Patent Publication Number: US-2013231111-A1

Title: Mobile terminal and network selection method

Description:
TECHNICAL FIELD 
     The present invention relates to a mobile terminal and a network selection method. 
     BACKGROUND ART 
     In a case where there are plural networks to which a mobile terminal can connect, a network of a connection destination is selected according to predetermined priority order normally. If the priority order is the same for networks, one network is selected at random from among networks in which a reception level is equal to or greater than a defined value. If there is no network in which the reception level is equal to or greater than the defined value, a network of a relatively high reception level is selected. The non-patent document 1 describes a conventional network selection scheme. 
     PRIOR ART DOCUMENT 
     [Non-patent document 1] 3GPP TS23.122 v6.5.0 (2005-06) 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     As communication services are diversified, various operators provide various services based on various fee schedules. A user may wish to select an operator of low charges such as a flat rate service in domestic and foreign areas. Or, a user may wish to select an operator providing high quality services of low charges. However, in a case of the conventional network selection method, it is not possible to select a network by properly reflecting such a user&#39;s intention. 
     An object of the present invention is to make it possible to select a network by properly reflecting a user&#39;s intention. 
     Means for Solving the Problem 
     A mobile terminal according to an embodiment of the present invention is a mobile terminal including:
     a storage unit configured to store a table of networks that a user desires to select;   a selection unit configured, when a network included in the table is found from networks detected by cell search, to select the network that is detected by cell search and that is included in the table; and   a processing unit configured to select a cell of the network selected by the selection unit, and performs position registration.   

     Effect of the Present Invention 
     According to an embodiment, it becomes possible to select a network by properly reflecting a user&#39;s intention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic flowchart showing an operation example of a mobile terminal; 
         FIG. 2  is a flowchart (semi-automatic mode) showing operation in steps S 12  and S 13  in  FIG. 1  in detail; 
         FIG. 3  is a flowchart (automatic mode) showing operation of steps S 12  and S 13  of  FIG. 1  in detail; and 
         FIG. 4  is a functional block diagram of parts related to an embodiment. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     As mentioned above, when selecting a network by using a conventional technique, the selection is performed by an automatic mode or a manual mode. However, there is no selection method in conventional techniques like a selection method according to the present invention, in which, when performing international (foreign) roaming, for example, only an operator (flat rate operator) that provides a flat rate service is searched, and if such an operator does not exist, the mobile terminal is set to out of range. 
     In an embodiment described below, the mobile terminal stores a table (“flat rate operator table”, that is, “priority network table” more generally) including priority networks of flat rate operators. When the mobile terminal is powered on, operators in the priority network are searched, and an operator is selected. In this point, this technique is largely different from conventional techniques, in which only one operator is designated, selection is made from UPLMN (User controlled PLMN), OPLMN (Operator controlled PLMN), and other Other PLMN stored in USIM (Universal Subscriber Identity Module). 
     In an embodiment, for example, the priority network table of overseas flat rate operators is changed according to USIM to be used in the mobile terminal. Depending on the USIM, use of the priority network table is forbidden. In a case where a particular operator included in the priority network table is displayed as a choice of manual selection by a user, it is also displayed that the service of the operator is flat rate. Accordingly, a user who desires a flat rate service can directly connect to a network of the desired operator. Instead of manual selection, a flat rate operator may be selected automatically. For example, only a flat rate operator is automatically selected when performing international roaming, so that communication charge can be easily restricted. In a mode for automatically selecting, after returning home from overseas, it is not necessary to re-select a domestic operator like a case of manual selection. 
     An embodiment is described from the viewpoint of the following aspects. 
     1. Operation example 
     1.1 In a case of semi-automatic mode 
     1.2 In a case of automatic mode 
     2. Mobile terminal 
     Embodiment 1 
     1. Operation Example 
       FIG. 1  shows a flowchart of an operation example of a mobile terminal. The operation example shown in the figure shows an outline after the mobile terminal is powered on until position registration completes. 
     In step S 11 , the mobile terminal is powered on. Or, the following steps may be performed when a predetermined timer expires in the mobile terminal that has gone out of the service range. 
     In step S 12 , the mobile terminal performs cell search (band search). The mobile terminal measures reception levels of a residing cell and a surrounding cell so as to detect a usable frequency and a cell of a move destination candidate. The “reception level” in the present embodiment is broadly defined as an amount representing good or bad of a radio state irrespective of an instant value or an average value. The reception level may be represented as, for example, received power, electric field strength RSSI, desired wave received power RSCP, path loss, SNR, SIR, Ec/N0 and the like. 
     In step S 13 , the mobile terminal refers to a pre-stored table so as to select a usable network (Public Land Mobile Network: PLMN) from among cells of move destination candidates selected in step S 12 . Although concrete selection methods are described later, the selection is performed by one of three methods of a semi-automatic mode, a manual mode and an automatic mode. The semi-automatic mode may be referred to as a half-automatic mode or a quasi-automatic mode. The automatic mode may be referred to as an automatic mode. 
     In step S 14 , the mobile terminal receives broadcast information of the selected PLMN, and detects a candidate of a usable cell from the broadcast information. That is, after the network is selected, a cell in the network is selected. 
     In step S 15 , the mobile terminal performs position registration processing based on the detected cell. More specifically, an uplink control signal including an identifier of the detected cell (cell ID) is transmitted to the base station, and a position registration area is set or updated in an exchange. 
     &lt;1.1 In a Case of Semi-Automatic Mode&gt; 
       FIG. 2  is a flowchart showing operation in steps S 12  and S 13  of  FIG. 1  in detail. 
     After the mobile terminal is powered on (or in a case where a predetermined cycle comes in an out-of-range area) in step S 11 , the mobile terminal performs cell search (band search) in step S 12 . For the sake of convenience of explanation, cell search is performed for a second generation mobile communication system (2G) such as GSM and a third generation mobile communication system (3G) such as IMT-2000. However, the present invention can be applied not only to 2G and 3G but also to other mobile communication systems. For example, mobile communication systems such as LTE (Long Term Evolution), LTE-Advanced, IMT-Advanced, WiFi, and WiMAX may be targets of the cell search. In step S 121 , the mobile terminal measures reception levels of a residing cell and a surrounding cell, and detects usable frequencies and cells of move destination candidates in step S 122 . 
     In step S 13 , the mobile terminal selects a usable network (PLMN) from among cells of the move destination candidates selected in step S 122  by referring to a pre-stored table. In this case, the mobile terminal compares each network of the cells detected in step S 122  with a priority network table that is held beforehand. The priority network table is a table of networks to which the user wishes to connect. As an example, the priority network table includes one or more networks of operators providing flat rate services. 
     In a case where there are networks of detected cells in the priority network table, any one of the networks is selected. In general, the selection is performed by one of the three methods of a semi-automatic mode, a manual mode and an automatic mode.  FIG. 2  shows the case of the semi-automatic mode. 
     In the case of the semi-automatic mode, a network is selected manually by a user in the priority network table. For example, it is assumed that the priority network table includes five networks of NW1, NW2, NW3, NW4 and NW5, and that four networks of NW1, NW2, NW7 and NW8 are detected as a result of cell search. In the case of the semi-automatic mode, the user can select one of NW1 and NW2 manually. Since two networks of NW7 and NW8 are not included in the priority network table, they are not included in choices. On the other hand, in a case of the manual mode, the user can arbitrarily select a network of a detected cell. In the case of the above example, the user can manually select any of NW1, NW2, NW7 and NW8. The case of the automatic mode is described later. In the semi-automatic mode and the manual mode, when the user selects a network from the priority network table, priority order of selection may be designated for networks in the priority network table. For example, in a case where five networks of NW1, NW2, NW3, NW4 and NW5 are included in the priority network table, NW1 may be assigned the highest priority, NW2 and NW3 may be assigned the second highest priority, and NW4 and NW5 may be assigned the lowest priority. In this case, if NW1 and NW2 are the choices, NW1 is selected preferentially. How the priority is set is designated by the user. 
     In step  131 , it is determined whether there is a network of a detected cell in the priority network table. In a case where such a network exists, the flow goes to step S 14 . After that, the cell of the network is selected, and position registration is performed (steps S 14  and S 15 ). 
     In step S 131 , when no network of detected cell exists in the priority network table, the flow goes to step S 132 . In this case, the user resides outside the service area, and information indicating “out of range” is displayed on the display of the mobile terminal. The “out of range” in step S 132  means that any network in the priority network table cannot be found, and it does not necessarily mean that communication itself is impossible. That is, in step S 132 , although any network corresponding to the priority network table does not exist, a network that enables the mobile terminal to perform communication may exist. 
     The priority network table used in step S 131  is stored in an storage unit in the mobile terminal beforehand. The priority network table may be stored in an information medium such as a SIM and a USIM, or may be stored in a storage unit other than the SIM and the USIM. In any case, it is only necessary that the mobile terminal can use the priority network table when selecting PLMN. The priority network table may be kept unchanged or may be changed or updated as necessary. For example, the priority network table may be changed according to USIM used for the mobile terminal. Or, the user may edit the priority network table. Further, the priority network table may be downloaded by some sort of application. 
     &lt;1.2 In a Case of Automatic Mode&gt; 
       FIG. 3  is also a flowchart, like  FIG. 2 , showing operation of S 12  and S 13  of  FIG. 1  in detail.  FIG. 3  shows operation in the case of the automatic mode. 
     In step S 11 , after the mobile terminal is powered on (or in a case where a predetermined cycle comes in an out-of-range area), the mobile terminal performs cell search (band search) in step S 12 . In step S 121 , the mobile terminal measures reception level of the residing cell and the surrounding cell, and, in step  122 , the mobile terminal detects usable frequencies and cells of move destination candidates. 
     In step S 13 , the mobile terminal selects a usable network (PLMN). In the case of the automatic mode, first, in step S 131 , the mobile terminal compares a network of a cell detected in step S 122  with the pre-stored priority network table. When there is the network of the detected cell in the priority network table, the flow goes to step S 14 , so that the cell of the network is selected and position registration is performed (steps S 14  and S 15 ). When there are plural selectable networks in the priority network table, the user can select any of the networks. 
     The explanation so far is the same as the operation example of the flowchart shown in  FIG. 2 . 
     In step S 131 , when there is no network of detected cell in the priority network, the flow goes to step S 132 . 
     In step S 132 , the mobile terminal determines whether a network of a detected cell is the same as the most recent network in which the mobile terminal resided. When the network of the detected cell is the same as the most recent network in which the mobile terminal resided, the flow goes to step S 14 , and the cell of the network is selected, and position registration is performed (steps S 14 , S 15 ). There is a case where the most recent network in which the mobile terminal resided is included in the priority network table. In this case, the result of step S 132  is not-match. 
     In step S 132 , when no network of detected cell is the same as the most recent network in which the mobile terminal resided, the flow goes to step S 133 . 
     In step S 133 , the mobile terminal determines whether a network of a detected cell is the same as HPLMN (Home PLMN). HPLMN is a home network, which is a network of a carrier with which the user of the mobile terminal contracts. When the network of the detected cell is the same as the HPLMN, the flow goes to step S 14 , so that the cell of the network is selected and position registration is performed (step S 14 , S 15 ). There is a case where HPLMN is included in the priority network table. In this case, the result of step S 133  is not-match. 
     In step S 133 , when no network of detected cell is the same as HPLMN, the flow goes to step S 134 . 
     In step S 134 , the mobile terminal determines whether a network of a detected cell is the same as UPLMN (User controlled PLMN). UPLMN is a network of a carrier that the user has selectively registered. When the network of the detected cell is the same as UPLMN, the flow goes to step S 14 , so that the cell of the network is selected and position registration is performed (step S 14 , S 15 ). There is a case where UPLMN is included in the priority network table. In this case, the result of step S 134  is not-match. 
     In step S 134 , when no network of detected cell is the same as UPLMN, the flow goes to step S 135 . 
     In step S 135 , the mobile terminal determines whether a network of a detected cell is the same as OPLMN (Operator controlled PLMN). OPLMN is a network of a carrier that the carrier has selectively registered. When the network of the detected cell is the same as OPLMN, the flow goes to step S 14 , so that the cell of the network is selected and position registration is performed (step S 14 , S 15 ). There is a case where OPLMN is included in the priority network table. In this case, the result of step S 135  is not-match. 
     In step S 135 , when no network of detected cell is the same as OPLMN, the flow goes to step S 136 . 
     In step S 136 , the mobile terminal compares a reception level of each of one or more networks of the detected cells with a threshold. The mobile terminal selects a network (Other PLMN) that causes a reception level equal to or greater than the threshold. When there are plural networks that cause the reception level equal to or greater than the threshold, a network of a relatively good reception level is selected. On the other hand, when there is no network that causes a reception level equal to or greater than the threshold in the detected networks, a network of a relatively good reception level is selected. As the threshold, any proper value may be used. As an example, a threshold in a case of 3G system is −95 dBm, and a threshold in a case of 2G system is −85 dBm. In either case, at least a network of a relatively good reception level is selected, the flow goes to step S 14 , the cell of the network is selected, and position registration is performed (step S 14 , S 15 ). 
     In either of the automatic mode and the semi-automatic mode, it is determined, first, that a network in the priority network table is the same as a detected network. In this point, they are common. However, in the case of the automatic mode, different from the semi-automatic mode, a network is selected by comparing the detected network with the past-resided network, HPLMN, UPLMN, OPLMN and other PLMN in that order to determine sameness. 
     2. Mobile Terminal  
       FIG. 4  is a functional block diagram of elements especially related to the present embodiment in various functional elements included in the mobile terminal.  FIG. 4  shows a network mode designation unit  41 , a priority network table  42 , a PLMN selection unit  43 , a cell selection unit  44 , a position registration unit  45  and a user interface  46 . The mobile terminal may be any proper apparatus that enables a user to perform communication via a network. More specifically, the mobile terminal is a mobile phone, an information terminal, a smart phone, a personal digital assistant, a mobile personal computer, or other user apparatus. But, the user apparatus is not limited to these apparatuses. 
     The network mode designation unit  41  reports, to the PLMN selection unit  43 , a mode for selecting a network. More specifically, the mode is the semi-automatic mode, the manual mode or the automatic mode, which are already described. The mode may be directly designated by the user, or the mode may be preset as a default mode in the mobile terminal. 
     The priority network table  42  is a table of networks to which the user wishes to connect. As an example, the priority network table includes one or more networks of operators providing flat rate services. As mentioned above, the priority network table may be kept unchanged or may be changed or updated as necessary. For example, the priority network table may be different according to USIM used in the mobile terminal. 
     The PLMN selection unit  43  selects a PLMN by using the priority network table  42  according to the mode designated from the network mode designation unit  41 . Concrete selection methods are described with reference to  FIGS. 2 and 3 . 
     The cell selection unit  44  receives a report indicating a PLMN selected by the PLMN selection unit  43 , and selects a cell of the reported PLMN. 
     The position registration unit  45  performs processing of position registration in the selected cell. For example, the mobile terminal transmits, to the base station, an uplink control signal for requesting position registration with a cell identifier of the selected cell from a transmission unit not shown in the figure. Accordingly, an exchange and the like connected to the base station performs processing of position registration. 
     The user interface  46  is an input-output unit for exchanging information with the user visually and/or acoustically. Concrete examples of the user interface are a display, a control panel including a keypad, a cathode-ray tube, a liquid crystal display, a keyboard, a touch pad, a mouse, a track ball, a microphone, a speaker, or combination of arbitrary ones of these. But, the user interface  46  is not limited to these. Especially, in the semi-automatic mode and the manual mode, when the user selects a network from the priority network table, some sort of information may be displayed together with selectable networks. For example, information indicating whether the selectable networks can provide a flat rate service may be displayed with choices of the networks for selection. 
     In the above, the present invention has been explained while referring to the specific embodiments. However, these are merely exemplary. Those skilled in the art will conceive of various modified examples, corrected examples, alternative examples, substituted examples, and the like. 
     For example, the present invention may be applied to any suitable mobile communication system for performing communication by selecting one of plural networks. For example, the present invention may be applied to systems of W-CDMA scheme, W-CDMA systems of the HSDPA/HSUPA scheme, systems of the LTE scheme, systems of the LTE-Advanced scheme, systems of the IMT-Advanced scheme, WiMAX, Wi-Fi scheme systems and the like. 
     While specific numerical value examples are used to facilitate understanding of the present invention, such numerical values are merely examples, and any appropriate value may be used unless specified otherwise. Classification into each embodiment or item in the description is not essential in the present invention, and features described in two or more items may be combined and used as necessary. Subject matter described in an item may be applied to subject matter described in another item (provided that they do not contradict). 
     For convenience of explanation, the apparatus according to the embodiment of the present invention has been explained by using a functional block diagram. However, the apparatus may be implemented in hardware, software, or a combination thereof. The software may be stored in any proper storage medium such as a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM), a register, a hard disk (HDD), a removable disk, a CD-ROM, database, server and the like. 
     Therefore, the present invention is not limited to the above-mentioned embodiment and is intended to include various variations, modifications, alterations, substitutions and so on without departing from the spirit of the present invention. 
     The present international application claims priority based on Japanese patent application No. 2010-250219, filed in the JPO on Nov. 8, 2010, and the entire contents of the Japanese patent application No. 2010-250219 are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
           41  network mode designation unit 
           42  priority network table 
           43  PLMN selection unit 
           44  cell selection unit 
           45  position registration unit 
           46  user interface