WO2019120541A1

WO2019120541A1 - A client device, a network device, a method and a computer program for plmn list

Info

Publication number: WO2019120541A1
Application number: PCT/EP2017/084074
Authority: WO
Inventors: Vishnu PREMAN
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-12-21
Filing date: 2017-12-21
Publication date: 2019-06-27

Abstract

A client device detects the available Public Land Mobile Networks and provides the information to the network - the network may use broader information and modify a PLMN list dynamically. The relevant, local information is delivered to the network device, wherein the network device may have broader information of the PLMN situation and return the modified PLMN list reflecting the broader information to the client device. Thus, an efficient concept for steering the registration process of the client device to a desired Public Land Mobile Network is realized.

Description

A CLIENT DEVICE, A NETWORK DEVICE, A METHOD AND A COMPUTER PROGRAM FOR PLMN LIST

This disclosure relates to the field of wireless communications, in particular to the selection of a Public Land Mobile Network.

BACKGROUND

To improve the development of wireless communications technologies, a Long Term Evolution (LTE) project has been set up by the 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP). Fifth-generation radio transmission 5G NR (Next Radio) has been set to further develop the transmission technologies.

In 5G NR wireless communication, a client device, for example a user equipment (UE), may select a Public Land Mobile Network (PLMN) according to roaming requirements based on agreements between operators or service requirements. One example of the PLMN selection is enabled by a PLMN list that the UE may receive from the USIM. The PLMN list comprises in a prioritized order a selection of networks where the UE attempts to register.

The network may steer the UE to the desired PLMN by rejecting a registration attempt. The UE may try to register to PLMNs as they are discovered, but as the first PLMN may reject the registration, the UE attempts registration to the second PLMN - repeating the process until one PLMN accepts the registration. The solution consumes network resources and radio bandwidth. The UE has to perform additional signalling towards the network. The process, having multiple unnecessary

registration attempts, may be time consuming. As another example, the network has no information of the PLMNs available to the UE while it keeps rejecting - the network may later have to accept the PLMN. Near a country border the number of available PLMNs may vary; the subscriber should be protected of unnecessary roaming situations - and the roaming costs - at the overlapping PLMN areas near country borders.

In one example, the network updates the PLMN list residing on the USIM over the air (OTA). The home PLMN may send the information via SMS messages directly to the USIM memory location, updating the previous PLMN list. The OTA update may be done in response to roaming agreements between operators, wherein the PLMN list has information of the preferred roaming partners in a prioritized order. The OTA update is usually done for all subscribers of the network, as the solution is not suitable for quick and dynamic PLMN list updates.

In one example, the PLMN may be selected according to the geographical location of the UE, wherein the UE has at least a data connection, for example a Wi-Fi connection. The UE may run an application configured to send the geographical location of the UE to a server. The server responds by sending a PLMN list suitable for the location of the UE. Upon receiving an updated list of preferred PLMN/access technology combinations, the UE may verify the integrity of the received list of preferred PLMN/access technology combinations. The network defines the PLMN list according to predefined measurements, wherein the solution is prone to errors. The positioning method may not be accurate, and the actual PLMN coverage at the defined location may be different than the predefined information. The coverage can temporarily vary in a specific location.

Technical specification 3GPP TS 24.890 V2.0.0 discloses situations for replacing the highest priority entries in the Operator Controlled PLMN Selector with Access Technology" list stored in the ME with the received list of preferred PLMN/access technology combinations.

SUMMARY

The inventor have found that it can be problematic that aforementioned solutions are static. In other words, the core network has no means to steer the UE’s PLMN selection in quickly changing situations. As an example, the home PLMN or the preferred PLMN may be temporarily down, for example due to technical challenges or environmental reasons. During an emergency situation or a crisis there is a need to inform the public despite the problems of a particular PLMN, but the core network cannot update the PLMN information without a data connection.

It is the object of the invention to provide an efficient concept for providing a list of Public Land Mobile Networks to a client device. This object is achieved by the features of the independent claims. Further embodiments of the invention are apparent from the dependent claims, the description and the figures.

The disclosed solution is based on the finding that a client device detects the available Public Land Mobile Networks and provides the information to the network - the network may use broader information and modify a PLMN list dynamically. The relevant, local information is delivered to the network device, wherein the network device may have broader information of the PLMN situation and return the modified PLMN list reflecting the broader information to the client device. Thus, an efficient concept for steering the registration process of the client device to a desired Public Land Mobile Network is realized.

According to a first aspect, a client device for wireless communication is disclosed. The client device is configured to detect Public Land Mobile Networks being available to the client device at its location; create a PLMN list comprising information of the available Public Land Mobile Networks; send the PLMN list to a network device; and receive an updated PLMN list from the network device.

The client device may detect the available Public Land Mobile Networks by scanning and measuring radio frequencies with a radio interface. In one example the client device is configured to detect the Public Land Mobile Networks available to the client device by executing a PLMN search. The client device gathers local information of transmission capabilities of the available Public Land Mobile Networks, for example as to which networks are available. The created PLMN list may comprise PLMN list information as defined by technical specification 3GPP TS 24.008 or corresponding later/parallel technical specifications. Alternatively, or in addition, the created PLMN list may comprise detailed measurement information or a transmission quality parameter. The sent PLMN list and the updated PLMN list may comprise similar formats. In one embodiment the sent information comprises a transmission quality parameter and the received PLMN list comprises a list of PLMNs in the order of priority. Alternatively, or in addition, the received PLMN list may comprise a

Forbidden PLMN list having a list of PLMNs that the client device should not register into. The client device establishes a connection to the Access Network, wherein the network device responding to the client device may reside in the Core Network. In one implementation of the first aspect, the PLMN list update is executed at the Core Network. The Core Network may comprise information from a higher protocol level, for example information about the general usability of certain Public Land Mobile Networks.

In a further implementation of the first aspect, the client device is configured to reside in a visiting Public Land Mobile Network, wherein the network device resides in a Core Network of a home Public Land Mobile Network of the client device. The client device may be roaming, or it may reside in the area of the home Public Land Mobile Network, being ready to connect and executing radio transmission measurements. The client device may be forced to roam into visiting Public Land Mobile Network from the home Public Land Mobile Network.

In a further implementation of the first aspect, the client device is configured to select a random visiting Public Land Mobile Network from the group of the Public Land Mobile Networks being available to the client device; send the PLMN list to the network device residing in a home Public Land Mobile Network in an ATTACH REQUEST message or in a TRACKING AREA UPDATE REQUEST message; and receive an updated PLMN list from the network device. Sometimes the client device may randomly select a PLMN while roaming. The created PLMN list comprising information of the available Public Land Mobile Networks may be sent to the network device without the Public Land Mobile Network requesting the information.

In a further implementation of the first aspect, the client device is configured to receive a request to gather the list of available Public Land Mobile Networks in a received ATTACH ACCEPT message or a received ATTACH REJECT message from the network device.

In a further implementation of the first aspect, the client device is configured to receive from the network device a request to gather a list of available Public Land Mobile Networks. In a further implementation of the first aspect, the client device is configured to send the PLMN list to the network device in a TRACKING AREA UPDATE REQUEST message.

In a further implementation of the first aspect, the client device is configured to receive the updated PLMN list from the network device in a TRACKING AREA UPDATE ACCEPT message, an ATTACH ACCEPT message or an ATTACH

REJECT message.

In a further implementation of the first aspect, the client device is configured to send the PLMN list to the network device in an ATTACH REQUEST message as a response to receiving an ATTACH REJECT message from the network device.

In a further implementation of the first aspect, the client device is configured to receive from the network device a request to gather a list of available Public Land Mobile Networks; and as a response to the request, detect Public Land Mobile Networks being available to the client device.

In a further implementation of the first aspect, the client device is configured to receive a request to gather the list of available Public Land Mobile Networks in a CONFIGURATION UPDATE COMMAND. The request to gather the list may be sent as a flag having ON/OFF information within an information element. For the purposes of distributing the information within this document, the feature is referred to as a Network Controlled PLMN Selection Policy (NCPSP), wherein the NCPSP flag may be set to ON or OFF.

In a further implementation of the first aspect, the client device is configured to respond to the request with a CONFIGURATION UPDATE COMPLETE message. The update message is optional. When the NCPSP is set to ON, the client device may decide, based on implementation, if it will send a CONFIGURATION UPDATE COMPELETE message or not.

In a further implementation of the first aspect, the client device is configured to replace the PLMN list with the updated PLMN list. The PLMN list may be updated to the USIM card, wherein the client device writes the information to a USIM memory location reserved for the PLMN list, thereby replacing the original PLMN list.

Alternatively, or in addition, the PLMN list is updated to the memory of the client device. The client device may store multiple PLMN lists, wherein the client device may store the received PLMN list with context information. The client device may utilize different PLMN lists stored to the client device memory according to the detected context. For example, an emergency situation PLMN list may be stored to be used only during emergency situations.

According to a second aspect, a network device is disclosed. The network device is configured to receive from a client device in a wireless network a PLMN list comprising information of the Public Land Mobile Networks being available to the client device at its location; update the PLMN list according to at least one update criterion; and send the updated PLMN list to the client device. The network device resides according to one implementation in the Core Network. In one embodiment the network device has been implemented into a cloud computing environment.

In a further implementation of the second aspect, the network device is configured to communicate with the client device residing in a visiting Public Land Mobile Network, wherein the network device resides in a Core Network of a home Public Land Mobile Network.

In a further implementation of the second aspect, the network device is configured to send to the client device a request to gather the list of available Public Land Mobile Networks in an ATTACH ACCEPT message or an ATTACH REJECT message.

In a further implementation of the second aspect, the network device is configured to send the request to gather the list of available Public Land Mobile Networks as a status flag in a message. The status flag is in one example the NCPSP flag.

In a further implementation of the second aspect, the network device is configured to receive the PLMN list from the client device in a TRACKING AREA UPDATE

REQUEST message.

In a further implementation of the second aspect, the network device is configured to send an updated PLMN list to the client device in a TRACKING AREA UPDATE ACCEPT message, an ATTACH ACCEPT message or an ATTACH REJECT message.

In a further implementation of the second aspect, the network device is configured to receive the PLMN list from the client device in an ATTACH REQUEST message as a response to sending an ATTACH REJECT message to the client device.

In a further implementation of the second aspect, the network device is configured to send a request to gather the list of available Public Land Mobile Networks in a CONFIGURATION UPDATE COMMAND.

In a further implementation of the second aspect, the network device is configured to receive a response to the request with a CONFIGURATION UPDATE COMPLETE message.

In a further implementation of the second aspect, the network device is configured to send to the client device a request to gather a list of available Public Land Mobile networks (e.g. at the location of the client device).

According to a third aspect, a method for a client device is disclosed. The method comprises detecting Public Land Mobile Networks being available to the client device at its location; creating a PLMN list comprising information of the available Public Land Mobile Networks; sending the PLMN list to a network device; and receiving an updated PLMN list from the network device.

According to a fourth aspect, a method for a network device is disclosed. The method comprises receiving from a client device in a wireless network a PLMN list comprising information of the Public Land Mobile Networks being available to the client device at its location; updating the PLMN list according to at least one update criterion; and sending the updated PLMN list to the client device.

According to a fifth aspect, a computer program is disclosed, comprising program code for performing the methods described hereinbefore, when executed on a computer. The various aspects disclosed herein provide a dynamic solution for modifying the client device’s PLMN list. The local, measured information may be delivered to the network device, wherein the network device has the ability to react quickly to various situations. For example, the billing model at the visiting PLMN may be dynamic and change according to season. As another example, if a first PLMN is down, transferring a large number of client devices to a second PLMN may help the restart procedure of the first PLMN. Network congestion may be avoided by distributing the load to other networks. During a crisis or an emergency situation the emergency organisation may take over the communications channels and provide information to the public regardless of the PLMN where each client device resides. The solution enables forcing the client device to a predefined PLMN.

Embodiments or aspects of the invention can be implemented in hardware, software or in any combination thereof. Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings. The aspects and implementations described herein are not limited to implementations which solve any or all the disadvantages of known radio transmission systems.

BRIEF DESCRIPTION OF THE FIGURES

Further embodiments of the invention will be described with respect to the following figures, in which:

FIG. 1 schematically illustrates an example of a telecommunication system for practicing embodiments of the present invention;

FIG. 2 illustrates a simplified signaling flowchart of an example of one embodiment;

FIG. 3 illustrates a simplified signaling flowchart of an example of one embodiment;

FIG. 4 illustrates a simplified signaling flowchart of an example of one embodiment;

FIG. 5 illustrates a simplified flowchart of an example of one method embodiment; and

FIG. 6 illustrates a simplified flowchart of an example of one method embodiment.

Identical reference signs are used for identical or at least functionally equivalent features. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized.

However, the same or equivalent functions and sequences may be accomplished by different examples.

FIG. 1 schematically illustrates one simplified example of a telecommunication network, disclosing one exemplary embodiment of a network device and a client device. In this example, client devices 130, 140, 150 are wirelessly connected to an access network 220. All client devices 130, 140, 150 comprise similar components to client device 130: at least one processor 131 and a memory 132 for storing instructions that, when the instructions are executed, cause the client device 130 to perform the functionality described hereinafter. A transceiver 133 is configured to provide a communication link to the telecommunication network via a radio link. The functionality of the transceiver 133 may be independent, as the transceiver may possess a dedicated processor. The processor 131 may be used to cause the transceiver to execute specific functions. One example of the client device 130 is a user equipment, a device configured to be wirelessly connected to the access network 220. The client device 130 may be a functional module configured to operate in the user equipment, for example a communication module of a smartphone.

The access network 220 provides a serving cell 221 to the user equipments 130,

140, 150. The apparatus representing the access network 220 may be an evolved NodeB (eNB) or a next generation NodeB (gNB) providing a direct radio link to the client devices 130, 140, 150, an aggregation of access networks, an access node or a network eNB. Examples of wireless communications technologies having embodiments disclosed herein are the LTE network or 5G NR network.

The portion of the core network 100 and the network device 1 10 residing in the core network define one example of a home Public Land Mobile Network. In this example the portion of the core network 100 is represented by a cloud, as the

telecommunication network may be implemented in various ways. The core network 100 may reside at least partially in a cloud computing environment. In one embodiment a portion of the functionality of the access network 220 is distributed to the network device 1 10 which is connected to the access network 220. The network device is a portion of the core network. The network device 1 10 comprises at least one processor 1 1 1 and a memory 1 12 for storing instructions that, when the instructions are executed, cause the network device 1 10 and the access network 220 to perform the functionality described herein. A transceiver 1 13 is configured to provide a communication link to the client devices 130, 140, 150 via the access network 220. Further, in one embodiment the network device 1 10 is configured to provide information to be sent to the client device 130 via the access network 220.

In this example the client device 130 is roaming in a first visiting Public Land Mobile Network. The core network portion 200 of the first visiting Public Land Mobile

Network is illustrated by a cloud. The visiting PLMN core network 200 is connected to the home PLMN core network 100. A second visiting PLMN 300 is available to the client device 130. The client device 130 may detect a serving cell 321 of the second PLMN. When the client device must register to the network, it must select either the first visiting PLMN 200 or the second visiting PLMN 300.

FIG. 2 illustrates a simplified signalling flowchart of an example of one embodiment, showing a simplified diagram of the client device 130, the Non Access Stratum and the network device 1 10 residing in a Core Network CN. In the initial scenario the client device 130 is not registered to any network, step 201 . The client device 130 attempts an initial registration into the network by sending a ATTACH REQUEST message 202 to the network. The message is relayed via the visiting PLMN to the home PLMN and to the network device 1 10 of the core network. In this example the home PLMN 1 10 is not satisfied with the visiting PLMN that the client device 130 has attempted to register to.

The network device 1 10 sets in this example a flag representing the Network

Controlled PLMN Selection Policy (NCPSP) as ON. The NCPSP is a conceptual term used to describe the functionality throughout this document. The network device 1 10 sends to the client device 130 an ATTACH ACCEPT message 203. The message 203 comprises information describing the PLMN selection procedure, such as the NCPSP flag set as ON in an information element of said message 203. Alternatively, the network device may send to the client device 130 an ATTACH REJECT message with the NCPSP flag set ON inside the information element of the message.

The client device 130 detects the NCPSP procedure and performs a PLMN search, step 204. The PLMN search may comprise radio interface measurements and/or data from the Access Stratum or Channels layers. The client device 130 gathers a list comprising information of the currently available PLMNs to the client device 130. Examples of the information on the PLMN list are Mobile Country Code (MCC),

Mobile Network Code (MNC) and any quality parameter obtained during the search procedure. In one embodiment the available PLMN list is encoded according to technical specification 3GPP TS 24.008, section 10.5.1 .13 or a corresponding later or parallel technical specification e.g. for another communication standard. In one embodiment the quality parameters are included in the list.

The client device 130 sends the available PLMN list to the network device 1 10 of the core network inside an information element in a TRACKING AREA UPDATE

REQUEST message, step 205. In step 206 the network device 1 10 encodes the PLMN list according to 3GPP TS 24.008, section 10.5.1 .13, thereby creating an updated PLMN list. The quality parameters are omitted from the updated PLMN list. The updated PLMN list is created according to at least one update criterion. The update criterion may relate to a quality parameter received from the client device 130. The update criterion may relate to a quality parameter received from the visiting PLMN 200. The network device 1 10 may update the PLMN list according to roaming agreements set between network operators. In case of emergency, the PLMN list update may be used to direct client devices 130 to another PLMN to enable safe communication.

The network device 1 10 sends the updated PLMN list to the client device 130 inside an information element in a TRACKING AREA UPDATE ACCEPT message 207.

If the message 203 had been ATTACH REJECT instead of ATTACH ACCEPT, the client device 130 would have triggered another ATTACH REQUEST procedure by sending an ATTACH REQUEST message with the available PLMN list, since the ATTACH REJECT message contained the NCPSP flag set ON. In this alternative scenario, the network element 1 10 updates the PLMN list and sends it back to the client device 130 as an information element in the ATTACH ACCEPT or the ATTACH REJECT message.

The client device 130 receives the updated PLMN list. The PLMN list may be stored to a USIM card, overwriting the previous PLMN list. The client device 130 may store multiple PLMN lists to its memory and select a suitable PLMN list according to context or other selection criteria. The PLMN list may comprise a Forbidden PLMN list. The client device 130 performs PLMN selection, step 208. As the list has a prioritized order, the client device 130 starts the procedure by giving the highest priority to the PLMNs presented in the order of their existence. In one embodiment the client device 130 utilises all the information stored in the USIM related to the network selection, e.g. HPLMN, Operator controlled PLMN Selector list, User Controlled PLMN Selector list or Forbidden PLMN list.

FIG. 3 illustrates a simplified signaling flowchart of an example of one embodiment.

In this scenario the client device 130 performs a T racking Area Update (TAU) due to entering a new registration area or expiration of a periodic registration timer, step 301 .

The client device 130 attempts an initial registration by sending a TRACKING AREA UPDATE REQUEST message 302 to the network device 1 10. The message is relayed via the visiting PLMN to the home PLMN and to the network device 1 10 of the core network. In this example the home PLMN 1 10 is not satisfied with the visiting PLMN that the client device 130 has attempted to register to.

The network device 1 10 sets in this example a flag representing the Network

Controlled PLMN Selection Policy (NCPSP) as ON. The network device 1 10 sends to the client device 130 a TRACKING AREA UPDATE ACCEPT message 303. The message 303 comprises information describing the PLMN selection procedure, such as the NCPSP flag set as ON in an information element of said message 303.

Alternatively, the network device may send to the client device 130 a TRACKING AREA UPDATE REJECT message with the NCPSP flag set ON inside the

information element of the message. Due to receiving the TRACKING AREA

UPDATE REJECT message, the client device 130 may no longer be registered to any network. In that case the client device 130 may proceed to attach procedure according to FIG. 2.

The client device 130 detects the NCPSP procedure and performs a PLMN search, step 304. The PLMN search may comprise radio interface measurements and/or data from the Access Stratum or Channels layers. The client device 130 gathers a list comprising information of the available PLMNs. The client device 130 sends the available PLMN list to the network device 1 10 of the core network inside an information element in a TRACKING AREA UPDATE REQUEST message, step 305. In step 306 the network device rearranges or sorts the PLMN list according to principles set in the previous example, thereby creating an updated PLMN list. The network device 130 sends the updated PLMN list to the client device 130 inside an information element in a TRACKING AREA UPDATE ACCEPT message 307.

If the message 303 had been TRACKING AREA UPDATE REJECT instead of TRACKING AREA UPDATE ACCEPT, the client device 130 may trigger another ATTACH procedure - as illustrated in FIG. 2 - with the available PLMN list, in response to the TRACKING AREA UPDATE REJECT message having the NCPSP flag set ON. In this alternative scenario, the network element 1 10 updates the PLMN list and sends it back to the client device 130 as an information element in the

TRACKING AREA UPDATE ACCEPT or the TRACKING AREA UPDATE REJECT message.

The client device 130 receives the updated PLMN list and performs the PLMN selection, step 308.

FIG. 4 illustrates a simplified signaling flowchart of an example of one embodiment.

In 5G NR, the network device 1 10 may update a configuration parameter in the client device 130 without waiting for a registration request. A CONFIGURATION UPDATE command from the network device 1 10 to the client device 130 is used to inform that the NCPSP is activated, step 401 .

The network device 1 10 is set to change the serving PLMN and send the

CONFIGURATION UPDATE command with NCPSP = ON to the client device 130, message 402. The client device 130 responds with a CONFIGURATION UPDATE COMPLETE message 403 to the network device 1 10.

The client device 130 detects the NCPSP procedure and performs a PLMN search, step 404. The PLMN search may comprise radio interface measurements and/or data from the Access Stratum or Channels layers. The client device 130 gathers a list comprising information of the available PLMNs. The client device 130 sends the available PLMN list to the network device 1 10 of the core network inside an information element in a TRACKING AREA UPDATE REQUEST message, step 405. In step 406 the network device rearranges or sorts the PLMN list according to principles set in the previous examples, thereby creating an updated PLMN list. The network device 130 sends the updated PLMN list to the client device 130 inside an information element in a TRACKING AREA UPDATE ACCEPT, message 407. The client device 130 receives the updated PLMN list and performs the PLMN selection, step 408.

The methods can be performed by a computer program.

FIG. 5 illustrates a simplified flowchart of an example of one method embodiment for a client device. The method comprises the steps of: detecting Public Land Mobile Networks being available to the client device at its location, step 501 ; creating a PLMN list comprising information of the available Public Land Mobile Networks, step 502; sending the PLMN list to a network device, step 503; and receiving an updated PLMN list from the network device, step 504. Based on this updated PLMN list the client device may perform a PLMN selection.

FIG. 6 illustrates a simplified flowchart of an example of one method embodiment for a network device. The method comprises the steps of: receiving from a client device in a wireless network a PLMN list comprising information of the Public Land Mobile Networks being available to the client device at its location, step 601 ; updating the PLMN list according to at least one update criterion, step 602; and sending the updated PLMN list to the client device, step 603.

The invention has been described in conjunction with various embodiments herein. However, other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article“a” or“an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a

combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.

Claims

1 . A client device (130) for wireless communication, configured to:

detect Public Land Mobile Networks being available to the client device at its location;

create a Public Land Mobile Network, PLMN, list comprising information of the available Public Land Mobile Networks;

send the PLMN list to a network device; and

receive an updated PLMN list from the network device.

2. A client device (130) according to claim 1 , configured to reside in a visiting Public Land Mobile Network, wherein the network device resides in a Core Network of a home Public Land Mobile Network of the client device.

3. A client device (130) according to claim 1 or 2, configured to:

select a random visiting Public Land Mobile Network from the group of the Public Land Mobile Networks being available to the client device;

send the PLMN list to the network device residing in a home Public Land Mobile Network in an ATTACH REQUEST message or in a TRACKING AREA UPDATE REQUEST message; and

receive an updated PLMN list from the network device.

4. A client device (130) according to any of the claims 1 to 3, configured to: receive from the network device a request to gather a list of available Public Land Mobile Networks; and

detect Public Land Mobile Networks being available to the client device based on the request.

5. A client device (130) according to claim 4, configured to receive the request to gather the list of available Public Land Mobile Networks in a received ATTACH ACCEPT message or a received ATTACH REJECT message from the network device.

6. A client device (130) according to claim 4, configured to receive the request to gather the list of available Public Land Mobile Networks in a CONFIGURATION UPDATE COMMAND.

7. A client device (130) according to claim 5 or 6, configured to respond to the request with a CONFIGURATION UPDATE COMPLETE message.

8. A client device (130) according to any of the claims 1 to 7, configured to receive the updated PLMN list from the network device in a TRACKING AREA UPDATE ACCEPT message, an ATTACH ACCEPT message or an ATTACH REJECT message.

9. A client device (130) according to any of the claims 1 to 8, configured to send the PLMN list to the network device in an ATTACH REQUEST message as a response to receiving an ATTACH REJECT message from the network device.

10. A client device (130) according to any of the claims 1 to 8, configured to send the PLMN list to the network device in a TRACKING AREA UPDATE REQUEST message.

1 1 . A client device (130) according to any of the claims 1 to 10, configured to replace the PLMN list with the updated PLMN list.

12. A network device (1 10), configured to:

receive from a client device in a wireless network a Public Land Mobile Network, PLMN, list comprising information of the Public Land Mobile Networks being available to the client device at its location;

update the PLMN list according to at least one update criterion; and

send the updated PLMN list to the client device.

13. A network device (1 10) according to claim 12, configured to communicate with the client device residing in a visiting Public Land Mobile Network, wherein the network device resides in a Core Network of a home Public Land Mobile Network.

14. A network device (1 10) according to claim 12 or 13, configured to communicate with the client device residing in a home Public Land Mobile Network, wherein the network device resides in a Core Network of a home Public Land Mobile Network.

15. A network device (1 10) according to any of the claims 12 to 14 configured to send to the client device a request to gather a list of available Public Land Mobile networks.

16. A network device (1 10) according to claim 15, configured to send to the client device the request to gather the list of available Public Land Mobile Networks in an ATTACH ACCEPT message or an ATTACH REJECT message.

17. A network device (1 10) according to claim 15, configured to send the request to gather the list of available Public Land Mobile Networks in a CONFIGURATION UPDATE COMMAND.

18. A network device (1 10) according to any of the claims 15 to 17, configured to send the request to gather the list of available Public Land Mobile Networks as a status flag in a message.

19. A network device (1 10) according to any of the claims 15 to 18, configured to receive a response to the request with a CONFIGURATION UPDATE COMPLETE message.

20. A network device (1 10) according to any of the claims 12 to 19, configured to receive the PLMN list from the client device in a TRACKING AREA UPDATE REQUEST message.

21 . A network device (1 10) according to any of the claims 12 to 20, configured to send an updated PLMN list to the client device in a TRACKING AREA UPDATE ACCEPT message, an ATTACH ACCEPT message or an ATTACH REJECT message.

22. A network device (1 10) according to any of the claims 12 to 21 , configured to receive the PLMN list from the client device in an ATTACH REQUEST message as a response to sending an ATTACH REJECT message to the client device.

23. A method for a client device, comprising:

detecting (501 ) Public Land Mobile Networks being available to the client device at its location;

creating (502) a PLMN list comprising information of the available Public Land Mobile Networks;

sending (503) the PLMN list to a network device; and

receiving (504) an updated PLMN list from the network device.

24. A method for a network device, comprising:

receiving (601 ) from a client device in a wireless network a PLMN list comprising information of the Public Land Mobile Networks being available to the client device at its location;

updating (602) the PLMN list according to at least one update criterion; and sending (603) the updated PLMN list to the client device.

25. A computer program comprising program code for performing the method according to claim 23 or claim 24 when executed on a computer.