Modification of information in a communication network

A method for modifying information stored in a mobile communication network includes steps of receiving, in a network element, a request for an operation in the mobile communication network relating to a user equipment; deriving information on the first register on the basis of the request; determining information on a second register for the user equipment in the network element; comparing information on the first register derived on the basis of the request with information on the second register determined for the user equipment in the network element; and if the outcome of the comparison indicates a mismatch between the information on the first and second registers, the second register is requested to initiate the modification of information in a third register. A network element implementing at least part of the steps of the method is also described.

TECHNICAL FIELD

The invention concerns in general the technical field of mobile communications. Especially the invention concerns information management in the mobile communications network.

BACKGROUND OF THE INVENTION

Mobile communication networks enable wireless communication to and from a mobile user equipment. Typically, the user terminal is served by a base station within an area and the base station is coupled to other network elements within the network. The connection of the base station to the other network elements is usually implemented by wired means in order to provide secure channels with high capacity for communication. As the mobile communication is based on the fundamental thinking that the user equipment may move from one place to another within the network coverage a reasonable amount of control and management relating to the mobility is needed.

Mobile communication network can be divided to two main entities. First one is so called core network (CN), which is a central part of the network providing various services to customers who are connected by the access network. The second entity is called radio access network (RAN), which implements a radio access technology for user equipments within the coverage of the network. The radio access network typically comprises base stations and possibly some controlling elements for the base stations. The radio access network is controlled and managed at least partly by the core network.

Mobile communication networks normally comprise a network element residing typically in the core network, which is mainly taking care of the control and management functions, such as end-to-end connection, mobility and handover related tasks. In GSM and UMTS such an element is a Mobile Switching Centre (MSC). In Long Term Evolution (LTE) network similar element is Mobility Management Entity (MME). Said network elements are normally specific to different location areas i.e. one network element takes care of the control and management functions within a location area.

In addition to a network element taking care of the control and management functions the core network comprises at least some registers in order to store and maintain subscriber related information. First such register is a so called Home Location Register (HLR), which is a database storing permanently information on subscribers. More specifically, HLR stores details of Subscriber Identity Module (SIM) cards issued by a telecom operator. Each SIM has a unique identifier called International Mobile Subscriber Identity (IMSI), which is primary identifier for each record stored in the HLR. The HLR also stores e.g. Mobile Subscriber Integrated Services Digital Network Number (MSISDN), which is a number uniquely identifying a subscription in a mobile communication network and used of routing calls to the subscriber. Other pieces of information stored in the HLR are location information of the UE and roaming related issues among others. Even if it is said that there is only one HLR for any given network, in practice the information stored in the HLR is spread out across the network into multiple physical HLRs.

Second register type belonging to core network is so called Visitor Location Register (VLR). VLR is a database containing at least partly the same information as stored in the HLR. The difference is that when the HLR contains the information on all the subscribers for the telecom operator, the VLR contains information on subscribers currently residing in its location area. This is consequence of the implementation of the mobile communication network in which the network is divided to different location areas comprising necessary network elements in order to provide the service for the subscribers residing in that specific area and reducing thus the load to the central network elements and registers, such as VLR, as well as reducing the network traffic. Different VLRs can be identified with a Location Area Code (LAC) for the area they serve. A typical way to implement a VLR is to integrate it to a network element taking care of a management and controlling functions, such as MSC.

FIG. 1illustrates a simplified network structure, which clarifies the hierarchy of the different network elements and devices as described above. TheFIG. 1illustrates two location areas A and B. Both location areas A and B comprise a network element101Aand101Bfor control and management functions, which are configured to interact with each other e.g. in a situation when a user equipment moves from a first location area A, B to the other location area A, B. The network element101A,101Bis configured to control and manage the radio access network.FIG. 1illustrates only the base stations102A,102Bbelonging to the corresponding radio access network. The radio access network may comprise some further elements for some further purposes, such as further controlling and management, which are not illustrated here. The base stations102A,102Bare configured to communicate with the user terminals103A,103Ballocated within the location area A, B. Furthermore, the network elements101A,101Bare configured to communicate with subscriber registers104A,104B, such as VLRs, belonging serving the same location area as the network element102A,102B. The subscriber registers104A,104Bserving the location area are configured to receive and transmit information to and from central subscriber register105, such as a HLR. Furthermore, the network elements101A,101Bmay communicate directly with the central subscriber register105(not illustrated inFIG. 1). The network element101A,101Bcan be e.g. MSC or MME depending on the implemented radio communication technology. Similarly, base stations102A,102Bmay implement GSM or 3G based radio technologies or LTE technology, in which case the base stations area called eNodeBs.

Each subscriber shall not be present in more than one VLR104A,104Bat a time. However, for some reasons it may happen that the same user equipment (UE)103A,103Bis registered to two VLRs104A,104Bsimultaneously which, in turn, causes call attempts toward the UE103A,103Bto fail until the dual VLR104A,104Bregistration is canceled. More specifically, when UE103A,103Bis registered in two VLRs104A,104B, one VLR104A,104Bis known by the HLR105in the mobile network, and terminated calls are directed to that VLR104A,104B. The other VLR104A,104Bis handling the UE103A,103B, and UE originated calls are handled by that VLR104A,104B. The former VLR104A,104Bis the wrong VLR104A,104B, and the latter is the correct VLR104A,104B.

Being registered in two VLRs104A,104Bis an error case that is caused by cancel location messages being lost between HLR105and VLRs104A,104B. The cancel location messages can be lost if there is a disturbance in the mobile communication network so that the VLR104A,104Bis not reachable by any other network element. Then no messages will be received by the VLR104A,104B, and an active UE will also be assigned to other VLRs104A,104B. When the disturbance in the communication network ceases, dual VLR registration may exist for some UEs.

Today the solution to correct the dual VLR104A,104Bsituation is to wait customer complaints and in response to that reset the VLR104A,104B. This makes the UE to register again to the mobile communication network and a correct VLR104A,104Bcan be allocated. However, resetting VLRs104A,104Bis a costly process causing disturbance to all subscribers allocated to the VLR104A,104Bto be reset i.e. subscribers are not able to receive calls during the downtime of the VLRs104A,104B.

The above described situation may especially cause problems in the current telecommunication network setup in which multiple networks with different technologies are available in a certain location. For example, one telecom operator may have a LTE, WCDMA and GSM networks available. As it is known that LTE network does not currently offer any circuit switched services i.e. in case of a subscriber is served by the LTE network and he or she receives a mobile terminated call, the subscriber needs to be transferred to either WCDMA or GSM network in order to establish the call connection. Such an operation between the network technologies is called circuit switched fallback (CSFB). If the subscriber in such a case is allocated to multiple VLRs, it is probable that the subscriber cannot be transferred into a circuit switched network without any problem and the establishment of a call connection fails. Thus, it is important that there exists only one VLR association for one user terminal in a LTE network at a time.

SUMMARY OF THE INVENTION

An objective of the invention is to present a method and a network element for maintaining the information in the mobile communication network up-to-date. Another objective of the invention is that the method and the network element enable a simple detection and modification of any misinformation in the network so that the quality of service can be at least partly improved.

The objects of the invention are reached by a method and a network element as defined by the respective independent claims.

According to a first aspect, a method for modifying information stored in a mobile communication network is provided, wherein the method comprises steps of receiving, in a network element, a request for an operation in the mobile communication network relating to a user equipment, deriving information on the first register on the basis of the request, determining information on a second register for the user equipment in the network element, comparing information on the first register derived on the basis of the request with information on the second register determined for the user equipment in the network element, and if the outcome of the comparison indicates a mismatch between the information on the first and second registers, requesting the second register to initiate the modification of information in a third register.

The initiation of the modification of information in a third register comprises a step of delivering a location update request to the second register.

If the comparison indicates a mismatch between information compared, an indication on this is added to the location update request. The location update request may be modified by setting any previous location area information to null by the network element.

The request for an operation in the mobile communication network may be a paging request from the first register or a tracking area update request from the user equipment.

The step of determining the information on the second register for the user equipment can be based on IMSI information.

The information on the first and second registers used in the comparison step may be an identifier of the corresponding register. The mismatch of the information on the first and the second registers may indicate that the registers are not the same.

The step of modifying information in the third register may comprise a step of removing information on the first register. Further, the step of modifying information in the third register may comprise a step of storing information on the second register.

According to a second aspect, a network element, comprising at least one processor and at least one memory comprising portions of computer program code, is provided wherein the memory and the portions of computer program code are configured to, with the at least one processor, cause the network element at least to perform the following: receive a request for an operation in the mobile communication network relating to a user equipment, derive information on the first register on the basis of the request, determine information on a second register for the user equipment, compare information on the first register and information on a second register, and if the outcome of the comparison indicates a mismatch between the information on the first and second registers, request the second register to initiate the modification of information in a third register.

The network element may be configured to request the initiation of the modification of information in a third register by delivering a location update request to the second register. Further, the network element may be configured to add an indication of the mismatch between information compared to the location update request.

The network element may still be configured to modify the location update request by setting any previous location area information to null in the request.

The network element may also be configured to detect that the request for an operation in the mobile communication network is a paging request received from the first register or a tracking area update request received from the user equipment.

Furthermore, the network element may be configured to determine information on the second register for the user equipment on the basis of IMSI information.

DETAILED DESCRIPTION OF THE INVENTION AND ITS ADVANTAGEOUS EMBODIMENTS

In the following the term user equipment is used to mean a subscriber terminal equipped with a necessary subscriber identity module, such as SIM card, in order to identity and authenticate the subscribers in one or more mobile communication network for enabling the communication in the networks.

FIG. 2illustrates an example of a network architecture in which the current invention is applicable. UE103comprises means for interacting with different communications technologies, such as GSM, 3G and LTE. Thus, UE103is able to utilize GERAN (GSM EDGE Radio Access Network)201over Um interface in the communication. Alternatively or in addition, the UE103is able to utilize UTRAN (Universal Terrestrial Radio Access Network)202over Uu interface in the communication. Furthermore, the UE103comprises means for being interaction with E-UTRAN (Evolved Universal Terrestrial Radio Access Network)203over LTE-Uu interface. Both the GERAN201and UTRAN202are at least partly controlled by MSC servers (MSC Server A, MSC Server B), which comprise VLRs104A,104Brespectively, over either interface A for GERAN201or interface Iu for UTRAN202. Moreover, the E-UTRAN203is at least partly controlled by MME204over S1-MME interface. In order to manage connections and roaming aspects of UEs103an interface SGs is configured to enable signaling between MME204and MSC servers thus enabling MME to access to the VLR104A,104Bof a MSC server. The MSC servers and especially VLRs104A,104Bare configured to exchange information with HLR105storing subscriber related information over an interface D.

FIG. 2brings out the challenge in e.g. a CSFB situation in which the UE103is served by the LTE network, but needs to be transferred to the WCDMA or GSM network in order to provide circuit switched services. In such a case, due to the fact that so many network elements are involved in the transfer, any additional malfunction, e.g. dual VLR information existing, is a fatal to the whole transition.

FIG. 3depicts the method steps according to the invention. In step301, a network element, such as MME204, receives a request to perform an operation in a mobile communication network. The request relates to a user equipment103residing in the mobile communication network.

According to an embodiment of the invention the operation to be performed is requested by a register104A,104Bstoring subscriber related information. The requested operation may be a paging operation, which is a broadcast operation organized by the network in order to set up channels for one to one communication between a user terminal and a base station. In practice, paging means that certain cells (i.e. base stations) within the location, where the UE is known to be, broadcast a paging message to the location area in order to find the UE for setting up a communication connection, such as a call. The UEs residing within the location area and receiving the paging request responds to the base station by sending so called channel request message so that the communication connection can be established.

According to another embodiment of the invention the request301to perform an operation in the mobile communication network is delivered by a UE103through radio access network to a network element, such as MME204. The requested operation by the UE103is a tracking area update request. A list of tracking areas (TA list) is allocated to the UE by the telecom operator. In order to maintain the network aware of the location the UE103is configured to deliver the tracking area update request to the network. The request is configured to be delivered periodically or when the UE moves to a tracking area that is not included in its TA list (e.g. the UE moves from one location area to another (the new serving cell is not listed in the TA list)).

Step303inFIG. 3relates to a derivation of information on the register at least partly on a basis of the request301. Object is to find information on the register, which is or at least has been involved in the management and controlling of the UE in the mobile communication network. The information is to be used in checking if the register is a correct one to the current status of the UE103.

According to an embodiment in which the paging request is delivered to the network element, such as MME204, the information on the register104A,104B, which delivers the request, is derived from the request. More precisely, the information on the register104A,104Bis derived by recognizing the register104A,104B. According to an embodiment of the invention an identifier, such as a name, of the register104A,104Bis derivable from the request. The identifier can be any other but the name as long as it can be derived from the request and it is identifying the register104A,104Bfrom other network nodes.

In a case that a network element has received a tracking area update request from a UE103, the network element is configured to derive information on the register associated to the UE103from a UE context maintained in the network element. More specifically, the network element serving the UE103, such as a MME204, is configured to establish, maintain and modify the context for the UE103. The UE context comprises at least the SGs interface association per UE103in the MME204so that the MME204knows the register for the UE. Thus, as the SGs interface indicates the register, such as VLR, identifier (e.g. name) to the MME204, the MME204may derive information on the register associated to the UE103through the UE context in response to receipt of tracking area update request from the UE103.

In addition to the derivation of the first register104A,104Bas described above the network element is configured to derive information on a register104A,104B, which would be optimal for the UE103in its current status. The optimal register104A,104Bis called here as a second register for clarity reasons. The second register is determined by an algorithm using IMSI information of the UE103as input information for the algorithm by the network element serving the UE103. The algorithm is known as IMSI hash algorithm. The information on the second register104A,104Bmay be calculated periodically and stored in the memory of the network element, or the information of the second register may be determined in response to the request received in the network element or in response to initiation or completion of the derivation of the information on the first register on the basis of the request, for example. Originally, the IMSI information is delivered to the network in the context of initial attach of the UE to the network and subsequently by using temporary identifiers, such as TMSI (Temporary Mobile Subscriber Identity), which are converted to IMSI by means of network procedures.

In step305of the method according to the invention the derived information on the first and the second registers104A,104Bare compared. If the outcome of the comparison305indicates a match between the information compared i.e. both derivations have resulted information on the same register, the monitoring of any further requests may be continued, or alternatively the process can be disabled if applicable. But, if the outcome of the comparison305indicates a mismatch between the information compared it is detected that there exists dual information on the register104A,104Bto be utilized in the management and controlling of the UE103and the information on the first register104A,104Bshall not exist. Information on the dual registers104A,104Bexisting in the UE related information may be notified by setting up an identifier indicating this, which can be recognized in the network, for instance.

If the comparison305indicates the mismatch between the compared pieces of information, it means that the UE103is registered in two different registers104A,104Bat the same time, which causes connection attempts to fail until the dual registration is corrected. In step307the information stored in the network is modified in such a manner that the UE103is removed from at least one of the registers104A,104B. The modification of information is initiated so that the network element, such as MME204, performs a location update request of the UE103to the second register104A,104B, the second register104A,104Bbeing the outcome of the derivation of the optimal register104A,104Bfor the UE103as described in the context of the step303. According to the invention the second register104A,104Bis configured to deliver an update location message to a third register i.e. to the HLR105, which is configured to master subscriber related information stored in the network. Generally speaking, the location area update request may comprise at least some of the following parameters: IMSI, a name of the network element (e.g. MME), EPS (Evolved Packet System) location update type, new location area identifier, old location area identifier.

According to an embodiment of the invention the second register104A,104Breceives an indication that dual registers104A,104Bexist for the UE103, to trigger the location updating towards the third register. If no such indication is delivered from the network element to the second register104A,104B, the second register104A,104Bwould not necessarily initiate the location update to the third register, because the subscriber and thus the UE is already registered to the second register104A,104Bwith the IMSI. The indication is coupled to the location update request by the network element and the indication informs the second register that the network element has detected a mismatch in comparison, i.e. in step305.

According to some other embodiment of the invention the network element is configured to modify the location update request to be delivered to the second register104A,104Bin such a manner that the network element clears any old location area information relating to the UE from the location update request. In practice, this means that any location area code is set to null. When such a location update request is delivered to the second register104A,104B, such as a VLR, the second register is forced to make the location update also to the third register, e.g. to the HLR105. Thus, the location update request is modified by setting any previous location area information to null in the request and then the request is delivered to the second register. The nullification can be achieved by setting the value of the corresponding Location Area Code (LAC) to 0000 or FFFE in hexadecimal representation. More specifically, Location Area Code (LAC) is a fixed length code (of 2 octets) for identifying a location area within a PLMN in question. This part of the location area identification can be coded using a full hexadecimal representation except for the following reserved hexadecimal values: 0000, and FFFE. These reserved values are used in some special cases when no valid LAI exists in the UE.

As the third register, such as HLR105, receives the location update request from the second register104A,104B, the third register gets to know the correct register104A,104Bto be utilized for the UE103in question. In response to the receipt of the location update request the third register is configured to remove information on the first register104A,104Bfrom the memory of the third register. This may result a delivery of a cancel location message towards the first register104A,104Band thus, the wrong register104A,104Bis removed from the context of the UE in the network. Additionally, information on the second register is derived from the location update request and stored in the memory of the third register.

FIG. 4illustrates the invention by disclosing the signaling between the network nodes. According to the invention MME204may receive a request either from the UE103through eNodeB belonging to E-UTRAN203or from a VLR1402. The request404from the UE103may be e.g. a periodic tracking area update request. The MME204as a serving network element for the UE103has established and maintained a UE context for the UE103. The UE context may comprise information on the wrong VLR402i.e. MME has an interface SGs association to the wrong VLR402. Correspondingly, the request405from the VLR402may be a paging request in order to find the103UE for communication purposes. As the MME204receives the request404or405it derives the information on the VLR at least partly on the basis of the request in question as described above. The MME203also derives information on the correct VLR403, which shall be associated to the UE103in question by defining it with a so called IMSI hash algorithm. The MME204is configured to compare the information on the first VLR402and the second VLR403and if the outcome of the comparison indicates a mismatch, the MME204is configured to deliver406a location update request406to the second register403, which is the correct VLR for the UE103. The location update request also comprises an identifier indicating that the MME204has recognized that there exists wrong VLR information in the network into which the UE103is associated to. The correct VLR403in response to the location update request and the indicator of the wrong VLR402is configured to deliver an update location message407to the HLR105being the master subscriber information database in the network. As the HLR105receives the update location message407from the correct VLR403the HLR105is configured to remove information on any wrong VLR402in the database and store the information with the information on the correct VLR403. Finally, the HLR105may be configured to deliver a cancel location message408to the wrong VLR402in order to prevent any further signaling causing malfunction in the network.

FIG. 5illustrates a network element, such as a MME204, according to an embodiment of the invention. The network element comprises a processing unit501including one or more processors suitable for executing at least portions of computer program code in order to achieve the network element to perform at least part of the method steps as disclosed. Furthermore, the network element may comprise network connectivity elements502, random access memory (RAM)503, read only memory (ROM)504and input/output (I/O) devices505. These components may communicate with one another via a bus506. In some cases, at least some of these components can locate in a single physical entity or in more than one physical entity.

The processing unit501is configured to execute instructions, portions of computer program code or scripts, which can be accessed via network connectivity elements502, or from RAM503or ROM504. While only one processor is disclosed inFIG. 5, multiple processors may be present.

The network connectivity elements502may comprise e.g. modems, Ethernet devices, universal serial bus (USB) interface devices, wireless local area (WLAN) devices, radio transceiver devices, such as GSM radio transceiver devices, WCDMA radio transceiver devices and/or LTE radio transceiver devices. The network connectivity elements may enable the processing unit to communicate with the corresponding telecommunication networks or Internet or other networks over the known interfaces. For example, the network connectivity elements of MME are configured to implement S1-MME interface towards eNode B and SGs interface towards one or more MSC servers containing VLRs.

The RAM503can be used to store volatile data and instructions typically in a form of computer program code that are at least partly executed by the processing unit. The ROM504is a non-volatile memory and it is used to store instructions in a form of computer program code and perhaps data that are read during execution of instructions.

According to an embodiment of the invention the network element, such as MME204, comprises portions of computer program code stored in at least one of the memory elements of the network element and executed by the processing unit to modify information stored in a mobile communication network. More precisely, the processing unit is configured, when executing at least portions of the computer program code stored in at least one of the memory elements of the network element to cause and thus enable the network element to receive a request for an operation in a mobile communication network, The network element is configured to derive information on the first register104A,104B,402on the basis of the request. This may mean that the network element either detects that the request is a paging request from a first register104A,104B,402or that the request is a tracking area update request from a user equipment103. If the request is a paging request from the first register104A,104B,402, the network element is configured to recognize the register delivering the request. According to an embodiment of the invention an identifier, such as a name, of the register is derived from the request. The identifier can be any other but the name as long as it can be derived from the request and it is identifying the register from other network nodes. If the request is the tracking area update request, the network element is configured to derive information on the first register by retrieving the information from a UE context, which is maintained in the network element.

Further, the network element is configured, by executing portions of computer program code stored in a memory element of the network element by means of the processing unit, to determine an optimal register for the UE103in question. The determination is performed by means of a predetermined algorithm, such as IMSI hash algorithm, which uses subscriber information, such as IMSI, as an input for the algorithm. The output information of the determination i.e. the optimal register (i.e. second register) information is compared with information on the first register104A,104B,402derived on the basis of the request as described. The network element is configured to detect a mismatch between the information on the first and second registers104A,104B,402,403and if the mismatch is detected the network element is configured to request the second register104A,104B,403to initiate the modification of information in a third register. The network element may request the initiation of the modification of information in a third register105by delivering a location update request to the second register104A,104B,403. According to an embodiment of the invention the request comprises an indication of the mismatch of the register information in the network as an outcome of the comparison. According to some other embodiment of the invention the network element is configured to modify the location update request by setting any previous location area information to null in the request before delivering it to the second register104A,104B,403. In this manner the network element may force the second register to deliver the location update request further to the third register, such as HLR105. In the described manner the network element may modify the information in the network and correct any misinformation stored in any of the network nodes.

The network element as described is according to an embodiment of the invention a MME204. According to some other embodiment the network element as described, which implements at least part of the method steps of the invention, is so called SGSN (Serving GPRS Support Node), which is responsible for the delivery of data packets from and to the UEs within its geographical service area. SGSN is configured to route and transfer packets, take care of the mobility management (attach/detach and location management) and logical link management, and authentication and charging functions. The location register of the SGSN stores location information, such as current cell and/or current VLR, and also information on user profiles (e.g., IMSI) of all GPRS users registered with this SGSN. Thus, the SGSN implements similar tasks as MME in LTE technology and thus, the current invention can be implemented also in SGSN in order to modify information stored in a mobile communication network if there exist faulty information with respect to registers the user equipment i.e. the subscriber is associated to. Especially, applying the invention in SGSN relates to management of user information for WCDMA and GSM networks.

Even if it is mainly described here that the VLR may be implemented in the MSC server, it is possible to that the VLR is coupled to any other network node than the MSC server. Moreover, the VLR can be independent network element within the network. The VLRs as well as other registers, such as HLR, may comprise processing and computing means in addition to the database structure in order to implement network related operations and tasks.

Some advantageous embodiments according to the invention were described above. The invention is not limited to the embodiments described. The inventive idea can be applied in numerous ways within the scope defined by the claims attached hereto.