FR2832585A1 - Telecommunications network congestion control system assigns own access classes to mobiles - Google Patents

Abstract

A telecommunications network congestion control system controls access to the core network (4) from the access control network (2) by assigning dynamically calculated access classes depending on mobile identifications assigned potentially randomly or by any element and including the TMSI or P-TMSI (Packet Temporary Mobile Subscriber Identity).

Description

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CONGESTION CONTROL METHOD IN A NETWORK OF
MOBILE TELECOMMUNICATION OF THE GSM OR UMTS TYPE Technical field
The invention relates to wireless telecommunications and relates more particularly to a congestion control method in a mobile telecommunications network of the GSM or UMTS type comprising an access network intended to connect a plurality of mobile stations to a network core intended to manage the services provided to said mobile stations, each mobile station is assigned an access class allowing the access network to select it to prevent it from establishing communication with the core network in the event of congestion.

State of the prior art
Figures 1 and 2 respectively represent a diagram of the architecture of a GSM network and a UMTS network. These networks are divided into two parts, a core network 2, called respectively, NSS (Network Subsystem, in English) for GSM and CN (Core Network, in English) for UMTS, which manages all subscribers and services provided to subscribers such as teleservices and additional services and an access network 4 called respectively, BSS for GSM and UTRAN for UMTS, which manages the interface and the resources allocated on the radio interface.

 Figure 1 includes both network elements for circuit switched services (telephony, circuit data applications) and

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 packet switching, used, for example for applications accessible via the Internet.

 The core 2 networks of GSM-circuit and GPRS have in common the following functional modules HLR (Home Location Register in English), EIR (Equipment Identity Register in English) and AuC (Authentication Center in English).

The HLR is a database containing information relating to subscribers managed by the operator. For each subscriber, the HLR stores the following information: * subscription information (data subscription or not, subscription to such additional service, maximum speed allowed, etc.) * mobile identity, or IMSI (International Station
Identity, in English); * the subscriber's telephone number, or MSISDN (Mobile
Station International ISDN number); the number of the VLR (Visitor Location Register in English) under which the subscriber is registered so that he can reach the subscriber in the event of a call intended for him.

 EIR is a database containing the list of prohibited telephones. It is optional equipment for GSM networks intended to combat the theft of mobile terminals.

 AuC is an element allowing the network to ensure certain security functions of the GSM network such as authentication of the subscriber's IMSI and encryption of the communication. The AuC is coupled to the HLR and contains a key for each subscriber

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 identification allowing it to provide authentication and encryption functions.

 The circuit switched part of the GSM network also includes the following functional elements: - the MSC (Mobile Service Switching Center, in English) representing a data and signaling switch responsible for establishing communication with the mobile.

 - the VLR (Visitor Location Register) representing a database attached to one or more MSCs, used to register subscribers who are in a given geographical area called LA (Location Area).

- the IWF (Interworking Function) is a gateway between the GSM network and the data networks (ISDN,
PSDN, PDN) respectively (integrated service digital networks, public digital service network, public digital network). This module performs a conversion between the data protocols used in the GSM network and those used in the data network.

 The purely GRPS part of the core network is made up of elements completely separate from those used for the circuit part. In this part, a module called SGSN (Serving GPRS Support Node, in English) plays the same role as the VLR, that is to say the location of the subscriber in a RA (Routing Area) which is l equivalent to an LA (Location Area).

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 As for the VLR, the SGSN performs a temporary identity allocation: the P-TMSI (Packet- TMSI).

 A GGSN module (Gateway GPRS Support Node in English) acts as a gateway to external packet switching networks (public Internet, private intranet, etc.).

The GSM 2 BSS access network comprises two types of equipment: the BSC (Base Station Controller in English) and the BTS (Base tranceiver Station in English);
The BTS is the radio transmission equipment of the GSM network. It performs various operations such as coding / decoding the information transmitted on the radio interface and modulation / demodulation.

 The BSC is a module intended to control one or more BTS and provides the following functions: - the routing of the call between the BTS and the MSC; - allocation and control of resources used on the radio interface; - BTS control (start-up, supervision, activation of radio resources used for communication).

 The UMTS UTRAN access network 2 comprises a logical entity called NodeB intended to provide the radio reception and transmission functions for one or more cells of the UTRAN and modules called RNC (Radio Network Controller, in English) on the one hand, ensuring the routing function of

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 communications between the NodeB and the core network, and secondly, the control of the supervision of the NodeB.

 There are two types of RNC modules, the SRNC (Serving RNC) responsible for communication between a mobile and an RNC called RNC drift responsible for controlling the resources used when a connection is established between a mobile and the RRC layer (Radio Resource Control in English) of the UTRAN interface. The RNC drift or RNC controlling is also responsible for the remote cells when the user moves through the network and changes cells during the communication.

 In the GSM and UMTS standards, a mobile equipment ME (Mobile Equipment, in English) is designated by the expression mobile station MS (Mobile Station in English) when it is equipped with a SIM card (Subscriber Identification Module, in English ) intended to contain the subscriber identification information such as the IMSI number (International Mobile Station Identity, in English) which represents the international identity of a mobile subscriber or the temporary identification number the TMSI (temporary Mobile Identity Station, in English) for GSM and PTMSI (Packet TMSI) for GPRS. This information is either permanently engraved on the SIM card and therefore cannot be modified, or is temporary and liable to be modified by the network during the life of the SIM card. Operators also write in the SIM card a number representing an access class used to block access to a network node in the event of congestion.

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- 0 à 9 pour les stations mobiles classiques (normaux) - 11 à 15 pour des stations mobiles prioritaires (police, pompier, ambulance...) - et le numéro 10 est réservé à la sécurité. The GSM standard provides for three types of access classes:

- 0 to 9 for conventional (normal) mobile stations - 11 to 15 for priority mobile stations (police, fire, ambulance ...) - and number 10 is reserved for security.

 Currently, to control the network load during initialization phases of communications and in the event that the core network is congested, the access network sends a request to prohibit access to all mobiles, including the class of access is previously stored in the SIM card. This control mechanism does not make it possible to limit the prohibition of access to the network to only a part of the mobiles connected to a particular node because neither the core network nor the access network can control the access class assigned to a mobile station. Therefore, this mechanism leads to a ban on access to all mobiles of a given access class regardless of the node to which these mobile stations are connected. In addition, this mechanism cannot be applied in future architectures of the GSM and UMTS access networks since it is based on fixed access classes which do not take account of the evolution of these architectures.

 Furthermore, since there is no distinction in the SIM card between the MSC / VLR and the SGSM, the connection ban affects mobile communications with an MSC / VLR and communications with an SGSM without distinction .

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 Another problem inherent in this control mechanism comes from the fact that the size of the BSS access networks is growing and requires the addition of MSCs which are not taken into account by the predefined access classes in the SIM card.

 The object of the invention is to overcome the drawbacks of the prior art described above by means of an overload management method based on a flexible mechanism making it possible to selectively limit access to the network.

Statement of the invention
The method according to the invention applies in a mobile telecommunications network comprising an access network intended to connect a plurality of mobile stations to a core network intended to manage the services provided to said mobile stations, each mobile station is assigned a access class allowing the access network to select it to prevent it from establishing communication with the network in the event of congestion.

 According to the invention, said access class is calculated dynamically as a function of identification information allocated to each mobile station by the core network.

 According to the invention, the access class is calculated by the mobile station.

 According to the invention, the access class is calculated by the access network.

 According to the invention, the access class is calculated by the core network.

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 According to the invention, the identification information is the temporary identifier TMSI / PTMSI of the mobile station.

 According to the invention, the identification information is a range of access classes defined randomly by the access network.

 According to the invention, the identification information is a range of access classes defined randomly by the core network.

- la figure 2 représente un schéma de l'architecture d'un réseau UMTS ; - la figure 3 représente schématiquement un premier mode de réalisation du procédé selon l'invention ; - la figure 4 représente schématiquement un deuxième mode de réalisation du procédé selon l'invention ; - la figure 5 représente schématiquement un troisième mode de réalisation du procédé selon l'invention ; - la figure 6 illustre schématiquement un exemple de mise en oeuvre du procédé selon l'invention. Brief description of the drawings
Other characteristics and advantages of the invention will emerge from the description which follows, taken by way of nonlimiting example, with reference to the appended figures in which: - Figure 1 represents a diagram of the architecture of a network GSM;

- Figure 2 shows a diagram of the architecture of a UMTS network; - Figure 3 schematically shows a first embodiment of the method according to the invention; - Figure 4 schematically shows a second embodiment of the method according to the invention; - Figure 5 shows schematically a third embodiment of the method according to the invention; - Figure 6 schematically illustrates an example of implementation of the method according to the invention.

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Detailed description of specific embodiments
FIGS. 1 and 2 described previously illustrate respectively and schematically the architecture of a GSM network and that of a UMTS network in which an access network 2 is associated with a core network 4. The access network 2 manages the resources allocated on the radio interface and user mobility. The core network 4 is responsible for establishing communications and provides the link between the GSM / UMTS network and the external networks.

 FIG. 3 schematically illustrates a first embodiment of the invention in which a given mobile station calculates a range of access classes AC = F (TMSI, PTMSI) as a function of the TMSI / PTMSI identifiers and randomly assigns a class of access Cl among the range of calculated access classes. Thus, in the event of congestion at a given node of the communication network, the core network 4 GSM / UMTS sends to the access network BSS / UTRAN 2 the range AC of access classes which must be prohibited from establishing a new connection. When the BSS / UTRAN 2 access network transmits the prohibition request to the mobile stations, only the mobile stations belonging to this range will be prevented from connecting to the network. The number of these mobile stations can then be chosen according to the extent of congestion.

 FIG. 4 illustrates a second embodiment of the invention in which the access classes are defined by the access network. In this case, the ten access classes currently used

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are divided into three ranges which can be of equal or different size and which are arbitrarily assigned to three nodes MSC1, MSC2, MSC3 as follows: - the range of access classes 0 .. 2 for the first node
MSC1.

 - the range of access classes 3 .. 5 for the second node MSC2.

 - the range of access classes 6 .. 8 for the third node MSC3.

 The access network BSC / UTRAN randomly assigns an access class C1 of the range 0 .. 2 to the mobile stations connected to the node MSC1, an access class C2 of the range 3 .. 5 to the connected mobile stations at the MSC2 node and an access class of the range 6 .. 8 to the mobile stations connected to the MSC3 node.

 When the BSS / UTRAN access network transmits a prohibition request to the mobile stations, only mobile stations whose access class belongs to the range designated in this request will be prevented from connecting to the network.

 FIG. 5 illustrates a third embodiment of the invention in which the access classes are defined by the core network.

 In this embodiment, it is the core network 4 which randomly assigns an access class C1 of the range 0 .. 2 to the mobile stations connected to the node MSC1, an access class C2 of the range 3. 5 to the mobile stations connected to the MSC2 node

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 and an access class C3 of the range 6 .. 8 to the mobile stations connected to the node MSC3.

 When the BSS / UTRAN access network transmits a prohibition request to the mobile stations, only mobile stations whose access class belongs to the range designated in this request will be prevented from connecting to the network.

 In the various embodiments described above, it is the access network 2 which controls the prohibition of new connections in the event of congestion problem at the core network 4. For this purpose, the access network 2 transmits to the mobile stations affected by the ban a message designating the AC range of access classes which must be temporarily prohibited from connecting to the network.

Each mobile station compares its own access class Ci with the access class previously calculated or assigned randomly and goes into standby if its access class is included in the range transmitted by the access network.

 FIG. 6 illustrates the case where the access classes which must be prohibited from connection are those included in the range 3 .. 5. The access network transmits a message to the mobile stations connected to the MSC2 whose access class is found in range 3 .. 5.

Claims (7)

1. Method for congestion control in a mobile telecommunications network comprising an access network (2) intended to connect a plurality of mobile stations to a core network (4) intended to manage the services provided to said mobile stations, to each station a mobile is assigned an access class allowing the access network (2) to select it to prevent it from establishing communication with the core network (4) in the event of congestion, a method characterized in that said class of access is calculated dynamically according to identification information allocated to each mobile station by the core network (4).  2. Method according to claim 1, characterized in that the access class is calculated by the mobile station.  3. Method according to claim 1, characterized in that the access class is calculated by the access network (2).  4. Method according to claim 1, characterized in that the access class is calculated by the core network (4).  5. Method according to claim 1 and 2, characterized in that the identification information is the temporary identifier TMSI / PTMSI of the mobile station.  6. Method according to claim 1 and'3, characterized in that the identification information is a range of access classes defined randomly by the access network (2). <Desc / Clms Page number 13>  7. Method according to claim 1 and 4, characterized in that the identification information is a range of access classes defined randomly by the core network (4).