EP2171942A1

EP2171942A1 - Method of managing communications in a cellular radiocommunication system, and equipment for implementing this method

Info

Publication number: EP2171942A1
Application number: EP08759700A
Authority: EP
Inventors: Cyrille Royer
Original assignee: Alcatel Lucent SAS
Current assignee: Alcatel Lucent SAS
Priority date: 2007-06-19
Filing date: 2008-05-16
Publication date: 2010-04-07
Also published as: FR2917936A1; WO2008155180A1; FR2917936B1

Abstract

In a cellular radiocommunication system comprising a core network able to support communications in circuit switching mode and communications in packet switching mode, as well as a radio access network connected to the core network, a condition for triggering the dispatching to a mobile station of an item of information is defined in relation to the mobile station in communication having an active radio link with a base station of the radio access network, the occurrence of such a condition is detected, and a message containing an item of information pertaining to the capabilities of the radio access network to support a communication in one or other of the aforesaid switching modes is dispatched by the radio access network to the mobile station.

Description

METHOD OF MANAGING COMMUNICATIONS IN A SYSTEM OF

CELL RADIOCOMMUNICATION AND EQUIPMENT FOR IMPLEMENTING SAID METHOD

The present invention relates to mobile radio communications, and more particularly to communications management procedures in a cellular radio system. It finds particular application in third-generation networks of the type UMTS ("Universal Mobile Telecommunication System") standardized by the organization 3GPP ("3rd Generation Partnership Project"), and Figure 1 shows the architecture.

Mobile radio communication networks, such as the Public Land Mobile Network (PLMN), typically include a core network (CN), comprising interconnected switches. , and a radio access network (RAN) providing radio links with the mobile stations, and are capable of providing circuit switched and / or packet switched mode services. This is the case of the GSM system, which provides voice communication services in circuit mode, and can also incorporate a GPRS ("General Packet Radio Service") type packet transmission service. In this case, the core network is split into two parts to distinguish between network elements providing circuit mode services, network elements providing packet mode services.

The core network in the UMTS standard comprises two distinct domains corresponding to a division between circuit switched (CS) and packet switched (PS) services. This distinguishes the PS ("Packet Switched Domain") domain from the CS domain ("Circuit Switched Domain"). Some functions, such as call setup, are managed differently, and performed in different core network equipment depending on whether they are performed in one or the other of these two areas.

SUBSTITUTE SHEET (RULE 26) The core network is connected to a radio access network by means of an interface, called interface A, Gb for GSM, and read, for UMTS.

The core network 16 is further connected to fixed networks 11 comprising one or more packet data networks using respective protocols (PDPs) such as X.25 or IP, as well as the Public Switched Telephone Network (PSTN). It includes for the packet mode switches 10a called GSN ("GPRS Support Node"), which communicate with each other through an interface. Packet switches connected to the access network are called SGSNs ("Serving GSNs"), while other packet switches, called GGSNs ("Gateway GSNs"), serve as gateways with packet networks, including the network. Internet and Intranet. These gateways are linked to the SGSNs to allow mobile stations access to the packet networks. It also includes for the circuit mode other switches 10b, including a data and signaling switch called MSC ("Mobile-Services Switching Center") and a gateway switch with the RTCP network called GMSC ("Gateway MSC"). .

The switches of the mobile service 10a, 10b belonging to the core network 16 are connected, by means of an interface called lu, to control equipment 12, or RNC ("Radio Network Controller"). Each RNC 12 is connected to one or more base stations 9 by means of an interface called lub. The base stations 9, distributed over the coverage territory of the network, are able to communicate by radio with the mobile terminals (also commonly called mobile stations) 14, 14a, 14b called UE ("User Equipment"). The base stations 9, also called "node B", can each serve one or more cells by means of respective transceivers 13. Some RNC 12 can further communicate with each other by means of an interface called lur. RNCs and base stations form a radio access network called UTRAN ("UMTS Terrestrial Radio Access Network") 15.

The UTRAN 15 includes elements of layers 1 and 2 of the ISO model to provide the required links on the radio interface (called Uu), and a Radio Resource Control (RRC) stage.

SUBSTITUTE SHEET (RULE 26) belonging to layer 3, as described in 3G TS 25.301, "Radio Interface Protocol Architecture", version 4.2.0 published in December 2001 by 3GPP. Seen from higher layers, the UTRAN 15 simply acts as a relay between the UE 14, 14a, 14b and the CN 16. Establishing a connection between the mobile and the network, in response to a mobile search message or at the initiative of the UE user, assumes the establishment of a level 3 connection called "RRC connection" between the UE 14, 14a, 14b and the access network 15. This procedure is described in paragraph 5.3.2 of P. Lescuyer's reference work: "UMTS, Origins, Architecture, The Standard" (2nd edition, Dunod, 2002), and section 8.1 of the technical specification. 3G TS 25.331, "Technical Specification Group Radio Access Network; Radio Resource Control (RRC); Protocol Specification (Release 6) ", version 6.13.0, released in March 2007 by 3GPP. In the case of network access, the message originally issued by the UE includes a RRC connection setup message called RRC CONNECTION REQUEST. The aforementioned technical specification 3G 25.331 specifies, in particular in paragraph 10.2.39, that the RRC CONNECTION REQUEST message includes an information element (IE, "Information Element"), called "IE Domain Indicator", by which the UE indicates the domain (CS or PS) on which he wishes the call to be established. Upon receipt of this message, the RNC processes the I UE request, and establishes an RRC connection in the access network as well as a connection with the core network, according to the required domain indication provided by the UE. . This service domain selection feature is described in section 7.2a of the technical specification 3GPP TS 23.221 ("Technical Specification Group Services and System Aspects: Architectural Requirements (Release 7)", version 7.1.0, published in March 2007 by the 3GPP.

The technical specification 3GPP TS 23.221 also provides an Access Domain Selection (ADS) function in the case of a call to I UE in order to select in the core network the domain ( CS or PS) on which a communication session will be established between the UE and the network. This function is preferably supported by

SUBSTITUTE SHEET (RULE 26) a node that is not attached to one domain or another, and must make a domain selection decision. This procedure is described in section 7.2b of TS 23.221 v.7.1.0. In particular, it states that the decision is made in addition on the basis of the indication of capabilities ("UE capabilities") transmitted by the EU to the network.

Such a procedure has loopholes, and is therefore unsatisfactory, since the choice of the access domain performed by the ADS node is not based on all the relevant information. Indeed, the question arises for each node of the access network whether or not it can support the establishment of the call on the chosen domain. If it is for example an establishment of a voice communication, and the chosen domain is the PS domain, which amounts to deciding the establishment of voice communication in voice over packet (VoP , "Voice over Packet") or Voice over IP (VoIP) if the external network is an IP network, it is not certain that the Node-B managing the cell under the cover of which the EU is located and / or that the RNC connected to this Node-B is able to support communication in VoP or VoIP mode. If the ADS makes a decision by ignoring the capabilities of the access network nodes that will be solicited for communication, the decision taken may lead to a failure to establish communication.

An object of the present invention is to optimize the communication mode selection procedure in order to reduce the risk of communication establishment failure.

The present invention thus proposes a method for managing communications in a cellular radio communication system comprising a core network able to support circuit-switched communications and packet-switched communications, as well as an access network. radio connected to the core network, comprising at least one base station, whose radio coverage defines at least one cell, capable of performing radio communications with mobile stations. The method comprises, in relation to a mobile station in communication having an active radio link with a base station of the radio access network, a step of defining a triggering condition of

SUBSTITUTE SHEET (RULE 26) sending to the mobile station information relating to the capabilities of the radio access network to support communication in one or other of the aforementioned modes of switching, a step of detecting the occurrence of said condition triggering, and a step of sending by the radio access network to the mobile station a message containing information relating to the capabilities of the radio access network to support communication in one or the other aforementioned switching modes.

In a preferred embodiment, the information sent to the mobile station includes information relating to the capabilities of at least one node of the radio access network to support communication in one or other of the aforementioned modes of switching.

For example, the information sent to the mobile station includes information relating to the connection capacities between the nodes of the radio access network and the nodes of the core network supporting communications in one or the other of the aforementioned modes of switching. to establish a communication in one or other of these two modes.

Advantageously, the information sent to the mobile station may include information relating to the capabilities of the base station to support communication in one or the other of the aforementioned modes of switching, and / or information relating to the capabilities of the mobile station. cell of the base station.

In a preferred embodiment, the step of detecting the occurrence of the trigger condition includes a step of detecting a cell change of the mobile station, the corresponding triggering condition being defined by a cell change of the mobile station. Advantageously, this step of detecting the occurrence of the trigger condition includes a step of detecting a cell change from the mobile station to a cell of the base station for which the capabilities of the radio access network are different from the the radio access network capabilities for the mobile station origin cell, the corresponding trigger condition being defined by a cell change to a cell of the base station for which the network capabilities

SUBSTITUTE SHEET (RULE 26) radio access are different from the capabilities of the radio access network for the original cell.

In another embodiment of the invention, the step of detecting the occurrence of the trigger condition includes a step of detecting a change in the capabilities of the radio access network for the cell under whose coverage finds the mobile station, the corresponding trigger condition being defined by a change in the capabilities of the radio access network for the cell. Another aspect of the invention relates to a radiocommunication base station for implementing such a management method.

A third aspect of the invention relates to a radiocommunication base station controller for implementing such a management method.

A fourth aspect of the invention relates to a mobile radiocommunication station, comprising transmitting and receiving means for communicating with an infrastructure of a radiocommunication network capable of transmitting messages containing information relating to the capabilities of the network. radio access device for supporting communication in packet switching mode or circuit switching mode, means for receiving said messages, means for analyzing said information, and means for transmitting to the communication network infrastructure , information relating to its capabilities taking into account information relating to the capabilities of the radio access network carried by the received message.

The invention finally proposes a computer program loadable in a memory associated with a processor, and comprising instructions for the implementation of a method as defined above during the execution of said program by the processor, as well as that a computer medium on which is recorded said program.

Other features and advantages of the present invention will emerge in the following description of examples of non-limiting implementation of the method according to the invention, with reference to the accompanying drawings, in which:

- Figure 1, previously commented, is a diagram of a network

SUBSTITUTE SHEET (RULE 26) UMTS;

FIG. 2 is a block diagram of a mobile radio communication station according to the invention.

The invention is described here in its application to the radio access network of a UMTS type cellular system.

A first solution to overcome the disadvantage mentioned above of the access domain selection process as described in paragraph 7.2b of the technical specification TS consists in adding, in the selection criteria, information relating to the capacities. the access network to support communication in a given mode (communication in circuit mode, or communication in packet mode). However, this solution has the disadvantage of requiring that information relating to the capabilities of the access network to support a communication in a given mode is transmitted to the node of the core network that provides the ADS access domain selection function. The transmission of this information involves a signaling exchange between the access network and the core network which can be quite heavy.

Another solution to overcome the disadvantage mentioned above of the access domain selection process as described in paragraph 7.2b of the technical specification TS 23.221 V7.1.0 consists in the communication by the access network to the access network. UE information relating to the capabilities of the access network for supporting communication in a given mode, for the purpose of being taken into account by the UE when selecting an access domain in the case of a call or a communication session initiated by the UE, and transmission to the access domain selection function in the core network for the case of a call or a communication session to the UE. Advantageously, the transmission of this information is effected via the addition or the taking into account, in the information relating to the capabilities of the UE to perform a communication in a given mode that the UE transmits to the ADS function, information on the capabilities of the access network to support communication in said mode. This last solution has the advantage of not requiring modification of the methods as defined for the domain selection, that this

SUBSTITUTE SHEET (RULE 26) either in the case of an EU-initiated call or communication session (paragraph 7.2a of TS 23.221) or in the case of a call or a communication session received by the EU (paragraph 7.2a of TS 23.221), but especially in the latter case. The UMTS system provides the possibility of having communications in CS and PS mode simultaneously. Two communications, each of which involves a separate domain of the core network 16, can therefore take place simultaneously. However, there will only be one RRC connection established between UE 14, 14a, 14b and the UTRAN 15, since the RRC layer manages all the resources allocated to the UE 14, 14a, 14b . This RRC connection may be in an idle state, in which no connection is established between UE 14, 14a and 14b and the network, or in one of the four specified connection states: CeII-DCH , CeII-FACH, URA-PCH and CeII-PCH. When the RRC connection is in one of these four states, the UEs 14, 14a and 14b are then in connected mode.

The invention provides for the transmission by the radio access network 15 to I ¹ EU 14, 14a and 14b when the UE 14, 14a and 14b is in connected mode, for example in Cell_DCH mode, a message containing information relating to the capabilities of the access network 15 to support communication in a given mode (CS mode or PS mode).

In one embodiment of the invention, a category of nodes of the access network 15 is able to decide on the transmission to a mobile of one or more information relating to the capabilities of the access network to support a communication in a network. a given mode, and stores in memory a condition data triggering this transmission to a mobile. The other nodes of the access network transmit to a node of this category the information of their own.

For example, in a preferred embodiment of the invention, the Node-Bs 9 can each transmit to the RNC 12 to which they are connected information on their ability to support communication in PS mode and / or CS mode. This information is gathered by the RNC 12 which can additionally supplement and / or combine them with information on its own ability to support communication in PS mode and / or mode

SUBSTITUTE SHEET (RULE 26) CS, in order to transmit the resulting information to the mobiles that are under the radio coverage of a cell 13 of a Node-B 9 that it controls.

In the preferred embodiment of the invention, each Node-B 9 can furthermore transmit to the RNC 12 to which it is connected information on its ability to support a communication in CS mode and / or in PS mode when it is implemented. service, or when changing or updating its capabilities. The technical specification 3GPP TS 25.433, "UTRAN lub interface Node B Application Part (NBAP); (Release 6) ", v 6.13.0, published in March 2007 by the 3GPP, provides (at paragraph 9.1.17) a status report message AUDIT_RESPONSE by which Node-B 9 indicates to RNC 12 its status, either at startup, either during operation. This message can be adapted to carry the information on the capacity of the Node-B 9 to support communication in CS mode and / or PS mode, which is one of the objects of the invention. Another possible message for conveying this information is the RESOURCE STATUS INDICATION message, which is also defined in technical specification TS 25.433 (8.2.15).

In another embodiment of the invention, each Node-B 9 can transmit to the RNC 12 information on the capacity of a serving cell 13 to support communication in CS and / or PS mode, and the information transmitted. according to the invention to the UE 14, 14a, 14b includes information relating to the capabilities of the cell 13 under the cover of which it is located.

In another embodiment of the invention, different types of nodes of the access network are able to transmit one or more information relating to their capacity to support a communication in a given mode and thus keep in memory, in addition to said information relating to to their ability to support communication in a given mode, a condition data triggering the transmission to a mobile of this information.

Information on the ability of the access network to support communication in a given mode may consist of information relating to the entire access network. It can also consist of or understand

SUBSTITUTE SHEET (RULE 26) information relating to one or more determined nodes of the access network. For example, it may be, in the case of the RNC 12 of the UMTS network of FIG. 1, information relating to either the RNC 12 alone, or to only one of the Node-Bs 9 connected to the RNC 12, or to all the Node-Bs 9 that are connected to the RNC 12, or a combination of these different possibilities.

This information typically takes the form of an information element (IE, "Information Element") in a message sent to a UE 14, 14a, 14b. It can also be limited or not to the support capacity of a certain type of communication in a given mode. This may be for example the ability to support a voice service in packet mode.

Thus, in a particular exemplary embodiment, the invention provides for the transmission to a UE 14, 14a, 14b in a message of the RRC layer of an information element, for example entitled "Conversational Service on PS Domain Supported" , to indicate to the UE UE 14, 14a, 14b recipient, including when already in communication, and for the cell under the cover of which it is located, that the radio access network supports the service conversely in packet switching mode (eg in voice over IP mode).

The present invention furthermore provides for the definition and monitoring of the realization of a condition for triggering the sending of a message to the mobile station UE 14, 14a, 14b containing information relating to the capabilities of the network of radio access for supporting packet mode or circuit switching communication. In the preferred embodiment of the invention, the RNC 12 stores in memory information relating to the capacity of the radio access network 15 to support a communication in a given mode, as well as the definition of one or more conditions. triggering the transmission to a mobile station UE 14, 14a, 14b of said information. It further comprises means for monitoring and detecting the execution of one of the triggering conditions, and for triggering accordingly the transmission to the mobile station UE 14, 14a, 14b of said information.

The trigger condition for sending the message can be set

SUBSTITUTE SHEET (RULE 26) by the detection by the radio access network 15 of a cell change of the mobile station. For example, this trigger condition definition can be written to RNC 12, and when UE 14, 14a, 14b comes under the coverage of a cell of base station 9 connected to RNC 12, this can trigger sending by this RNC 12 an RRC protocol message containing information relating to its own capabilities to support packet-switched or circuit-switched communication, and / or information relating to the capabilities of the station base 9 to support communication in packet switching mode or circuit switching mode, or a combination information information relating to each of these two nodes. Advantageously, the condition for triggering the sending of the message will be defined by the detection by the radio access network 15 of a cell change of the mobile station UE 14, 14a, 14b, insofar as the capacities of the network radio access are different for the arrival cell, radio access network capabilities for the cell under the cover of which the mobile station was previously located.

The RRC protocol includes several messages relating to a serving cell change for a mobile station (defined in the aforementioned TS 25.331 specification). The procedures and messages for managing the radio link between the mobile station UE 14, 14a, 14b and the radio access network 15 define, for example, establishment and reconfiguration messages for the radio link RADIO BEARER SETUP and RADIO BEARER RECONFIGURATION. Another example is provided by the mobility management procedures that define an update message for all the cells in which the mobile station is in "soft handover" (ACTIVE-SET-UPDATE messages). These messages, which are messages of the RRC protocol and therefore intended for a given mobile station, can provide the support required to carry the information sent to the mobile station according to the invention. They have the advantage of being sent to the mobile station and processed by it even though the mobile station UE 14, 14a, 14b is in connected mode, for example in CeII-DCH mode.

The trigger condition for sending the message can also be

SUBSTITUTE SHEET (RULE 26) also be defined by the detection of a change in the capabilities of the radio access network 15 for the cell 13 under the cover of which the mobile station UE 14, 14a, 14b is located. In this case, it is not necessary for the mobile station UE 14, 14a, 14b to change cells, and this situation may arise, for example when a software or hardware incident occurs on a network node. radio access. This situation can also arise when the operator of the radio access network 15 modifies through his operation management system (O & M, "Operation &Management") of the radio access network 15, the capabilities of the radio access network 15. cell 13 under the cover of which the mobile station UE 14, 14a, 14b is located. Again, this trigger condition definition may be recorded at RNC 12, and when for example the capabilities of base station 9 of cell 13 under whose coverage the mobile station is located, this may trigger sending by the controller 12 which controls the base station 9 of an RRC message containing information relating to the capabilities of the base station 9 to support packet switched mode or circuit-switched communication.

The method according to the invention is advantageously implemented in a radio network controller 12, which contains means for defining and storing in memory a triggering condition for the sending to the mobile station UE 14, 14a, 14b information relating to the capabilities of the radio access network 15 for supporting packet switched mode and / or circuit switching communication, means for detecting the occurrence of said trigger condition, and means for detecting sending to the mobile station UE 14, 14a, 14b of a message, for example a message of the RRC protocol, containing information relating to the capabilities of the radio access network 15 to support a communication in one or the other other of the aforementioned switching modes. The means for generating and sending to an UE mobile station 14, 14a, 14b of messages of the RRC protocol present in an RNC 12 are therefore adapted according to the invention to include in at least some of these messages information, for example in the form of an information element IE, relating to the capabilities of the radio access network to support a

SUBSTITUTE SHEET (RULE 26) communication in PS switching mode and / or in CS switching mode. In a preferred embodiment of the invention, said means are arranged to include in at least some of these messages information, for example in the form of an information element IE, relating to the capabilities of a cell. a base station 9 controlled by the RNC 12, to support communication in PS switching mode and / or CS switching mode.

FIG. 2 illustrates the means of implementing the invention within an UE mobile station 14, 14a, 14b. The signals received via the reception antenna 20 are processed within the reception unit 21. The unit 21 is arranged to receive and extract information relating to the capabilities of the access network according to the invention. messages that carry it. Once extracted, the information is transmitted to a processing module 22, for updating the data recorded in the UE 14, 14a, 14b relating to the capabilities of the access network with respect to the cell under the cover of which EU 14, 14a, 14b is located. This data is then consolidated with the data relating to the UE's own capacities 14, 14a, 14b ("UE capabilities"), which are transmitted by the transmission unit 24 under the control of the control unit 23. On the other hand, these data are transmitted to the control unit 23, in order to prevent the latter initiating a communication by requiring a switching mode incompatible with the capabilities of the nodes and equipment 9, 12, 13 of the access network 15 serving UE 14, 14a, 14b.

SUBSTITUTE SHEET (RULE 26)

Claims

A method of managing communications in a cellular radio system comprising a core network capable of supporting circuit-switched communications and packet-switched communications, and a network-connected radio access network core, comprising at least one base station, whose radio coverage defines at least one cell, capable of performing radio communications with mobile stations, the method comprising the following steps, with respect to a mobile station in communication having a radio link active with a base station of the radio access network:

- defining a condition for triggering the sending to the mobile station of information relating to the capabilities of the radio access network to support communication in one or the other of the aforementioned switching modes;

detecting the occurrence of said triggering condition;

- sending by the radio access network to the mobile station a message containing information on the capabilities of the radio access network to support communication in any of the aforementioned switching modes.

The method of claim 1, wherein the information sent to the mobile station includes information relating to the capabilities of at least one node of the radio access network to support communication in either of the modes. aforementioned switching

3. Method according to one of claims 1 or 2, wherein the information sent to the mobile station includes information relating to the connection capabilities between the nodes of the radio access network and the nodes of the core network supporting communications in one or other of the modes

SUBSTITUTE SHEET (RULE 26) aforementioned switching devices to establish a communication in one or the other of these two modes.

The method of claim 1 or 2, wherein the information sent to the mobile station includes information relating to the capabilities of the base station for supporting communication in one or other of the aforementioned switching modes.

The method of claim 4, wherein the information sent to the mobile station includes information relating to the capabilities of the cell of the base station.

The method of claim 1, wherein the step of detecting the occurrence of the trigger condition includes a step of detecting a cell change of the mobile station, the corresponding trigger condition being defined by a change of cell of the mobile station.

The method of claim 6, wherein the step of detecting the occurrence of the trigger condition includes a step of detecting a cell change from the mobile station to a cell of the base station for which the capabilities of the radio access network are different from the capabilities of the radio access network for the originating cell of the mobile station, the corresponding trigger condition being defined by a cell change to a cell of the base station for which the The capabilities of the radio access network are different from the capabilities of the radio access network for the original cell.

The method of claim 1, wherein the step of detecting the occurrence of the trigger condition includes a step of detecting a change in the capabilities of the radio access network for the cell under whose coverage it is located. the mobile station, the corresponding trigger condition being defined by a change in the capabilities of the radio access network for the cell.

SUBSTITUTE SHEET (RULE 26)

9. Radiocommunication base station, comprising means for implementing the method according to any one of claims 1 to 8.

Radiocommunication base station controller, comprising means for carrying out the method according to any one of claims 1 to 8.

11. Mobile radio communication station, comprising transmitting and receiving means for communicating with an infrastructure of a radio network capable of transmitting messages containing information relating to the capabilities of the radio access network to support a communication in communication. packet switching mode or circuit switching mode, means for receiving said messages, means for analyzing said information, and means for transmitting, to the communication network infrastructure, information relating to its capabilities taking into account information relating to the capabilities of the radio access network carried by the received message.

12. Computer program, loadable in a memory associated with a processor, and including instructions for the implementation of a method according to any one of claims 1 to 8 during the execution of said program by the processor.

Computer medium on which a program according to claim 12 is recorded.

SUBSTITUTE SHEET (RULE 26)