Technical Field

The present invention relates to a method for attaching to a communication network, or more particularly to a method according to the preamble of claim 1. Furthermore, the invention also relates to a method in a communication device, a method in a communication network entity, a computer program, a computer program product, a communication device and a communication network entity.

Background

In current 3 GPP networks, when a User Equipment (UE) attaches to a communication network of a communication system, the individual subscription for the UE is downloaded from a subscription database, such as a Home Location Register/Home Subscriber Server (HLR/HSS); and an individual UE context is created for the UE in the network. This individual UE context is kept in the network to memorize the subscription information obtained from the subscription database until the UE detaches from the network. The communication network also memorizes other more dynamic information such as UE location, the bearer it has established. As a note: a database in the home Public Lan Mobile

Network (PLMN) for a UE can be a HSS or an HLR depending on the version of the network. Generally, HLR is for UMTS systems and HSS is for LTE systems. The HLR/HSS contains subscription data and routing information The procedure for attachment to a communication network is described for Universal Mobile Telecommunications System (UMTS) and General Packet Radio Service (GPRS) in the 3 GPP specification TS 23.060, and for Long Term Evolution (LTE) in TS 23.401. In these systems subscriptions are distinct for each UE in the subscription database, so for each UE that attaches to a network an individual UE subscription needs to be retrieved from the

subscription database (for example from HLR/HSS), which means that when a UE attaches to the network a mobility management entity, such as Serving GPRS Support Node/Mobility Management Entity (SGSN/MME) in 3GPP networks, retrieves the subscription information for each UE. This procedure will bring as many interactions between the mobility management entity and the subscription database as the number of UEs attaching to the network.

Currently, as illustrated in Figure 1 , when a UE attaches to a communication network, a mobility management entity requests a UE subscription based on a unique UE identity called International Mobile Subscriber Identity (IMSI). This identity is provided by the UE when attaching to the mobility management entity, which allows the system to retrieve the subscriptions from the HLR/HSS to be used for the UE from the subscription database; and this procedure is repeated for each UE attaching to the SGSN/MME.

Moreover, it is expected in the future that the number of Machine-to-Machine (M2M) devices will be much higher than the number of UEs in wireless communication systems. It has for example been estimated that 10 to 20 M2M devices per human end-user will be deployed compared to 1.5 UEs per human end-user. It is therefore foreseen that the number of M2M devices will increase rapidly in the future. When seen from the network, M2M devices are also denoted as Machine Type Communication (MTC) devices in 3GPP communication systems (TS 22.368), which in these types of systems communicate through a communication network such as a 3 GPP PLMN with MTC servers exchanging data with MTC devices. A M2M device may be stand alone device or a device integrated in a mobile station, such as a mobile phone, smart phone, PDA, etc.

Summary

The object of the present invention is to provide a method for attaching to a communication system with reduced overhead/signalling compared to prior art solutions. Another object of the invention is to provide a method for attaching to a communication network that can cope with a large number of communication devices wanting to attach/detach to the communication network in an efficient way. A yet another object of the invention is to provide an alternative method for communication devices to attach to a communication network.

According to one aspect of the invention, the objects are achieved with a method in a communication system for attaching to a communication network of said communication system, in which communication devices attaches to said communication network by requesting and using a subscription, said subscription being provided by a subscription database (HLR/HSS), said method comprising the steps of:

dividing communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a common subscription (CS) for attaching to said communication network; and providing one common subscription (CS) for each group of communication devices, wherein said common subscription (CS) is used by all communication devices belonging to the same group for attaching to said communication network. Embodiments of the method in a communication system above are disclosed in the dependent claims 2-14.

According to another aspect of the invention, the objects are also achieved with a method in a communication device for attaching to a communication network, said communication devices attaches to said communication network by requesting and using a subscription, said subscription being provided by a subscription database (HLR/HSS), said method comprising the steps of:

receiving a group identity;

- requesting a common subscription (CS) associated with said group identity; and using said common subscription (CS) for attaching to said communication network.

The method in a communication device above may further comprise the step of:

providing information about the identity of said communication device to a communication network entity, wherein said communication network entity is arranged for mobility management of communication devices in a communication system.

According to yet another aspect of the invention, the objects are also achieved with a method in a communication network entity, such as a mobility management entity (SGSN/MME), said communication network entity being arranged for mobility management of communication devices in a communication system in which communication devices attaches to a communication network of said communication system by requesting and using a subscription, said subscription being provided by a subscription database (HLR/HSS), said method comprising the steps of:

dividing communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a common subscription (CS) for attaching to said communication network; and using one common subscription (CS) for each group of communication devices for the management of the interaction of the communication devices with said communication network. The method in a communication network entity may further comprise the steps of:

- determining the group identity for each communication device wanting to attach to said communication network; and

- determining whether the common subscription (CS) associated with said group identity is stored in said communication network entity or has to be downloaded from said subscription database (HLR/HSS).

The invention also relates to a computer program and a computer program product when run in a computer causes the computer to execute the method in a communication device and the method in a communication network entity described above.

According to yet another aspect of the invention, the objects are also achieved with a communication device for a communication system, said communication device being arranged for attaching to a communication network of said communication system by requesting and using a subscription, said subscription being provided by a subscription database (HLR/HSS), said communication device being:

configured for receiving a group identity;

configured for requesting a common subscription associated with said group identity; and

configured for using said common subscription (CS) for attaching to said communication network.

According to yet another aspect of the invention, the objects are also achieved with a communication network entity, such as a mobility management entity (SGSN/MME), said communication network entity being arranged for mobility management of communication devices in a communication system, in which communication devices attaches to a communication network of said communication system by requesting and using a subscription, said subscription being provided by a subscription database (HLR/HSS), said communication network entity being:

- configured for dividing communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a common subscription (CS) for attaching to said communication network; and

- configured for using one common subscription (CS) for each group of communication devices for the management of the interaction of the communication devices with said communication network.

The communication device and the communication network entity according to the invention may also be arranged according to the different embodiment of the methods above.

The invention advantageously reduces the number of interactions with a subscription database of a communication network, thereby reducing signalling and overhead in a communication system and increasing the efficiency of the communication system. The invention will also reduce the amount of memory storage in the communication network since the common subscription can be used by more than one communication device for attaching to the communication network. Further, the invention also reduces the number of subscriptions needed in a subscription database, such as a HLR/HSS, since only one subscription is needed per group of devices according to the invention. Other advantages and applications of the present invention will be apparent from the following disclosure.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention in which:

- Figure 1 show an example of the procedure for attaching according to prior art.

Figure 2 shows a first example implementation of the invention.

Figure 3 shows a second example implementation of the invention. Figure 4 shows an example of security check performed by the network in accordance with the invention.

Figure 5 shows another example of security check performed by the network in accordance with the invention.

- Figure 6 shows an example of security check performed by the application layer.

Figure 7 schematically illustrates an example communication device according to the invention.

Figure 8 illustrates an example communication network entity according to the invention, such as a mobility management entity.

Detailed description

From the above description, it is expected that the total number of communication devices will increase, and a large number of these devices will be M2M type of devices. It is also expected that many of these M2M devices will have the same characteristics in common, e.g. having the same subscriber characteristics, which are denoted as MTC features in the 3GPP specifications meaning that they will have the same HLR/HSS subscription.

If using the same HLR/HSS interaction procedures for M2M devices as for H2H UEs, according to the above mentioned 3 GPP prior art solution, it will result in a high level of signalling in a communication system, which will increase the overhead in the communication system, and thereby reduce the efficiency of the same.

The present invention therefore relates to a method for attaching to a communication network belonging to a communication system in which communication devices attaches to the communication network by requesting and using a subscription from a subscription database.

The method comprises the steps of: dividing the communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a Common Subscription (CS) for attaching to the communication network; and providing one CS for each group of communication devices, wherein the CS is used by all communication devices belonging to the same group for attaching to the communication network of the communication system. Therefore, the invention advantageously reduces signalling overhead in a communication system over prior art by providing CSs for groups of communication devices.

A communication device is a device that is arranged for communication in a communication system and may be a mobile station, such as a UE, a M2M device or a hybrid thereof; meaning that the mobile station both comprises a H2H unit and a M2M unit. Further, the characteristics of communication devices belonging to the same group are the same.

Also, the CS is common for all communication devices of a specific group which implies that: devices of the same group have no subscription information that is not found in the CS, such as individual Quality of Service (QoS), individual subscribed APN, individual security parameters in the subscription database (HLR), etc. However, if a communication device of the group for example has to update its location information in the subscription database or has to retrieve additional subscription information different from the common information; additional access to the subscription database may be needed. Still the present method will be advantages over prior art.

The CS comprises information about the characteristics of the communication devices, such as system optimisation categories, information about transportation of data, QoS for data transportation, etc.

According to another embodiment of the invention, a mobility management entity (such as a SGSN/MME) of the network retrieves a CS from a subscription database. This is performed only once by the mobility management entity for each group of communication devices, thereby reducing the signalling still further with the method according to this embodiment. The mobility management entity uses the CS for controlling the interaction of the communication devices with the communication network, such as the geographical area a device is allowed to attach to, the communication channel a device is allowed to establish for transferring data, etc.

Further, the system has also to be configured when the CS shall be retrieved by mobility management entity from the subscription database, which relates to the system setting of the communication network. According to an embodiment of the invention, the CS for each group of communication devices is retrieved when a first device of a group attaches to a mobility management entity, which makes it possible to avoid storing data in the mobility management entity when no device is attached. Another solution is to retrieve the CS in advance before any of the devices in the group attaches. This latter approach has the advantage that data is already available when a device of the group attaches, which speeds up the attachment acceptation process, and thereby also access to different services of the network.

Regardless of how the CS is retrieved by the mobility management entity from the subscription database, considerations have to be given to the storage of the CS when it has been retrieved from the subscription database. According to an embodiment of the invention, the CS is preferably stored in the mobility management entity independently and regardless of the attachment or detachment of communication devices belonging to a given group of devices with an associated CS. With this embodiment the situation can be avoided that the CS is removed from the mobility management entity when a communication device of the group is detached from the network. Also, further retrieval of the CS from the subscription database is avoided with this embodiment.

The mobility management entity can keep the CS until the last communication device of the group detaches, or when a certain time has lapsed after that the last communication device of the group has detached. In the case that a device of the group changes mobility management entity, e.g. due to a mobility procedure, the CS is provided to a target mobility management entity to allow the target mobility management entity to know the CS information to be used for said device. Hence, the CS can be kept for a certain time in the original mobility management entity even if no more devices of the group are present at the time.

Other aspects relating to the storage of the CS is that the subscription database (HLR/HSS) can store CS either in a group subscription (a single subscription for all devices of the same group) or replicate the CS information in each device subscription. The first approach reduces the amount of data to be stored, but the second approach allows re-using existing subscription database with the only addition of parameters to already existing subscriptions. When the subscription is stored per device, an access key to retrieve information in the subscription database (HLR) can remain the IMSI key of each device. When a group subscription is used, a common key known by all devices can be used, it can e.g. be a common IMSI or a group identity.

Other considerations when using CSs according to the invention is whether communication devices have a right to use a CS or not, which can be reformulated as how to check a communication device's right to use a CS associated with a particular group. Hence, one or more security checks have to be performed for communication devices wanting to attach to a communication network using a CS.

Therefore, according to an embodiment of the invention, the check is performed by the network, and preferably by a mobility management entity which performs security checks, for example by authentication of communication devices wanting to attach to a communication network. The authentication can be performed by the mobility management entity by means of one or more of:

- A group identity which is provided by communication devices belonging to a group with an associated CS to the mobility management entity. The group identity is then compared to a group identity of the CS;

- A group security information key which is downloaded with the CS from the subscription database. The group security information key is checked with the security information of a communication device belonging to the group (see Figure 4); and - A list of allowed international mobile subscriber identities (IMSIs) for the group, which can be provided by the subscription database. The allowed IMSIs are then compared to the IMSI of each communication device attaching to the network (see Figure 5). Figure 4 shows an example how communication device are checked using a group security information key. When a device attaches, it provides its group identity (step 1), wherein the group identity is used to retrieve the CS of the group (step 2 and 3, respectively). The CS information contains security information for devices of the group, and this security information is used in a security check procedure (step 4) of the device before the attachment can be accepted.

Moreover, Figure 5 shows an example how communication device are checked using a list of IMSIs. When a device attaches, the device provides its IMSI and the IMSI for one or more groups to it belongs (step 1). The IMSIs are used to retrieve the CS for the group(s) to which the device belongs (step 2 and 3, respectively). The CS information for each group contains a list of IMSIs for devices that are part of the group, and the mobility management entity checks whether the IMSI provided by the device in step 1 is in the list of IMSIs of each group, and accept attachment to groups that contain the IMSI for the device.

The security check is, according to yet another embodiment of the invention, performed by the application layer, e.g. by an application layer entity (MTC Server/MTC User in 3GPP). Hence, the security checks, for example by authentication, are in this latter embodiment performed outside the network control.

However, it is also possible to use a security check procedure in which the application layer performs the security check on request by the network, which also supervises the security check of the application layer and uses the result of the security check for further processing. For example, the mobility management entity may request the application layer to perform the security check, and use the result of this security check in other applications.

Figure 6 shows an example how communication device are checked by the application layer. A device attaches and provides identity of the group(s) it belongs to (stepl). The mobility management entity retrieves the CS of the requested group from the subscription database if this has not already been done. Then the mobility management entity forwards the attachment request to an application layer entity (step 2). This application layer entity will perform the security check of the device and will reply to the mobility management entity whether the device is accepted for the group(s) or not (step 3). The mobility management entity will consider the response in step 3 to accept the device attachment or not. For example, if the device is not accepted by the application layer, its attachment will not be accepted by the mobility management entity, or a further security procedure may be initiated by the network.

In the following disclosure two exemplary implementations of the present invention are described.

Exemplary implementation 1

CS retrieval from a subscription database (in this example a HLR) allows retrieval of CS information for groups requested by communication devices, wherein devices provide a key to retrieve group subscription by e.g. using a common IMSI or Group IMSI/Group identity when requesting attachment to the network. If there is no information stored for a group requested by a device in a mobility management entity (in this example a MME) then the MME requests CS from the HLR. The CS for the missing group can be downloaded by the MME, and in order to avoid further requests from the HLR, the MME get the CS for all relevant groups (i.e. groups having at least one communication device that wants get access to the communication network) and stores the CSs for these groups for future use. However, the MME can avoid to download the CS for groups for which it already has the CS information stored, e.g. due to an earlier attachment of a device belonging to the group.

The advantages with this first implementation is that since communication devices provide their group identities in an attach request, the MME can check whether it already has the subscription information for these groups, and therefore interacts with the HLR only if the CS information is not available. Further, the subscription information for all groups requested by a device is downloaded only in one procedure exchanged with the HLR. No more interaction with the HLR for new devices wanting to attach to the same group subscription is needed. It should be noted that a communication device may need to provide, in addition to the group identifier, its own personal identifier (e.g. device IMSI), which relates to different security aspects discussed above in the description.

Exemplary implementation 2

CS retrieval from a subscription database (in this example a HLR) allows the retrieval of a list of groups and the associated CS information. In this implementation communication devices provide its own IMSI and the IMSI for the group to which it belong when requesting attachment to the communication network. If there is no CS information stored for at least one of the groups requested by a device in a mobility management entity (in this example a MME), the MME requests download of the CSs for the missing groups from the HLR. In order to avoid further requests from the subscription database for other devices, it is preferable that the MME gets all groups subscribed for this device to be downloaded and not only the current group requested for this attach request by the device, but the MME can avoid the downloading of group information for groups for which it does already have the subscription information, due to an earlier attachment of a device belonging to the group. The HLR provides IMS I lists of groups for the device and their associated CSs, and when a device changes MME, for example due to mobility, group information of this specific device are also transferred to the target MME. The advantages with this second implementation is that no change in the request signalling with the HLR (request per IMSI) is needed since a device provides its group identities in the attach request, and hence the MME can check whether it already has the CS information for these groups and interacts with the HLR only if the CS information is not available, which reduces the interaction with the HLR. Further, since group information is downloaded via single subscription retrieval procedure sent to the HLR for the first device of a group and not for subsequent devices belonging to the same group, multiple CS information can be retrieved at the same procedure; if a device belongs to many different groups, CS information for these groups can be downloaded during one procedure for the device which further reduces overhead in the communication system.

Since devices are not reliable, the communication system cannot rely on the group

information provided by a device to ensure that the device is actually allowed to use the CS of a group, if such CS has previously been downloaded for another device of that same group. Therefore, a group access right check may have to be performed, which also in this example relates to different security aspects discussed above in the description.

It should also be noted in this second implementation that the communication device needs to provide its own group identity when requesting attachment to a communication network, or else it may be problematic for the MME to check whether it already has downloaded the group information for a previously attached device belonging to that group.

Furthermore, the present invention also relates to a method in a communication device and a method in a communication network entity. The method in a communication device for attaching to a communication network involves the steps of: receiving a group identity; requesting a CS associated with the group identity; and using CS for attaching to the communication network. According to embodiment the method further comprises the step of: providing information about the identity of the communication device to a communication network entity, wherein the communication network entity is arranged for mobility management of communication devices in a communication system.

The method in a communication network entity, such as a mobility management entity, involves the steps of: dividing communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a CS for attaching to a communication network; and using one CS for each group of communication devices for the management of the interaction of the communication devices with the communication network. The communication network entity is arranged for mobility management of communication devices in a communication system.

According to embodiment the method further comprises the steps of: determining the group identity for each communication device wanting to attach to the communication network; and determining whether the CS associated with the group identity is stored in the communication network entity or has to be downloaded from a subscription database.

Furthermore, as understood by the person skilled in the art, a method in a communication device and a method in a communication network entity according to the present invention may be implemented in a computer program, having code means, which when run in a computer causes the computer to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may consist of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, the invention also relates to a communication device and a communication network entity. Figure 7 schematically illustrates an example of such a communication device.

The communication device is arranged for communication in a communication system and is arranged for attaching to a communication network by requesting and using a subscription, provided by a subscription database, such as a HLR/HSS. The communication device (70) is configured for receiving a group identity; requesting a CS associated with the group identity; and using the CS for attaching to the communication network. A receiver (71) receives one or more signals comprising group identity data. This data is processed in processing circuitry (72), (74), processing the group identity for providing a common subscription request. Depending on response to said common subscription request, processing circuitry (73), (74) provides processing for attaching the device to the communication network and/or system according to the common subscription. The various processing circuitry (72-74) may be one common or general processing circuitry appropriately arranged (74), or distinguishable processing circuitry (72), (73) for dedicated processing.

The communication network entity, such as a mobility management entity, is arranged for mobility management of communication devices in a communication system. Figure 8 illustrates an example of such an entity (80). The communication network entity is configured for: dividing communication devices into one or more different groups of communication devices, wherein communication devices belonging to the same group have a CS for attaching to the communication network; and using one CS for each group of communication devices for the management of the interaction of the communication devices with the communication network. The example communication network entity comprises processing circuitry (81), (82) arranged for the dividing into groups and processing circuitry (81), (83) arranged for interacting with individual communication devices according to a common subscription. The processing circuitry may be a single processing circuitry (81) or dedicated circuitry (82), (83) that need not necessarily be located to or arranged in a single physical unit.

Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.