A signalling method

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DESCRIPTION

Signaling procedure.

Technical field of the invention

The invention relates to the control of connections in cellular telecommunications systems, in particular to the establishment and release of connections.

Background of the invention

For clarification of common terms used in this document, an overview of certain cellular telecommunications systems is presented below.

Proposals for third generation systems include UMTS (Universal Mobile Telecommunications System) and FPLMTS / IMT-2000 (Future System of Public Land Mobile Telecommunications / International Mobile Telecommunications at 2000 MHz). In these schedules, cells are classified according to their size and characteristics into pico-, nano-, micro- and macrocells, an example of the level of service is the bit rate. The bit rate is higher in picocells and lower in macrocells. Cells may partially or completely overlap and there may be different terminals so that not all terminals are necessarily able to use all levels of service offered by cells.

Figure 1 shows a version of a future cellular radio system which is not entirely new compared to the known GSM system, but which includes both known elements and completely new elements. In current cellular radio systems, the bottleneck that avoids offering the most advanced services to terminals comprises the radio access network RAN ​​that includes base stations and base station controllers. The core network of a cellular radio system comprises mobile services switching centers (MSCs), other network elements (in GSM, for example, SGSN and GGSN, that is, server GPRS support node and gateway GPRS support node, in that GPRS stands for General Packet Radio Service) and related transmission systems. According to, for example, the GSM + specifications developed from GSM, the core network can also provide new services.

In Figure 1, the core network of a cellular radio system 20 comprises a CN core network 931 having three parallel radio access networks linked to it. Of those, networks 932 and 933 are UMTS radio access networks and network 934 is a GSM radio access network. The upper UMTS radio access network 932 is, for example, a commercial radio access network, which belongs to a telecommunications operator that offers mobile services, which also provides service to all subscribers of said telecommunications operator. The UMTS radio access network 933 is, for example, private and belongs, for example, to a company in whose facilities the mentioned radio access network operates. Typically, the cells of the private radio access network 933 are nano- and / or picocells in which only the terminals of the employees of said company can operate. The three radio access networks can have cells of different sizes that offer different types of services. Additionally, the cells of the three radio access networks 932, 933 and 934 may overlap in whole or in part. The bit rate used at a given moment in time depends, among other things, on the radio path conditions, the characteristics of the services used, the global regional capacity of the cellular system and the capacity needs of other users. The new types of radio access networks mentioned above are called UMTS Terrestrial Radio Access Networks (UTRAN). Said network can operate at the same time with different types of fixed core networks CN and especially with the GPRS network of the GSM system. The UMTS Terrestrial Radio Access Network (UTRAN) can be defined as a set of base stations (BS) and radio network controllers (RNC) that are capable of communicating with each other using signaling messages.

The terminal 10 shown in Figure 1 is preferably a so-called dual mode terminal that can serve as a second generation GSM terminal, or as a third generation UMTS terminal according to what kind of services are available in each. of the particular locations and what communication needs of the user there are. It can also be a multimode terminal that can function as a terminal for several different communication systems according to need and available services. Radio access networks and services available to the user are specified in a subscriber identity module 936 (SIM) connected to the terminal.

Figure 1 additionally shows some details of the structure of a radio access network. A radio access network 932, 934 typically comprises one or more base stations 937 and a control unit 42. In UMTS radio access networks 932, 933, the control unit is called the radio network controller (RNC). , and in GSM 934 networks, the control unit is called a base station controller (BSC). Radio access networks also typically comprise other network elements such as transcoder units. Figure 1 further shows mobile services switching centers (MSCs) 43 that basically control the circuit-switched connections of mobile stations 10 and a serving GPRS support node (SGSN) 41 that basically controls packet-switched connections of mobile stations 10.

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In cellular telecommunications systems, connections are established and resources are reserved on demand and released when they are no longer needed. Mobile stations in motion set additional requirements for the system, connections need to be transferred from one base station to another, which often requires a substantial change in the routing of the connection through the network. The information exchanges between various network elements that are necessary to execute said functionality are handled by the mobility management protocols (NIM) and the radio resource control protocols (RRC). Mobility management protocols mainly deal with the mechanisms allowing a mobile station to move within the cellular network and with security issues, while RRC protocols mainly deal with the control of the use of radio resources over the interface. air, the connection between a mobile station and the BSC / RNC, and handovers. The execution of the RRC protocols are carried out mainly by the mobile station and the BSC / RNC. Some parts of the RRC protocol, such as functionality related to handovers between MSCs, are implemented by the MSC. The execution of the MM protocols is mainly performed by the mobile station and the MSC. The protocols used in the GSM system are further described in the book "The GSM system for mobile communications" by Michel Mouly and Marie-Bernadette Paulet, ISBN 2-9507190-0-7, Palaiseau, 1992. Mobility management protocols for third-generation cellular networks are discussed, for example, in patent application WO 98/37721, in which the emphasis is placed on minimizing the number of MM messages sent over the radio interface in situations, in which a radio access network is connected to, for example, many core networks, each of them having a dedicated mobility management.

In principle, the MM and RRC protocols are mainly independent. However, in order to reduce signaling, many MM functions are started or terminated as a result of events at the RRC level, without explicit messaging at the MM level. For example, during the release of a connection in the current GSM system, the MM protocol changes its state from a WAIT FOR NETWORK COMMAND state to a STANDBY state in response to the release of radio resources at the RRC level. Therefore, the release of radio resources at the RRC level implicitly acts as a control signal for the MM level. However, this approach creates problems in new cellular systems under development, such as the UMTS system. Some of these problems are described below with reference to Figure 2.

Figure 2 shows a mobile station 10 and the cellular network 20, several entities take over the execution of the protocols, such as the MM protocol entity 11 and the RRC protocol entity 12 of the mobile station. On the network side, the corresponding entities are the MM protocol entities 21 at the MSC, and the RRC protocol entity 22 at the RNC. The MM and RRC entities are typically carried out using software programs executed by means of a processing unit such as a microprocessor in the control unit of an MS or a network element.

Some services take care of the mobility management of their connections themselves, independent of the MSC. An example of such services is the GPRS service. Its independent mobility management results in the execution of an additional MM protocol, which is independent of the MM protocol executed by the MSC. In GPRS, the SGSN runs its own MM protocol. The second MM protocol has corresponding MM protocol entities 13, 23 in the mS and in the SGSN. However, only one RRC protocol is used, since it is advantageous to have control of all the necessary radio resources by the mobile station in a single protocol, and in a single control entity at each end of the radio connection. For example, it is advantageous to use one encryption mode for all mobile station transmissions, rather than negotiating and using one encryption mode for connections through the MSC, and another encryption mode for packet connections through the MSC. SGSN.

As only one RRC protocol is used, MM-level mechanisms based on implicit event messaging at the RRC level do not work properly when using two MM protocols. For example, if packet transmission carriers are released while voice carriers are still active, at least some of the RRC 30 connections will remain in use. As the mobile station packet connection MM entity 13 expects to observe the release of RRC connections as an indication of the release of the MM connection 32, 34, it remains in the WAIT FOR NETWORK COMMAND state, as RRC connections still are in use by the connections controlled by the other MM 11, 31, 33, 21 protocol.

Problems also arise during connection establishment. During the establishment of a connection, the MM protocol authenticates the terminal and controls the start of communication in encrypted mode over the air interface. For example, if a packet data connection is established when voice connections are already in use, communication over the air interface is already encrypted, so no encryption is initiated for the new packet connection. However, since the receipt of an encryption mode command by the MS is interpreted as an indication of a successful establishment of a connection at the MM level, the MM entity 13 of the MS 10 does not receive any indication of the establishment of the connection at the MM level.

Summary of the invention

An object of the invention is to provide connection control that avoids the aforementioned problems of the prior art.

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According to a first aspect, the invention provides a method for establishing a mobility management protocol connection in a cellular telecommunications network, according to the subject matter of claim 1.

Another aspect of the invention is directed to a method for carrying out a mobility management protocol connection in a cellular telecommunications network, according to the subject matter of claim 8.

Another additional aspect of the invention is directed to a device that can be operated to establish a mobility management protocol connection in a cellular communication network, in accordance with the subject matter of claim 11.

Another additional aspect of the invention is directed to a device that can be operated to carry out a mobility management protocol connection in a cellular telecommunications network, in accordance with the subject matter of claim 19.

Another additional aspect of the invention is directed to a system for establishing a mobility management protocol connection in a cellular telecommunications network, according to the subject matter of claim 24.

Additional aspects and embodiments are set forth in the dependent claims, in the following description and in the drawings.

According to one embodiment, it is checked whether more than one protocol is active. If only one MM protocol is active, RRC level events can be used to control MM level events. If more than one MM protocol is active, explicit signaling is used for those MM level events, which would be implicit in the case of a single MM protocol controlled by RRC level events.

According to another embodiment, during the establishment of a new MM connection, it is checked whether an RRC connection is already active. If an RRC connection is already active, explicit signaling is used. In any other case, RRC level events can be used to implicitly handle MM level events. During the release of the MM connections, it is checked whether another MM protocol uses RRC connections and if this is the case, the release of the MM connections is explicitly signaled.

Brief description of the drawings

The invention is described in more detail below with reference to the accompanying drawings, of which,

Figure 1 illustrates an example of the UMTS system structure,

Figure 2 illustrates various protocol entities in a mobile communication medium and in the network,

Figure 3 illustrates a method according to an advantageous embodiment of the invention,

Figure 4 illustrates another example of a method according to an advantageous embodiment of the invention, and

Figure 5 illustrates a still further example of a method according to an advantageous embodiment of the invention.

The same reference numbers are used for similar entities in the figures.

Detailed description

Figure 3 illustrates a method according to an advantageous embodiment of the invention. Figure 3 illustrates events during connection establishment. At the beginning, the establishment procedure is initiated, for example, by the user of the mobile station, who requests 100 a new service. This new service could be, for example, a packet data connection to surf the Internet, in which case, the MM entity that takes over the establishment of the MM connection on the MS side is the data controlling MM entity. per MS packets. In the next step 105, the MM entity of the mobile station that controls the requested service checks whether the connection has already been established at the RRC level. If the RRC level connection has not been established at this point, the MM connection is the first MM connection, and can be established in the normal way by continuing with step 115. If an RRC level connection has already been established, the new MM connection to be established is the second MM connection at that point in time. Accordingly, the MM entity includes an indication of the existence of the RRC connection within the MM configuration information to be sent to the network. For example, this could be done by adding a new parameter within one of the setup messages. In the next step 115, the MM entity of the MS sends the necessary MM configuration information messages to the network, the messages of which are received by the corresponding MM entity on the network side in step 120. The entity

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MM on the network side checks in step 125 whether an indication of the existence of an RRC connection has been included in the received MM messages. If no such indication is found, connection establishment continues as normal. If such an indication is found, the MM entity on the network side informs 130 the corresponding MM entity of the MS about those events, which in the case that only one MM protocol is used, would be implicitly signaled by the events RRC level. For example, such an event could be the successful establishment of the MM-level connection. The step of informing 130 in such a case could be an explicit acknowledgment of the establishment of the connection MM, for example, by sending an ACCEPT SERVICE CM message. The reporting step may take place at a later point in time during the MM connection establishment or for example after the connection establishment.

Figure 4 illustrates another example of a method according to an advantageous embodiment of the invention. This example shows events during the release of a connection. Such events could take place, for example, when the connections between a mobile station and a CN element are released. In the first step 205, a core network element releases the connections between itself and the RNC, that is, the Iu interface connections. In the next step 210, the RRC protocol control entity in the RNC checks, if any other Iu connection to another CN element remains. If Iu connections to other CN elements remain, there is at least one other active MM protocol, in which case the RRC entity in the RNC indicates 215 to the MS, that the released Iu connections were released. The information can be carried out for example by sending a specific message to the MS, such as for example an RRC status message. Receipt of the message indicates to the MM entity of the MS that it may enter 225 the IDLE state. If no other Iu connections are found to remain in step 210, in which case only one MM protocol is active, the RRC entity releases the RRC connections in step 220, which implicitly tells the MS entity MM that 225 can enter the STANDBY state.

Figure 5 illustrates a still further example of a method according to an advantageous embodiment of the invention. In this example, the MS has active connections to a CN element, for example voice connections to an MSC, during which the MS performs a Location Area Update (LA) for an idle MM entity, such as the MM entity. of an SGSN. In step 250, the MS performs the location area update, during which among other procedural steps, an Iu connection is created between the RNC and the SGSN. After performing the update LA, the packet connection entity MM enters 255 into the state in WAITING FOR NETWORK COMMAND, from which, according to the prior art, it should enter the state of IDLE as a response to the release of RRC connections. In the next step 205, the SGSN releases the connections between itself and the RNC, that is, the Iu interface connections. In the next step 210, the RRC protocol control entity in the RNC checks whether any other Iu connection to another CN element remains. If Iu connections to other CN elements remain, there is at least one other active MM protocol, in which case the RRC entity in the RNC indicates 215 to the MS that the released Iu connections were released. The information can be carried out for example by sending a specific message to the MS. Receipt of the message indicates to the MM entity of the MS that it may enter 225 into the IDLE state. If no other permanent Iu connections are found in step 210, in which case only one MM protocol is active, the RRC entity releases the RRC connections in step 220, implicitly indicating to the MS entity MM that it can enter 225 into the STANDBY state.

In a further advantageous example, a procedure substantially similar to that illustrated in Figure 5 is used with a SEPARATION procedure.

The invention clarifies the use of the only radio signaling carrier, that is, the RRC connection in cases where more than one independent MM protocol is running. The invention allows the use of RRC level events to implicitly signal the MM level even in the case where more than one independent MM protocol is being used. Therefore, even current GSM mobile stations that support the use of only one MM protocol are capable of communicating with a radio access network of the GSM type of the UMTS system in the conventional way, even though the radio access network supports the use of simultaneous voice and packet data services, and consequently the use of two MM protocols.

Although in the above examples the establishment and release of the connections have been independently described in separate examples, the invention is not limited to those examples. In some embodiments of the invention, signaling according to the invention is used both in establishing and releasing a connection. For example, a packet data connection can be established, used, and released while voice connections are active. In such an embodiment, the signaling procedures according to the invention can be used in the establishment and release of the packet data connection.

In view of the above description, it will be obvious to a person skilled in the art that various modifications can be made within the scope of the invention. Although a preferred embodiment of the invention has been described in detail, it should be apparent that many modifications and variations thereof are possible.