communication
The intent of ACDC is to apply access controls in a less indiscriminate way compared to ACB.
Whereas ACB applies equally on all ordinary UEs, regardless of the purpose of an access attempt from a UE, ACDC groups applications in categories of importance, and applies access controls to lesser categories first, sparing more important applications from denial or deferral of access until and unless level of congestion is severe enough that they must also be affected.

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