GB2434055A

GB2434055A - System and method for network selection for a communication device

Info

Publication number: GB2434055A
Application number: GB0600339A
Authority: GB
Inventors: Pierre-Jean Muller
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2006-01-09
Filing date: 2006-01-09
Publication date: 2007-07-11
Anticipated expiration: 2026-01-09
Also published as: GB2434055B; GB0600339D0

Abstract

System for controlling network selection for a communication device comprising a home network (60), at least one visiting network available for communication (20-50) and a mobile communication device (10) associated with the home network and communicating with a first visiting network wherein the home network comprises means for transmitting data identifying whether the first visiting network is a preferred network to the visiting network and the device comprises means for maintaining communication with the first visiting network in dependence on the first visiting network being the most preferred of any available network.

Description

System and Method for Network Selection for a Communication Device The

present invention relates to a system and method for network selection for a communication device and in particular to a system and method for network selection when a home network is unavailable.

There is a strong demand for subscriber (home) mobile telephone networks (HPLMN) to be able to select which networks are used by their customers when those customers are operating in an area in which the home network is not available. This is known as roaming mode and the device communicates on a network other than the home network. The roaming network is known as the visiting network (VPLMN). Network selection by the HPLMN is becoming increasingly desirable since mobile users are more frequently using their devices abroad and in areas in which their home network does not provide coverage.

Additionally, as the mobile network becomes increasingly global, network providers are creating partnerships with overseas networks in order to offer roaming facilities to their subscribers at reduced costs. For example, a network may negotiate a discount from a VPLMN partner which requires, for instance, the network's customers to communicate on a VPLMN for a minimum number of minutes each month. In order to meet such a quota, the home network should ensure that its users operate on the partner VPLMN when it is available in preference to other available VPLMNs.

Presently, network operators store details of preferred VPLMNs in the SIM/USIM of the handsets. These may be stored at sale or manufacture, typically as a list, and identify the preferential VPLMNs that the device should use when roaming.

The VPLMN preferences of home networks change at different times due to, for example, the home network negotiating better rates with different VPLMNs. For example, if the home network has negotiated a cost reduction with a preferred VPLMN on the basis of its subscribers using at total of X minutes of time on that network each month, on the last day of the month, if the necessary X minutes have not been used, the home network would want to direct new roamers to the preferred network in order to meet its contractual obligations to that network.

I

In present systems the home network operator can indicate its current VPLMN preferences to its users at a given time by remotely reconfiguring the preferred VPLMN lists stored in the SIM/USIM using Over the Air (OTA) signalling.

Additionally, the home network can issue a reject/forbid cause related to a particular VPLMN. When a UE registers with a VPLMN the VPLMN contacts the home network for confirmation of the subscriber's data. In response to the VPLMN request, the home network is able to refuse the registration of the device with the VPLMN using a reject/forbid cause. The reject cause prevents the UE from communicating with the VPLMN. This provides the home operator with the control to prevent its subscribers from communicating on particular, non-preferred, networks.

A problem with the Over the Air (OTA) based system is that it cannot guarantee that handsets have stored up to date preferred VPLMN lists which are identical to those of the home network. It is possible that a handset may be out of range or switched off when the OTA signal is transmitted and so will not receive the OTA signal from its network. In this situation, the handset has not updated its preferred VPLMN list. Additionally, the "refresh" command subsequent to an OTA re-configuration is not uniformly implemented on all handsets. This can result in the update not being made when the home network operator requires it. Therefore, the OTA system can result in different handsets storing different preference lists.

The reject cause system in which the home network refuses to allow the device to communicate with a roaming network can result in a situation in which the home network rejects the VPLMN roaming network and the handset is unable to locate any further VPLMNs. The handset is then unable to communicate despite the fact that a non-preferred VPLMN is available.

We have appreciated that it is beneficial for a network to be able influence on which network each of its customers' handsets communicates in order that the handsets communicate on a VPLMN preferred by the home operator when it is available. It is also beneficial that a handset is aware of the home network's current VPLMN preferences in order that it searches for and attempts to communicate with networks preferred by the home operator. However, if the only VPLMN that is available is not preferred by the home network, the handset should be permitted to operate on that VPLMN in order that it is able to obtain a network service.

Embodiments of the present invention overcome the problems of the prior art by enabling the home network to transmit data regarding the VPLMN preferences of the home network to the VPLMN with which the UE is communicating. This data is then transmitted to the UE. In preferred embodiments, the VPLMN transmits a preferred VPLMN list to the UE. In alternative embodiments the VPLMN merely indicates to the UE that it is not a preferred network but that the UE may communicate with the non-preferred VPLMN it if it is unable to locate a preferred VPLMN. Further embodiments transmit a time period for which the VPLMN is not preferred.

Embodiments of the invention provide the advantage that the UE receives data confirming the current VPLMN preferences of its home network. This facilitates that the handset communicates with VPLMNs which are preferred by the home network when those preferred VPLMNs are available.

The invention is now defined in its various aspects in the appended claims to which reference should now be made.

A specific embodiment of the invention is now described with reference to the figures in which: Figure 1 shows a UE operating in an area in which the home network is not available but for which service is provided by VPLMNI-4.

Figure 2 is a flow diagram showing the steps taken when a UE attempts to register with a VPLMN in an embodiment of the invention.

Figure 3 is a flow diagram showing the steps taken when a UE attempts to register with a VPLMN in a further embodiment of the invention.

In Figure 1, a user equipment (UE) is located in an area in which network coverage is not provided by its home network 60. This situation is particularly applicable when the UE is located in a different country from the home network but is applicable in any area or at any time at which the home network is not available. The area in which the UE is located is served by alternative networks VPLMNI 20, VPLMN2 30, VPLMN3 40 and VPLMN4 50.

The UE or SIM/USIM may be programmed at manufacture or sale with a list of VPLMNs which are preferred by the home network. When the UE 10 executes a network search, it tries to locate its home network. If the home network is not available, it searches for the alternative VPLMNs in the order provided in the preferred VPLMN list. Alternatively, the UE may execute a full network availability search and then attempt to communicate with the available network which is most preferable in accordance with the preferred VPLMN list.

Figure 2 indicates the steps taken by embodiments of the invention during the network registration procedure. The registration procedure typically occurs at power up of the UE and periodically after power up. At 210 the UE determines whether the home network is available. If the home network is available, the UE connects to the home network at 220. If the home network is not available, the UE searches for and locates a visiting network (VPLMNI) at 230. VPLMNI may have been identified as a result of a full network availability search, may be the highest available network of the preferred VPLMN list stored within the UE or SIM or may be the first available network that the device has encountered.

At 240 the device communicates with VPLMN1 by sending a registration request.

VPLMNI then contacts the home network (HPLMN) to indicate that it has received a communication from the UE and that the UE is attempting to register with it at 250. Communication between the VPLMN and the HPLMN is made between a module switching centre and location register associated with the visiting network (VMSCNLR) and a module switching centre and location register of the home network (HMSC/HLR). The protocol for such communication is defined in 3GPP IS 29.002 and is known to those skilled in the art. The communication from the VMSCNLR to the HMSCNLR includes identification of the UE using its International Mobile Subscriber Identity (IMSI) which is known by both the home network (HPLMN) and the VPLMN.

In response to the communication from VPLMN1, the HPLMN sends data associated with the particular UE, for example, subscriber data and, additionally, the VPLMN preference list of the home network to VPLMNI at 260. The information transmitted by the HPLMN to VPLMN1 should not impact significantly on the standard signalling and procedures as defined in SGPP TS29.002.

When VPLMN has received the VPLMN preference list from the HPLMN, it forwards the list to the UE at 270. Preferably, the list is transmitted to the UE using layer 3 mobility management/GPRS mobility management (MM/GMM) signalling messages, i.e. ATTACH-ACCEPT.

The home operator VPLMN preference list is contained in an new Information Element (IE) which is carried in the layer 3 MM/GMM signalling messages. The new lE is included in the mobility management (MM) and GPRS mobility management (GMM) CN to UE messages standards (3GPP TS 24.008).

Once the UE has received the VPLMN preference list from VPLMNI, with which it is trying to register, IT COMPLETES REGISTRATION AT 280. The UE then determines whether VPLMNI is the highest preference VPLMN at 285. If VPLMN1 is the highest preference, the UE maintains communiation with VPLMNI at 290 and continues to communicate on VPLMN1.

If VPLMNI is not the highest VPLMN in the preference list, preferably, the UE completes registration with VPLMNI and at the next network selection opportunity will search for a VPLMN which appears higher in the preference list at 292. If no higher preference VPLMN5 are available at 292, the UE continues to communicate on VPLMN1 at 290. Alternatively, if higher preference VPLMNs are available, the UE terminates the communication with VPLMN1 by sending a detach request and communicates with the highest preference VPLMN which is available at 294 in order to attempt to register with that VPLMN.

The UE stores the home operator's PLMN preference list which it received from VPLMN and stores this in its memory and uses this for all subsequent PLMN selection, for example during background scans, following the loss of coverage or at user reselection. Typically, the updated list does not replace that stored during manufacture but will be used in preference to the list stored on the SIM while in that country or location.

In further embodiments of the invention the UE executes a full network search before attempting to communicate with a VPLMN and during initial communication the UE transmits the details of all available VPLMNs that it has established from its initial network search. The VPLMN can then transmit this information to the HPLMN along with its subscriber data request. In response, the HPLMN can indicate the order of preference of the available VPLMNs. This list can then be transmitted to the UE from the VPLMN. Such embodiments would avoid the UE executing further searches for preferred networks which appear in the home operator's preferred list but which are not currently available.

While the UE is connected to a VPLMN, the VPLMN and HPLMN continue to exchange data. An example of a time at which the VPLMN contacts the HPLMN is when the UE updates its location or its routing area. At these times the UE advises the VPLMN of the location or routing area update and the VPLMN contacts the HPLMN sending a ROUTING AREA UPDATE REQUEST or LOCATION UPDATE REQUEST. Such requests are sent from the VPLMN to the HPLMN in order to advise the HPLMN of the UE's current location and operating status. In response to such signals, embodiments of the invention transmit the preferred VPLMN list from the HPLMN to the VPLMN. In preferred embodiments of the invention, the HPLMN may transmit details of its current preferred VPLMN list to the VPLMN with which the UE is currently operating at any time, rather than only transmitting those details in response to the data received from the VPLMN.

If, after receiving the VPLMN preference list, the UE identifies that the VPLMN with which it is currently communicating is no longer a preferred network, it will conduct a VPLMN scan at the next available opportunity and attempt to identify a more preferable and available VPLMN. If a more preferable VPLMN is available, the UE will break its communication link with the current VPLMN and attempt to register with the more preferred VPLMN.

In further embodiments of the invention the UE does not receive the complete preferred VPLMN list from the UE. In such embodiments, the home operator merely indicates that the VPLMN is not the current preferred network.

Alternatively, the VPLMN may receive the full preference list but not transmit this to the UE. Such an embodiment is now described with reference to figure 3.

Figure 3 is a flow diagram representing the steps taken by embodiments in which the VPLMN does not transmit the full preference list to the UE. Steps 310-350 correspond to steps 210-250 of Figure 2 during which the UE takes the same steps to registering with VPLMNI as those described above with respect to figure 2. As discussed above, the data may be transmitted from HPLMN in response to a specific prompt, for example a LOCATION UPDATE REQUEST, or may be transmitted at a time determined by the HPLMN.

At 360, the home network (HPLMN) informs VPLMNI that it is not the current most preferred network in that area according to the home network's preference list. VPLMNI then indicates to the UE that it is not the preferred network at 370.

The not preferred VPLMN' indication may be transmitted to the UE as a new Information Element (IE). The new IE is included in the mobility management (MM) and GPRS mobility management (GMM) CN to UE messages standards (3GPP TS 24.008).

On receipt of the not preferred PLMN' indication, the UE determines that it should communicate with a more preferred VPLMN if one is available. At the next available opportunity, the UE searches for other available VPLMNs at 380. The UE may consult its preference list stored on the SIM or conduct a standard scan in order to identify other available networks.

If no further networks are available, the UE will maintain communication on the non-preferred VPLMN in order to provide the user with a network service at 385.

However, if a more preferable network is available, the UE will break communication with the current VPLMN at the next available opportunity and commence communication with the preferred VPLMN at 390.

It will be clear to those skilled in the art that the not preferred PLMN' indication is not a reject cause. Instead, the non-preferred PLMN' indication advises the UE that it should communicate with a different and more preferred VPLMN if available. If such a network is not available, the UE is permitted to maintain communication with the non-preferred VPLMN. Thus, embodiments of the invention ensure that the UE searches for and communicates on a more preferred network if such a network is available. Such embodiments prevent the device entering limited service state when a network is available, even if that network is not preferred.

In further embodiments of the invention the non-preferred VPLMN transmits a time indication of how long the not preferred PLMN' indication is valid, for example two days. This information may be included in the IE. During the time period indicated by the timer, the UE will be aware that the PLMN is not preferred by its home operator and will not try to communicate with that PLMN during that period unless no other valid network is available. If that non-preferred VPLMN is the only available VPLMN, the UE will communicate on it on it. In preferred embodiments the identification of the non-preferred VPLMN is stored in a list and is maintained in the list until the time expires or the device is powered down.

An example of coding that could be used for the Information Element to indicate the time period is: IE.Timer.day (octet 1, bit 8 to 1) 00000000 is reserved Valid range is from 00000001 (1 day) to 11111111(255 days) Define the number of day (24 hours) the IE.I is valid and shall be taken into account by the UE.

In preferred embodiments of the invention the UE continues to monitor the availability of VPLMNs even if they are not preferred. In this way the UE is able to communicate with a non-preferred VPLMN if it is the only network available.

This allows the UE to be provided with network coverage even if this is not provided by a preferred PLMN.

In further embodiments of the invention the UE provides a manual VPLMN selection mode. In this case, the details of non-preferred VPLMNs may be presented to the user along with any preference lists which may be stored and the user can decide whether to use the HPLMN preferences or to communicate on an alternative network.

Typically, the details of non-preferred VPLMNs or the preference lists may be erased when the device is powered down. On powering up the device, the preference list store don the SIM/USIM is used as the default list.

In preferred embodiments, the updated VPLMN preference list does not replace the VPLMN preference list stored on the SIM or UE during manufacture. Instead, these lists are maintained and the manufacturer or user can decide which of the lists has preference over the other.

It will be clear to those skilled in the art that embodiments of the invention provide a home network with the facility to control the roaming network preferences of its subscribers. Thus, the home network can control the selection of the roaming network for its subscribers in accordance with its current preferences. The HPLMN can transmit data regarding its VPLMN preferences at any time while the device is communicating with a VPLMN.

Claims

CLAIMS

1. Method for controlling network selection for a communication device, the device being associated with a home network and communicating with a first visiting network, wherein at least one visiting network is available for communication with the device; comprising the steps of: the home network transmitting data identifying whether the first visiting network is a preferred network to the visiting network; and, the device maintaining communication with the first visiting network in dependence on the first visiting network being the most preferred of any available network.

2. Method according to claim I wherein the step of the home network transmitting data to the visiting network is performed in response to the visiting network transmitting data regarding the communication device to the home network.

3. Method according to claim I or 2 comprising the further step of the device searching for a further visiting network if the first visiting network is not preferred.

4. Method according to claim 2 or 3 wherein the step of the visiting network transmitting data regarding the communication device is performed at the time of registration.

5. Method according to claim 2, 3 or 4 wherein the step of the visiting network transmitting data regarding the communication device is performed at the time of location update.

6. Method according to claim 2, 3, 4 or 5 wherein the step of the visiting network transmitting data regarding the communication device is performed at the time of routing area update.

7. Method according to claim 2, 3, 4, 5 or 6 wherein the step of the visiting network transmitting data regarding the communication device is performed at the time of a service request.

8. Method according to any of claims 1-7 wherein the data identifying whether the visiting network is a preferred network is a list of preferred networks.

9. Method according to claim 8 wherein the list of preferred networks provides the networks in order of preference of the home network.

10. Method according to claim 8 or 9 comprising the further steps of the first visiting network transmitting the list of the preferred networks to the communication device and the device storing the list.

11. Method according to claim 8, 9 or 10 wherein if the first visiting network is not the most preferred network on the list, the device searches for and attempts to communicate with, networks on the list which are more preferred than the first visiting network.

12 Method according to any of claims 1-7 wherein, if the first visiting network is not a preferred network, the first visiting network transmits time period data to the device identifying the time period for which the first network is not a preferred network.

13. Method according to claim 12 wherein the device does not attempt to register with the first visiting network during the time period unless no preferred networks are available.

14. Method according to any preceding claim wherein the step of transmitting between the first visiting network and the home network is performed using layer 3 mobility management signalling messages.

15. Method according to any preceding claim wherein the step of transmitting from the first visiting network to the device is performed using an Information Element.

16. Method for controlling network selection on a communication device substantially as herein described with reference to the accompanying figures.

17. System for controlling network selection for a communication device comprising a home network, at least one visiting network available for communication and a mobile communication device associated with the home network and communicating with a first visiting network: wherein the home network comprises means for transmitting data identifying whether the first visiting network is a preferred network to the visiting network; and, the device comprises means for maintaining communication with the first visiting network in dependence on the first visiting network being the most preferred of any available network.

18. System according to claim 17 wherein the home network comprises means for receiving data from the visiting network and transmits data to the visiting network in response to the visiting network transmitting data regarding the communication of the device to the home network.

19. System according to claim 17 or 18 wherein the device further comprises means for searching for a further visiting network if the first visiting network is not preferred.

20. System according to claim 18 or 19 wherein the data from the visiting network is transmitted at the time of registration.

21. System according to claim 18, 19 or 20 wherein the data from the visiting network is transmitted at the time of location update.

22 System according to claim 18, 19, 20 or 21 wherein the data from the visiting network is transmitted at the time of routing area update.

23. System according to claim 18, 19, 20, 21 or 22wherein the data from the visiting network is transmitted at the time of service request.

24. System according to any of claims 17-23 wherein the data identifying whether the visiting network is a preferred network is a list of preferred networks.

25. System according to claim 24 wherein the list of preferred networks provides the networks in order of preference of the home network.

26. System according to claim 24 or 25 the first visiting network comprising means for transmitting the list of the preferred networks to the communication device and the device comprising means for storing the list.

27. System according to claim 24-26 the device comprising means for searching for, and attempting to communicate with, networks on the list which are more preferred than the first visiting network if the first visiting network is not the most preferred network on the list.

28. System according to any of claims 17-23 wherein the first visiting network comprises means for transmitting time period data to the device identifying the time period for which the first network is not a preferred network if the first visiting network is not a preferred network.

29. System according to claim 28 wherein the device does not attempt to register with the first visiting network during the time period unless no preferred networks are available.

30. System according to any of claims 17-29 wherein transmissions between the first visiting network and the home network are performed using layer 3 mobility management signalling messages.

31. System according to any of claims 17-30 wherein transmissions from the first visiting network to the device are performed using an Information Element.

32. System for controlling network selection on a communication device substantially as herein described with reference to the accompanying figures.