KR20030007810A - Method for supporting a handover between radio access networks - Google Patents

Abstract

The present invention relates to a method for supporting handover of user equipment from a first wireless access network (11) to a second wireless access network (13). In order to ensure the success of the handover, it is proposed that the core network store a list for at least which user equipment 15 identifies all radio access networks 11 and 13 which are allowed to handover of the user equipment 15. . Next, the core network may transmit the stored information about the specific user equipment 15 to the first wireless access network 11 before the first wireless access network 11 performs the handover (step c), so that the first wireless access network ( 11) may correctly determine another radio access network 13 to be allowed for handover before performing the handover. The present invention relates to a core network, a component of a core network, and a component of a radio access network designed to perform the same proposed method.

Description

How to support handover between wireless access networks {METHOD FOR SUPPORTING A HANDOVER BETWEEN RADIO ACCESS NETWORKS}

In a mobile communication system, a wireless access network provides a user equipment with a wireless connection for mobile communication. Each radio access network is connected to the core network, through which the user equipment is connected to the radio access network of the same mobile communication system or to the components of the other mobile communication system, depending on the desired connection. The term user equipment is used for a mobile terminal having a subscriber identity module such as a Global System for Mobile Communications (GSM) Subscriber Identity Module (SIM) or Universal Mobile Telecommunications System (UMTS) UMTS Subscriber Identity Module (USIM).

When the user equipment connected to the first wireless access network should be handed over to the second wireless access network for some reason, the first wireless access network should select this second wireless access network. Such handover is necessary for various reasons. For example, if the user equipment is out of the service area of the first wireless access network, if there is no longer enough capacity for the first wireless access network, if the requested service cannot be provided by the first wireless access network, If you move too fast.

If the user equipment is handed over to a wireless access network that does not support connection by the user equipment, the established connection is broken. The core network does not allow access to the radio access network (the radio network to which the user equipment is going to handover) by subscribers using such user equipment, which means that when subscribers are allowed to other types of subscribers (eg only UMTS subscribers) Subscribers). In addition, the ongoing service may not be supported in the target network.

Another reason for potential disruption in handover is when a user equipment joins a Mobile Virtual Network Operator (MVNO) and not directly with a general mobile network operator.

MVNO is a mobile operator that provides its own brand and wireless service to its subscribers without owning a wireless license or wireless access infrastructure. MVNOs rely on general mobile network operators for radio resources and other network subsystems.

In accordance with the agreement between the MVNO and the mobile network operator, various options exist for sharing the infrastructure of the mobile network operator. MVNO does not mean precise network structure or association with a particular group of standard system components. For minimal implementation, the MVNO entrusts most of its operations to the host network operator and only receives billing information related to its customers from the host network operator. At the extreme, the MVNO subscribers only share a connection with the wireless interface. In this case, the MVNO interconnects the radio access network by duplicating existing network functions and adapting them to specific service offerings. The agreement between the MVNO and the mobile network operator may also include, for example, when an MVNO subscriber moves from the mobile network operator's network and an inter PLMN handover is to be performed, the subscriber hands over to one of the other specific networks. May include. Visited operators coordinate network equipment to support this requirement.

An example of an MVNO is "Virgin Mobile" in the UK and "Sense" in Norway.

When a subscriber of such an MVNO is involved in handover, which of the other available radio access networks actually allows handover of the MVNO subscriber's user equipment depends on at least two factors. First, it should be technically possible to perform a handover from a serving radio access network to a target radio access network. Second, it depends on the roaming agreement between the operator of the visited network and the operator of the subscriber. Thus, an additional reason for potential disruption of the connection during the handover of the MVNO subscriber is, for example, that the target network does not have roaming agreement with the user's home network or other roaming restrictions (in this case the connection may be lost but the connection must be lost). Is not).

1 illustrates an example in which a problem may occur while a user equipment subscribed to an MVNO is handed over. In the figure, three radio access networks are shown. The first wireless access network 11 is a UMTS wireless access network of the first public land mobile network (PLMN 1) owned by the first network operator (A). The second wireless access network 12 is a GSM wireless access network of the first public land mobile network (PLMN 1) owned by the first network operator (A). Finally, the third wireless access network 13 is a GSM wireless access network of the second public land mobile network (PLMN 2) owned by the second network operator B.

In addition, in the situation of FIG. 1, the first user equipment 14 is subscribed to the first network operator A, and the second user equipment 15 is subscribed to the second network operator B. FIG.

Based on the agreement between the first network operator A and the second network operator B, the MVNO uses the first and third wireless access networks 11 and 13 to provide wireless access to its subscribers. Each International Mobile Subscriber Identity (IMSI) of an MVNO subscriber is assigned from the IMSI of the first or third network operator (A, B). Equally, MVNO subscribers use Mobile Country Codes (MCCs) and Mobile Network Codes (MNCs) (which identify one of the radio access networks 11 and 13 to which subscribers are allowed to connect) as part of their identification.

The user equipment 14, 15 in FIG. 1 is handed over to another radio access network, for example, because it moves out of the service area of the first radio access network 11. Therefore, the first wireless access network 11 must determine which user equipment is handed over to another of the wireless access networks 12 and 13.

Technically, the two user equipments 14 and 15 can be handed over to any other two radio access networks 12 and 13. However, since the first user equipment 14 is subscribed only to the first network operator A and the second user equipment 15 is subscribed only to the MVNO, the first user equipment 14 is merely a second wireless access network ( 12 can be successfully handed over and the second user equipment 15 can only successfully hand over to the third wireless access network 13. For the first user equipment 14 subscribing to the first network operator A, the first wireless access network 11 is the default information indicating another wireless access network 12 to which the first user equipment 14 is handed over. Have However, the radio access network 11 may not know that the target radio access network 12 is not applied to the second user equipment 15 and that the target radio access network 13 should be selected for the second user equipment 15. . In this case, the first wireless access network 11 selects an incorrect target radio access network for the handover of the second user equipment 15, so that the connection of the second user equipment 15 will be lost.

The same problem can occur in several different situations involving user equipment subscribed to MVNO.

Similar problems may also arise, for example, in the handover of international roaming subscribers in border areas, without the involvement of user equipment subscribed to MVNO. In such a scenario, the foreign network operator serving the international roaming subscriber should hand over the international roaming subscriber to the subscriber home network when the international roaming subscriber moves back to the service area of the subscriber home network. On the other hand, network operators with cooperative agreements with foreign network operators are interested in handing over subscribers to the business partner's wireless access network across borders.

Networks shared by other owners also have a similar problem. UMTS licensees, for example, are looking for ways to reduce the initial investment required to build their networks by sharing a common network. In the service area of the shared UMTS network, again there are two or more possible target networks and when the handover occurs the correct target network must be selected or the call can be dropped.

The present invention relates to a method for supporting handover of user equipment from a first wireless access network to a second wireless access network. The invention likewise relates to a core network for a communication system, a network component for a core network and a network component for a radio access network.

1 illustrates a situation with the possibility of different handovers.

2 shows a signal flow for an embodiment of the present invention.

It is an object of the present invention to ensure the success of a handover from a first wireless access network to a second wireless access network.

The object is achieved by a method for supporting handover of user equipment from a first wireless access network to a second wireless access network, in which the core network to which the first wireless access network is connected receives information stored in the core network. Transmitted to the access network, the information indicating to which radio access network the handover of the user equipment is allowed.

On the other hand, the object includes mobile means for storing at least one user equipment or for at least one group of user equipment, the storage means for storing information indicating which wireless access network a handover of each user equipment is allowed to. This is achieved by the core network of the system. In addition, the core network according to the present invention transmits the information stored for a specific user equipment or a specific user equipment group to a wireless access network to which the specific user equipment or a member of the user equipment group is currently connected or establishing a connection. A transmission means. The object is also achieved by a network component for the core network of a communication system comprising this characteristic. The user equipment group may be a subscriber of a specific category of user equipment, for example a particular network.

After all, the object is a core of a mobile communication system including receiving means for receiving information indicating which wireless access network is allowed for handover of the user equipment to the user equipment currently connected to or establishing a connection to the network component. Achieved by a network component for the network. The network component may additionally select a network component of another radio access network for handover of the user equipment to the network element of another radio access network according to the information about the user equipment received by the receiving means. Selection means.

The present invention contemplates from the technical idea that for a successful handover of a user equipment currently connected to a first radio access network to another radio access network, the first radio access network must know which radio access network will allow handover of this user equipment. It is. To this end, the first wireless access network must be provided with relevant information. Since the PLMN's core network is aware of roaming agreements with operators of other networks, it is best to store such information and provide it to the primary wireless access network whenever necessary. The information must be present in the first radio access network at least before handover of the connected user equipment. On the other hand, the information cannot be provided until the core network knows that the user equipment wants to establish a connection with the first wireless access network.

Preferred embodiments of the invention are apparent in the dependent claims.

The information is transmitted from the core network to the first wireless access network during the establishment of the connection between the user equipment and the core network via the first wireless access network. The present invention has the advantage that the information can be used immediately in the first radio access network when another radio access network is selected for handover. Specifically, the information is transmitted after authentication of the user equipment by the core network. The authentication procedure provides the IMSI of the user equipment to the core network, at which point the core network selects the stored information about the user equipment for transmission.

The information may also be transmitted by the first wireless access network in the core network during a handover signal transmitted to handover the user equipment from the first network component of the first wireless access network to the second component of the first wireless access network. Is sent. As such, the information will be provided even after handover of the user equipment in the same radio access network.

The combination of the MMC and the MNC assigned to each radio access network can clearly identify each radio access network. Accordingly, the transmitted information includes the MCC and MNC of each radio access network to which handover of the user equipment is allowed.

The information not only indicates to which radio access network the handover is allowed, but also indicates the order in which these radio access networks are selected by the first radio access network.

The information is provided to the core network by the operator of the communication system to which the core network belongs. The information need not be stored for each user equipment that the core network can service, only for those selected by the network operator. Furthermore, there may be multiple groups of information about allowed target networks, each group applying to a specific group of users. Thus, in the radio access network, the default information can be used, for example, for user equipment whose core network does not indicate the target network. In addition, the transmission of the information may be optional, so that the core network first determines whether to transmit the stored information for each user equipment.

The network component of the present invention is specifically for a Serving General Packet Radio System Support Node (SGSN) such as 2G / 3G (2nd / 3rd Generation) SGSN, Mobile Services Switching Center / Visitor Location Register (MSC / VLR), communication There is an MSC server introduced in 3GGP Publication 4 for the core network of the system. Information stored in the SGSN of the packet switching core network and information stored in the MSC / VLR of the circuit switching core network may be supplied to a UMTS or GSM radio access network. The network component of the present invention may be specifically a UMTS RNC (Radio Network Controller) or a GSM BSC (Base Station Controller) for a radio access network of a communication system. In PLMN, the characteristics can be realized in all SGSN, MSC / VLR, UMTS RNC and GSM BSC of PLMN.

If the user equipment is subscribed to the virtual mobile network operator and not the general mobile network operator, since the subscriber identity does not necessarily provide information about the service provider, the first wireless access network can accurately select the target wireless access network allowed for handover. The present invention is particularly advantageous in that it is not present. Equally, the present invention is advantageous in supporting handover of international roaming service subscribers in the border area and in a network shared by several owners.

The present invention can be applied to all mobile networks that support handover between other radio access networks.

In the following, with reference to the accompanying drawings will be described the present invention in detail.

1 is described in the background of the invention.

User equipment can access the PLMN through other radio access networks. Embodiments of the method of the present invention described below include other possibilities for implementing the method of the present invention for other types of connections.

The user equipment can, for example, access the PLMN via Node B of the UMTS radio access network. Each Node B is connected to the RNC of the radio access network. The RNC of the UMTS radio access network is also connected to the MSC / VLR of the circuit switching core network through the lu interface, and to the SGSN of the packet switching core network through the lu interface.

User equipment may also access the PLMN through the base station of the GSM radio access network. Each base station is connected to a BSC of a radio access network. The BSC of the GSM radio access network is also connected to the MSC / VLR of the circuit switching core network via the A-interface and to the SGSN of the packet switching core network via the Gb interface.

2 shows a signal exchanged for establishing a call between a user equipment in a circuit switching (CS) domain and a UMTS radio access network in a mobile communication system, to which signal information according to the present invention is added.

On the left side of the figure, the user equipment 21 is displayed. In the center of the figure, an RNC 22 of a UMTS radio access network is shown. The right side of the figure shows the MSC / VRL 23 of the core network connected to the RNC 22. The arrows and rectangles connecting the units indicate the signals between the units in steps (a-j).

The user equipment 21 is not currently connected to any radio access network, but will be connected to the RNC 22. It is subscribed to the MVNO, which has an agreement with the network operators of the PLMN to which the RNC 22 belongs and the same with other network operators. This agreement allows the user equipment 21 to access the radio access network of the RNC 22 and certain other radio access networks belonging to one of the network operators. This corresponds to the situation of the second user equipment 15 shown in FIG. 1, in which the second user equipment 15 is subscribed to the MVNO and the first wireless access network 11 and the second of the first network operator A. The third wireless access network 13 of the network operator B can be connected.

If handover is needed at some point after the connection is established, the RNC 22 does not currently have any information about the radio access network that is allowed to handover of the user equipment 21.

In contrast, the MSC / VLR 23 includes a storage means in which the network operator stores a list for each of the various user equipments or a list of other groups of user equipments in the storage means. It is subscribed to the MVNO with an agreement to share network resources. Each list contains an MCC / MNC pair, which identifies all radio access networks to which each user equipment can be handed over according to an agreement between the network operator and the MVNO.

Most of the signals shown in FIG. 2 are published in Technical Specification 3GPP TS 24.008 V3.6.0: "3rd Generation Partnership Project; Technical Group Core Network; Mobile Wireless Interface Layer 3 Specification; Core Network Protocol-Phase 3", for example, published. 1999 and 3GPP TS 25.413 V3.4.0: "Third Generation Partnership Project; Technical Group Radio Access Network; UTRAN Iu Interface RANAP Signals", for example, corresponds to the signals specified in Publication 1999.

According to this standard, in the first step (a), the L3-MM (layer 3 mobility management) CM (connection management) service request is transmitted from the mobile station 21 to the MSC / VLR 23 via the RNC 22. This message is sent by the mobile station to the network to request services (e.g., circuit switching connection establishment, assistive service activation, short message transmission and location service) for the connection management underlying entity. In the next step (b), an authentication procedure is performed to authenticate the mobile station 21. In step (c), a RANAP (Radio Access Network Application) common ID message is sent from the MSC / VLR 23 to the RNC 22. This message supplies the RNC 22 with the common ID of the mobile station 21, i.e., the permanent NAS (Non Access Stratum) ID of the mobile station 21. In addition, the common ID message carries a list of target PLMNs allowed for a particular user. The security setting procedure is performed in step (d). The purpose of this procedure is to allow the core network to communicate cryptographic and integrity mode information to the UMTS radio access network. The radio access network uses this information to select and load the encryption device for the user and signal data with the appropriate parameters and also to store the appropriate parameters for the integrity algorithm. Step (e) is used to transmit the L3-CC (call control) setting signal from the mobile station 21 to the MSC / VLR 23 via the RNC 22. The setup message includes all the information (such as call counterpart address information) required by the network that handles the call. The reverse transmission in step f carries the L3-CC call progress indicating that the call is being processed. In step (g), the RAB (Radio Access Carrier) allocation procedure is performed. The purpose of the RAB allocation procedure is to set up a new RAB and / or to enable modification and / or release of an already established RAB for a given user equipment. Steps h and i include alternative transmissions from the MSC / VLR 23 to the mobile station 21 via the RNC 22. In step (h), the L3-CC warning signal indicates that the warning has started on the other end of the call. In step (i), the L3-CC connection signal indicates that the call is accepted at the call partner user. Finally, the L3-CC connection signal is responded by the mobile station 21 to the L3-CC connection confirmation message sent through the RNC 22 to the MSC / VLR 23. Details regarding other signals and procedures can be obtained from the standards mentioned.

In a preferred embodiment of the present invention, in addition to the signals described in the standard, the MSC / VLR 23 of the core network may also display a list of allowed target radio access networks stored for the user equipment 21 during call setup (more specifically, In the RANAP common ID message of step (c)). In addition to the list, the IMSI of the user equipment 21 is transmitted.

The RNC 22 stores the reception list with the IMSI of the user equipment 21 and deletes this list only after the user equipment 21 is disconnected from the RNC 22. Thus, the RNC 22 may know the potential target radio access network for possible handover of the user equipment 21.

The RANAP common ID message may be sent at any time after the subscriber's IMSI is known to the core network. Typically, as shown in Fig. 2, after the subscriber authentication is successfully executed, it is transmitted.

The signal flow described can also be employed in the UMTS packet switching PS domain. However, in this case, since the UMTS radio access network is connected to the SGSN of the packet switching core network through the lu interface, a list of allowed target radio access networks must be stored in the SGSN. Signals for the UMTS packet domain are defined in the same standard as the circuit switching domain.

In a UMTS radio access network, the list of allowed target radio access networks is transmitted to the RNC 22 and also to the user equipment 21 by the core network in particular to request the target RNC to allocate RANAP relocation requests (allocation of resources necessary for relocation). Can be transmitted at a later time when it has already been set.

In order to be able to provide a list of allowed target radio networks to the circuit switched GSM radio network, such a list is stored back in the MSC / VLR while the GSM BSC of the GSM radio network is connected to the MSC / VLR of the core network via the A-interface. Should be. The selected user equipment specific list may then be included in the BSSMAP (Base Station Subsystem Application) Common ID message to the GSM BSC during call setup. Similar to the RANAP Common ID message for UMTS, a BSSMAP Common ID message is sent to inform the user of the BSC for IMSI. In this case, the security setting and allocation procedure is not specified in one of the above mentioned standards, but technical specification 3GPP TS 48.008 V4.2.0: "3rd generation partnership projector; technical group GSM EDGE wireless access network; mobile service switching center A base station system (MSC-BSS) interface; layer 3 specification ", for example published 1999.

In the GSM 2G PS domain, the GSM BSC of the GSM radio network is connected back to the SGSN via the Gb interface. Therefore, also for this option, a list of allowed target radio access networks must be stored in the SGSN. The user equipment specific list may then be included in a DL (downlink) -UNIDATA message (including information elements on the downlink) or in a BSS-CREATE-PFC (Packet Flow Context) message from SGSN to GSM BSC using the Gb interface. Can be. The BSS-CREATE-PFC message allows the SGSN to request that the BSS create or modify the BSS Packet Flow Context. Signals between BSC and SGSN for session establishment are specified for the GSM PS domain. Technical Specification 3GPP TS 48.018 V4.0.0: "3rd Generation Partnership Project; Technical Group GSM EDGE Radio Access Network; General Packet Radio Service (GPRS); Base Station System. (BBS)-Serving GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP) ", for example as defined in Publication 2000.

Also in GSM, the list may be transmitted to the GSM BSC at a later point in time, especially in a BSSMAP handover request message (sent from the MSC to the BSS to indicate that the user equipment should be handed over to the BSS).

As a result of the different possibilities of access to the user equipment to the PLMN, all SGSNs and MSCs / VLRs of the PLMN shall be provided with a list indicating which radio access network the handover of the user equipment is permitted for the selected user equipment. Successful handover is then possible in a wide range of ways.

Sending the list is only optional for the core network. Whether the list is actually sent to the RNC is at the discretion of the core network.

Claims (16)

In the method for supporting the handover of the user equipment 15 from the first wireless access network 11 to the second wireless access network 13, The core network to which the first wireless access network 11 is connected transmits the information stored in the core network to the first wireless access network 11, and the information indicates that the wireless communication network 13 has a handover of the user equipment 15. ) To indicate whether it is allowed. The method according to claim 1, wherein during the connection establishment between the user equipment 15 and the core network via the first wireless access network 11, the information is transmitted from the core network to the first wireless access network 11. Characterized in that the method. 3. The method according to claim 2, wherein said information is transmitted from said core network to said first wireless access network (11) after authentication of said user equipment (15) by said core network. 4. The user equipment according to any one of claims 1 to 3, wherein the information is from a first network component of the first wireless access network 11 to a second network component of the first wireless access network 11. And from said core network to said first wireless access network (11) during a handover signal transmitted for handover. 5. The radio access network (13) according to any one of claims 1 to 4, wherein said information transmitted from said core network to said first radio access network (11) is allowed for handover of said user equipment (15). MCC (Mobile Country Code) and MNC (Mobile Network Code). 6. The method according to any one of claims 1 to 5, wherein the information transmitted from the core network to the first wireless access network 11 is provided to the core network by an operator of a mobile communication network to which the core network belongs. How to feature. Method according to one of the preceding claims, characterized in that the core network determines whether the information should be transmitted for a particular user equipment (15). 8. The wireless access network (11) according to any one of claims 1 to 7, wherein the information transmitted from the core network to the first wireless access network (11) is allowed for handover by the user equipment (15). And 13) indicating in which order the handover by the first wireless access network (11) is selected. 9. Method according to any one of the preceding claims, characterized in that the user equipment (15) is subscribed to a virtual mobile network operator. Storage means for storing information indicating to which radio access network (11, 13) handover of each user equipment (15) is permitted for at least one user equipment or for at least one user equipment group; Transmitting the information stored for a specific user equipment 15 or for a specific user equipment group to a wireless access network 11 to which the particular user equipment 15 or a member of the user equipment group is currently connected or establishing a connection. A core network of a mobile communication system comprising a transmitting means. As a network component for a core network of a mobile communication system, Storage means for storing information indicating to which radio access network (11, 13) handover of each user equipment (15) is permitted for at least one user equipment or for at least one user equipment group; Transmitting the information stored for a specific user equipment 15 or for a specific user equipment group to a wireless access network 11 to which the particular user equipment 15 or a member of the user equipment group is currently connected or establishing a connection. Network element comprising a transmitting means. 12. The network component of claim 11, wherein the network component is a serving general packet wireless system support node (SGSN). 12. The network component of claim 11, wherein the network component is a mobile service switching center / visitor location register (MSC / VLR) or an MSC server. As a network component for a core network of a mobile communication system, Receiving means for receiving information indicating to which user equipment 15 a handover of the user equipment 15 is permitted to the user equipment 15 that is currently connected or establishes a connection to the network component; , And selecting means for selecting a network component of another wireless access network for handover of the user equipment 15 to the network component of another wireless access network according to the information about the user equipment received by the receiving means. Network component characterized in that. 15. The network component of claim 14, wherein the network component is a UMTS radio network controller (UMTS RNC). 15. The network component of claim 14, wherein the network component is a GSM base station controller (BSC).