GB2455064A

GB2455064A - Network reselection method

Info

Publication number: GB2455064A
Application number: GB0722161A
Authority: GB
Inventors: Vincent Roger; Ludovic Haessler; Frederic Ah Chuen Fok
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2007-11-12
Filing date: 2007-11-12
Publication date: 2009-06-03
Also published as: WO2009063924A1; GB0722161D0

Abstract

A mobile radio communications device accesses a PLMN by way of a WLAN supporting the said PLMN. The method comprises retrieving identifiers of possible PLMN and WLAN associations for reselection from the device memory, the associations having been identified during a previous selection procedure, wherein the retrieval is effected responsive to the extent of movement of the device from its location at the time of the previous selection procedure.

Description

NETWORK RESELECTION METHOD

The present invention relates to a method of network reselection for mobile radio communication devices operating within mobile radio communication networks.

In particular, the present invention relates to reselection for Public Land Mobile Network (PLMN) accessed via a Wireless Local Area Network (WLAN network).

It is increasingly common for User Equipment (UE) such as mobile radio communications devices to support several Radio Access Technologies (RATs) such as WLAN, GSM or UMTS and wherein the communication to the PLMN is achieved through any of these RATs.

It is currently known that, according to 3GPP Proposals wherein the PLMN is accessed \ia a WLAN, a WLAN-enabled UE builds a list of WLAN Specific Identifiers (WSIDs) and associated PLMNs on each of the WSIDs. An exhaustive list of the network environment will be build for instance when the UE is in roaming situations or when the user initiated a manual network selection.

According to such known 3GPP specifications, user resclection can be employed to enable a user to request, at any particular time, that a WLAN-enabled UE initiates a reselection procedure onto a supported PLMN through a supported WLAN. This is currently achieved according to predefined procedures which are generally dependent upon the PLMN selection mode, which can either he automatic or manual.

The known procedure consists of first a step of disassociation from a currently associated WSID by initiating a disassociation procedure as specified in IEEE 802.11 1999 and secondly initiating an association procedure as specified in IEEE 802.11 1999, taking into account PLMN selection procedures as outlined in the 3GPP specification iS 23.234; and thirdly. depending upon whether an automatic or manual PLMN selection mode is employed, performing a new PLMIN selection in accordance with the requirements of said specification. It is however appreciated that the disassociation of the current WSID according to the above mentioned procedure, and the initiation procedure as specified in IEEE 802.111999 and additionally the PLMN selection procedure according to 3GPP requirements, are far from optimised since they require the WLAN-enabled UE to scan again for all available WSIDs and to perform the discovery of associated PLMNs before selecting a desired network (i.e. a WLAN Access Network and an associated PLMN).

Such procedure is not only disadvantageously time consuming but also leads to a reduction in battery life in the UE due to the power consumption required.

The present invention therefore seeks to provide for a mobile radio communication network reselection method and, related mobile radio communications device, having advantages over known such methods and related devices.

According to one aspect of the present invention there is provided a mobile radio communications network reselection method for an I-WLAN communication system in which a mobile radio communications device accesses a PLMN by way of a WLAN supporting the said PLMN, and comprising the steps of retrieving identifiers of possible PLMN and WLAN associations for reselection from device memory, the said possible associations having been identified during a previous selection procedure, and wherein the said identifiers of the possible associations are retrieved responsive to the extent of movement of the device from its location at the time of the said previous selection procedure.

It will be appreciated from the following that the present invention can thereibre relate to a method of enabling fast user-reselection by optimizing the user-reselection procedure without having to start full PLMN search and selection for an Interworking WLAN system and which would include WSIDs scanning and PLMNs discovery.

Substantially faster, and then more efficient a user-reselection can therefore be provided.

The present invention can therefore enable a WLAN UE to select the PLMN upon desired user reselection and without having either to scan again the available access networks, nor having to perform a network discovery procedure.

The invention can, in particular, achieve relatively fast user-reselection since the user reselection procedure can be accelerated on the basis of an assumption that the UE will maintain an acceptable knowledge of the, for example, WSIDs and associated PLMNs available by way of the previous radio coverage.

In one advantageous arrangement, the said extent of movement can be determined by the device user.

In particular, said extent of movement is determined by means of a Global Positioning System (GPS) capability within the device.

Alternatively the said extent of movement is determined on the basis of a scan of the said identifiers.

In particular, the said identifiers can comprise a list of WSIDs each with a list of supported PLMNs.

As will thereibre be appreciated, in one particular embodiment, the possible networks comprise an interworking-WIAN system, i.e. a range of WLANS Access Networks offering access to a range of PLMNs Mobile Networks.

As such, the said reselection procedure can then comprise reselection of the WLAN and the PLMN. wherein the communication to the PLMN is achieved through a Vv LAN Access Network.

Further the said identifiers can comprise related WSII)s and PLMNs.

Advantageously the said retrieval can be selectively responsive to user requirement.

Further the said retrieval is automatically responsive to the extent of movement exceeding a threshold value.

According to another aspect of the present invention there is provided a mobile radio communications device arranged for accessing a PLMN by way of a WLAN supporting that PLMN and arranged for reselection of mobile radio communications networks, and including means for the storage and retrieval of identifiers of possible PLMN and WLAN associations stored from a previous selection procedure, and for use in a subsequent reselection procedure, and means for initiating retrieval of the said identifiers of the associations responsive to the extent of movement of the device from its location at the time of the said previous selection procedure.

In one embodiment, the extent of movement can be user-determined.

Further, the said device can include GPS functionality for determining the said extent of movement.

Alternatively the said device can include means for scanning the said identifiers for the determination of the said extent of movement.

The said device can he arranged for operating the communication to the PJMN through a WLAN.

The said device can further include means by which the said retrieval can be disabled and/or enabled by a network operator.

Athantageously enabling/disabling means can be provided comprising controlling information stored within a UICC of the device.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a diagram illustrating the possible movement of a UE within an area covered by a variety of different Interworking WLANs; Fig. 2 is a similar network configuration to that illustrated in Fig. I but with a different range of movement of the UE; and Fig. 3 is a signalling diagram for signalling arising in accordance with an embodiment of the reselection procedure embodying the present invention.

It has been identified that, while a UE such as, for example, a mobile radio communication device, is moving, a network list will still be valid until the next Network reselection triggered either by user reselection or the loss of WLAN radio coverage. As long as the WLAN UE is connected to the same wireless network Access Point (AP), the WLAN UE keeps the same lists of WSIDs and PLMNs. With the WLAN UE experiencing reduced mobility (WLAN Access Point radio coverage) the lists may only differ slightly from the lists that would have been re-built if the complete network selection procedure was restarted as described further in relation to Figs. 1 and 2.

From a user's perspective, the present invention has the advantage of enabling either a "Fast User Reselection" as defined in present proposal or a User Reselection" as currently defined in 3GPP specifications, hereinafter referred to as Full User Reselection. This choice can be made available to the user using a configuration menu in the mobile device system environment or in an automatic selection of fast user-reselection whenever possible. For example the WLAN UE could embed a decision function based on mobility estimation since the last computation and employing GPS functionality. As a consequence of selecting Fast User Reselection, the PLMN selection procedure can then advantageously be accelerated. Furthermore, network operator can in one option also enable/disable this feature in the UE, using for example information stored in the UICC, in order to be able to control WLAN UE behaviour regarding user reselection strategy. Such information can be either updated statically, e.g. at the time of subscription or dynamically, e.g. using SIM application toolkit technology or Over the Air (OTA) functionality.

An example of a method embodying the present invention employs the following steps and for either of an automated or manual mode: -check whether Fast User Reselectjon feature is enabled/disabled; -eventually estimate a change of WSID based on a mobility estimation such as by GPS functionality or based on a WSID scanning in order for the device to ascertain whether to perform Fast or Full User Reselection; -reuse of the already stored PLMNs List and WSIDs List previously discovered; -perform the Fast User Reselection (if selected) procedure either in manual or automatic mode as highlighting in the following points - -in automatic mode: -disassociate with the current associated WSID by initiating disassociation procedure as specified in IEEE 802.111999.

-initiate association procedure as specified in IEEE 802.11 1999 taking into account the procedure as defined in 3GPP TS 24.234 �5.2.4. (automatic PLMN Selection Mode Procedure) -in manual mode: -wherein a first difference with 3GPP iS 24.234 �5.2.3 is that the supported PLMNs list displayed to the user is based on already stored PLMNs and WSIDs Lists, instead of resulting from WLAN LIE 1-WLAN Selection procedure (3GPP I'S 24.234 �5.2.1).

-wherein a second difference with 3GPP TS 24.234 �5.2.3 is that if the selected {PLMN, WSID is the same as the already registered {PLMN, WSID} then the procedure stops; and -in order to avoid repetitive failures using Fast User Reselection (e.g. N tentatives) the WLAN UE should be able to switch to Full User Reselection mode.

Turning now to Fig. I, there is illustrated radio coverage in relation to WLAN UE 10.

At its initial location, the WLAN UE 10 is under radio coverage of three possible WLANs, 12, 14, 16. While being associated with the AP 18 of WLAN 12 the WLAN UE 10 moves slightly from its initial location to a further location 1 OA at which it is under radio coverage of WLANs, 12, 14, 16, 20.

Then, depending on the type of UE 10 and the nature of the user reselection enabled the functioning of the UE will be as follows: -with UEs not implementing the fast user-reselection, and upon full user reselection, a new WLAN UF list of {WLANs. PLMNs} will be computed taking into account the new WLAN 20 and its associated PLMNs; -with UEs implementing the fast user reselection: -upon full user reselection, a new WLAN UE list of {WLANs. PLMNs} will be computed taking into account the new WLAN 20 and its associated PLMNs.

-upon fast user-reselection, a WLAN UE list of {WLANs, PLMNs} will not be re-computed but rather will be retrieved according to the invention from an existing one. Thus, this list will differ slightly from the one that would have been entirely re-computed (using full user reselection procedure) since it will not take into account the WLAN 20 and its associated PLMNs.

Turning now to Fig. 2, here a scenario is illustrated in which radio coverage remains the same after WLAN UE 10 has moved.

At its initial location, WLAN UE 10 is under radio coverage of WLANs 12. 14, 16.

Again, and while being associated with the API 8 of WLAN 12, the WLAN UE 10 moves slightly from its initial location to a further location 1 OA at which it still remains under radio coverage of the WLANs 12, 14. 16.

Thus. depending on the type of UE and the type of user-reselection the behaviour will be as follows: -for UE not implementing fast user-reselection: upon full user reselection, a new WLAN UE list of {WLANs, PLMNs} will be unnecessarily computed since the WLAN radio coverage has not changed.

-for UE implementing fast user-reselection according to the invention: -upon full user-reselection, a new WLAN UE list of WLANs, PLMNs} will be unnecessarily computed since WLAN radio coverage has not changed; but -upon fast user-reselection. WLAN UE list of {WLANs, PLMNsI will not be re-computed but will rather be retrieved from an existing one.

Thus, since the WLAN radio coverage has not changed. this list will correctly take into account the available WLAN APs and their associated PLMNs.

An embodiment of the present invention is described further by way of the signalling diagram of Fig. 3.

l'his relates to a system which comprises a WLAN UE, WLAN Access Networks and PLMNs wherein communication between the WLAN UE and PLMN is achieved through a WLAN Access Network. Vv LAN 1 is connected to PLMN 1 and WLAN 2 is connected to PLMN 2.

PLMN I and 2 include AAA Proxy/Server for authentication purpose, and the pre-conditions are: -WLAN UE is associated with the AP (WSID 1) in the WLAN 1 and connected to PLMN 1 and authenticated to its HPLMN through PLMN I. -WLAN UE has an available list of its environment (WSIDs, PLMNs). For example it has performed a manual selection that had enabled having all PLMNs available for each WSID. Another example is when the WLAN UE is in automatic mode and roaming on PLMN I due to 1-IPLMN unavailability. In this latter case the WLAN UE has performed a complete PLMN discovery procedure while trying to register on 1-IPLMN.

-Fast user reselection feature is enabled in the WLAN UE by the network operator.

The means to enable a fast reselection of PLMN by the user, the Fast User Reselectiori method is performed using the original list of WS1Ds, PLMNs} instead of a rediscovered list.

As noted above, the Fast User Reselection could be based on user decision, UE decision or other means. For example. a user could choose to employ fast user-reselection when it is determined that the UE's radio environment remains unchanged due to no, or little, change in its radio environment due to reduce mobility conditions when the user moves only a short distance while being connected to its current WLAN AP. In such situations the user will rather favour fast user reselection performances rather than having an exact knowledge of its radio environment. Furthermore, the WLAN UF could also perform a WSJD Scanning to build an exact WSID List Rased on the scanning result, the user can then choose to perform either the Fast User Reselection or the Full User Reselection. In this case the Fast User Reselection avoids the Network Discovery phase of the specification TS 24.234, v7.5.O. section 4.4.

Further, the WLAN lIE could also embed a GPS solution for mobility purpose and that enables the UE to determine, the extent of travel and then whether the list of PLMNs can still be reused for fast user-reselectjon.

UE retrieves the combinations list of (WLANs; PLMNs) from its memory (this list has been stored at previous IWLAN network selection).

In this example, {WLAN 2, PLMN 2) is supposed to be the combination of {WLAN, PLMN} on which to perform IWLAN network selection.

-In manual mode the list is displayed to the user who performs a choice.

-In automatic mode the highest prioritized combination is selected.

For fast user reselection, the following is performed: -having stored on the previous IWLAN network selection procedure the list of all the combinations of {WLANs, PLMNs} of its radio coverage, the UE then retrieves this List, and follows the procedures in manual or automatic mode.

-in automatic mode and as illustrated by signalling 22 in Fig. 3: -the UE is disassociated from the current WSID by initiating disassociation procedure as specified in IEEE 802.11 1999.

-initiate association procedure as specified in IEEE 802.11 1999 taking into account the procedure as defined in 3GPP TS 24.234 �5.2.4.

(automatic PLMN Selection Mode Procedure).

-in manual mode: -the WLAN UE indicates to the user the list of PLMNs already stored from the previous IWLAN Network Selection. If more than one I-WLAN is capable of being used to establish a direct connection with a PLMN the WLAN UE should indicate each of the candidate I-WLANs along with the PLMN to the user. If displayed, PLMNs from this list shall be presented in the following order: -HPLMN.

If the "User Controlled PLMN Selector for I-WLAN access" data file is available, PLMNs in the "User Controlled PLMN Selector for I-WLAN access" data file in the USIM (in priority order).

If the "Operator Controlled PLMN Selector for J-WLAN access" data file is available, PLMNs in the "Operator Controlled PLMN Selector for I-WLAN access" data file in the USIM (in priority order).

If neither "User Controlled PLMN Selector for I-WLAN access" nor "Operator Controlled PLMN Selector for WLAN access" data file is available in the USIM or in a case when the SIM is inserted: -each PLMN in the "User Controlled PLMN Selector with Access Technology" data file, if available in the USIM/SIM (in priority order); or -each PLMN in the "Operator Controlled PLMN Selector with Access Technology "data file, if available in the USIM/SIM (in priority order).

If none of the PLMN selector lists in the above steps is available and the ME supports at least one of the optional "User Controlled PLMN Selector for I-WLAN access" and "Operator Controlled PLMN Selector for I-WLAN access" lists in the ME: -each PLMN in the "User Controlled PLMN Selector for I-WLAN access "data file in the ME (in priority order): -each PLMN in the "Operator Controlled PLMN Selector for I-WLAN access" data file in the ME (in priority order).

Any other PLMN in random order.

If a PLMN,WSID} was selected before the procedure and if the user does not select a {PLMN, WSID} or select the same {PLMN. WSIDJ.

the procedure is stopped and the WLAN UE indicates the currently selected {PLMN, WSID}.

-Otherwise: -the WLAN UE disassociates with the current associated WSID by initiating disassociation procedure as specified in IEEE 802.11 1999.

-the WLAN UE initiates association procedure as specified in IEEE 802.11 1999.

-the WLAN UE initiates authentication with the selected PLMN.

-if successful authentication is achieved, the WLAN UE shall indicate the Selected PLMN.

-if no PLMN is found, the WLAN IJE behaviour is implementation dependent.

From the perspective of the WLAN UE, the proposed innovation also enables: -an increase in battery life as the procedure reduces the messages exchange with the Network.

-the avoidance of repetitive scanning and PLMN discovery -in manual mode specifically and if the same {PLMN,WSID} as the already registered {PLMN,WSID is selected, the invention avoids new association with the WSID and authentication with the PLMN.

Thus, the method of fast user-reselection of the present invention significantly enhances WLAN UE performances (e.g. power consumption), since user-reselection under low mobility conditions is likely to be encountered often by typical WLAN [JE users. For example. while being under coverage of WLAN hot spots, users could frequently decide to change either WLAN AP or PLMN in order to access different services, to benefit from enhanced security features provided by WLAN/PLMN, etc.

Claims

1. A mobile radio communications network reselection method for an I-WLAN communication system in which a mobile radio communications device accesses a PLMN by way of a WLAN supporting the said PLMN, and comprising the steps of retrieving identifiers of possible PLMN and WLAN associations for reselection from device memory, the said possible associations having been identified during a previous selection procedure, and wherein the said identifiers of the possible associations are retrieved responsive to the extent of movement of the device from its location at the time of the said previous selection procedure.

2. A method as claimed in Claim 1, wherein the said extent of movement is determined by the device user.

3. A method as claimed in Claim 1, wherein the said extent of movement is determined by means of a GPS capability within the device.

4. A method as claimed in Claim 1, wherein the said extent of movement is determined on the basis of a scan of the said identifiers.

5. A method as claimed in any one or more of Claims 1-4, and wherein said identifiers comprise a list of WSIDs each with a list of supported PLMNs.

6. A method as claimed in any one or more of the preceding claims, wherein the said identifiers comprise related WSIDs and PLMNs.

7. A method as claimed in any one or more of the preceding claims, wherein the said retrieval is selectively responsive to user requirement.

8. A method as claimed in any one more of Claims 1-6, wherein the said retrieval is automatically responsive to the extent of movement exceeding a threshold value.

9. A mobile radio communications device arranged for accessing a PLMN by way of a WLAN supporting the PLMN and arranged for reselection of mobile radio communications networks, and including means for the storage and retrieval of identifiers of possible PLMN and WLAN associations stored from a previous selection procedure, and for use in a subsequent reselection procedure, and means for initiating retrieval of the said identifiers of the associations responsive to the extent of movement of the device from its location at the time of the said previous selection procedure.

10. A device as claimed in Claim 9, and arranged to allow for the extent of movement to the user-determined.

11. A device as claimed in Claim 9, and including GPS functionality for determining the said extent of movement.

12. A device as claimed in Claim 9, and including means for scanning the said identifiers for the determination of the said extent of movement.

13. A device as claimed in any one or more of Claims 9-12 and including means by which the said retrieval is disabled and/or enabled by a network operator.

14. A device as claimed in Claim 13, wherein the enabling/disabling means comprises the control of information stored within a UICC of the device.

15. A mobile radio communications network reselection method substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

16. A mobile radio communications device substantially as hereinbefore described with reference to the accompanying drawings.