# Patent

## Title
Multimode roaming mobile devices

## Abstract

A mobile device for roaming between wireless communications networks in different geographical regions is provided. The mobile device includes an interface configured to transmit and receive signals over a wireless channel according to a communication mode using one of a plurality of access technologies. The device also includes a store holding a preferred roaming list having a common block holding data common to the plurality of access technologies, and a set of access technology-specific blocks each holding channel acquisition data specific to one of the plurality of access technologies for setting up the communication mode.

## Background
FIELD OF THE INVENTION
This invention relates to multimode roaming mobile devices.
BACKGROUND TO THE INVENTION
Service providers set up roaming agreements with other service providers in different geographic regions so that when the user is in a region where the home service provider does not offer a service, nevertheless the service can be provided by a different service provider who has a billing arrangement with the home service provider. Any particular region may support different systems and networks. For CDMA (Code Division Multiplex Access) networks, a Preferred Roaming List PRL which is stored at the mobile device provides information about which system/network is preferred in the region for that device. Over-the-air (OTA) Management protocols allow data to be transmitted to mobile devices via wireless transmission media. One example of OTA Device Management is the re-programming of the Preferred Roaming List (PRL). When a mobile user is abroad and switches on the mobile device for the first time, the mobile device performs a search for all available networks. The mobile device then reads from the PRL the preferred networks and the order in which they should be offered to the user. Since preferred networks are constantly changing as new roaming agreements are made, it is necessary to frequently update the PRL in the mobile device. This is achieved by downloading the revised PRL remotely using OTA technology. OTA protocols are defined for example in the over-the-air service provisioning/parameter administration (OTASP/OTAPA) and Open Mobile Alliance (OMA) device management standards.
Current protocols developed in OMA (Open Mobile Alliance) DM (Device Management) provide an integrated framework for OTA management of 3G mobile devices. The existing OMA DM protocol defines a management framework and a set of messages exchanged between one mobile device and an entity in the network called the management server. A management session is set up between the management server and the mobile device, and an OTA message is constructed which is unique to the mobile device.
FIG. 1 illustrates the structure of a preferred roaming list PRL for CDMA networks. There is a system table ST1 . . . STi . . . STn associated with each geographical region which contains a list of system descriptions keyed by system identifier/network identifier (SIN/NID) pairs and associated with an acquisition index. The acquisition index is used as a pointer to an acquisition table AT which contains an indexed list of RF channels for channel acquisition purposes in the new network.
According to the current standard, system acquisition can be carried out using frequency blocks with Personal Communication Systems (PCS) assigned values, or by using channel numbers with the highest priority channel first.
To date preferred roaming lists are provided only in the context of CDMA operation, which includes system selection in analogue mode and CDMA mode.
Currently, for GSM mobile equipment, a list of preferred Public Land Mobile Networks (PLMNs) is stored in the Subscriber Identity Module (SIM) of the mobile device. This enables roaming through PLMN selection when the mobile equipment is outside the home network. However, a GSM mobile device would have no information about a CDMA network in its geographical region or vice-versa.
So-called multimode devices are currently being developed which should be capable of roaming in heterogeneous network environments. For example, a device originally provisioned in a CDMA network should be capable of roaming in a GSM, WLAN (Wide Local Area Network), UMTS (Universal Mobile Telecommunications Systems) or any other network.
SUMMARY OF THE INVENTION
It is an aim of the invention to enable selection of preferred access technology in a geographical region for multimode mobile devices and to improve OTA management of preferred roaming lists for differing access technologies.
According to one aspect of the invention there is provided a mobile device for roaming between wireless communications networks in different geographical regions, the mobile device comprising: an interface adapted to transmit and receive signals over a wireless channel according to a communication mode using one of a plurality of access technologies; and a store holding a preferred roaming list having a common block holding data common to said plurality of access technologies, and a set of access technology-specific blocks each holding channel acquisition data specific to one of the plurality of access technologies for setting up said communication mode.
Another aspect of the invention provides a method of selecting a communication mode for a mobile device roaming between wireless communications networks in different geographical regions, the method comprising the steps of: receiving network parameters identifying wireless communications networks in the region where the mobile device is located; comparing said parameters with preferences among a plurality of access technologies and selecting one of said access technologies; and scanning channel acquisition data for the selected access technology to set up a communication mode using the selected access technology.
A further aspect of the invention provides a method of managing a preferred roaming list of a mobile device capable of transmitting and receiving signals using each of a plurality of access technologies, the method comprising: transmitting a notification message from a mobile device to a management server, said notification message including parameters identifying the device and the access technology of a current communication mode; and transmitting an update message from the management server to the mobile device according to said communication mode, for performing an update to access technology-specific blocks of a preferred roaming list stored at the mobile device.
A further aspect of the invention provides a computer program product comprising a code sequence which, when executed by a processor in a mobile device, carries out the following steps: receiving network parameters identifying wireless communications networks in the region where the mobile device is located; comparing said parameters with preferences among a plurality of access technologies and selecting one of said access technologies; and scanning channel acquisition data for the selected access technology to set up a communication mode using the selected access technology.
A further aspect of the invention provides a method of managing a preferred roaming list of a mobile device capable of transmitting and receiving signals using each of a plurality of access technologies, the method comprising: transmitting a notification message from a mobile device to a management server, said notification message including parameters identifying the device and the access technology of a current communication mode; and transmitting an update message from the management server to the mobile device according to said communication mode, for performing an update to a preferred roaming list stored at the mobile device, said update message indicating whether it is performing an update to a common block of the preferred roaming list holding data common to said plurality of access technologies or performing an update to access technology-specific blocks of the preferred roaming list.
Another aspect of the invention provides [claim 28]
In a possible embodiment of the invention, a common data block carrying data related to roaming in different networks (CDMA, GSM, WLAN, and future networks) is linked to preferred roaming lists for each network access system.
In a possible embodiment of the invention, preferred roaming lists for each access system as well as the common data block can be stored in the R-UIM or SIM card.
In a possible embodiment of the invention, preferred roaming lists for each access system as well as the common data block can be stored in the mobile equipment.
In a possible embodiment of the invention, the common data block stores access level information, enabling the mobile station to decide which access system is preferred in a given geographical region. E.g. to decide whether CDMA or GSM is preferred in a region.
In a possible embodiment of the invention, the common data block stores parameters related to accessing the management station, as well as security parameters.
In a possible embodiment of the invention, there may be a common identity parameter, which can identify the mobile station in each access network.
In a possible embodiment of the invention, the common data block stores parameters related to identity of the mobile station, such as a common identity that can be used in all networks. Currently we have ESN (Electronic Serial Number), MEID (Mobile Equipment Identifier) etc. in CDMA, and IMEI (International Mobile Equipment Identity) in GSM for equipment id. There can be a future id common to all access system or a common id designed for the purpose of multi-mode roaming. Such an id can be stored in the common block.
In a possible embodiment of the invention, the preferred roaming lists linked to the common data block stores information specific to each radio network. For example, there is a preferred list that stores preferences of system and channel for operation in CDMA mode, another one for storing preference list of systems and channels in GSM network and another similar list for WLAN.
In a possible embodiment of the invention, there can be such preferred lists for future access technologies.
In a possible embodiment of the invention, the common data block and various preferred lists may be represented and implemented using a hierarchical tree which is implemented in the mobile station and stored either in the mobile equipment (ME) or the R-UIM/SIM card. The hierarchical tree is used for over-the-air management purpose, especially when OMA DM and similar protocols are used for managing multi-mode roaming data.
In a possible embodiment of the invention, the common data block carries pointers to or the address of location in the R-UIM/SIM or the hierarchical tree where the actual preferred list for a specific access system is stored. For example, the mobile station radio software can use this information to access the preferred list and select a system in a region.
In a possible embodiment of the invention, the common data block and the different preferred lists could be created and updated in the mobile station using over-the-air methods.
In a possible embodiment of the invention, the common data block and different preferred lists can be retrieved from the mobile station using over-the-air method.
In a possible embodiment of the invention, the retrieval can be based on algorithms of tree encoding and compression.
In a possible embodiment of the invention, over-the-air method can be based on the OMA DM protocol.
In a possible embodiment of the invention, over-the-air method can be based on the IOTA-HCM (Handset Configuration Management) protocol, described in GPP2 C.S0040-0 v1.0.
In a possible embodiment of the invention, over-the-air method can be based on the OTASP/OTAPA protocol.
In a possible embodiment of the invention, over-the-air method can be based on pure air-interface messaging.
In a possible embodiment of the invention, the information created or updated or retrieved from the mobile station can be stored in a network location, associated with the management station.
In a possible embodiment of the invention, the information stored in the network location can be sent to another network, to a management station in that network.
In a possible embodiment of the invention, the information sent to another network can be created and updated in a mobile station of the same user in that network. As an example, a user visits a new network, and he lost his mobile station afterwards, this mechanism helps creating and updating roaming related data in the new mobile station.
In a possible embodiment of the invention, in order to have control of managing preferred lists in the mobile station, the mobile station stores a ‘current mode’ parameter value and sends it to the management station. The management station uses this information to update the correct Preferred Roaming List.
In a possible embodiment of the invention, a management station associated with a network can update also preferred lists corresponding to other access networks. For example the security parameters in the common data block can be set to allow this. This allows a management station in the GSM network to update also CDMA preferred lists.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an existing preferred roaming list;
FIG. 2 is a schematic diagram illustrating a roaming mobile device;
FIG. 3 is a schematic diagram illustrating a preferred roaming list in accordance with one embodiment of the invention; and
FIG. 4 is a schematic diagram illustrating use and updating of the preferred roaming list in a roaming mobile device.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 is a schematic diagram illustrating the principle of a user roaming between networks. A mobile device is referred to in the following as a mobile equipment ME and is illustrated located in a first region, Region 1 and in communication with a first network NW1 over a radio link RL. As is well know, the radio link constitutes a physical signalling channel over the air interface between the mobile equipment ME and the network. In this case, the network that the mobile equipment ME is in communication with is a CDMA (Code Division Multiplex Access) network, and the communication mode for the radio link is CDMA. However, the Region 1 also supports a second network NW2, which in the illustrated case is a GSM network. So-called multimode mobile devices can operate using different access technologies such as CDMA, GSM, WLAN, UMTS etc. To this end, they are provided with a wireless interface for receiving and transmitting signals according to each of a plurality of different access technologies supported by appropriate client software operating in the mobile equipment. Different geographical regions can provide one or more networks or systems of different access technologies, though in any particular region it is likely that one of the networks or systems will be preferred.
When the mobile equipment ME moves to a second region, Region 2, that region similarly provides more than one network with different access technologies (NW3-CDMA, NW4-GSM). In Region 2, the mobile equipment ME needs to determine which would be the preferred access technology for that particular region.
As is well known, the mobile equipment includes a memory 2. Amongst other things, the memory 2 stores a preferred roaming list PRL. In some types of mobile equipment ME, a replaceable user identity module (R-UIM) is used to store the preferred roaming list PRL instead of the memory 2. Although in many cases the mobile equipment is a mobile telephone, it will be appreciated that other types of mobile equipment can be utilised, in particular a mobile computer.
FIG. 3 illustrates the structure of the preferred roaming list which is stored at the mobile equipment ME. The preferred roaming list PRL illustrated in FIG. 3 has a common PRL data block 4 which stores preferences regarding which access technology and system is preferred in a given region. For example, the common PRL data block 4 can include preferences for geographical regions, for example CDMA can be the first preference for the first region Region 1. The common PRL block 4 can also store any other parameters common to the different access technologies. Such parameters can include, for example, location of the provisioning server or security parameters.
The PRL illustrated in FIG. 3 also has a set of access technology specific PRL blocks including a CDMA PRL block 6, a GSM PRL block 8, and a PRL block 10 for other access technologies. The common PRL data block 4 includes pointers to these blocks from the access technologies identified for particular regions. Each of the individual access technology specific blocks 6, 8, 10 includes channel acquisition data for use by the mobile equipment ME in setting up a radio link for communication in that particular region via the selected access technology.
When a user roams between networks, the mobile equipment ME can look in the common PRL data block 4 to identify if there is a preferred access technology and system in the new region in which it has arrived. Consider in FIG. 4, the mobile equipment ME arriving in the second region Region 2 where the CDMA network NW3 causes a base station BTS2 to transmit a broadcast message 20 identifying the system and network parameters to all users in the region; in the case of CDMA these are SID/NID pairs for the available CDMA systems. The mobile equipment compares this with data in the common PRL data block 4 and identifies the preferred access technology and system. This comparison is done by appropriate client software at the mobile equipment ME1. Using the pointer to the access technology specific PRL block for the preferred access technology, the mobile equipment ME can access the PRL corresponding to the preferred access technology, and can then scan that PRL block for channel acquisition. This is faster than using a single large preferred roaming list which combines parameters for all of the possible access technologies. In GSM networks, the base station transmits beacon frequencies, and the mobile equipment compares the signal strength of any beacon frequencies listed in the common PRL block 4 to locate the preferred GSM system, in the case that GSM is preferred or no CDMA network is available.
Initial provisioning of the PRL in the home network can be done using Internet Protocol (IP) based over-the-air device management (IOTA-DM) or over-the-air service provisioning/parameter administration (OTASP/OTAPA) protocols, depending on the chosen method and in particular whether the data is to be supplied via an IP-based protocol in data bursts or using pure air-interface signalling in the home network. Alternatively, initial provisioning can be implemented through the manufacturing or distribution process by placing roaming information and parameters onto devices such as SIM cards or R-UIMs at the time of manufacture. At the time of the initial provisioning, common parameters are stored in the common data PRL block 4 so that these parameters (related to the roaming list in multimode operation) can be accessed regardless of the access technology.
Management of the preferred roaming list PRL is carried out in the following way. Effective roaming requires up-to-date management of the PRLs when carrier and user preferences change.
Management of roaming lists is effected using a management server (MS) in the network.
As explained above, the PRL initially provisioned in the home network enables the mobile equipment ME to select a preferred access technology for the region where it is located. After the preferred access technology has been selected, a device information tree at the mobile equipment ME is updated with the “current mode” parameter cmp. As illustrated in FIG. 4, a notification message 22 is sent according to a communication mode using the selected access technology from an OTA management client 18 in the mobile equipment ME to the management server MS in the geographical region where the mobile equipment is now located, the notification message 22 including current mode parameters <cmp> and other parameters identifying the user/equipment identity and subscribed service of the specific user. Based on this information, the management server MS sends an update message 24 back to the mobile equipment to update the preferred roaming list stored in the memory 2.
FIG. 4 shows schematically part of the architecture of a UMTS (Universal Mobile Telecommunications Network). This shows an RNC (Radio Network Controller); an SGSN (Serving GPRS Support Node); a GGSN (Gateway GPRS Support Node); a management server (MS); and the Internet. In FIG. 4 the management server MS is directly connected to an operator's GPRS domain via the GGSN. In an alternative embodiment, the management server may be connected to an operator's GGSN through the Internet.
It will be understood that the security mechanisms which are defined in the existing protocol for over-the-air device management needs to be applied to ensure the authenticities of the updated information and the rights of the user. The update message 24 transmitted from the management server MS to the mobile equipment ME relates to the access technology specific PRL block which is associated with the access technology identified by the common mode parameter cmp which was identified in the original notification message.
It is also possible for the update message to update an access specific technology PRL block for a different access technology than the one in which the mobile equipment ME is currently operating. For example, the management server can update the PRL corresponding to the GSM mode when the mobile is operating in a CDMA mode, provided that there are suitable access restrictions and authentication procedures in place. If the over-the-air management is done using the OMA device management protocol, the preferred roaming lists can be abstracted using a management tree and appropriate access restrictions defined for each.
The common part can be updated by the management server when there are changes in the priorities of access system selection, security parameters, information about the management server itself etc. In these cases, the management server can trigger an updating session.

## Claims

1. A mobile device comprising:
an interface configured to transmit and receive signals over a wireless channel according to a communication mode using one of a plurality of access technologies; and
a store configured to hold a preferred roaming list having a common block holding data common to said plurality of access technologies, and a set of access technology-specific blocks each block configured to hold channel acquisition data specific to only one of the plurality of access technologies,
wherein the mobile device is configured to roam between wireless communications networks in different geographical regions.

2. The mobile device according to claim 1, wherein said common data comprises access level information indicating preferred access technologies associated with different geographical regions.

3. The mobile device according to claim 2, comprising a comparator configured to compare network parameters received in broadcast messages from the wireless communication networks in the region where the mobile device is located with the access level information to select one of said plurality of access technologies for said communication mode.

4. The mobile device according to claim 1, wherein the common block has a set of pointers identifying respective ones of the set of access technology-specific blocks.

5. The mobile device according to claim 1, wherein the store comprises a memory.

6. The mobile device according to claim 1, wherein the store comprises a removable user identity module.

7. The mobile device according to claim 1, wherein the store comprises a subscriber identity module.

8. The mobile device according to claim 1, wherein the common data comprises parameters relating to accessing a management station for a region where the mobile device is located.

9. The mobile device according to claim 1, wherein the common data comprises security parameters.

10. The mobile device according to claim 1, wherein the common data comprises a common identity parameter capable of identifying the mobile device in each of the wireless communications networks.

11. The mobile device according to claim 1, wherein the common block and access technology-specific blocks are stored in the form of a hierarchical tree.

12. A method comprising:
managing a preferred roaming list of a mobile device capable of transmitting and receiving signals using each of a plurality of access technologies;
transmitting a notification message from a mobile device to a management server, said notification message including parameters identifying the device and an access technology of a current communication mode; and
transmitting an update message from the management server to the mobile device according to said communication mode, for performing an update to only one access technology-specific blocks of a preferred roaming list stored at the mobile device, the access technology-specific block being one of a set of access technology-specific blocks, each holding channel acquisition data specific to one of the plurality of access technologies.

13. The method according to claim 12, further comprising: configuring the update to the at least one access technology-specific block to relate to the access technology of the current communication mode.

14. The method according to claim 12, further comprising: configuring the update to the at least one access technology-specific block to relate to an access technology other than the one which is being used for the current communication mode.

15. The method according to claim 12, wherein the transmitting the notification message and the transmitting the update message comprise transmitting said notification message and said update message over a wireless interface.

16. The method according to claim 12, further comprising: retrieving the preferred roaming list from the mobile device over a wireless interface.

17. The method according to claim 16, further comprising: storing the preferred roaming list retrieved from the mobile device at a network location associated with the management server.

18. The method according to claim 17, further comprising: transmitting the preferred roaming list from the management server to a remote management server in a different network.

19. The method according to claim 18, further comprising: transmitting the preferred roaming list from the remote management server to the mobile device in said different network.

20. The method according to claim 16, further comprising: configuring the retrieving the preferred roaming list from the mobile device over the wireless interface to be based on algorithms of tree encoding and compression.

21. The method according to claim 12, further comprising: implementing the transmitting of the notification message and the update message according to open mobile alliance device management protocol.

22. The method according to claim 12, further comprising: configuring the transmitting of the notification message and the update message to be based on internet protocol over-the-air-HCM protocol.

23. The method according to claim 12, further comprising: configuring the transmitting of the notification message and the update message to be based on over-the-air service provisioning/parameter administration protocol.

24. The method according to claim 12, further comprising: configuring the transmitting of the notification message and the update message to be based on air interface messaging.

25. A computer program product comprising a code sequence which, when executed by a processor on a mobile device, performs the following:
transmitting a notification message from the mobile device to a management server in a network, said notification message including parameters identifying the mobile device and an access technology of a current communication mode; and
receiving an update message from the management server and performing an update to only one access technology-specific blocks of a preferred roaming list, the access technology-specific block being one of a set of access technology-specific blocks each holding channel acquisition data specific to one of a plurality of access technologies.

26. A communications system comprising a management server, the management server comprising:
means for receiving a notification message from a mobile device, said notification message including parameters identifying the mobile device and an access technology of a current communication mode; and
means for transmitting an update message for performing an update to only one access technology-specific blocks of a preferred roaming list stored at the mobile device, the access technology-specific block being one of a set of access technology-specific blocks each holding channel acquisition data specific to one of a plurality of access technologies.

27. A mobile device configured to transmit and receive signals using each of a plurality of access technologies, the mobile device comprising:
means for transmitting a notification message to a management server, said notification message including parameters identifying the device and an access technology of a current communication mode; and
means for receiving an update message from the management server according to said communication mode, for performing an update to only one access technology-specific block of a preferred roaming list stored at the mobile device, the access technology-specific block being one of a set of access technology-specific blocks, each holding channel acquisition data specific to one of the plurality of access technologies.