Method for selecting a preferred land mobile network and / or a preferred access method for connecting a telematics control unit

Abstract

The invention relates to a method for connecting a telematics control unit (TCU) (2) of a vehicle (1) to a preferred land mobile network (Public Land Mobile Network, PLMN) (3) and / or via a preferred access method (Radio Access Technology RAT). In a first partial path (P1), a check is made as to whether a currently set RAT is equivalent to or better than a predetermined minimum RAT; otherwise, a parameterizable action or, alternatively, a manual search is started to search for a preferred PLMN (3). In a second partial path (P2), a check is made as to whether the TCU (2) is logged into a preferred PLMN (3) using a Mobile Country Code (MCC) and / or Mobile Network Code (MNC) assigned to the TCU (2) via a Subscriber Identification Module (SIM). If the TCU (2) is logged into a preferred PLMN (3), a parameterizable action or, alternatively, a manual search is started to search for a preferred PLMN (3).

Description

[0001] The invention relates to a method for connecting a telematics control unit (TCU) of a vehicle to a preferred land mobile network (Public Land Mobile Network, PLMN) and / or for connecting a TCU of a vehicle via a preferred access method (Radio Access Technology RAT) according to the preamble of claim 1.

[0002] Document DE 10 2016 114 321 A1 describes a vehicle mobile operator switching system comprising a controller that, in response to a notification indicating that the access signal quality of a first public land mobile network is below a threshold and a successful registration with a second PLMN selected from a set of PLMNs provided by at least two subscriber identity modules associated with non-roaming partner carriers according to a priority defined by the carriers, provides network access using the second PLMN.

[0003] Document DE 10 2021 005 115 A1 describes a method for connecting a telematics control unit (TCU) of a vehicle to a preferred land mobile network (Public Land Mobile Network, PLMN) and / or via a preferred access method (Radio Access Technology RAT). In a first sub-path, a check is made to determine whether a currently set RAT is equivalent to or better than a predetermined minimum RAT. If not, the system runs through at least a first to third waiting loop (W1 to W3) with a predetermined waiting time until the predetermined minimum RAT is reached or exceeded, or until a predetermined maximum number of waiting loop runs has been reached.In a second sub-path, a Mobile Country Code (MCC) and / or Mobile Network Code (MNC) assigned to the TCU via a Subscriber Identification Module (SIM) is used to check whether the TCU is logged on to a preferred PLMN. If not, the TCU undergoes a waiting period determined via a fourth waiting loop (W4) or alternatively via an Elementary File Higher Priority PLMN (EFHPPLMN) time value until the TCU is logged on to a preferred PLMN or until a predetermined maximum number of waiting periods have been completed. After the first sub-path and / or after the second sub-path, a third sub-path is executed in which a preconfigured recovery measure for the TCU is executed and the system waits until the TCU is logged on to another PLMN and / or with another RAT or until a predetermined waiting period has elapsed.

[0004] Document CN 1 15 460 568 A describes a network management method for a vehicle-mounted terminal, comprising the following steps: querying whether a modem in a vehicle-mounted terminal establishes a connection, starting with a first query period; if the modem is not started, maintaining a current state and continuing to query whether the modem is started or not; if the modem is started, entering an initialization state; querying whether the modem establishes a public data network connection in a second query period in the initialization state; if the public data network connection is established, skipping to a data dialing process state; otherwise, if the public data network connection is not established, entering a network drop state; executing a data dialing registration action in a data dialing process state and entering a normal working state,after the data dial registration action has been executed; otherwise, return to an initialization state if the data dial registration action is not executed, and query whether the modem establishes a public data network connection in a second polling period. In the normal working state, a service connection detection is performed in a third polling period. A network connection abnormality of the vehicle-mounted terminal is judged after the service connection detection of a single third polling period has been continued N times, and the network connection abnormality of the vehicle-mounted terminal is determined and a dialing process stopped state is entered. In the normal working state, the modem detects whether a data registration error or a registration exception occurs. Normally, if the modem detects a data registration error or a registration exception,returns to an initialization state and queries whether a connection to the public data network has been established in a second polling period. In the state in which the dialing process is stopped, the modem is controlled to stop data registration, jump to an initialization state, and query whether the modem establishes a public data network connection in a second polling period. In a fourth polling period, an interface interlayer connection state and a public data network connection state of the modem are queried. If the modem has re-established a public data network connection within a preset modem restart period, the modem enters an initialization state. Otherwise, when the modem reaches a preset modem restart period, the modem is reset and jumps to an initialization state.if the modem does not terminate the public data network connection.

[0005] The invention is based on the object of providing an improved method for connecting a TCU to a PLMN.

[0006] The object is achieved according to the invention by a method having the features of claim 1.

[0007] Advantageous embodiments of the invention are the subject of the subclaims.

[0008] In a method for connecting a vehicle's TCU to a preferred PLMN and / or for connecting a vehicle's TCU to a PLMN by selecting a preferred access method (Radio Access Technology, or RAT) that is at least equivalent to a minimum RAT, the TCU is initially placed in a first state, also referred to as normal operating state or normal mode. In this state, all counters and timers are reset to zero.

[0009] The TCU is then logged into an initial PLMN and made ready for communication, thus reaching a second state, which is called Network Attach or Online State.

[0010] The invention is based on the finding that the TCU of a vehicle continuously transmits data provided by the TCU itself or by other control units of the vehicle. As a result, the TCU is essentially permanently operated in a modem-connected state.

[0011] Based on criteria explained in more detail below, such as counter values, if the TCU is not connected to a preferred PLMN, a manual search for a preferred PLMN or one of three parameterizable actions is initiated. A preferred PLMN is understood in particular to be a PLMN that provides the vehicle user with preferred protocols and services, such as Internet in the Car (IITC).

[0012] If the TCU is already connected to a preferred PLMN, a check is carried out to determine whether this achieves the best possible or at least the intended (minimum required) minimum RAT. If not, a manual search for a preferred PLMN or one of three parameterizable actions is initiated.

[0013] Starting from the second state, a first subpath for monitoring and adjusting the RAT (RAT Monitoring) and / or a second subpath for selecting the PLMN are followed. The first and second subpaths can be coded in or out independently of each other. The decision whether to switch to the first or second subpath is made in a first decision step, which is explained in more detail below.

[0014] In the second subpath, an identification of the PLMN to which the TCU is logged on, formed by a Mobile Country Code (MCC) and a Mobile Network Code (MNC), is used to check whether this PLMN is a preferred PLMN. The PLMN identification is compared with the information provided by a Subscriber Identity Module (SIM). The preferred PLMN can be any PLMN selected from a set or list of preferred PLMNs that was also detected by a standalone modem scan.

[0015] In the first sub-path (RAT Monitoring), it is continuously checked whether a currently set RAT is equivalent to or better than a predetermined minimum RAT.

[0016] If the currently set RAT is not equivalent to or better than a predetermined minimum RAT, at least one parameterizable action is started, in which a first to third waiting loop with a predetermined waiting time is run through, during which a recovery attempt is started.

[0017] The queue is repeated until the predetermined minimum RAT is reached or exceeded, or until the best possible RAT is reached, or until a predetermined maximum number of recovery attempts is reached.

[0018] The queue can be selected depending on whether it is a first or subsequent recovery attempt. The queue can also be selected depending on whether RAT degradation was triggered by a voice call. If RAT degradation was triggered by a voice call, the associated queue (i.e., the recovery attempt) is only initiated once the end of the voice call has been detected and if the RAT has not been restored to at least the predetermined minimum RAT within the expiration of a separately initiated timer.

[0019] If the TCU is not logged into a preferred PLMN, a wait period determined by a fourth queue is entered. The wait period continues until the TCU is logged into a preferred PLMN or until a predetermined maximum number of wait periods have been entered.

[0020] Following the first sub-path, a third sub-path is executed in which a preconfigured recovery action is executed for the TCU and waits until the TCU is logged into another PLMN and / or with another RAT or a predetermined waiting time has elapsed.

[0021] After the third partial path, the system switches back to the second state.

[0022] According to the invention, starting from the first subpath, a manual search is initiated in a fourth subpath, in which a preferred PLMN is searched for that provides a better RAT than the currently available one. The manual search is initiated when the current PLMN (in which the TCU is logged on) provides a worse RAT than the specified minimum and when a predetermined maximum number of such manual searches has not yet been reached.

[0023] Optionally, the fourth subpath can wait for the end of any ongoing voice call and then disconnect the existing connections to access points (APNs). A check is then made to see if the RAT has been improved to at least the specified minimum RAT. The manual scan is then only performed if such an improvement has not occurred. If at least the specified RAT has been reached, the first subpath is traversed again.

[0024] If the search is unsuccessful, a counter for manual searches is incremented. The APNs are then reconnected, and the first sub-path is traversed again. Before the fourth sub-path is traversed again, this counter is compared with the predetermined maximum number of searches.

[0025] If the search is successful, the manual search counter is reset to zero and then changes to the second state.

[0026] Alternatively or additionally, after the second sub-path, a manual search is started in a fifth sub-path in which a preferred PLMN is searched for if the TCU is not currently connected to a preferred PLMN. In the fifth sub-path, the existing connections to APNs are disconnected. Furthermore, all preferred PLMNs are recorded and a check is carried out to determine whether there is at least one preferred PLMN among them that provides at least the specified required (minimum) RAT. If successful, a counter of the unsuccessful searches performed up to that point is reset to zero and the system switches to the second state. If the search is unsuccessful, this counter is incremented. Furthermore, previously existing connections to the APNs are restored and the system switches to the second state.

[0027] This method ensures that the TCU is not operated for an unnecessarily long time, for example, beyond a voice call, in an access method (in a RAT) that is offered by the PLMN but is inferior to the access method required or desired for data transmission. Furthermore, this method ensures that the TCU is not logged in for an unnecessarily long time in a PLMN that is not among the preferred PLMNs.

[0028] Furthermore, this ensures that the TCU is always connected to a PLMN that has the best possible RAT among the available PLMNs. This can increase the bandwidth available in a vehicle. Furthermore, it ensures that the TCU is connected to a preferred PLMN, provided such a preferred PLMN is available and accessible.

[0029] Embodiments of the invention are explained in more detail below with reference to drawings.

[0030] It shows: Fig. 1 schematically shows a vehicle with a telematics control unit and Fig. 2 schematically shows a flowchart for a method for selecting a land mobile network and / or an access method for a land mobile network.

[0031] Corresponding parts are provided with the same reference numerals in all figures.

[0032] Fig. 1 schematically shows a vehicle 1 with a telematics control unit (TCU) 2. The TCU 2 comprises a modem 2.1 configured to communicate with at least one public land mobile network (PLMN) 3. For this purpose, the PLMN 3 provides a network infrastructure 4, for example, mobile radio or wireless base stations. The modem 2.1 may comprise a SIM on which information about at least one preferred PLMN 3 is stored.

[0033] Fig. 2 schematically shows a flowchart for a method by which a preferred PLMN 3 and / or a preferred access method (Radio Access Technology, RAT) for such a PLMN 3 are selected for a TCU 2.

[0034] In an initial first step S1, counters DTI_RAT_FailedCnt, DTI_MNO_FailedCnt, DTI_MNO_MonCycICnt, DTI_RAT_MonCycICnt, and DTI_RATPLMNSearchCnt are reset to zero, where - the counter DTI_RAT_FailedCnt records the number of failed attempts to switch to a RAT that is equivalent to or better than a predetermined minimum RAT (Minimum RAT) during an ignition run or until waking from bus sleep, - the counter DTI_MNO_FailedCnt records the number of consecutive failed dial-in attempts to a preferred PLMN 3 due to a timeout, i.e. the number of consecutive failed connection attempts in a life cycle, - the DTI_MNO_MonCyclCnt counter records the number of consecutive dial-ins to a non-preferred PLMN 3, i.e., the number of consecutive failed connection attempts in a Network Attach / Online state due to the same error cause. (In other words, DTI_MNO_MonCyclCnt records the number of unsuccessful connection attempts caused by a certain, common error, which is compared with a maximum number of connection attempts. If the DTI_MNO_MonCyclCnt counter reaches the specified maximum number of connection attempts without a dial-in to a non-preferred PLMN 3 being successful, the connection will only continue after a bus rest.) - the counter DTI_RATPLMNSearchCnt records the number of searches for a preferred RAT and / or for a preferred PLMN 3 already performed in an ignition cycle (since the ignition was switched on) or after entering a normal mode after a successful re-establishment of a connection - the counter DTI_RAT_MonCyclCnt records the number of consecutive unsuccessful searches for a preferred RAT along a first path P1, which is explained in more detail below.

[0035] Furthermore, in the first step S1, a new event DTI_RAT_MonitorSwitch is triggered, i.e., the variable DTI_RAT_MonitorSwitch is set to the value NewEvent. The value NewEvent indicates that a new RAT monitoring cycle (i.e., a check to determine whether the selected RAT is equivalent to or better than the predetermined minimum RAT) should be started.

[0036] Following the first step S1, a first state Z1 (normal mode) is reached. With the first state Z1, a new life cycle of the process begins.

[0037] Following the first state Z1, all timers are reset in a second step S2 each time a network attach is performed.

[0038] Furthermore, in the second step S2, the TCU 2 is logged into the PLMN 3 available with the best reception quality and communication readiness is established.

[0039] Following the second step S2, a second state Z2 (Network Attached State or Online State) is reached.

[0040] Following the second state Z2, an initial (zeroth) decision step E0 checks whether the search for an improved PLMN 3 is activated. If not, the method continues with the second decision step E2 in a first sub-path P1, which is explained in more detail below.

[0041] If the search for an improved PLMN 3 is activated, a subsequent first decision step E1 checks whether the TCU 2 is registered in a preferred PLMN 3. The check is performed using the Mobile Network Code (MNC) and the Mobile Country Code (MCC), which are provided by a Subscriber Identity Module (SIM) and compared with the value provided by the current PLMN 3. The Subscriber Identity Module is designed as an embedded Subscriber Identity Module (eSIM).

[0042] If the TCU 2 is registered in a preferred PLMN 3, the RAT is checked and adjusted along a first sub-path P1. If the TCU 2 is not registered in a preferred PLMN 3, a preferred PLMN 3 is searched for along a second sub-path P2.

[0043] First, the first subpath P1 is explained. In a third step S3, the counter DTI_MNO_MonCyclCnt is reset to zero. Subsequently, in the second decision step E2, a check is made to determine whether the RAT check and adaptation has been activated via the variant coding of TCU 2. If no RAT is accessible, the system switches to the first state Z1. The first subpath P1 is only followed if the RAT check and adaptation has been activated via the variant coding of TCU 2. If the RAT check and adaptation is deactivated, the first subpath P1 is not followed.

[0044] If a RAT is activated, i.e., physically accessible, a subsequent third decision step E3 checks whether this RAT is equivalent to or better than the predetermined minimum RAT. If this condition is met, in a fourth step S4, the timers DTI_RAT_InitMonTimer, DTI_RAT_VoiceCallTimer, and DTI_MonTimer are reset to zero, the counters DTI_RAT_MonCyclCnt and DTI_RATPLMNSearchCnt are reset to zero, and the state variable DTI_RAT_MonitorSwitch is reset to the value NewEvent. The third decision step E3 is then repeated.

[0045] If the check in the third decision step E3 results in a RAT below the minimum RAT, a subsequent fourth decision step E4 checks whether the counter DTI_RAT_FailedCnt reaches or exceeds an assigned, predetermined maximum counter value DTI_RAT_maxFailedCnt. If this condition is met, the system switches to the first state Z1.

[0046] If the counter DTI_RAT_FailedCnt is still below the assigned maximum counter value DTI_RAT_maxFailedCnt, the value of the state variable DTI_RAT_MonitorSwitch is checked in a fifth decision step E5 following the fourth decision step E4.

[0047] If the state variable DTI_RAT_MonitorSwitch has the value MonitoringOver in the fifth decision step E5, a subsequent sixth decision step E6 checks whether the RAT has been changed. If the RAT has not been changed, the process continues with the third decision step E3 explained above.

[0048] If the RAT has been changed, the state variable DTI_RAT_MonitorSwitch is set to the value NewEvent in a fifth step S5, and the third decision step E3 is subsequently repeated. If the RAT has not been changed, the third decision step E3 is repeated immediately, i.e., without reassigning the state variable DTI_RAT_MonitorSwitch.

[0049] If the state variable DTI_RAT_MonitorSwitch has the value Monitoring in the fifth decision step E5, a seventh decision step E7 checks whether a variable DTI_RATPLMNSearch_enable is set and thus the search for a better RAT is activated.

[0050] If the variable DTI_RATPLMNSearch_enable is set, in a twentieth decision step E20, the counter DTI_RATPLMNSearchCnt is compared with an associated preset maximum value DTI_RATPLMNSearch_maxCnt. If the comparison of the counter DTI_RATPLMNSearchCnt with the preset maximum value DTI_RATPLMNSearch_maxCnt shows that the predetermined maximum permitted number of searches for an improved RAT has not yet been reached, a search is conducted along a fourth subpath P4 for an improved RAT or for a preferred PLMN 3. The fourth subpath P4 will be explained in more detail below.

[0051] If it is determined in the twentieth decision step E20 that the search for a RAT and / or for a PLMN 3 is deactivated or the counter DTI_RATPLMNSearchCnt has already reached the specified maximum number of searches with the assigned preset maximum value DTI_RATPLMNSearch_maxCnt, then in a subsequent twenty-third decision step E23 it is checked whether the counter DTI_RAT _MonCyclCnt reaches or exceeds an assigned, predetermined counter maximum value DTI_RAT_maxMonCyclCnt.

[0052] If this condition is met, in a sixth step S6 the state variable DTI_RAT_MoniorSwitch is set to the value MonitoringOver and subsequently the third decision step E3 is repeated.

[0053] If, in the twenty-third decision step E23, the counter DTI_RAT_MonCyclCnt has not yet reached the assigned maximum counter value DTI_RAT_maxMonCyclCnt, a timer DTI_RAT_MonTimer is started in a first waiting loop W1 and waits until this timer has reached its predetermined time value. The tenth decision step E10 is then executed, which is explained in more detail below.

[0054] If the state variable DTI_RAT_MonitorSwitch has the value NewEvent in the fifth decision step E5, a check is carried out in a subsequent eighth decision step E8 to determine whether a reduction in the RAT was triggered by a voice call that was routed via TCU 2. Such RAT downgrades can be triggered via a circuit switch fallback (CSFB) if voice transmission via a higher-order packet-bound RAT is not possible. If the check in the eighth decision step E8 shows that the RAT downgrade was not triggered as a result of a CSFB, a timer DTI_RAT_InitMonTimer is started in a second waiting loop W2 and waits until this timer has reached its predetermined time value. The tenth decision step E10 is then executed, which is explained in more detail below.

[0055] If, however, the check in the eighth decision step E8 reveals that the RAT downgrade was triggered by a CSFB, a ninth decision step E9 continuously checks whether the voice call that triggered the downgrade has ended. Once the voice call has ended, a timer DTI_RAT_VoideCallTimer is started in a third waiting loop W3, and the system waits until this timer reaches its predetermined time value. The tenth decision step E10 is then executed.

[0056] During a waiting loop W1 to W3, the RAT can be changed by the TCU 2. In the tenth decision step E10, analogous to the third decision step E3, it is checked whether the RAT after the respective waiting loop W1 to W3 has expired is equal to or better than the predetermined minimum RAT. If this is the case, the fourth step S4 is executed again.

[0057] If, in the tenth decision step E10, a RAT is determined that is still worse than the predetermined minimum RAT (i.e., even after the respective waiting loops W1 to W3 have expired), the state variable DTI_RAT_MonitorSwitch is set to the value "Monitoring" in a seventh step S7, and the counter DTI_RAT_MonCyclCnt is incremented. Subsequently, the eighteenth decision step E18 is executed, which is explained in more detail below.

[0058] This completes the first sub-path P1 for RAT monitoring. In other words, the first sub-path P1 runs through a queue W1 to W3. The selection of the queue W1 to W3 depends on whether RAT monitoring was continued or newly initiated. If RAT monitoring was initiated by a voice call, the system waits for the completion of the voice call before starting the associated third queue W1.

[0059] If the predetermined minimum RAT is not reached even after the respective waiting loops W1 to W3 have expired, the counter DTI_RAT_MonCyclCnt, which records the number of consecutively unsuccessfully completed waiting loops W1 to W3, is incremented, and RAT monitoring is then resumed. RAT monitoring is aborted if this counter exceeds a predetermined maximum value.

[0060] In case of success, i.e. if the predetermined minimum RAT is reached after one or more waiting loops W1 to W3 have expired, all counter and timer values ​​are reset and the system waits for the next RAT change that will result in the minimum RAT being undershot.

[0061] The second partial path P2 is explained in more detail below, which is traversed if it was determined in the first decision step E1 that the TCU 2 is not logged into a PLMN 3 that belongs to the preferred PLMNs 3.

[0062] In a twelfth decision step E12, a check is made to determine whether the counter DTI_MNO_FailedCnt reaches or exceeds an assigned, predetermined maximum counter value. If this is the case, the system switches to the first state Z1 (Normal Mode). In other words, the system switches to the first state Z1 when a predetermined maximum number of consecutive failed connection attempts has been reached within a life cycle.

[0063] If the assigned maximum counter value for the DTI_MNO_FailedCnt counter has not yet been reached, a subsequent thirteenth decision step E13 checks whether the DTI_LMNO_MonCyclCnt counter reaches or exceeds an assigned, predetermined maximum counter value. If so, the system switches to the second state Z2 (Network Attached / Online Status). In other words, the system switches to the second state Z2 when a predetermined number of consecutive failed connection attempts have been reached within a Network Attach Mode (online mode).

[0064] If the assigned maximum counter value for the counter DTI_MNO_FailedCnt has not yet been reached, a timer DTI_MNO_DelayTimer is subsequently started in a fourth waiting loop W4 and waited until this timer has reached its predetermined time value.

[0065] After the DTI_MNO_DelayTimer timer has expired, a subsequent seventeenth decision step E17 checks, based on the MCC and the MNC, analogous to the first decision step E1, whether the TCU 2 is logged into a preferred PLMN 3. If the check is successful (i.e., if the TCU 2 is logged into a preferred PLMN 3), the counter DTI_MNO_MonCyclCnt is reset to zero in an eighth step S8, and then the system switches to the second state Z2.

[0066] If the TCU 2 is not logged into a preferred PLMN 3 even after the respective timer has expired, a subsequent sixteenth decision step E16 checks whether a voice call is active, for example, a Voice over Long Term Evolution (LTE) (VoLTE) voice call. This check is repeated until no more voice calls are active (i.e., the system waits for the end of an ongoing voice call).

[0067] Subsequently, in a twenty-first decision step E21, it is checked whether a variable DTI_MNO_Disconnect_APNs is set.

[0068] If the variable DTI_MNO_Disconnect_APNs is set, in a sixteenth step S16 the connection to all access point names (APNs) is disconnected, whereby the TCU 2 remains logged into the network of the mobile operator.

[0069] Following the sixteenth step S16 (if the variable DTI_MNO_Disconnect_APNs was set) or following the twenty-first decision step E21 (if the variable DTI_MNO_Disconnect_APNs was not set), a twenty-second decision step E22 checks again, analogous to the seventeenth decision step E17, whether the TCU 2 is logged into a preferred PLMN 3. If successful (as with a successful check in the seventeenth decision step E17), the counter DTI_MNO_MonCyclCnt is reset to zero in the eighth step S8 and then changes to the second state Z2.

[0070] If the TCU 2 is not registered in a preferred PLMN 3 even after disconnecting the connection to all APNs in the sixteenth step S16, a search is carried out for a preferred PLMN 3 along a fifth partial path P5 following the twenty-second decision step E22. The fifth partial path P5 will be explained in more detail below.

[0071] In other words, in the second subpath P2, controlled by the DTI_MNO_DelayTimer timer, the system waits for the completion of a voice call and then checks whether the TCU 2 is logged into a preferred PLMN 3. If successful, the system switches to the second state Z2 (Network Attached / Online State). If this fails, the fifth subpath P5 is executed.

[0072] The third sub-path P3 is explained below, which begins with the eighteenth decision step E18, which is reached from the first sub-path P1 by the seventh step S7.

[0073] In the eighteenth decision step E18, it is checked which recovery measure is configured (coded) for TCU 2. Depending on the configuration, one of the following three steps S10 to S12 is then executed: - either the tenth step S10, in which the modem 2.1 of the TCU 2 is put into airplane mode, whereby the SIM is reset and the TCU 2 is disconnected from the network of the mobile operator; - or the eleventh step S11, in which the modem 2.1 of the TCU 2 is put into an IDLE mode (waiting state), in which the TCU 2 remains logged on to the network of the mobile operator; - or the twelfth step S12, in which the connection to all access point names is disconnected, whereby the TCU 2 remains logged into the mobile operator's network.

[0074] Subsequently, in a thirteenth step S13, a DTI_IDLETimer timer is started, which runs until it is determined in a subsequent nineteenth decision step E19 that this DTI_IDLETimer timer has reached an associated, predetermined timeout or that the TCU 2 has changed the RAT or the mobile network provider in the meantime.

[0075] If a change of RAT or mobile provider was detected in the nineteenth decision step E19, or if a timeout of the DTI_IDLETimer timer was determined, modem 2.1 is immediately switched to normal mode in a fifteenth step S15. Otherwise, after the nineteenth decision step E19, the counter DTI_RAT_FailedCnt is incremented in a fourteenth step S14, and only then is the fifteenth step S15 executed.

[0076] The process in the third subpath P3 ends with the fifteenth step S15. After the fifteenth step S15, the TCU 2 switches to the second state Z2 (Network Attach / Online State).

[0077] In other words: in the third subpath P3, a preconfigured recovery action is executed for the TCU 2 (setting the modem 2.1 to airplane mode or setting the modem 2.1 to IDLE mode or disconnecting the modem 2.1 from all access point names) and then, during a predetermined waiting period, a check is made to determine whether the RAT or the mobile network provider, and thus also the PLMN 3, has been changed. If not, the counter indicating the number of failed RAT changes (DTI_RAT_FailedCnt), is incremented and the modem is set to normal mode, i.e., the recovery action is reversed.

[0078] The fourth sub-path P4, which is taken starting from the twentieth decision step E20, is explained in more detail below.

[0079] In the fourth subpath P4, a DTI_RATPLMNSearchTimer timer is started, which determines the duration of the search for a better RAT. After this time has elapsed, a check is made to determine whether a RAT has been set that is equal to or better than a specified RAT quality. If successful, the system proceeds to the third decision step E3, which was already described as part of the first subpath P1.

[0080] Otherwise, the system waits for the end of a possibly active voice call. Subsequently, if the variable DTI_RAT_DisconnectAPNs is set, all APNs are reset in the same way as in the sixteenth step S16 of the second subpath P2.

[0081] If no RAT is set that is equal to or better than the specified RAT quality, a manual search for PLMNs is initiated. After the manual search is completed, a check is made to see if a preferred PLMN 3 has been found.

[0082] If no preferred PLMN 3 was found or none of the found PLMNs is accessible, the counters DTI_RATPLMNSearchCnt and DTI_RAT_FailedCnt are incremented.

[0083] If at least one preferred PLMN 3 is found, the one with the highest RAT and priority is selected from the PLMNs 3 found and then the automatic mode is set.

[0084] Starting from the automatic mode, the counters DTI_RATPLMNSearchCnt and DTI_RAT_FailedCnt are incremented if none of the discovered preferred PLMNs is accessible or does not lead to an improved RAT.

[0085] If successful, the preferred PLMN 3 found in the fourth subpath P4 provides an improved RAT.

[0086] At the end of the fourth subpath P4 (regardless of whether an improvement in the RAT was successfully achieved or not), a reconnect of the APNs is performed if the variable DTI_RAT_DisconnectAPNs is set. The control flow then transitions to the second state Z2.

[0087] The fifth sub-path P5 is explained in more detail below. The fifth sub-path P5 is taken if it was determined in the twenty-second decision step E22 that the TCU 2 is not registered in a preferred PLMN 3 even after the connection to all APNs was severed in the sixteenth step S16.

[0088] A manual search for a PLMN 3 is then started in the fifth subpath P5. Once all available PLMNs 3 have been recorded, a check is performed to determine whether at least one preferred PLMN 3 is present among the available PLMNs 3.

[0089] If at least one preferred PLMN 3 is found, the one that is accessible and has the highest RAT and priority is selected from the found preferred PLMNs 3. The system then switches to automatic mode.

[0090] If no preferred PLMN 3 was found in the manual search or if none of the found preferred PLMNs 3 is accessible, the counters DTI_MNO_FailedCnt and DTI_MNO_MonCyclCnt are incremented.

[0091] If at least one of the discovered preferred PLMNs 3 is accessible, the counter DTI_MNO_MonCyclCnt is reset to zero (after switching to automatic mode).

[0092] After the counters DTI_MNO_FailedCnt and DTI_MNO_MonCyclCnt have been incremented (if the search was unsuccessful) or the counter DTI_MNO_MonCyclCnt has been reset to zero (if the search was successful), a check is made to see if the variable DTI_MNO_Disconnect_APNs is set. If the variable DTI_MNO_Disconnect_APNs is not set, the fifth path P5 is exited and the system switches to the second state Z2.

[0093] If the variable DTI_MNO_Disconnect_APNs is set, an APN reconnect is performed, meaning the APNs are restored. The fifth path P5 is then left and the second state Z2 is entered. List of reference symbols 1 vehicle 2 Telematics control unit, Telematic Control Unit TCU 2.1 Modem 3 Land Mobile Network, Public Land Mobile Network PLMN 4 Network infrastructure E0 initial (zeroth) decision step E1 to E10 first to tenth decision step E12 to E23 twelfth to twenty-third decision step P1 to P5 first to fifth sub-path S1 to S16 first to sixteenth step W1 to W4 first to fourth queue Z1, Z2 first, second state

Claims

[1] Method for connecting a telematics control unit (TCU) (2) of a vehicle (1) to a preferred land mobile network (Public Land Mobile Network, PLMN) (3) and / or via a preferred access method (Radio Access Technology, RAT), wherein - the TCU (2) is set to a first state (Normal Mode) (Z1) and then - logged into an initial PLMN (3) and communication readiness is established in a second state (Network Attach / Online State) (Z2) and then - in a first sub-path (P1) it is checked whether a currently set RAT is equivalent to or better than a predetermined minimum RAT and otherwise at least a first to third waiting loop (W1 to W3) with a predetermined waiting time is run through until the predetermined minimum RAT is reached or exceeded or until a predetermined maximum number of waiting loop runs has been reached and / or - in a second partial path (P2), a check is carried out on the basis of a Mobile Country Code (MCC) and / or Mobile Network Code (MNC) assigned to the TCU (2) via a Subscriber Identification Module (SIM) to determine whether the TCU (2) is logged into a preferred PLMN (3) and, if not, a waiting time is passed through, which is determined via a fourth waiting loop (W4), until the TCU (2) is logged into a preferred PLMN (3) or until a predetermined maximum number of waiting times has been passed through and - after the first partial path (P1), a third partial path (P3) is traversed, in which a preconfigured recovery measure for the TCU (2) is executed and waited until the TCU (2) is logged into another PLMN (3) and / or with another RAT or until a predetermined waiting time has elapsed and - after the third partial path (P3) the system changes to the second state (Z2), characterized by , that - in the first partial path (P1), a manual search for a preferred PLMN (3) with an improved RAT compared to the available RAT is started along a fourth partial path (P4) if a predetermined minimum RAT is not active and a predetermined maximum number of searches has not yet been reached, and - after the second partial path (P2), a manual search for a preferred PLMN (3) along a fifth partial path (P5) is started if the TCU (2) is not logged into a preferred PLMN (3). [2] Method according to claim 1, characterized by that is preconfigurable as a recovery measure for the TCU (2), a modem (2.1) of the TCU (2) - to put into airplane mode or alternatively - to put into a waiting mode (IDLE Mode) or alternatively - to be separated from all access points (access point names). [3] Method according to claim 1 or 2, characterized by that in the first sub-path (P1), - if no change of RAT has been made since the last run of the first partial path (P1), a first waiting loop (W1) is run through, - if a reduction in the RAT not caused by a voice call has been triggered since the last run of the first partial path (P1), a second waiting loop (W2) is run through and - if a reduction in the RAT caused by a voice call has been triggered since the last run of the first partial path (P1), a third waiting loop (W3) is run through, wherein a predetermined waiting time is assigned to each of the first to third waiting loops (W1 to W3). [4] Method according to one of the preceding claims, characterized bythat in the fourth sub-path (P4) and / or in the fifth sub-path (P5) the end of a voice call is waited for before starting a manual search, then the connection to the at least one access point (APN) is disconnected and the availability of a preferred PLMN (3) is checked and the manual search is only started if no preferred PLMN (3) is available.

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