Enhancement to PLMN selection process while roaming

A method and apparatus for a mobile wireless device configured to adaptively scan for a preferred wireless network while roaming is described. In one embodiment, at least a portion of a database including characteristic information regarding wireless networks can be stored within the mobile wireless device. Network characteristic information can include mobile country codes, mobile network codes, location area codes and cell-IDs. When the mobile wireless device is connected to a network that is not a preferred network, the mobile wireless device can use the database information in conjunction with characteristics from a connected wireless network to determine when to scan for the preferred wireless network.

FIELD OF THE DESCRIBED EMBODIMENTS

The described embodiments relate generally to wireless communications and more particularly to searching for and selecting a preferred public land mobile network (PLMN) while roaming on another PLMN.

BACKGROUND

Mobile wireless communications systems are deployed extensively. These vast wireless networks can provide extensive coverage for a user with a mobile device such as a cellular telephone, personal digital assistant or other mobile device that can connect to and exchange voice and data information. The wireless networks can be arranged by providers such that a particular provider may be responsible for a particular wireless network. Any one particular network can be referred to as a public land mobile network (PLMN). Typically, any one particular mobile wireless device can connect to one of several PLMNs. The mobile wireless device can have a preferred PLMN oftentimes referred to as a home PLMN (HPLMN). The HPLMN can be a network that can provide wireless services to the user of a mobile wireless device for the lowest cost. For example, the HPLMN can be the network associated with a provider through which the user can have purchased the mobile wireless device and can services the region that the user most frequently operates the mobile wireless device.

As the mobile wireless device moves beyond the coverage area of the HPLMN, the mobile wireless device can connect to other PLMNs to continue to receive service. For example, a user can travel from a home region with a HPLMN to foreign country. The foreign country may have other compatible PLMNs that can support the users' mobile wireless device. These other PLMNs can service the user's mobile wireless device, but oftentimes the service provided to a visiting mobile wireless device can require an additional service fee to be paid to the provider of the PLMN. When a users' mobile wireless device connects to a PLMN that is not a HPLMN, the other networks is often referred to as a visited PLMN (VPLMN).

Since connecting to a VPLMN can accrue additional service fees, the user can desire the mobile wireless device to search for and connect to a preferred network or HPLMN as soon as possible. The search for a HPLMN is not without drawbacks, however. For example, the mobile wireless device can be configured to automatically scan for and connect to a HPLMN when roaming (i.e., when not connected to a HPLMN). However, such an automatic selection configuration can cause the mobile wireless device to periodically scan for a HPLMN. If the wireless device has moved to a region where the HPLMN do not exist, such as a distant foreign country, then the periodic scans can needlessly consume battery power. One alternative is to configure the mobile wireless device to manually connect to different network PLMNs when roaming (manual selection). While this configuration can save battery power, if the user forgets to connect to the HPLMN, the user can be responsible for significant roaming fees, particularly if a VPLMN exists near the users' normal operating region.

Therefore, what is desired is a reliable way to identify and avoid those operating conditions where a mobile wireless device can connect to a PLMN and unnecessarily scan for a preferred PLMN, adversely affecting battery life. Prompt detection of a preferred PLMN should be enabled to allow the mobile wireless device to switch to a HPLMN when possible.

SUMMARY OF THE DESCRIBED EMBODIMENTS

This paper describes various embodiments that relate to adapting a scanning for a home or preferred network by a mobile wireless device when the mobile wireless device is connected to a network.

A method for selecting a network by a mobile wireless device while the mobile wireless device is roaming can include the steps of associating the mobile wireless device with a wireless network that is not a home wireless network, storing network adjacency within the mobile wireless device, determining when the wireless network is nearby the home wireless network and scanning for the home wireless network.

In another embodiment, a mobile wireless device can include a wireless transceiver for transmitting and receiving wireless data to and from a wireless network, a memory for storing data a processor instructions, a processor configured to determine when a preferred wireless network is near to a currently connected wireless network by connecting to a wireless network other than the preferred wireless network, storing adjacency information for wireless network and scanning for preferred wireless networks next to the mobile wireless device in accordance with at least one characteristic of the connected wireless network and stored adjacency information.

A method for adaptively scanning for a home public land mobile network can include the steps of storing adjacency information in the mobile wireless device prior to operating the mobile wireless device away from the home public land mobile network, connecting to a public land mobile network, other than the home public land mobile network and scanning for the home public land mobile network in accordance with characteristics from the public land mobile network and the stored adjacency information.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

In one embodiment, a mobile wireless device can maintain a one or more databases of network and geographic information regarding nearby networks within the mobile wireless device. In one embodiment, a first database can include information regarding country codes (i.e., mobile country code, MCC) and one or more PLMNs. A second database can include information associating networks (PLMNs) and location area codes (LAC), mobile network codes (MNC) and cell-ID. When the mobile wireless device is connected to a PLMN (a visited PLMN or VPLMN), a first determination can be made to determine if a scan for a HPLMN should be provided. In one embodiment, this determination can be done in accordance with data in the first database and a current country code from a serving cell. If the device determines that a scan for a HPLMN should be provided, then data from the second data base can be used to further refine that determination.

In one embodiment, the first database can be stored in the device prior to roaming from the HPLMN. In another embodiment, the second database can be updated with data from a location server, in some cases while the device is roaming. For example, the location server can respond to a query from the mobile wireless device by providing information (MCC, MNC, LAC and cell-ID, for example) regarding networks and cells adjacent to and nearby a position of the mobile wireless device.

If a HPLMN is determined to be nearby to the mobile wireless device, then the mobile wireless device can scan for and connect to the HPLMN if automatic network selection is enabled. In another embodiment, if a HPLMN is determined to be nearby, then the mobile wireless device can notify the user that such a network is available, when the mobile wireless device is configured for manual network selection. In some embodiments an equivalent HPLMN (EHPLMN) can be selected instead of a HPLMN.

FIG. 1is a diagram100of a mobile wireless device101operating in the presence of multiple PLMNs. The mobile wireless device101can be connected to (camped on) serving cell102. In the example, serving cell102is served by base transceiver station104. Also in this example, serving cell102is a member of mobile wireless devices'101HPLMN. Neighbor cell103and neighbor cell105are also members of the HPLMN. Thus, wireless device101can move to neighbor cell103or neighbor cell105and can still connect with the HPLMN. On the other hand, neighbor cell106is not a member of the HPLMN, therefore if the mobile wireless device101were to operate in the bounds of neighbor cell106, then the mobile wireless device101can be required to connect to a network (such as VPLMN). As described above, connecting to a network other than a HPLMN may incur additional operating costs.

The diagram100ofFIG. 1illustrates one scenario associated with operating a mobile wireless device101in a network, other than a HPLMN, but the scenario is presented in a very simplified manner. Oftentimes, neighboring cells can be served by a common network. More frequently, however, the mobile wireless device101can travel a relatively large distance before connecting to a PLMN that is not a HPLMN. This scenario is illustrated inFIG. 2.

FIG. 2is a diagram200of mobile wireless device101connected to a new serving cell202. In this example, mobile wireless device101was initially connected to old serving cell102. Old serving cell102can be associated with a HPLMN. Next the user can move mobile wireless device101a large distance such as may occur when the user travels by plane to a different country. After the displacement, mobile wireless device101can connect to new serving cell202. In this example, new serving cell202can be served by a different PLMN (VPLMN). Since mobile wireless device101has connected to a VPLMN, the mobile wireless device101typically will periodically scan for a nearby HPLMN. The periodic scans, however, will be fruitless in this case, since there are no HPLMNs nearby the mobile wireless device101. The battery life of the mobile wireless device101can be impacted by the constant, periodic network scans. One way to avoid the periodic network scans is to configure the mobile wireless device101to manually connect to PLMNs. The manual setting can cause the mobile wireless device101to cease scanning and remain connected to the VPLMN. However, when mobile wireless device101returns to old serving cell102, if the device is set to manually connect to PLMNs, then the mobile wireless device101may not have any service until the user manually scans for nearby networks and connects to the HPLMN. Or alternatively, as shown inFIG. 1, the mobile wireless device can remain connected to a VPLMN, even when nearby to one or more HPLMNs.

The shortcomings illustrated byFIG. 1andFIG. 2can be addressed, at least in part, by adaptively scanning for a presence of nearby PLMNs that can be either a HPLMN or a EHPLMN. This can be described inFIG. 3AandFIG. 3B.FIG. 3AandFIG. 3Bare flow charts of method steps300for performing an adaptive PLMN scan, in accordance with one embodiment of the specification. Persons skilled in the art will understand that any system configured to perform the method steps in any order is within the scope of this description. The method begins in step301where at least a portion of a first database is stored in the mobile wireless device101. The first database can include information regarding country codes (MCC) and their associated networks (PLMNs). In another embodiment, the first database can link MCC-PLMN information to adjacent or nearby MCCs. For example, the first database can associate one or more PLMNs with one or more MCCs. In yet another embodiment, the first database can be refreshed periodically, such as every two weeks. In step303, the mobile wireless device101can camped on a new VPLMN. In this step, the mobile wireless device101can determine that the device is currently connected to a PLMN that is not a HPLMN or an EHPLMN. In step305, the mobile wireless device101can determine if the MCC of the VPLMN is included in the first database stored in the device. If the MCC of the VPLMN is included in the first database, the mobile wireless device101can be operating near a HPLMN. Conversely, if the MCC of the VPLMN is not included in the first database, then mobile wireless device101may not be operating near a HPLMN. Returning to step305, if the MCC of the VPLMN is not included in the database, then in step313(FIG. 3B), the mobile wireless device can perform a limited high priority PLMN (HPPLMN) search. In one embodiment, the HPPLMN search can be scan for particular PLMN networks in accordance with a priority set forth in a user controlled PLMN list and/or an operator controlled PLMN list. In some conditions, the mobile wireless device101may determine that the HPPLMN scan can be unnecessary. For example, the mobile wireless device101can determine that a prior HPPLMN search has determined that there are no HPLMNs nearby and the device has determined that the position of the device has not substantially changed.

Returning to step305, if the device determines that the MCC of the VPLMN is included in the first database, then in step307, the device can examine the second database. Data included in the second database can include adjacency information that can be used to determine if a HPLMN can be nearby or adjacent to the mobile wireless device101. The device can determine a state of a “perform-search” flag that can indicate that a scan should be provided to determine if a HPLMN can be nearby and can be used by the mobile wireless device101. In some embodiments, the second database information can be updated in this step, particularly if information regarding the VPLMN is absent from the second database and the mobile wireless device101has a data connection. In step309the state of the perform-search flag can be examined. If the perform-search flag is not set then the method can proceed to step313. On the other hand, if the perform-search flag is set, then in step311a network scan can be performed and when a HPLMN is located and when manual network selection is chosen by the user, the user can be notified that a HPLMN can be selected for use and the method ends. In cases when automatic network selection has been selected by the user, the HPLMN can be selected and the method ends.

One embodiment of the adaptive PLMN scanning method described inFIGS. 3A and 3Bcan be described in more detail by dividing the method into two parts. A first stage can include steps301,303, and305. A second stage can include steps307,309,311and313. The first stage is described in more detail inFIG. 4A, while the second stage is described in more detail inFIGS. 4B and 4C.

FIGS. 4A,4B and4C illustrate a flow chart400of another embodiment of method steps for adaptively scanning for a network, in accordance with one embodiment of the specification. The first stage of the present method (shown inFIG. 4A) can provide a first determination regarding if a network scan for a HPLMN should be provided. Steps301and303can be substantially similar to same numbered steps described inFIG. 3A. Thus in step301, at least a portion of the first database is stored in the mobile wireless device101. In step303, the mobile wireless device101can camp on a VPLMN. In step403, the MCC of the VPLMN currently in use can be compared to the MCC of the HPLMN. If the country code of the VPLMN is the same as the country code of the HPLMN, then the mobile wireless device101can determine that an adaptive network scan can be provided. Many times, if the country code of the current network matches the country code of the HPLMN, then the mobile wireless device101can be near a HPLMN. Therefore, returning to step403, if the MCC of the VPLMN is the same as the MCC of the HPLMN, then the method proceeds to step407ofFIG. 4B. On the other hand, if the MCC of the VPLMN is not the same as the MCC of the HPLMN, then in step405, the MCC of the VPLMN is compared to a list of MCCs that can be adjacent or proximate to the HPLMN as determined by the first database stored in the mobile wireless device101. In one embodiment, data included in the first database can be used to determine if the currently indicated country code can be associated (linked) to a PLMN that can be a HPLMN. Thus, if the MCC of the VPLMN is not on the list of MCCs that can be adjacent or proximate to the HPLMN, then in step313, the device can perform a limited HPPLMN search as described in conjunction withFIG. 3Band the method ends. On the other hand, if the MCC of the VPLMN is determined to be adjacent or near the MCC of the HPLMN, then the method proceeds to step407ofFIG. 4B.

FIGS. 4B and 4Cdescribe the second stage of the adaptive PLMN scanning method described inFIG. 3. The second stage can refine a decision to provide an adaptive network scan, provide the network scan and act upon the scan results. In step407, the second database also stored in the mobile wireless device101can be examined to see if any information regarding the current VPLMN is included in the database. As described above, the second database can include adjacency information that can be used to determine if a HPLMN is nearby or adjacent to the mobile wireless device. More particularly, the second database can correlate location information such as LAC, MNC and cell-ID with one or more PLMNs. In one embodiment, the mobile wireless device101can examine location information of the current VPLMN and together with the data included in the second database determine if a HPLMN can be nearby. In one embodiment, at least a portion of the second database can be stored in mobile wireless device prior to roaming away from the HPLMN.

Returning to step407, if there is information in the second database related to the VPLMN, particularly information suggesting that proximate to the VPLMN there may be a HPLMN, then a perform-search flag can be set and the method proceeds to step417. On the other hand, if there is no data related to the VPLMN in the second database, then in step409, the mobile wireless device101can check for the existence of a data connection. If there is no data connection, then the method can proceed to step419inFIG. 4C. On the other hand, if there is a data connection, then in step411, the mobile wireless device101can submit a location based query to a location server. The location server can provide data for the second database that can be missing with respect to a current copy of the second database in mobile wireless device101. In one embodiment, the location server can provide MMC, MNC, LAC and cell-IDs of networks and cells nearby the mobile wireless device101. In some embodiments, the second database can be periodically updated with data from the location server.

Next in step413, the mobile wireless device101can determine if new data for the second database was received. If no new data was received then the method can proceed to step419inFIG. 4c. On the other hand, if new data was received, then in step415the new data can be examined to determine if an adaptive scan should be performed. For example, if there is information in the updated second database suggesting that there can be a HPLMN nearby, then in response, the mobile wireless device can set the perform-search flag. In another embodiment, data from the location server can include a determination of whether an adaptive scan should be performed. For example, a state setting of the perform-search flag can be included with the data. In other words, in one embodiment the location server can determine if a search should be provided while in another embodiment, the device can determine if a search should be provided. The method can proceed to step417where the device examines the state of the perform search flag. If the perform search flag is not set, then the method can return to step313inFIG. 4Aand the device can perform a limited HPPLMN scan. On the other hand, if the perform-search flag is set, then the method can proceed to step419inFIG. 4C.

In step419inFIG. 4C, the mobile wireless device and perform a scan for a HPPLMN. In one embodiment, the device can scan for a HPLMN or an EHPLMN. In step421, if the HPLMN or an (EHPLMN) is not found, then the method returns to step313inFIG. 4A. On the other hand, if the HPLMN or EHPLMN is found, then in step423the PLMN selection mode for the mobile wireless device101is determined. If the mobile wireless device101is not configured to be in a manual PLMN selection mode (i.e., the mobile wireless device101is configured for automatic PLMN selection), then in step425, the mobile wireless device101can register and camp on the HPLMN or EHPLMN and the method ends. On the other hand, if the mobile wireless device101is configured to be in a manual PLMN selection mode, then in step427the mobile wireless device101can display a notification to indicate to the user that a HPLMN has been located. In step429, if the user does not select the HPLMN, then the method returns to step313. On the other hand, if the user does select the HPLMN, then in step431the user can select the HPLMN or EHPLMN and manually and the method ends.

The adaptive PLMN scanning method set forth inFIG. 3andFIGS. 4A-4Ccan advantageously enhance battery life by scanning for a HPLMN only when there is a likelihood that a HPLMN may be near to the mobile wireless device101. Also, the adaptive scanning method can be applied when the mobile wireless device101is configured for either automatic or manual PLMN selection.

FIG. 5is a block diagram500of a mobile wireless device101, in accordance with one embodiment of the specification. Mobile wireless device101can include a processor502coupled to memory506and also coupled to a wireless transceiver504. Processor502can be configured to read, write and execute processor instructions stored in memory506. Processor502can also be configured to control wireless transceiver504. In one embodiment, wireless transceiver504can connect to networks PLMNs such as HPLMNs and VPLNMs through antenna508.